"""
Compliance schema migration helpers.

This module applies additive migrations for SQLite databases used by this project.
It is intentionally lightweight and idempotent because the project does not yet
use Alembic-style versioned migrations.
"""

import os
import sqlite3
from pathlib import Path


DEFAULT_DB_URL = "sqlite:///./data/drugs.db"


def _resolve_sqlite_path(db_url: str) -> Path | None:
    if not db_url.startswith("sqlite:///"):
        print(f"Unsupported database URL for compliance migration: {db_url}")
        return None

    raw_path = db_url.replace("sqlite:///", "")
    if raw_path.startswith("/"):
        return Path(raw_path)
    return Path(raw_path)


def _column_exists(cursor: sqlite3.Cursor, table_name: str, column_name: str) -> bool:
    cursor.execute(f"PRAGMA table_info({table_name})")
    columns = [row[1] for row in cursor.fetchall()]
    return column_name in columns


def _table_exists(cursor: sqlite3.Cursor, table_name: str) -> bool:
    cursor.execute(
        "SELECT name FROM sqlite_master WHERE type='table' AND name=?",
        (table_name,),
    )
    return cursor.fetchone() is not None


def migrate_compliance_schema() -> None:
    """Apply additive schema changes needed for compliance features."""
    db_url = os.getenv("DATABASE_URL", DEFAULT_DB_URL)
    db_path = _resolve_sqlite_path(db_url)
    if db_path is None:
        return

    if not db_path.exists():
        print(f"Database does not exist at {db_path}, skipping compliance migration")
        return

    print(f"Running compliance migration on {db_path}")

    conn = sqlite3.connect(str(db_path))
    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")

        if _table_exists(cursor, "dispensings") and not _column_exists(cursor, "dispensings", "batch_id"):
            cursor.execute("ALTER TABLE dispensings ADD COLUMN batch_id INTEGER")
            print("Added dispensings.batch_id")

        if _table_exists(cursor, "dispensings") and not _column_exists(cursor, "dispensings", "actor_user_id"):
            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, "batches") and not _column_exists(cursor, "batches", "disposed_at"):
            cursor.execute("ALTER TABLE batches ADD COLUMN disposed_at DATETIME")
            print("Added batches.disposed_at")

        if _table_exists(cursor, "batches") and not _column_exists(cursor, "batches", "disposed_by_user_id"):
            cursor.execute("ALTER TABLE batches ADD COLUMN disposed_by_user_id INTEGER")
            print("Added batches.disposed_by_user_id")

        if _table_exists(cursor, "batches") and not _column_exists(cursor, "batches", "disposed_quantity"):
            cursor.execute("ALTER TABLE batches ADD COLUMN disposed_quantity FLOAT")
            print("Added batches.disposed_quantity")

        if _table_exists(cursor, "batches") and not _column_exists(cursor, "batches", "disposal_notes"):
            cursor.execute("ALTER TABLE batches ADD COLUMN disposal_notes VARCHAR")
            print("Added batches.disposal_notes")

        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)")
            cursor.execute("INSERT OR IGNORE INTO locations(name, is_active) VALUES ('Fridge', 1)")
            print("Ensured default locations exist")

        conn.commit()
        print("Compliance migration completed")
    except sqlite3.Error as exc:
        conn.rollback()
        raise RuntimeError(f"Compliance migration failed: {exc}") from exc
    finally:
        conn.close()