WIP

backend/app/main.py

@@ -3,6 +3,7 @@ from fastapi.middleware.cors import CORSMiddleware
 from sqlalchemy.orm import Session
 from typing import List, Optional, Dict, Any
 from datetime import datetime, timedelta, date
+import math
 import json
 import csv
 import io
@@ -10,6 +11,7 @@ from .database import engine, get_db, Base
 from .models import (
     Drug,
     DrugVariant,
+    VariantPack,
     Dispensing,
     DispensingAllocation,
     Location,
@@ -114,7 +116,9 @@ class LocationResponse(BaseModel):
 
 class BatchCreate(BaseModel):
     batch_number: str
-    quantity: float
+    quantity: Optional[float] = None
+    received_pack_id: Optional[int] = None
+    received_pack_count: Optional[float] = None
     expiry_date: date
     location_id: int
     notes: Optional[str] = None
@@ -123,6 +127,8 @@ class BatchCreate(BaseModel):
 class BatchUpdate(BaseModel):
     batch_number: Optional[str] = None
     quantity: Optional[float] = None
+    received_pack_id: Optional[int] = None
+    received_pack_count: Optional[float] = None
     expiry_date: Optional[date] = None
     location_id: Optional[int] = None
     notes: Optional[str] = None
@@ -133,6 +139,12 @@ class BatchResponse(BaseModel):
     drug_variant_id: int
     batch_number: str
     quantity: float
+    received_pack_id: Optional[int] = None
+    received_pack_label: Optional[str] = None
+    received_pack_count: Optional[float] = None
+    received_pack_size_snapshot: Optional[float] = None
+    current_full_pack_count: Optional[float] = None
+    current_loose_base_units: Optional[float] = None
     expiry_date: date
     location_id: int
     location_name: Optional[str] = None
@@ -155,21 +167,51 @@ class DrugVariantCreate(BaseModel):
     strength: str
     quantity: float
     unit: str = "units"
+    base_unit: Optional[str] = None
     low_stock_threshold: float = 10
 
 class DrugVariantUpdate(BaseModel):
     strength: str = None
     quantity: float = None
     unit: str = None
+    base_unit: str = None
     low_stock_threshold: float = None
 
+
+class VariantPackCreate(BaseModel):
+    label: str
+    pack_unit_name: str
+    pack_size_in_base_units: float
+    is_active: bool = True
+
+
+class VariantPackUpdate(BaseModel):
+    label: Optional[str] = None
+    pack_unit_name: Optional[str] = None
+    pack_size_in_base_units: Optional[float] = None
+    is_active: Optional[bool] = None
+
+
+class VariantPackResponse(BaseModel):
+    id: int
+    drug_variant_id: int
+    label: str
+    pack_unit_name: str
+    pack_size_in_base_units: float
+    is_active: bool
+
+    class Config:
+        from_attributes = True
+
 class DrugVariantResponse(BaseModel):
     id: int
     drug_id: int
     strength: str
     quantity: float
     unit: str
+    base_unit: str
     low_stock_threshold: float
+    packs: List[VariantPackResponse] = []
     batches: List[BatchResponse] = []
     
     class Config:
@@ -187,8 +229,11 @@ class DrugWithVariantsResponse(BaseModel):
 
 class DispensingCreate(BaseModel):
     drug_variant_id: int
-    quantity: float
+    quantity: Optional[float] = None
+    dispense_mode: str = "subunit"
     batch_id: Optional[int] = None
+    requested_pack_id: Optional[int] = None
+    requested_pack_count: Optional[float] = None
     allow_split: bool = True
     animal_name: Optional[str] = None
     user_name: Optional[str] = None
@@ -208,6 +253,9 @@ class DispensingResponse(BaseModel):
     batch_id: Optional[int] = None
     actor_user_id: Optional[int] = None
     quantity: float
+    dispense_mode: str = "subunit"
+    requested_pack_id: Optional[int] = None
+    requested_pack_count: Optional[float] = None
     animal_name: Optional[str] = None
     user_name: str
     notes: Optional[str] = None
@@ -276,8 +324,16 @@ def enrich_variant_with_batches(db: Session, variant: DrugVariant) -> Dict[str,
         "strength": variant.strength,
         "quantity": variant.quantity,
         "unit": variant.unit,
+        "base_unit": variant.unit,
         "low_stock_threshold": variant.low_stock_threshold,
     }
+    packs = (
+        db.query(VariantPack)
+        .filter(VariantPack.drug_variant_id == variant.id)
+        .order_by(VariantPack.is_active.desc(), VariantPack.id.asc())
+        .all()
+    )
+    variant_dict["packs"] = [serialize_variant_pack(pack) for pack in packs]
     batches = (
         db.query(Batch)
         .filter(Batch.drug_variant_id == variant.id, Batch.quantity > 0)
@@ -290,11 +346,20 @@ def enrich_variant_with_batches(db: Session, variant: DrugVariant) -> Dict[str,
 
 def serialize_batch_response(db: Session, batch: Batch) -> Dict[str, Any]:
     location = db.query(Location).filter(Location.id == batch.location_id).first()
+    pack = None
+    if batch.received_pack_id is not None:
+        pack = db.query(VariantPack).filter(VariantPack.id == batch.received_pack_id).first()
     return {
         "id": batch.id,
         "drug_variant_id": batch.drug_variant_id,
         "batch_number": batch.batch_number,
         "quantity": batch.quantity,
+        "received_pack_id": batch.received_pack_id,
+        "received_pack_label": pack.label if pack else None,
+        "received_pack_count": batch.received_pack_count,
+        "received_pack_size_snapshot": batch.received_pack_size_snapshot,
+        "current_full_pack_count": batch.current_full_pack_count,
+        "current_loose_base_units": batch.current_loose_base_units,
         "expiry_date": batch.expiry_date,
         "location_id": batch.location_id,
         "location_name": location.name if location else None,
@@ -303,6 +368,96 @@ def serialize_batch_response(db: Session, batch: Batch) -> Dict[str, Any]:
     }
 
 
+def resolve_pack_size_snapshot(db: Session, pack_id: Optional[int]) -> Optional[float]:
+    if pack_id is None:
+        return None
+    pack = db.query(VariantPack).filter(VariantPack.id == pack_id).first()
+    if not pack:
+        return None
+    return pack.pack_size_in_base_units
+
+
+def recompute_batch_pack_state(batch: Batch) -> None:
+    pack_size = batch.received_pack_size_snapshot
+    if pack_size is None or pack_size <= 0 or batch.quantity < 0:
+        batch.current_full_pack_count = None
+        batch.current_loose_base_units = None
+        return
+
+    full_packs = math.floor((batch.quantity + 1e-9) / pack_size)
+    loose_units = batch.quantity - (full_packs * pack_size)
+    if loose_units < 1e-9:
+        loose_units = 0.0
+
+    batch.current_full_pack_count = float(full_packs)
+    batch.current_loose_base_units = loose_units
+
+
+def serialize_variant_pack(pack: VariantPack) -> Dict[str, Any]:
+    return {
+        "id": pack.id,
+        "drug_variant_id": pack.drug_variant_id,
+        "label": pack.label,
+        "pack_unit_name": pack.pack_unit_name,
+        "pack_size_in_base_units": pack.pack_size_in_base_units,
+        "is_active": pack.is_active,
+    }
+
+
+def resolve_pack_quantity(
+    db: Session,
+    variant_id: int,
+    quantity: Optional[float],
+    pack_id: Optional[int],
+    pack_count: Optional[float],
+) -> Dict[str, Any]:
+    """Resolve canonical base-unit quantity from either direct quantity or pack input."""
+    if quantity is None and pack_id is None and pack_count is None:
+        raise HTTPException(status_code=400, detail="Either quantity or pack fields must be provided")
+
+    resolved_quantity = quantity
+    resolved_pack: Optional[VariantPack] = None
+
+    if pack_id is not None or pack_count is not None:
+        if pack_id is None or pack_count is None:
+            raise HTTPException(status_code=400, detail="Both pack_id and pack_count are required when using pack input")
+        if pack_count <= 0:
+            raise HTTPException(status_code=400, detail="Pack count must be greater than zero")
+
+        resolved_pack = (
+            db.query(VariantPack)
+            .filter(
+                VariantPack.id == pack_id,
+                VariantPack.drug_variant_id == variant_id,
+                VariantPack.is_active.is_(True),
+            )
+            .first()
+        )
+        if resolved_pack is None:
+            raise HTTPException(status_code=400, detail="Pack not found for variant or is inactive")
+
+        derived_quantity = pack_count * resolved_pack.pack_size_in_base_units
+        if derived_quantity <= 0:
+            raise HTTPException(status_code=400, detail="Derived quantity from pack must be greater than zero")
+
+        if resolved_quantity is None:
+            resolved_quantity = derived_quantity
+        elif abs(resolved_quantity - derived_quantity) > 1e-6:
+            raise HTTPException(
+                status_code=400,
+                detail="Quantity does not match pack conversion for selected pack",
+            )
+
+    if resolved_quantity is None or resolved_quantity <= 0:
+        raise HTTPException(status_code=400, detail="Quantity must be greater than zero")
+
+    return {
+        "quantity": resolved_quantity,
+        "pack_id": resolved_pack.id if resolved_pack else None,
+        "pack_count": pack_count,
+    }
+
+
 def select_batches_for_dispense(
     db: Session,
     variant_id: int,
@@ -712,6 +867,7 @@ def delete_drug(drug_id: int, db: Session = Depends(get_db), current_user: User
             db.query(DispensingAllocation).filter(DispensingAllocation.batch_id.in_(batch_ids)).delete(synchronize_session=False)
             db.query(Batch).filter(Batch.id.in_(batch_ids)).delete(synchronize_session=False)
         db.query(Dispensing).filter(Dispensing.drug_variant_id.in_(variant_ids)).delete(synchronize_session=False)
+        db.query(VariantPack).filter(VariantPack.drug_variant_id.in_(variant_ids)).delete(synchronize_session=False)
         db.query(DrugVariant).filter(DrugVariant.id.in_(variant_ids)).delete(synchronize_session=False)
 
     write_audit_log(
@@ -745,14 +901,31 @@ def create_drug_variant(drug_id: int, variant: DrugVariantCreate, db: Session =
     if existing:
         raise HTTPException(status_code=400, detail="Variant with this strength already exists for this drug")
     
+    base_unit = (variant.base_unit or variant.unit).strip()
+    if not base_unit:
+        raise HTTPException(status_code=400, detail="Variant unit/base_unit cannot be empty")
+
     db_variant = DrugVariant(
         drug_id=drug_id,
         strength=variant.strength,
         quantity=variant.quantity,
-        unit=variant.unit,
+        unit=base_unit,
         low_stock_threshold=variant.low_stock_threshold
     )
     db.add(db_variant)
+    db.flush()
+
+    # Ensure each variant has at least one active default 1:1 pack representation.
+    db.add(
+        VariantPack(
+            drug_variant_id=db_variant.id,
+            label=f"1 {base_unit}",
+            pack_unit_name=base_unit,
+            pack_size_in_base_units=1,
+            is_active=True,
+        )
+    )
+
     write_audit_log(
         db,
         action="variant.create",
@@ -763,7 +936,7 @@ def create_drug_variant(drug_id: int, variant: DrugVariantCreate, db: Session =
             "drug_id": drug_id,
             "strength": variant.strength,
             "quantity": variant.quantity,
-            "unit": variant.unit,
+            "unit": base_unit,
         },
     )
     db.commit()
@@ -791,7 +964,15 @@ def update_drug_variant(variant_id: int, variant_update: DrugVariantUpdate, db:
         "unit": variant.unit,
         "low_stock_threshold": variant.low_stock_threshold,
     }
-    for field, value in variant_update.dict(exclude_unset=True).items():
+    payload = variant_update.dict(exclude_unset=True)
+    if "base_unit" in payload and payload["base_unit"] is not None:
+        cleaned_base_unit = payload["base_unit"].strip()
+        if not cleaned_base_unit:
+            raise HTTPException(status_code=400, detail="base_unit cannot be empty")
+        payload["unit"] = cleaned_base_unit
+    payload.pop("base_unit", None)
+
+    for field, value in payload.items():
         setattr(variant, field, value)
 
     write_audit_log(
@@ -800,7 +981,7 @@ def update_drug_variant(variant_id: int, variant_update: DrugVariantUpdate, db:
         entity_type="drug_variant",
         entity_id=variant.id,
         actor=current_user,
-        details={"before": before, "after": variant_update.dict(exclude_unset=True)},
+        details={"before": before, "after": payload},
     )
     
     db.commit()
@@ -820,6 +1001,7 @@ def delete_drug_variant(variant_id: int, db: Session = Depends(get_db), current_
         db.query(Batch).filter(Batch.id.in_(batch_ids)).delete(synchronize_session=False)
 
     db.query(Dispensing).filter(Dispensing.drug_variant_id == variant_id).delete(synchronize_session=False)
+    db.query(VariantPack).filter(VariantPack.drug_variant_id == variant_id).delete(synchronize_session=False)
     write_audit_log(
         db,
         action="variant.delete",
@@ -833,29 +1015,180 @@ def delete_drug_variant(variant_id: int, db: Session = Depends(get_db), current_
     
     return {"message": "Drug variant deleted successfully"}
 
+
+@router.get("/variants/{variant_id}/packs", response_model=List[VariantPackResponse])
+def list_variant_packs(
+    variant_id: int,
+    active_only: bool = False,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+):
+    variant = db.query(DrugVariant).filter(DrugVariant.id == variant_id).first()
+    if not variant:
+        raise HTTPException(status_code=404, detail="Drug variant not found")
+
+    query = db.query(VariantPack).filter(VariantPack.drug_variant_id == variant_id)
+    if active_only:
+        query = query.filter(VariantPack.is_active.is_(True))
+
+    packs = query.order_by(VariantPack.is_active.desc(), VariantPack.id.asc()).all()
+    return [serialize_variant_pack(pack) for pack in packs]
+
+
+@router.post("/variants/{variant_id}/packs", response_model=VariantPackResponse)
+def create_variant_pack(
+    variant_id: int,
+    payload: VariantPackCreate,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_non_readonly_user),
+):
+    variant = db.query(DrugVariant).filter(DrugVariant.id == variant_id).first()
+    if not variant:
+        raise HTTPException(status_code=404, detail="Drug variant not found")
+
+    label = payload.label.strip()
+    pack_unit_name = payload.pack_unit_name.strip()
+    if not label:
+        raise HTTPException(status_code=400, detail="Pack label cannot be empty")
+    if not pack_unit_name:
+        raise HTTPException(status_code=400, detail="Pack unit name cannot be empty")
+    if payload.pack_size_in_base_units <= 0:
+        raise HTTPException(status_code=400, detail="Pack size in base units must be greater than zero")
+
+    row = VariantPack(
+        drug_variant_id=variant_id,
+        label=label,
+        pack_unit_name=pack_unit_name,
+        pack_size_in_base_units=payload.pack_size_in_base_units,
+        is_active=payload.is_active,
+    )
+    db.add(row)
+    write_audit_log(
+        db,
+        action="variant_pack.create",
+        entity_type="variant_pack",
+        entity_id=None,
+        actor=current_user,
+        details={
+            "variant_id": variant_id,
+            "label": label,
+            "pack_unit_name": pack_unit_name,
+            "pack_size_in_base_units": payload.pack_size_in_base_units,
+            "is_active": payload.is_active,
+        },
+    )
+    db.commit()
+    db.refresh(row)
+    return serialize_variant_pack(row)
+
+
+@router.put("/variant-packs/{pack_id}", response_model=VariantPackResponse)
+def update_variant_pack(
+    pack_id: int,
+    payload: VariantPackUpdate,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_non_readonly_user),
+):
+    row = db.query(VariantPack).filter(VariantPack.id == pack_id).first()
+    if not row:
+        raise HTTPException(status_code=404, detail="Variant pack not found")
+
+    before = serialize_variant_pack(row)
+
+    if payload.label is not None:
+        cleaned = payload.label.strip()
+        if not cleaned:
+            raise HTTPException(status_code=400, detail="Pack label cannot be empty")
+        row.label = cleaned
+
+    if payload.pack_unit_name is not None:
+        cleaned = payload.pack_unit_name.strip()
+        if not cleaned:
+            raise HTTPException(status_code=400, detail="Pack unit name cannot be empty")
+        row.pack_unit_name = cleaned
+
+    if payload.pack_size_in_base_units is not None:
+        if payload.pack_size_in_base_units <= 0:
+            raise HTTPException(status_code=400, detail="Pack size in base units must be greater than zero")
+        row.pack_size_in_base_units = payload.pack_size_in_base_units
+
+    if payload.is_active is not None and payload.is_active is False:
+        # Keep at least one active pack per variant to preserve usable receive/dispense UX.
+        active_count = db.query(VariantPack).filter(
+            VariantPack.drug_variant_id == row.drug_variant_id,
+            VariantPack.is_active.is_(True),
+            VariantPack.id != row.id,
+        ).count()
+        if active_count == 0:
+            raise HTTPException(status_code=400, detail="At least one active pack must remain for this variant")
+        row.is_active = False
+    elif payload.is_active is not None and payload.is_active is True:
+        row.is_active = True
+
+    write_audit_log(
+        db,
+        action="variant_pack.update",
+        entity_type="variant_pack",
+        entity_id=pack_id,
+        actor=current_user,
+        details={"before": before, "after": payload.dict(exclude_unset=True)},
+    )
+    db.commit()
+    db.refresh(row)
+    return serialize_variant_pack(row)
+
 # Dispensing endpoints
 @router.post("/dispense", response_model=DispensingResponse)
 def dispense_drug(dispensing: DispensingCreate, db: Session = Depends(get_db), current_user: User = Depends(get_current_non_readonly_user)):
     """Record a drug dispensing and reduce inventory"""
-    if dispensing.quantity <= 0:
-        raise HTTPException(status_code=400, detail="Quantity must be greater than zero")
-
     # Check if drug variant exists
     variant = db.query(DrugVariant).filter(DrugVariant.id == dispensing.drug_variant_id).first()
     if not variant:
         raise HTTPException(status_code=404, detail="Drug variant not found")
 
+    dispense_mode = (dispensing.dispense_mode or "subunit").strip().lower()
+    if dispense_mode not in {"subunit", "pack"}:
+        raise HTTPException(status_code=400, detail="dispense_mode must be either 'subunit' or 'pack'")
+
+    if dispense_mode == "pack":
+        if dispensing.requested_pack_id is None or dispensing.requested_pack_count is None:
+            raise HTTPException(status_code=400, detail="Pack dispense requires requested_pack_id and requested_pack_count")
+        if dispensing.requested_pack_count <= 0:
+            raise HTTPException(status_code=400, detail="Pack count must be greater than zero")
+        if abs(dispensing.requested_pack_count - round(dispensing.requested_pack_count)) > 1e-6:
+            raise HTTPException(status_code=400, detail="Whole-pack dispense requires an integer pack count")
+
+        resolved = resolve_pack_quantity(
+            db,
+            variant_id=variant.id,
+            quantity=None,
+            pack_id=dispensing.requested_pack_id,
+            pack_count=dispensing.requested_pack_count,
+        )
+    else:
+        if dispensing.quantity is None or dispensing.quantity <= 0:
+            raise HTTPException(status_code=400, detail="Subunit dispense requires quantity > 0")
+        resolved = resolve_pack_quantity(
+            db,
+            variant_id=variant.id,
+            quantity=dispensing.quantity,
+            pack_id=None,
+            pack_count=None,
+        )
+
+    dispense_qty = resolved["quantity"]
+    
     # Check if enough total quantity available from active stock (legacy and batch-based remain in sync).
-    if variant.quantity < dispensing.quantity:
+    if variant.quantity < dispense_qty:
         raise HTTPException(
             status_code=400,
-            detail=f"Insufficient quantity. Available: {variant.quantity}, Requested: {dispensing.quantity}",
+            detail=f"Insufficient quantity. Available: {variant.quantity}, Requested: {dispense_qty}",
         )
 
     allocations = select_batches_for_dispense(
         db,
         variant_id=variant.id,
-        requested_quantity=dispensing.quantity,
+        requested_quantity=dispense_qty,
         preferred_batch_id=dispensing.batch_id,
         allow_split=dispensing.allow_split,
     )
@@ -867,7 +1200,10 @@ def dispense_drug(dispensing: DispensingCreate, db: Session = Depends(get_db), c
         drug_variant_id=dispensing.drug_variant_id,
         batch_id=primary_batch_id,
         actor_user_id=current_user.id,
-        quantity=dispensing.quantity,
+        quantity=dispense_qty,
+        dispense_mode=dispense_mode,
+        requested_pack_id=resolved["pack_id"],
+        requested_pack_count=resolved["pack_count"],
         animal_name=dispensing.animal_name,
         user_name=user_name,
         notes=dispensing.notes,
@@ -880,11 +1216,12 @@ def dispense_drug(dispensing: DispensingCreate, db: Session = Depends(get_db), c
         batch = allocation["batch"]
         qty = allocation["quantity"]
         batch.quantity -= qty
+        recompute_batch_pack_state(batch)
         allocation_payload.append({"batch_id": batch.id, "quantity": qty})
         db.add(DispensingAllocation(dispensing_id=db_dispensing.id, batch_id=batch.id, quantity=qty))
 
     # Keep legacy variant quantity field in sync for existing frontend flows.
-    variant.quantity -= dispensing.quantity
+    variant.quantity -= dispense_qty
 
     write_audit_log(
         db,
@@ -894,7 +1231,10 @@ def dispense_drug(dispensing: DispensingCreate, db: Session = Depends(get_db), c
         actor=current_user,
         details={
             "drug_variant_id": dispensing.drug_variant_id,
-            "requested_quantity": dispensing.quantity,
+            "requested_quantity": dispense_qty,
+            "dispense_mode": dispense_mode,
+            "requested_pack_id": resolved["pack_id"],
+            "requested_pack_count": resolved["pack_count"],
             "allocations": allocation_payload,
             "animal_name": dispensing.animal_name,
             "notes": dispensing.notes,
@@ -909,6 +1249,9 @@ def dispense_drug(dispensing: DispensingCreate, db: Session = Depends(get_db), c
         "batch_id": db_dispensing.batch_id,
         "actor_user_id": db_dispensing.actor_user_id,
         "quantity": db_dispensing.quantity,
+        "dispense_mode": db_dispensing.dispense_mode,
+        "requested_pack_id": db_dispensing.requested_pack_id,
+        "requested_pack_count": db_dispensing.requested_pack_count,
         "animal_name": db_dispensing.animal_name,
         "user_name": db_dispensing.user_name,
         "notes": db_dispensing.notes,
@@ -930,6 +1273,9 @@ def list_dispensings(skip: int = 0, limit: int = 100, db: Session = Depends(get_
                 "batch_id": item.batch_id,
                 "actor_user_id": item.actor_user_id,
                 "quantity": item.quantity,
+                "dispense_mode": item.dispense_mode,
+                "requested_pack_id": item.requested_pack_id,
+                "requested_pack_count": item.requested_pack_count,
                 "animal_name": item.animal_name,
                 "user_name": item.user_name,
                 "notes": item.notes,
@@ -961,6 +1307,9 @@ def get_drug_dispensings(drug_id: int, db: Session = Depends(get_db), current_us
                 "batch_id": item.batch_id,
                 "actor_user_id": item.actor_user_id,
                 "quantity": item.quantity,
+                "dispense_mode": item.dispense_mode,
+                "requested_pack_id": item.requested_pack_id,
+                "requested_pack_count": item.requested_pack_count,
                 "animal_name": item.animal_name,
                 "user_name": item.user_name,
                 "notes": item.notes,
@@ -989,6 +1338,9 @@ def get_variant_dispensings(variant_id: int, db: Session = Depends(get_db), curr
                 "batch_id": item.batch_id,
                 "actor_user_id": item.actor_user_id,
                 "quantity": item.quantity,
+                "dispense_mode": item.dispense_mode,
+                "requested_pack_id": item.requested_pack_id,
+                "requested_pack_count": item.requested_pack_count,
                 "animal_name": item.animal_name,
                 "user_name": item.user_name,
                 "notes": item.notes,
@@ -1090,8 +1442,15 @@ def create_variant_batch(variant_id: int, payload: BatchCreate, db: Session = De
     variant = db.query(DrugVariant).filter(DrugVariant.id == variant_id).first()
     if not variant:
         raise HTTPException(status_code=404, detail="Drug variant not found")
-    if payload.quantity <= 0:
+
-        raise HTTPException(status_code=400, detail="Batch quantity must be greater than zero")
+    resolved = resolve_pack_quantity(
+        db,
+        variant_id=variant_id,
+        quantity=payload.quantity,
+        pack_id=payload.received_pack_id,
+        pack_count=payload.received_pack_count,
+    )
+    batch_quantity = resolved["quantity"]
 
     location = db.query(Location).filter(Location.id == payload.location_id, Location.is_active.is_(True)).first()
     if not location:
@@ -1112,14 +1471,18 @@ def create_variant_batch(variant_id: int, payload: BatchCreate, db: Session = De
     row = Batch(
         drug_variant_id=variant_id,
         batch_number=batch_number,
-        quantity=payload.quantity,
+        quantity=batch_quantity,
+        received_pack_id=resolved["pack_id"],
+        received_pack_count=resolved["pack_count"],
+        received_pack_size_snapshot=resolve_pack_size_snapshot(db, resolved["pack_id"]),
         expiry_date=payload.expiry_date,
         location_id=payload.location_id,
         notes=payload.notes,
     )
+    recompute_batch_pack_state(row)
     db.add(row)
 
-    variant.quantity += payload.quantity
+    variant.quantity += batch_quantity
 
     write_audit_log(
         db,
@@ -1130,7 +1493,10 @@ def create_variant_batch(variant_id: int, payload: BatchCreate, db: Session = De
         details={
             "variant_id": variant_id,
             "batch_number": batch_number,
-            "quantity": payload.quantity,
+            "quantity": batch_quantity,
+            "received_pack_id": resolved["pack_id"],
+            "received_pack_count": resolved["pack_count"],
+            "received_pack_size_snapshot": row.received_pack_size_snapshot,
             "expiry_date": payload.expiry_date,
             "location_id": payload.location_id,
         },
@@ -1153,6 +1519,11 @@ def update_batch(batch_id: int, payload: BatchUpdate, db: Session = Depends(get_
     before = {
         "batch_number": batch.batch_number,
         "quantity": batch.quantity,
+        "received_pack_id": batch.received_pack_id,
+        "received_pack_count": batch.received_pack_count,
+        "received_pack_size_snapshot": batch.received_pack_size_snapshot,
+        "current_full_pack_count": batch.current_full_pack_count,
+        "current_loose_base_units": batch.current_loose_base_units,
         "expiry_date": batch.expiry_date,
         "location_id": batch.location_id,
         "notes": batch.notes,
@@ -1187,14 +1558,42 @@ def update_batch(batch_id: int, payload: BatchUpdate, db: Session = Depends(get_
     if payload.notes is not None:
         batch.notes = payload.notes
 
-    if payload.quantity is not None:
+    if payload.received_pack_id is not None or payload.received_pack_count is not None or payload.quantity is not None:
-        if payload.quantity < 0:
+        if payload.quantity is not None and payload.quantity < 0:
             raise HTTPException(status_code=400, detail="Batch quantity cannot be negative")
-        delta = payload.quantity - batch.quantity
+
+        if payload.received_pack_id is None and payload.received_pack_count is None:
+            if payload.quantity is None:
+                raise HTTPException(status_code=400, detail="Batch quantity cannot be empty")
+            resolved_quantity = payload.quantity
+            resolved_pack_id = batch.received_pack_id
+            resolved_pack_count = batch.received_pack_count
+        else:
+            target_pack_id = payload.received_pack_id if payload.received_pack_id is not None else batch.received_pack_id
+            target_pack_count = payload.received_pack_count if payload.received_pack_count is not None else batch.received_pack_count
+            if target_pack_id is None or target_pack_count is None:
+                raise HTTPException(status_code=400, detail="Both pack_id and pack_count are required for pack-based updates")
+
+            resolved = resolve_pack_quantity(
+                db,
+                variant_id=batch.drug_variant_id,
+                quantity=payload.quantity,
+                pack_id=target_pack_id,
+                pack_count=target_pack_count,
+            )
+            resolved_quantity = resolved["quantity"]
+            resolved_pack_id = resolved["pack_id"]
+            resolved_pack_count = resolved["pack_count"]
+
+        delta = resolved_quantity - batch.quantity
         projected_variant_qty = variant.quantity + delta
         if projected_variant_qty < 0:
             raise HTTPException(status_code=400, detail="Variant quantity cannot become negative")
-        batch.quantity = payload.quantity
+        batch.quantity = resolved_quantity
+        batch.received_pack_id = resolved_pack_id
+        batch.received_pack_count = resolved_pack_count
+        batch.received_pack_size_snapshot = resolve_pack_size_snapshot(db, resolved_pack_id)
+        recompute_batch_pack_state(batch)
         variant.quantity = projected_variant_qty
 
     write_audit_log(
@@ -1276,6 +1675,9 @@ def report_controlled_movement(
             "drug_name": drug.name,
             "strength": variant.strength,
             "quantity": d.quantity,
+            "dispense_mode": d.dispense_mode,
+            "requested_pack_id": d.requested_pack_id,
+            "requested_pack_count": d.requested_pack_count,
             "user_name": d.user_name,
             "animal_name": d.animal_name,
             "batch_id": d.batch_id,

backend/app/migrate_compliance.py

@@ -56,6 +56,25 @@ def migrate_compliance_schema() -> None:
     cursor = conn.cursor()
 
     try:
+        if _table_exists(cursor, "drug_variants") and not _table_exists(cursor, "variant_packs"):
+            cursor.execute(
+                """
+                CREATE TABLE variant_packs (
+                    id INTEGER PRIMARY KEY,
+                    drug_variant_id INTEGER NOT NULL,
+                    label VARCHAR NOT NULL,
+                    pack_unit_name VARCHAR NOT NULL DEFAULT 'pack',
+                    pack_size_in_base_units FLOAT NOT NULL DEFAULT 1,
+                    is_active BOOLEAN NOT NULL DEFAULT 1,
+                    created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+                    updated_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+                    FOREIGN KEY(drug_variant_id) REFERENCES drug_variants(id)
+                )
+                """
+            )
+            cursor.execute("CREATE INDEX IF NOT EXISTS ix_variant_packs_drug_variant_id ON variant_packs(drug_variant_id)")
+            print("Created variant_packs table")
+
         if _table_exists(cursor, "drugs") and not _column_exists(cursor, "drugs", "is_controlled"):
             cursor.execute("ALTER TABLE drugs ADD COLUMN is_controlled BOOLEAN NOT NULL DEFAULT 0")
             print("Added drugs.is_controlled")
@@ -68,6 +87,133 @@ def migrate_compliance_schema() -> None:
             cursor.execute("ALTER TABLE dispensings ADD COLUMN actor_user_id INTEGER")
             print("Added dispensings.actor_user_id")
 
+        if _table_exists(cursor, "batches") and not _column_exists(cursor, "batches", "received_pack_id"):
+            cursor.execute("ALTER TABLE batches ADD COLUMN received_pack_id INTEGER")
+            print("Added batches.received_pack_id")
+
+        if _table_exists(cursor, "batches") and not _column_exists(cursor, "batches", "received_pack_count"):
+            cursor.execute("ALTER TABLE batches ADD COLUMN received_pack_count FLOAT")
+            print("Added batches.received_pack_count")
+
+        if _table_exists(cursor, "batches") and not _column_exists(cursor, "batches", "received_pack_size_snapshot"):
+            cursor.execute("ALTER TABLE batches ADD COLUMN received_pack_size_snapshot FLOAT")
+            print("Added batches.received_pack_size_snapshot")
+
+        if _table_exists(cursor, "batches") and not _column_exists(cursor, "batches", "current_full_pack_count"):
+            cursor.execute("ALTER TABLE batches ADD COLUMN current_full_pack_count FLOAT")
+            print("Added batches.current_full_pack_count")
+
+        if _table_exists(cursor, "batches") and not _column_exists(cursor, "batches", "current_loose_base_units"):
+            cursor.execute("ALTER TABLE batches ADD COLUMN current_loose_base_units FLOAT")
+            print("Added batches.current_loose_base_units")
+
+        if _table_exists(cursor, "dispensings") and not _column_exists(cursor, "dispensings", "requested_pack_id"):
+            cursor.execute("ALTER TABLE dispensings ADD COLUMN requested_pack_id INTEGER")
+            print("Added dispensings.requested_pack_id")
+
+        if _table_exists(cursor, "dispensings") and not _column_exists(cursor, "dispensings", "requested_pack_count"):
+            cursor.execute("ALTER TABLE dispensings ADD COLUMN requested_pack_count FLOAT")
+            print("Added dispensings.requested_pack_count")
+
+        if _table_exists(cursor, "dispensings") and not _column_exists(cursor, "dispensings", "dispense_mode"):
+            cursor.execute("ALTER TABLE dispensings ADD COLUMN dispense_mode VARCHAR NOT NULL DEFAULT 'subunit'")
+            print("Added dispensings.dispense_mode")
+
+        if _table_exists(cursor, "variant_packs") and _table_exists(cursor, "drug_variants"):
+            cursor.execute(
+                """
+                INSERT INTO variant_packs (drug_variant_id, label, pack_unit_name, pack_size_in_base_units, is_active)
+                SELECT v.id,
+                       '1 ' || COALESCE(NULLIF(v.unit, ''), 'unit'),
+                       COALESCE(NULLIF(v.unit, ''), 'unit'),
+                       1,
+                       1
+                FROM drug_variants v
+                WHERE NOT EXISTS (
+                    SELECT 1
+                    FROM variant_packs p
+                    WHERE p.drug_variant_id = v.id
+                )
+                """
+            )
+            print("Ensured default pack rows for variants")
+
+        if _table_exists(cursor, "batches") and _table_exists(cursor, "variant_packs"):
+            cursor.execute(
+                """
+                UPDATE batches
+                SET received_pack_id = (
+                        SELECT p.id
+                        FROM variant_packs p
+                        WHERE p.drug_variant_id = batches.drug_variant_id
+                        ORDER BY p.id ASC
+                        LIMIT 1
+                    ),
+                    received_pack_count = quantity
+                WHERE received_pack_id IS NULL
+                """
+            )
+            print("Backfilled batches pack context where missing")
+
+            cursor.execute(
+                """
+                UPDATE batches
+                SET received_pack_size_snapshot = (
+                        SELECT p.pack_size_in_base_units
+                        FROM variant_packs p
+                        WHERE p.id = batches.received_pack_id
+                        LIMIT 1
+                    )
+                WHERE received_pack_id IS NOT NULL
+                  AND (received_pack_size_snapshot IS NULL OR received_pack_size_snapshot <= 0)
+                """
+            )
+            print("Backfilled batches pack size snapshot where missing")
+
+            cursor.execute(
+                """
+                UPDATE batches
+                SET current_full_pack_count = CASE
+                        WHEN COALESCE(received_pack_size_snapshot, 0) > 0 THEN CAST(quantity / received_pack_size_snapshot AS INTEGER)
+                        ELSE NULL
+                    END,
+                    current_loose_base_units = CASE
+                        WHEN COALESCE(received_pack_size_snapshot, 0) > 0 THEN quantity - (CAST(quantity / received_pack_size_snapshot AS INTEGER) * received_pack_size_snapshot)
+                        ELSE NULL
+                    END
+                """
+            )
+            print("Backfilled batches live pack state")
+
+        if _table_exists(cursor, "dispensings") and _table_exists(cursor, "variant_packs"):
+            cursor.execute(
+                """
+                UPDATE dispensings
+                SET requested_pack_id = (
+                        SELECT p.id
+                        FROM variant_packs p
+                        WHERE p.drug_variant_id = dispensings.drug_variant_id
+                        ORDER BY p.id ASC
+                        LIMIT 1
+                    ),
+                    requested_pack_count = quantity
+                WHERE requested_pack_id IS NULL
+                """
+            )
+            print("Backfilled dispensing pack context where missing")
+
+            cursor.execute(
+                """
+                UPDATE dispensings
+                SET dispense_mode = CASE
+                        WHEN requested_pack_id IS NOT NULL AND requested_pack_count IS NOT NULL THEN 'pack'
+                        ELSE 'subunit'
+                    END
+                WHERE dispense_mode IS NULL OR TRIM(dispense_mode) = ''
+                """
+            )
+            print("Backfilled dispensing mode where missing")
+
         # Seed default locations once table exists (created via SQLAlchemy create_all).
         if _table_exists(cursor, "locations"):
             cursor.execute("INSERT OR IGNORE INTO locations(name, is_active) VALUES ('Cupboard', 1)")

backend/app/models.py

@@ -36,6 +36,19 @@ class DrugVariant(Base):
     updated_at = Column(DateTime(timezone=True), onupdate=func.now(), server_default=func.now())
 
 
+class VariantPack(Base):
+    __tablename__ = "variant_packs"
+
+    id = Column(Integer, primary_key=True, index=True)
+    drug_variant_id = Column(Integer, ForeignKey("drug_variants.id"), nullable=False, index=True)
+    label = Column(String, nullable=False)
+    pack_unit_name = Column(String, nullable=False, default="pack")
+    pack_size_in_base_units = Column(Float, nullable=False, default=1)
+    is_active = Column(Boolean, nullable=False, default=True)
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+    updated_at = Column(DateTime(timezone=True), onupdate=func.now(), server_default=func.now())
+
+
 class Dispensing(Base):
     __tablename__ = "dispensings"
 
@@ -44,6 +57,9 @@ class Dispensing(Base):
     batch_id = Column(Integer, ForeignKey("batches.id"), nullable=True)
     actor_user_id = Column(Integer, ForeignKey("users.id"), nullable=True)
     quantity = Column(Float, nullable=False)
+    dispense_mode = Column(String, nullable=False, default="subunit")
+    requested_pack_id = Column(Integer, ForeignKey("variant_packs.id"), nullable=True)
+    requested_pack_count = Column(Float, nullable=True)
     animal_name = Column(String, nullable=True)  # Name/ID of the animal (optional)
     user_name = Column(String, nullable=False)  # User who dispensed
     dispensed_at = Column(DateTime(timezone=True), server_default=func.now(), index=True)
@@ -67,6 +83,11 @@ class Batch(Base):
     drug_variant_id = Column(Integer, ForeignKey("drug_variants.id"), nullable=False, index=True)
     batch_number = Column(String, nullable=False, index=True)
     quantity = Column(Float, nullable=False, default=0)
+    received_pack_id = Column(Integer, ForeignKey("variant_packs.id"), nullable=True)
+    received_pack_count = Column(Float, nullable=True)
+    received_pack_size_snapshot = Column(Float, nullable=True)
+    current_full_pack_count = Column(Float, nullable=True)
+    current_loose_base_units = Column(Float, nullable=True)
     expiry_date = Column(Date, nullable=False, index=True)
     location_id = Column(Integer, ForeignKey("locations.id"), nullable=False, index=True)
     received_at = Column(DateTime(timezone=True), nullable=False, server_default=func.now(), index=True)

frontend/app.js

@@ -7,6 +7,10 @@ let searchTerm = '';
 let expandedDrugs = new Set();
 let currentUser = null;
 let accessToken = null;
+let deliveryDrugId = null;
+let deliveryLineCounter = 0;
+let deliveryLocations = [];
+let activeVariantPacksVariantId = null;
 
 // Toast notification system
 function showToast(message, type = 'info', duration = 3000) {
@@ -212,6 +216,7 @@ function setupEventListeners() {
     const editModal = document.getElementById('editModal');
     const printNotesModal = document.getElementById('printNotesModal');
     const batchReceiveModal = document.getElementById('batchReceiveModal');
+    const receiveDeliveryModal = document.getElementById('receiveDeliveryModal');
     const addDrugBtn = document.getElementById('addDrugBtn');
     const dispenseBtn = document.getElementById('dispenseBtn');
     const printNotesBtn = document.getElementById('printNotesBtn');
@@ -222,6 +227,15 @@ function setupEventListeners() {
     const cancelPrescribeBtn = document.getElementById('cancelPrescribeBtn');
     const cancelEditBtn = document.getElementById('cancelEditBtn');
     const cancelBatchReceiveBtn = document.getElementById('cancelBatchReceiveBtn');
+    const cancelReceiveDeliveryBtn = document.getElementById('cancelReceiveDeliveryBtn');
+    const addDeliveryLineBtn = document.getElementById('addDeliveryLineBtn');
+    const addVariantFromDeliveryBtn = document.getElementById('addVariantFromDeliveryBtn');
+    const addVariantPackRowBtn = document.getElementById('addVariantPackRowBtn');
+    const variantUnitSelect = document.getElementById('variantUnit');
+    const variantStrengthInput = document.getElementById('variantStrength');
+    const dispenseModeSelect = document.getElementById('dispenseMode');
+    const variantPacksForm = document.getElementById('variantPacksForm');
+    const closeVariantPacksBtn = document.getElementById('closeVariantPacksBtn');
     const showAllBtn = document.getElementById('showAllBtn');
     const showLowStockBtn = document.getElementById('showLowStockBtn');
     const locationFilterSelect = document.getElementById('locationFilterSelect');
@@ -247,10 +261,30 @@ function setupEventListeners() {
     if (batchReceiveForm) batchReceiveForm.addEventListener('submit', handleBatchReceive);
     if (cancelBatchReceiveBtn) cancelBatchReceiveBtn.addEventListener('click', () => closeModal(batchReceiveModal));
 
+    const receiveDeliveryForm = document.getElementById('receiveDeliveryForm');
+    if (receiveDeliveryForm) receiveDeliveryForm.addEventListener('submit', handleReceiveDelivery);
+    if (cancelReceiveDeliveryBtn) cancelReceiveDeliveryBtn.addEventListener('click', () => closeModal(receiveDeliveryModal));
+    if (addDeliveryLineBtn) addDeliveryLineBtn.addEventListener('click', () => appendDeliveryLine());
+    if (addVariantFromDeliveryBtn) addVariantFromDeliveryBtn.addEventListener('click', handleAddVariantFromDelivery);
+    if (addVariantPackRowBtn) addVariantPackRowBtn.addEventListener('click', () => appendVariantPackRow());
+    if (variantUnitSelect) {
+        variantUnitSelect.addEventListener('change', () => {
+            refreshVariantPackRowLabels();
+        });
+    }
+    if (variantStrengthInput && variantUnitSelect) {
+        variantStrengthInput.addEventListener('blur', () => {
+            variantUnitSelect.value = inferBaseUnitFromStrength(variantStrengthInput.value);
+            refreshVariantPackRowLabels();
+        });
+    }
+    if (dispenseModeSelect) dispenseModeSelect.addEventListener('change', updateDispenseModeUi);
+    
     if (addDrugBtn) addDrugBtn.addEventListener('click', () => openModal(addModal));
     if (printNotesBtn) printNotesBtn.addEventListener('click', () => openModal(printNotesModal));
     if (dispenseBtn) dispenseBtn.addEventListener('click', () => {
         updateDispenseDrugSelect();
+        updateDispenseModeUi();
         openModal(dispenseModal);
     });
     
@@ -273,6 +307,9 @@ function setupEventListeners() {
     const closeLocationManagementBtn = document.getElementById('closeLocationManagementBtn');
     if (closeLocationManagementBtn) closeLocationManagementBtn.addEventListener('click', () => closeModal(document.getElementById('locationManagementModal')));
 
+    if (variantPacksForm) variantPacksForm.addEventListener('submit', handleCreateVariantPack);
+    if (closeVariantPacksBtn) closeVariantPacksBtn.addEventListener('click', () => closeModal(document.getElementById('variantPacksModal')));
+    
     const createLocationForm = document.getElementById('createLocationForm');
     if (createLocationForm) createLocationForm.addEventListener('submit', createLocation);
     
@@ -333,6 +370,28 @@ function setupEventListeners() {
         });
     }
 
+    const dispenseQuantityInput = document.getElementById('dispenseQuantity');
+    if (dispenseQuantityInput) {
+        dispenseQuantityInput.addEventListener('input', () => {
+            const mode = document.getElementById('dispenseMode')?.value || 'subunit';
+            if (mode !== 'subunit') {
+                return;
+            }
+
+            const packSelect = document.getElementById('dispensePackSelect');
+            const packCount = document.getElementById('dispensePackCount');
+            const packPreview = document.getElementById('dispensePackPreview');
+            const variantId = parseInt(document.getElementById('dispenseDrugSelect')?.value || '', 10);
+            const variant = getVariantById(variantId);
+
+            if (packSelect) packSelect.value = '';
+            if (packCount) packCount.value = '';
+            if (packPreview && variant) {
+                packPreview.textContent = `Enter direct quantity in ${variant.unit}.`;
+            }
+        });
+    }
+
     // Close modal when clicking outside
     window.addEventListener('click', (e) => {
         if (e.target.classList.contains('modal')) {
@@ -398,6 +457,108 @@ function updateDispenseDrugSelect() {
             select.appendChild(option);
         });
     });
+
+    const packSelect = document.getElementById('dispensePackSelect');
+    const packCount = document.getElementById('dispensePackCount');
+    const packPreview = document.getElementById('dispensePackPreview');
+    const modeSelect = document.getElementById('dispenseMode');
+    if (packSelect) {
+        packSelect.innerHTML = '<option value="">-- Select pack --</option>';
+    }
+    if (packCount) {
+        packCount.value = '';
+    }
+    if (modeSelect) {
+        modeSelect.value = 'subunit';
+    }
+    if (packPreview) {
+        packPreview.textContent = 'Select a pack and whole-number count.';
+    }
+
+    updateDispenseModeUi();
+}
+
+function populateDispensePackSelect(variant) {
+    const packSelect = document.getElementById('dispensePackSelect');
+    const packCount = document.getElementById('dispensePackCount');
+    const packPreview = document.getElementById('dispensePackPreview');
+    if (!packSelect) return;
+
+    const activePacks = getActivePacksForVariant(variant);
+    packSelect.innerHTML = '<option value="">-- Select pack --</option>';
+
+    activePacks.forEach(pack => {
+        const option = document.createElement('option');
+        option.value = String(pack.id);
+        option.textContent = `${pack.label} (${pack.pack_size_in_base_units} ${variant.unit})`;
+        packSelect.appendChild(option);
+    });
+
+    if (packCount) packCount.value = '';
+    if (packPreview) {
+        packPreview.textContent = activePacks.length > 0
+            ? `Select a pack and whole-number count (${variant.unit} base unit).`
+            : `No active packs for this variant.`;
+    }
+}
+
+function updateDispenseModeUi() {
+    const mode = document.getElementById('dispenseMode')?.value || 'subunit';
+    const quantityGroup = document.getElementById('dispenseQuantityGroup');
+    const packRow = document.getElementById('dispensePackRow');
+    const quantityInput = document.getElementById('dispenseQuantity');
+    const packSelect = document.getElementById('dispensePackSelect');
+    const packCount = document.getElementById('dispensePackCount');
+
+    if (quantityGroup) {
+        quantityGroup.style.display = mode === 'subunit' ? '' : 'none';
+    }
+    if (packRow) {
+        packRow.style.display = mode === 'pack' ? '' : 'none';
+    }
+
+    if (quantityInput) {
+        quantityInput.required = mode === 'subunit';
+    }
+    if (packSelect) {
+        packSelect.required = mode === 'pack';
+    }
+    if (packCount) {
+        packCount.required = mode === 'pack';
+    }
+
+    updateAllocationPreview();
+}
+
+function updateDispenseQuantityFromPack() {
+    const mode = document.getElementById('dispenseMode')?.value || 'subunit';
+    if (mode !== 'pack') return;
+
+    const variantId = parseInt(document.getElementById('dispenseDrugSelect')?.value || '', 10);
+    const packId = parseInt(document.getElementById('dispensePackSelect')?.value || '', 10);
+    const packCount = parseFloat(document.getElementById('dispensePackCount')?.value || '');
+    const quantityInput = document.getElementById('dispenseQuantity');
+    const preview = document.getElementById('dispensePackPreview');
+
+    const variant = getVariantById(variantId);
+    if (!quantityInput || !preview || !variant) return;
+
+    const selectedPack = getActivePacksForVariant(variant).find(pack => pack.id === packId);
+    if (selectedPack && !Number.isNaN(packCount) && packCount > 0) {
+        if (Math.abs(packCount - Math.round(packCount)) > 1e-6) {
+            preview.textContent = 'Whole-pack mode requires a whole-number pack count.';
+            return;
+        }
+        const quantity = packCount * selectedPack.pack_size_in_base_units;
+        quantityInput.value = String(quantity);
+        preview.textContent = `${packCount} × ${selectedPack.pack_size_in_base_units} = ${quantity} ${variant.unit}`;
+        updateAllocationPreview();
+        return;
+    }
+
+    preview.textContent = selectedPack
+        ? `1 ${selectedPack.pack_unit_name} = ${selectedPack.pack_size_in_base_units} ${variant.unit}`
+        : `Select a pack to calculate quantity.`;
 }
 
 function formatDisplayDate(value) {
@@ -455,6 +616,8 @@ function updateLocationFilterOptions() {
 
 function populateDispenseBatchSelect(activeBatches) {
     const batchSelect = document.getElementById('dispenseBatchSelect');
+    const selectedVariantId = parseInt(document.getElementById('dispenseDrugSelect').value || '', 10);
+    const unitLabel = getVariantById(selectedVariantId)?.unit || 'units';
     const previousValue = batchSelect.value;
 
     batchSelect.innerHTML = '<option value="">Automatic FEFO Selection</option>';
@@ -465,7 +628,7 @@ function populateDispenseBatchSelect(activeBatches) {
         const locationLabel = getBatchLocationLabel(batch);
         const fefoLabel = index === 0 ? ' [FEFO default]' : '';
         option.value = batch.id;
-        option.textContent = `${batch.batch_number} | ${batch.quantity} units | ${locationLabel} | Expires ${expiryLabel}${fefoLabel}`;
+        option.textContent = `${batch.batch_number} | ${batch.quantity} ${unitLabel} | ${locationLabel} | Expires ${expiryLabel}${fefoLabel}`;
         batchSelect.appendChild(option);
     });
 
@@ -484,9 +647,17 @@ async function updateBatchInfo() {
     if (!variantId) {
         batchInfoSection.style.display = 'none';
         batchSelect.innerHTML = '<option value="">Automatic FEFO Selection</option>';
+        const packSelect = document.getElementById('dispensePackSelect');
+        if (packSelect) packSelect.innerHTML = '<option value="">-- Select pack --</option>';
         return;
     }
 
+    const variant = getVariantById(variantId);
+    if (variant) {
+        populateDispensePackSelect(variant);
+    }
+    updateDispenseModeUi();
+    
     batchInfoSection.style.display = 'block';
     batchInfoContent.innerHTML = '<p class="loading">Loading batches...</p>';
     
@@ -558,6 +729,7 @@ async function updateBatchInfo() {
 // Update allocation preview based on quantity and allow_split flag
 async function updateAllocationPreview() {
     const variantId = parseInt(document.getElementById('dispenseDrugSelect').value);
+    const unitLabel = getVariantById(variantId)?.unit || 'units';
     const quantity = parseFloat(document.getElementById('dispenseQuantity').value);
     const allowSplit = document.getElementById('dispenseAllowSplit').checked;
     const preferredBatchId = parseInt(document.getElementById('dispenseBatchSelect').value);
@@ -626,10 +798,10 @@ async function updateAllocationPreview() {
         
         if (remainingQty > 0 && allowSplit) {
             allocationPreviewContent.innerHTML = `
-                <p style="color: #d32f2f; margin: 0 0 10px 0;">✕ Warning: Only ${quantity - remainingQty} units available across all batches (${remainingQty} short)</p>
+                <p style="color: #d32f2f; margin: 0 0 10px 0;">✕ Warning: Only ${quantity - remainingQty} ${escapeHtml(unitLabel)} available across all batches (${remainingQty} short)</p>
                 <div>${allocations.map(a => `
                     <div style="padding: 5px; margin: 3px 0; background: white; border-radius: 2px; font-size: 0.9em;">
-                        <strong>${a.batchNumber}</strong>${a.preferred ? ' <span style="color: #1565c0;">(preferred)</span>' : ''}: ${a.quantity} units (${escapeHtml(a.location)}) - Expires ${formatDisplayDate(a.expiryDate)}
+                        <strong>${a.batchNumber}</strong>${a.preferred ? ' <span style="color: #1565c0;">(preferred)</span>' : ''}: ${a.quantity} ${escapeHtml(unitLabel)} (${escapeHtml(a.location)}) - Expires ${formatDisplayDate(a.expiryDate)}
                     </div>
                 `).join('')}</div>
             `;
@@ -638,7 +810,7 @@ async function updateAllocationPreview() {
         
         const allocationHtml = allocations.map(a => `
             <div style="padding: 5px; margin: 3px 0; background: white; border-radius: 2px; font-size: 0.9em;">
-                <strong>${a.batchNumber}</strong>${a.preferred ? ' <span style="color: #1565c0;">(preferred)</span>' : ''}: ${a.quantity} units (${escapeHtml(a.location)}) - Expires ${formatDisplayDate(a.expiryDate)}
+                <strong>${a.batchNumber}</strong>${a.preferred ? ' <span style="color: #1565c0;">(preferred)</span>' : ''}: ${a.quantity} ${escapeHtml(unitLabel)} (${escapeHtml(a.location)}) - Expires ${formatDisplayDate(a.expiryDate)}
             </div>
         `).join('');
         
@@ -725,7 +897,7 @@ function renderDrugs() {
                         </div>
                         <div class="variant-actions">
                             ${!isReadOnly ? `
-                                <button class="btn btn-success btn-small" onclick="openBatchReceiveModal(${variant.id})">📦 Receive Batch</button>
+                                <button class="btn btn-info btn-small" onclick="event.stopPropagation(); openVariantPacksModal(${variant.id})">📦 Packs</button>
                                 <button class="btn btn-primary btn-small" onclick="prescribeVariant(${variant.id}, '${drug.name.replace(/'/g, "\\'")}', '${variant.strength.replace(/'/g, "\\'")}', '${variant.unit.replace(/'/g, "\\'")}')">🏷️ Prescribe & Print</button>
                                 <button class="btn btn-success btn-small" onclick="dispenseVariant(${variant.id})">💊 Dispense</button>
                                 <button class="btn btn-warning btn-small" onclick="openEditVariantModal(${variant.id})">Edit</button>
@@ -753,6 +925,7 @@ function renderDrugs() {
                 </div>
                 <div class="drug-actions">
                     ${!isReadOnly ? `
+                        <button class="btn btn-success btn-small" onclick="event.stopPropagation(); openReceiveDeliveryModal(${drug.id})">📦 Receive Delivery</button>
                         <button class="btn btn-primary btn-small" onclick="event.stopPropagation(); openAddVariantModal(${drug.id})">➕ Add</button>
                     ` : ''}
                     <button class="btn btn-info btn-small" onclick="event.stopPropagation(); showDrugHistory(${drug.id})">📋 History</button>
@@ -825,13 +998,45 @@ async function handleDispenseDrug(e) {
     e.preventDefault();
 
     const variantId = parseInt(document.getElementById('dispenseDrugSelect').value);
-    const quantity = parseFloat(document.getElementById('dispenseQuantity').value);
+    let quantity = parseFloat(document.getElementById('dispenseQuantity').value);
+    const dispenseMode = (document.getElementById('dispenseMode').value || 'subunit').toLowerCase();
     const preferredBatchIdValue = document.getElementById('dispenseBatchSelect').value;
+    const requestedPackIdValue = document.getElementById('dispensePackSelect').value;
+    const requestedPackCountValue = document.getElementById('dispensePackCount').value;
     const animalName = document.getElementById('dispenseAnimal').value;
     const userName = document.getElementById('dispenseUser').value;
     const notes = document.getElementById('dispenseNotes').value;
     const allowSplit = document.getElementById('dispenseAllowSplit').checked;
 
+    const selectedPackId = requestedPackIdValue ? parseInt(requestedPackIdValue, 10) : null;
+    const selectedPackCount = requestedPackCountValue ? parseFloat(requestedPackCountValue) : null;
+    const variant = getVariantById(variantId);
+    const selectedPack = variant && selectedPackId
+        ? getActivePacksForVariant(variant).find(pack => pack.id === selectedPackId)
+        : null;
+
+    if (!['subunit', 'pack'].includes(dispenseMode)) {
+        showToast('Please select a valid dispense mode.', 'warning');
+        return;
+    }
+
+    if (dispenseMode === 'pack') {
+        if (!selectedPack) {
+            showToast('Please select a pack type for whole-pack dispensing.', 'warning');
+            return;
+        }
+        if (selectedPackCount == null || Number.isNaN(selectedPackCount) || selectedPackCount <= 0) {
+            showToast('Please enter a valid pack count greater than zero.', 'warning');
+            return;
+        }
+        if (Math.abs(selectedPackCount - Math.round(selectedPackCount)) > 1e-6) {
+            showToast('Whole-pack dispensing requires a whole-number pack count.', 'warning');
+            return;
+        }
+
+        quantity = selectedPackCount * selectedPack.pack_size_in_base_units;
+    }
+
     if (!variantId || isNaN(quantity) || quantity <= 0 || !userName) {
         showToast('Please fill in all required fields (Drug Variant, Quantity > 0, Dispensed by)', 'warning');
         return;
@@ -840,7 +1045,10 @@ async function handleDispenseDrug(e) {
     const dispensingData = {
         drug_variant_id: variantId,
         quantity: quantity,
+        dispense_mode: dispenseMode,
         batch_id: preferredBatchIdValue ? parseInt(preferredBatchIdValue) : null,
+        requested_pack_id: dispenseMode === 'pack' ? selectedPackId : null,
+        requested_pack_count: dispenseMode === 'pack' ? selectedPackCount : null,
         animal_name: animalName || null,
         user_name: userName,
         notes: notes || null,
@@ -903,19 +1111,143 @@ function openAddVariantModal(drugId) {
     if (!drug) return;
     
     currentDrug = drug;
+    const form = document.getElementById('variantForm');
+    if (form) form.reset();
     document.getElementById('variantDrugId').value = drug.id;
+    initializeVariantPackRows();
     document.getElementById('addVariantModal').classList.add('show');
 }
 
+function inferBaseUnitFromStrength(strength) {
+    const value = String(strength || '').toLowerCase();
+    if (value.includes('/ml') || value.includes('ml')) return 'ml';
+    if (value.includes('tablet')) return 'tablets';
+    if (value.includes('capsule')) return 'capsules';
+    return 'units';
+}
+
+function getVariantPackRowsContainer() {
+    return document.getElementById('variantPackRows');
+}
+
+function refreshVariantPackRowLabels() {
+    const container = getVariantPackRowsContainer();
+    const baseUnit = document.getElementById('variantUnit')?.value || 'units';
+    if (!container) return;
+
+    container.querySelectorAll('.variant-pack-row').forEach(row => {
+        const packUnit = row.querySelector('.variant-pack-unit')?.value || 'pack';
+        const label = row.querySelector('.variant-pack-size-label');
+        if (!label) return;
+        const titleCasePack = packUnit.charAt(0).toUpperCase() + packUnit.slice(1);
+        label.textContent = `${titleCasePack} Size (${baseUnit}) *`;
+    });
+}
+
+function appendVariantPackRow(prefill = {}) {
+    const container = getVariantPackRowsContainer();
+    if (!container) return;
+
+    const row = document.createElement('div');
+    row.className = 'delivery-line variant-pack-row';
+
+    const selectedPackUnit = prefill.packUnit || 'bottle';
+    const selectedSize = prefill.packSize || '';
+    const baseUnit = document.getElementById('variantUnit')?.value || 'units';
+
+    row.innerHTML = `
+        <div class="delivery-line-grid" style="grid-template-columns: 1.2fr 1.2fr auto;">
+            <div class="form-group">
+                <label>Pack Type *</label>
+                <select class="variant-pack-unit" required>
+                    <option value="bottle" ${selectedPackUnit === 'bottle' ? 'selected' : ''}>Bottle</option>
+                    <option value="box" ${selectedPackUnit === 'box' ? 'selected' : ''}>Box</option>
+                    <option value="vial" ${selectedPackUnit === 'vial' ? 'selected' : ''}>Vial</option>
+                    <option value="packet" ${selectedPackUnit === 'packet' ? 'selected' : ''}>Packet</option>
+                </select>
+            </div>
+            <div class="form-group">
+                <label class="variant-pack-size-label">Bottle Size (${baseUnit}) *</label>
+                <input type="number" class="variant-pack-size" min="0.0001" step="0.0001" value="${selectedSize}" required>
+            </div>
+            <button type="button" class="btn btn-danger btn-small variant-pack-remove-btn">Remove</button>
+        </div>
+    `;
+
+    const removeBtn = row.querySelector('.variant-pack-remove-btn');
+    const unitSelect = row.querySelector('.variant-pack-unit');
+    if (removeBtn) {
+        removeBtn.addEventListener('click', () => {
+            if (container.querySelectorAll('.variant-pack-row').length <= 1) {
+                showToast('At least one pack size is required', 'warning');
+                return;
+            }
+            row.remove();
+        });
+    }
+
+    if (unitSelect) {
+        unitSelect.addEventListener('change', refreshVariantPackRowLabels);
+    }
+
+    container.appendChild(row);
+    refreshVariantPackRowLabels();
+}
+
+function initializeVariantPackRows() {
+    const container = getVariantPackRowsContainer();
+    if (!container) return;
+    container.innerHTML = '';
+
+    const strengthValue = document.getElementById('variantStrength')?.value || '';
+    const inferredBaseUnit = inferBaseUnitFromStrength(strengthValue);
+    const variantUnitSelect = document.getElementById('variantUnit');
+    if (variantUnitSelect) {
+        variantUnitSelect.value = inferredBaseUnit;
+    }
+
+    appendVariantPackRow({ packUnit: 'bottle' });
+}
+
 // Handle add variant form
 async function handleAddVariant(e) {
     e.preventDefault();
 
     const drugId = parseInt(document.getElementById('variantDrugId').value);
+    const baseUnit = document.getElementById('variantUnit').value;
+    const rows = Array.from(document.querySelectorAll('#variantPackRows .variant-pack-row'));
+
+    if (rows.length === 0) {
+        showToast('Please add at least one pack size', 'warning');
+        return;
+    }
+
+    const packPayloads = [];
+    for (let i = 0; i < rows.length; i += 1) {
+        const row = rows[i];
+        const packUnit = row.querySelector('.variant-pack-unit')?.value;
+        const packSize = parseFloat(row.querySelector('.variant-pack-size')?.value || '');
+
+        if (!packUnit || Number.isNaN(packSize) || packSize <= 0) {
+            showToast(`Pack row ${i + 1} is incomplete`, 'warning');
+            return;
+        }
+
+        const normalizedPackUnit = packUnit.trim().toLowerCase();
+        const titleCasePack = normalizedPackUnit.charAt(0).toUpperCase() + normalizedPackUnit.slice(1);
+        packPayloads.push({
+            label: `${titleCasePack} ${packSize} ${baseUnit}`,
+            pack_unit_name: normalizedPackUnit,
+            pack_size_in_base_units: packSize,
+            is_active: true
+        });
+    }
+
     const variantData = {
         strength: document.getElementById('variantStrength').value,
-        quantity: parseFloat(document.getElementById('variantQuantity').value),
+        quantity: 0,
-        unit: document.getElementById('variantUnit').value,
+        unit: baseUnit,
+        base_unit: baseUnit,
         low_stock_threshold: parseFloat(document.getElementById('variantThreshold').value)
     };
 
@@ -927,9 +1259,41 @@ async function handleAddVariant(e) {
 
         if (!response.ok) throw new Error('Failed to add variant');
 
+        const createdVariant = await response.json();
+
+        for (const packPayload of packPayloads) {
+            const packResponse = await apiCall(`/variants/${createdVariant.id}/packs`, {
+                method: 'POST',
+                body: JSON.stringify(packPayload)
+            });
+
+            if (!packResponse.ok) {
+                const packError = await packResponse.json();
+                throw new Error(packError.detail || 'Variant created but pack size creation failed');
+            }
+        }
+
+        // Archive the auto-created default 1:1 pack when custom pack sizes are configured.
+        const packsResponse = await apiCall(`/variants/${createdVariant.id}/packs`);
+        if (packsResponse.ok) {
+            const packs = await packsResponse.json();
+            const defaultPack = packs.find(
+                p => p.is_active && Number(p.pack_size_in_base_units) === 1 && (p.pack_unit_name || '').toLowerCase() === baseUnit.toLowerCase()
+            );
+            if (defaultPack && packs.filter(p => p.is_active).length > 1) {
+                await apiCall(`/variant-packs/${defaultPack.id}`, {
+                    method: 'PUT',
+                    body: JSON.stringify({ is_active: false })
+                });
+            }
+        }
+
         document.getElementById('variantForm').reset();
         closeModal(document.getElementById('addVariantModal'));
         await loadDrugs();
+        if (document.getElementById('receiveDeliveryModal')?.classList.contains('show')) {
+            refreshDeliveryVariantSelects();
+        }
         renderDrugs();
         showToast('Variant added successfully!', 'success');
     } catch (error) {
@@ -958,6 +1322,13 @@ function openEditVariantModal(variantId) {
     document.getElementById('editVariantModal').classList.add('show');
 }
 
+function inferPackUnitName(baseUnit) {
+    const value = String(baseUnit || 'pack').trim().toLowerCase();
+    if (!value) return 'pack';
+    if (value.endsWith('s') && value.length > 1) return value.slice(0, -1);
+    return value;
+}
+
 // Handle edit variant form
 async function handleEditVariant(e) {
     e.preventDefault();
@@ -988,6 +1359,140 @@ async function handleEditVariant(e) {
     }
 }
 
+async function openVariantPacksModal(variantId) {
+    const variant = getVariantById(variantId);
+    if (!variant) {
+        showToast('Variant not found', 'error');
+        return;
+    }
+
+    const parentDrug = allDrugs.find(d => (d.variants || []).some(v => v.id === variantId));
+    activeVariantPacksVariantId = variantId;
+
+    const label = document.getElementById('variantPacksLabel');
+    if (label) {
+        const drugName = parentDrug ? parentDrug.name : 'Drug';
+        label.textContent = `${drugName} ${variant.strength} | Base Unit: ${variant.unit}`;
+    }
+
+    const form = document.getElementById('variantPacksForm');
+    if (form) form.reset();
+    document.getElementById('variantPacksVariantId').value = String(variantId);
+    document.getElementById('variantPacksNewUnit').value = inferPackUnitName(variant.unit);
+
+    await refreshVariantPacksList();
+    openModal(document.getElementById('variantPacksModal'));
+}
+
+async function refreshVariantPacksList() {
+    const variantId = parseInt(document.getElementById('variantPacksVariantId')?.value || '', 10);
+    const list = document.getElementById('variantPacksList');
+    if (!variantId || !list) return;
+
+    list.innerHTML = '<p class="loading">Loading packs...</p>';
+
+    try {
+        const response = await apiCall(`/variants/${variantId}/packs`);
+        if (!response.ok) throw new Error('Failed to load pack presentations');
+        const packs = await response.json();
+
+        if (!Array.isArray(packs) || packs.length === 0) {
+            list.innerHTML = '<p class="empty">No pack presentations defined.</p>';
+            return;
+        }
+
+        list.innerHTML = `
+            <div class="locations-table">
+                ${packs.map(pack => `
+                    <div class="location-item" style="${pack.is_active ? '' : 'opacity: 0.6;'}">
+                        <div style="flex: 1;">
+                            <strong>${escapeHtml(pack.label)}</strong>
+                            <div style="font-size: 0.88em; color: #666;">
+                                ${escapeHtml(pack.pack_unit_name)} | ${pack.pack_size_in_base_units} base units
+                                ${pack.is_active ? '' : ' | archived'}
+                            </div>
+                        </div>
+                        <button class="btn ${pack.is_active ? 'btn-danger' : 'btn-secondary'} btn-small" onclick="toggleVariantPackActive(${pack.id}, ${pack.is_active ? 'false' : 'true'})">
+                            ${pack.is_active ? 'Archive' : 'Restore'}
+                        </button>
+                    </div>
+                `).join('')}
+            </div>
+        `;
+    } catch (error) {
+        console.error('Error loading variant packs:', error);
+        list.innerHTML = '<p class="empty">Failed to load pack presentations</p>';
+    }
+}
+
+async function handleCreateVariantPack(e) {
+    e.preventDefault();
+
+    const variantId = parseInt(document.getElementById('variantPacksVariantId').value, 10);
+    const label = document.getElementById('variantPacksNewLabel').value.trim();
+    const packUnitName = document.getElementById('variantPacksNewUnit').value.trim();
+    const size = parseFloat(document.getElementById('variantPacksNewSize').value);
+
+    if (!variantId || !label || !packUnitName || Number.isNaN(size) || size <= 0) {
+        showToast('Please complete all pack fields', 'warning');
+        return;
+    }
+
+    try {
+        const response = await apiCall(`/variants/${variantId}/packs`, {
+            method: 'POST',
+            body: JSON.stringify({
+                label,
+                pack_unit_name: packUnitName,
+                pack_size_in_base_units: size,
+                is_active: true
+            })
+        });
+
+        if (!response.ok) {
+            const error = await response.json();
+            throw new Error(error.detail || 'Failed to add pack presentation');
+        }
+
+        document.getElementById('variantPacksForm').reset();
+        const variant = getVariantById(variantId);
+        document.getElementById('variantPacksNewUnit').value = inferPackUnitName(variant?.unit || 'pack');
+        await loadDrugs();
+        await refreshVariantPacksList();
+        if (document.getElementById('receiveDeliveryModal')?.classList.contains('show')) {
+            refreshDeliveryVariantSelects();
+        }
+        showToast('Pack presentation added', 'success');
+    } catch (error) {
+        console.error('Error creating pack presentation:', error);
+        showToast('Failed to add pack presentation: ' + error.message, 'error');
+    }
+}
+
+async function toggleVariantPackActive(packId, nextActiveState) {
+    try {
+        const response = await apiCall(`/variant-packs/${packId}`, {
+            method: 'PUT',
+            body: JSON.stringify({ is_active: Boolean(nextActiveState) })
+        });
+
+        if (!response.ok) {
+            const error = await response.json();
+            throw new Error(error.detail || 'Failed to update pack state');
+        }
+
+        await loadDrugs();
+        await refreshVariantPacksList();
+        if (document.getElementById('receiveDeliveryModal')?.classList.contains('show')) {
+            refreshDeliveryVariantSelects();
+        }
+        showToast('Pack updated', 'success');
+    } catch (error) {
+        console.error('Error updating pack state:', error);
+        showToast('Failed to update pack: ' + error.message, 'error');
+    }
+}
+
 // Dispense from variant
 function dispenseVariant(variantId) {
     // Update the dropdown display with all variants
@@ -1751,3 +2256,306 @@ async function handleBatchReceive(e) {
         showToast('Failed to receive batch: ' + error.message, 'error');
     }
 }
+
+function getActiveDeliveryDrug() {
+    return allDrugs.find(d => d.id === deliveryDrugId);
+}
+
+function getVariantById(variantId) {
+    for (const drug of allDrugs) {
+        const found = (drug.variants || []).find(v => v.id === variantId);
+        if (found) return found;
+    }
+    return null;
+}
+
+function buildDeliveryVariantOptions(drug, selectedVariantId = '') {
+    if (!drug || !drug.variants || drug.variants.length === 0) {
+        return '<option value="">-- No variants available --</option>';
+    }
+
+    return [`<option value="">-- Select variant --</option>`, ...drug.variants.map(v => {
+        const selected = String(v.id) === String(selectedVariantId) ? ' selected' : '';
+        return `<option value="${v.id}"${selected}>${escapeHtml(v.strength)} (${escapeHtml(v.unit)})</option>`;
+    })].join('');
+}
+
+function getActivePacksForVariant(variant) {
+    if (!variant || !Array.isArray(variant.packs)) return [];
+    return variant.packs.filter(pack => pack.is_active);
+}
+
+function buildDeliveryPackOptions(variant, selectedPackId = '') {
+    const packs = getActivePacksForVariant(variant);
+    if (packs.length === 0) {
+        return '<option value="">-- No active packs --</option>';
+    }
+
+    return [`<option value="">-- Select pack --</option>`, ...packs.map(pack => {
+        const selected = String(pack.id) === String(selectedPackId) ? ' selected' : '';
+        const label = `${pack.label} (${pack.pack_size_in_base_units} ${variant.unit})`;
+        return `<option value="${pack.id}"${selected}>${escapeHtml(label)}</option>`;
+    })].join('');
+}
+
+function buildDeliveryLocationOptions(selectedLocationId = '') {
+    return [`<option value="">-- Select location --</option>`, ...deliveryLocations.map(location => {
+        const selected = String(location.id) === String(selectedLocationId) ? ' selected' : '';
+        return `<option value="${location.id}"${selected}>${escapeHtml(location.name)}</option>`;
+    })].join('');
+}
+
+function updateDeliveryLineQuantityDisplay(line) {
+    const variantId = parseInt(line.querySelector('.delivery-variant-select')?.value || '', 10);
+    const packSelect = line.querySelector('.delivery-pack-select');
+
+    const variant = getVariantById(variantId);
+    if (!variant || !packSelect) {
+        return;
+    }
+
+    const currentPackId = packSelect.value;
+    packSelect.innerHTML = buildDeliveryPackOptions(variant, currentPackId);
+}
+
+function wireDeliveryLineEvents(line) {
+    const variantSelect = line.querySelector('.delivery-variant-select');
+    const packSelect = line.querySelector('.delivery-pack-select');
+    const packCountInput = line.querySelector('.delivery-pack-count');
+
+    if (variantSelect && packSelect) {
+        variantSelect.addEventListener('change', () => {
+            const variantId = parseInt(variantSelect.value || '', 10);
+            const variant = getVariantById(variantId);
+            packSelect.innerHTML = buildDeliveryPackOptions(variant, '');
+            if (packCountInput) packCountInput.value = '';
+            updateDeliveryLineQuantityDisplay(line);
+        });
+    }
+
+    if (packSelect) {
+        packSelect.addEventListener('change', () => {
+            updateDeliveryLineQuantityDisplay(line);
+        });
+    }
+
+    if (packCountInput) {
+        packCountInput.addEventListener('input', () => {
+            updateDeliveryLineQuantityDisplay(line);
+        });
+    }
+}
+
+function appendDeliveryLine(prefill = {}) {
+    const container = document.getElementById('deliveryLinesContainer');
+    const drug = getActiveDeliveryDrug();
+    if (!container || !drug) return;
+
+    deliveryLineCounter += 1;
+    const lineId = `delivery-line-${deliveryLineCounter}`;
+
+    const line = document.createElement('div');
+    line.className = 'delivery-line';
+    line.dataset.lineId = lineId;
+
+    const initialVariant = drug.variants.find(v => String(v.id) === String(prefill.variantId)) || drug.variants[0] || null;
+    const initialVariantId = prefill.variantId || (initialVariant ? initialVariant.id : '');
+    const initialPackId = prefill.packId || '';
+    const initialPackCount = prefill.packCount || '';
+
+    line.innerHTML = `
+        <div class="delivery-line-grid">
+            <div class="form-group">
+                <label>Variant</label>
+                <select class="delivery-variant-select" required>
+                    ${buildDeliveryVariantOptions(drug, initialVariantId)}
+                </select>
+            </div>
+            <div class="form-group">
+                <label>Pack Type</label>
+                <select class="delivery-pack-select" required>
+                    ${buildDeliveryPackOptions(initialVariant, initialPackId)}
+                </select>
+            </div>
+            <div class="form-group">
+                <label>Pack Count</label>
+                <input type="number" class="delivery-pack-count" min="0.0001" step="0.0001" value="${initialPackCount}" required>
+            </div>
+            <div class="form-group">
+                <label>Batch Number</label>
+                <input type="text" class="delivery-batch-number" value="${prefill.batchNumber || ''}" placeholder="e.g. ABC123" required>
+            </div>
+            <div class="form-group">
+                <label>Expiry</label>
+                <input type="date" class="delivery-expiry-date" value="${prefill.expiryDate || ''}" required>
+            </div>
+            <div class="form-group">
+                <label>Location</label>
+                <select class="delivery-location-select" required>
+                    ${buildDeliveryLocationOptions(prefill.locationId || '')}
+                </select>
+            </div>
+            <button type="button" class="btn btn-danger btn-small delivery-remove-btn">Remove</button>
+        </div>
+    `;
+
+    const removeBtn = line.querySelector('.delivery-remove-btn');
+    if (removeBtn) {
+        removeBtn.addEventListener('click', () => {
+            if (container.children.length <= 1) {
+                showToast('At least one delivery line is required', 'warning');
+                return;
+            }
+            line.remove();
+        });
+    }
+
+    wireDeliveryLineEvents(line);
+    updateDeliveryLineQuantityDisplay(line);
+
+    container.appendChild(line);
+}
+
+function refreshDeliveryVariantSelects() {
+    const drug = getActiveDeliveryDrug();
+    const container = document.getElementById('deliveryLinesContainer');
+    if (!drug || !container) return;
+
+    container.querySelectorAll('.delivery-line').forEach(line => {
+        const select = line.querySelector('.delivery-variant-select');
+        const packSelect = line.querySelector('.delivery-pack-select');
+        if (!select) return;
+
+        const currentVariantId = select.value;
+        select.innerHTML = buildDeliveryVariantOptions(drug, currentVariantId);
+
+        const variant = getVariantById(parseInt(select.value || '', 10));
+        if (packSelect) {
+            const currentPackId = packSelect.value;
+            packSelect.innerHTML = buildDeliveryPackOptions(variant, currentPackId);
+        }
+
+        updateDeliveryLineQuantityDisplay(line);
+    });
+}
+
+async function initializeDeliveryLocations() {
+    try {
+        const response = await apiCall('/locations');
+        if (!response.ok) throw new Error('Failed to load locations');
+        const locations = await response.json();
+        deliveryLocations = locations.filter(location => location.is_active);
+    } catch (error) {
+        console.error('Error loading delivery locations:', error);
+        showToast('Failed to load storage locations', 'error');
+        deliveryLocations = [];
+    }
+}
+
+async function openReceiveDeliveryModal(drugId) {
+    deliveryDrugId = drugId;
+    const drug = getActiveDeliveryDrug();
+    if (!drug) {
+        showToast('Drug not found', 'error');
+        return;
+    }
+
+    const form = document.getElementById('receiveDeliveryForm');
+    const container = document.getElementById('deliveryLinesContainer');
+    const label = document.getElementById('receiveDeliveryDrugLabel');
+
+    if (form) form.reset();
+    if (container) container.innerHTML = '';
+    if (label) label.textContent = `Drug: ${drug.name}`;
+
+    await initializeDeliveryLocations();
+    appendDeliveryLine();
+
+    openModal(document.getElementById('receiveDeliveryModal'));
+}
+
+function handleAddVariantFromDelivery() {
+    if (!deliveryDrugId) {
+        showToast('Select a drug first', 'warning');
+        return;
+    }
+    openAddVariantModal(deliveryDrugId);
+}
+
+async function handleReceiveDelivery(e) {
+    e.preventDefault();
+
+    const drug = getActiveDeliveryDrug();
+    const container = document.getElementById('deliveryLinesContainer');
+    if (!drug || !container) {
+        showToast('Delivery context unavailable', 'error');
+        return;
+    }
+
+    const lines = Array.from(container.querySelectorAll('.delivery-line'));
+    if (lines.length === 0) {
+        showToast('Add at least one delivery line', 'warning');
+        return;
+    }
+
+    const payloads = [];
+
+    for (let i = 0; i < lines.length; i += 1) {
+        const line = lines[i];
+        const variantId = parseInt(line.querySelector('.delivery-variant-select')?.value || '', 10);
+        const packIdRaw = line.querySelector('.delivery-pack-select')?.value || '';
+        const packId = packIdRaw ? parseInt(packIdRaw, 10) : null;
+        const packCountRaw = line.querySelector('.delivery-pack-count')?.value || '';
+        const packCount = packCountRaw ? parseFloat(packCountRaw) : null;
+        const batchNumber = (line.querySelector('.delivery-batch-number')?.value || '').trim();
+        const expiryDate = line.querySelector('.delivery-expiry-date')?.value || '';
+        const locationId = parseInt(line.querySelector('.delivery-location-select')?.value || '', 10);
+
+        if (!variantId || !packId || packCount === null || Number.isNaN(packCount) || packCount <= 0 || !batchNumber || !expiryDate || !locationId) {
+            showToast(`Delivery line ${i + 1} is incomplete`, 'warning');
+            return;
+        }
+
+        const variant = drug.variants.find(v => v.id === variantId);
+        const selectedPack = variant ? getActivePacksForVariant(variant).find(pack => pack.id === packId) : null;
+        if (!selectedPack) {
+            showToast(`Delivery line ${i + 1} has an invalid pack selection`, 'warning');
+            return;
+        }
+        const computedQuantity = packCount * selectedPack.pack_size_in_base_units;
+
+        payloads.push({
+            variantId,
+            payload: {
+                batch_number: batchNumber,
+                received_pack_id: packId,
+                received_pack_count: packCount,
+                expiry_date: expiryDate,
+                location_id: locationId,
+                notes: `Received ${packCount} ${selectedPack.pack_unit_name}(s), total ${computedQuantity} ${variant ? variant.unit : 'units'}`
+            }
+        });
+    }
+
+    try {
+        for (let i = 0; i < payloads.length; i += 1) {
+            const entry = payloads[i];
+            const response = await apiCall(`/variants/${entry.variantId}/batches`, {
+                method: 'POST',
+                body: JSON.stringify(entry.payload)
+            });
+
+            if (!response.ok) {
+                const error = await response.json();
+                throw new Error(`Line ${i + 1}: ${error.detail || 'Failed to receive delivery line'}`);
+            }
+        }
+
+        closeModal(document.getElementById('receiveDeliveryModal'));
+        await loadDrugs();
+        showToast(`Delivery received successfully (${payloads.length} line${payloads.length === 1 ? '' : 's'})`, 'success');
+    } catch (error) {
+        console.error('Error receiving delivery:', error);
+        showToast('Failed to receive delivery: ' + error.message, 'error');
+    }
+}

frontend/index.html

@@ -205,10 +205,32 @@
                     </div>
 
                     <div class="form-group">
+                        <label for="dispenseMode">Dispense Mode *</label>
+                        <select id="dispenseMode" onchange="updateDispenseModeUi()">
+                            <option value="subunit">Subunit Quantity</option>
+                            <option value="pack">Whole Packs</option>
+                        </select>
+                    </div>
+                    
+                    <div class="form-group" id="dispenseQuantityGroup">
                         <label for="dispenseQuantity">Quantity *</label>
                         <input type="number" id="dispenseQuantity" step="0.1" onchange="updateAllocationPreview()">
                     </div>
 
+                    <div class="form-row" id="dispensePackRow" style="display: none;">
+                        <div class="form-group">
+                            <label for="dispensePackSelect">Pack Type *</label>
+                            <select id="dispensePackSelect" onchange="updateDispenseQuantityFromPack()">
+                                <option value="">-- Select pack --</option>
+                            </select>
+                        </div>
+                        <div class="form-group">
+                            <label for="dispensePackCount">Pack Count *</label>
+                            <input type="number" id="dispensePackCount" min="0.0001" step="0.0001" onchange="updateDispenseQuantityFromPack()">
+                            <small id="dispensePackPreview" style="display: block; margin-top: 6px; color: #666;">Select a pack and whole-number count.</small>
+                        </div>
+                    </div>
+                    
                     <div class="form-group">
                         <label>
                             <input type="checkbox" id="dispenseAllowSplit" onchange="updateAllocationPreview()">
@@ -307,23 +329,21 @@
                         <input type="text" id="variantStrength" placeholder="e.g., 5.4mg, 10.8mg, 100ml" required>
                     </div>
                     
-                    <div class="form-row">
+                    <div class="form-group">
-                        <div class="form-group">
+                        <label for="variantUnit">Base Unit *</label>
-                            <label for="variantQuantity">Quantity *</label>
+                        <select id="variantUnit">
-                            <input type="number" id="variantQuantity" step="0.1" required>
+                            <option value="ml">ml</option>
-                        </div>
+                            <option value="tablets">tablets</option>
+                            <option value="capsules">capsules</option>
+                            <option value="units">units</option>
+                            <option value="vials">vials</option>
+                        </select>
+                    </div>
 
-                        <div class="form-group">
+                    <div class="form-group">
-                            <label for="variantUnit">Unit *</label>
+                        <label>Pack Sizes *</label>
-                            <select id="variantUnit">
+                        <div id="variantPackRows" class="delivery-lines"></div>
-                                <option value="tablets">Tablets</option>
+                        <button type="button" id="addVariantPackRowBtn" class="btn btn-secondary btn-small">+ Add Another Size</button>
-                                <option value="bottles">Bottles</option>
-                                <option value="boxes">boxes</option>
-                                <option value="vials">Vials</option>
-                                <option value="units">Units</option>
-                                <option value="packets">Packets</option>
-                            </select>
-                        </div>
                     </div>
                     
                     <div class="form-group">
@@ -358,7 +378,7 @@
                         </div>
                         
                         <div class="form-group">
-                            <label for="editVariantUnit">Unit *</label>
+                            <label for="editVariantUnit">Base Unit *</label>
                             <select id="editVariantUnit">
                                 <option value="tablets">Tablets</option>
                                 <option value="bottles">Bottles</option>
@@ -575,6 +595,56 @@
                 </form>
             </div>
         </div>
+
+        <!-- Receive Delivery Modal -->
+        <div id="receiveDeliveryModal" class="modal">
+            <div class="modal-content modal-large receive-delivery-modal-content">
+                <span class="close">&times;</span>
+                <h2>Receive Delivery</h2>
+                <p id="receiveDeliveryDrugLabel" style="margin: 6px 0 16px; color: #666; font-weight: 600;"></p>
+                <form id="receiveDeliveryForm" novalidate>
+                    <div id="deliveryLinesContainer" class="delivery-lines"></div>
+                    <div class="delivery-toolbar">
+                        <button type="button" id="addDeliveryLineBtn" class="btn btn-secondary">+ Add Delivery Line</button>
+                        <button type="button" id="addVariantFromDeliveryBtn" class="btn btn-info">+ Add Variant</button>
+                    </div>
+                    <div class="form-actions">
+                        <button type="submit" class="btn btn-primary">Receive Delivery</button>
+                        <button type="button" class="btn btn-secondary" id="cancelReceiveDeliveryBtn">Cancel</button>
+                    </div>
+                </form>
+            </div>
+        </div>
+
+        <!-- Variant Pack Management Modal -->
+        <div id="variantPacksModal" class="modal">
+            <div class="modal-content modal-large">
+                <span class="close">&times;</span>
+                <h2>Pack Presentations</h2>
+                <p id="variantPacksLabel" style="margin: 6px 0 16px; color: #666; font-weight: 600;"></p>
+
+                <div class="form-group">
+                    <h3 style="margin-bottom: 8px;">Add Pack Presentation</h3>
+                    <form id="variantPacksForm">
+                        <input type="hidden" id="variantPacksVariantId">
+                        <div class="form-row">
+                            <input type="text" id="variantPacksNewLabel" placeholder="Label (e.g., Bottle 300 ml)" required>
+                            <input type="text" id="variantPacksNewUnit" placeholder="Pack Unit Name (e.g., bottle, box)" required>
+                            <input type="number" id="variantPacksNewSize" min="0.0001" step="0.0001" placeholder="Size in base units" required>
+                            <button type="submit" class="btn btn-primary btn-small">Add Pack</button>
+                        </div>
+                    </form>
+                </div>
+
+                <div id="variantPacksList" class="locations-list">
+                    <p class="loading">Loading packs...</p>
+                </div>
+
+                <div class="form-actions">
+                    <button type="button" class="btn btn-secondary" id="closeVariantPacksBtn">Close</button>
+                </div>
+            </div>
+        </div>
     </div>
 
     <script src="app.js"></script>

frontend/styles.css

@@ -673,6 +673,18 @@ footer {
     overflow-y: auto;
 }
 
+#receiveDeliveryModal.show {
+    align-items: flex-start;
+    overflow-y: auto;
+    padding: 24px 0;
+}
+
+#receiveDeliveryModal .modal-content {
+    width: min(1280px, 96vw) !important;
+    max-width: min(1280px, 96vw) !important;
+    max-height: calc(100vh - 48px) !important;
+}
+
 #dispenseModal.show {
     align-items: flex-start;
     overflow-y: auto;
@@ -877,6 +889,103 @@ footer {
     color: #1f2937;
 }
 
+.delivery-lines {
+    display: flex;
+    flex-direction: column;
+    gap: 12px;
+    margin: 8px 0 16px;
+}
+
+.delivery-line {
+    border: 1px solid var(--border-color);
+    border-radius: 8px;
+    padding: 14px;
+    background: #f9fbfd;
+    overflow-x: hidden;
+}
+
+.receive-delivery-modal-content {
+    width: min(1320px, 98vw);
+    max-width: 1320px;
+    max-height: 88vh;
+    overflow-y: auto;
+}
+
+.delivery-line-grid {
+    display: grid;
+    grid-template-columns: 1.9fr 1.8fr 0.9fr 1.4fr 1.2fr 1.3fr auto;
+    gap: 12px;
+    align-items: end;
+}
+
+.delivery-line-grid > * {
+    min-width: 0;
+}
+
+.delivery-line-grid .form-group {
+    margin-bottom: 0;
+}
+
+.delivery-line-grid label {
+    display: block;
+    margin-bottom: 6px;
+    font-weight: 600;
+    font-size: 0.88em;
+}
+
+.delivery-line-grid input,
+.delivery-line-grid select {
+    width: 100%;
+    min-height: 40px;
+    padding: 8px 10px;
+    border: 1px solid var(--border-color);
+    border-radius: 6px;
+}
+
+.delivery-toolbar {
+    display: flex;
+    gap: 10px;
+    margin: 6px 0 10px;
+    flex-wrap: wrap;
+}
+
+.delivery-remove-btn {
+    align-self: end;
+    white-space: nowrap;
+}
+
+@media (max-width: 1200px) {
+    .receive-delivery-modal-content {
+        width: min(1120px, 97vw);
+        max-width: 1120px;
+    }
+
+    .delivery-line-grid {
+        grid-template-columns: 1.7fr 1.4fr 0.95fr 1.2fr 1.1fr 1.15fr;
+    }
+
+    .delivery-remove-btn {
+        grid-column: 1 / -1;
+        justify-self: end;
+    }
+}
+
+@media (max-width: 980px) {
+    #receiveDeliveryModal .modal-content {
+        width: 94vw !important;
+        max-width: 94vw !important;
+    }
+
+    .delivery-line-grid {
+        grid-template-columns: 1fr 1fr;
+    }
+
+    .delivery-remove-btn {
+        grid-column: 1 / -1;
+        justify-self: end;
+    }
+}
+
 /* Responsive Design */
 @media (max-width: 768px) {
     main {
@@ -935,6 +1044,14 @@ footer {
         min-width: 0;
     }
 
+    .delivery-line-grid {
+        grid-template-columns: 1fr;
+    }
+
+    .delivery-toolbar {
+        flex-direction: column;
+    }
+
     .drug-details {
         grid-template-columns: 1fr;
     }