"""
GTIN mapping table migration.

Creates the gtin_mappings table if it does not already exist.
Idempotent and safe to run on every startup.
"""

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 GTIN migration: {db_url}")
        return None
    raw_path = db_url.replace("sqlite:///", "")
    if raw_path.startswith("/"):
        return Path(raw_path)
    return Path(raw_path)


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


def migrate_gtin_schema() -> None:
    """Create gtin_mappings table if it does not exist, and drop label from variant_packs."""
    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 GTIN migration")
        return

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

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

    try:
        if not _table_exists(cursor, "gtin_mappings"):
            cursor.execute("""
                CREATE TABLE gtin_mappings (
                    id INTEGER PRIMARY KEY AUTOINCREMENT,
                    gtin VARCHAR(14) NOT NULL,
                    drug_variant_id INTEGER NOT NULL REFERENCES drug_variants(id),
                    variant_pack_id INTEGER NOT NULL REFERENCES variant_packs(id),
                    created_by_user_id INTEGER REFERENCES users(id),
                    created_at DATETIME DEFAULT CURRENT_TIMESTAMP
                )
            """)
            cursor.execute("CREATE UNIQUE INDEX ix_gtin_mappings_gtin ON gtin_mappings (gtin)")
            cursor.execute("CREATE INDEX ix_gtin_mappings_drug_variant_id ON gtin_mappings (drug_variant_id)")
            cursor.execute("CREATE INDEX ix_gtin_mappings_variant_pack_id ON gtin_mappings (variant_pack_id)")
            print("Created gtin_mappings table")
        else:
            print("gtin_mappings table already exists, skipping")

        # Drop label column from variant_packs if it still exists
        if _table_exists(cursor, "variant_packs") and _column_exists(cursor, "variant_packs", "label"):
            print("Dropping label column from variant_packs")
            cursor.execute("""
                CREATE TABLE variant_packs_new (
                    id INTEGER PRIMARY KEY AUTOINCREMENT,
                    drug_variant_id INTEGER NOT NULL REFERENCES drug_variants(id),
                    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
                )
            """)
            cursor.execute("""
                INSERT INTO variant_packs_new (id, drug_variant_id, pack_unit_name, pack_size_in_base_units, is_active, created_at, updated_at)
                SELECT id, drug_variant_id, pack_unit_name, pack_size_in_base_units, is_active, created_at, updated_at
                FROM variant_packs
            """)
            # Re-create indexes
            cursor.execute("DROP INDEX IF EXISTS ix_variant_packs_drug_variant_id")
            cursor.execute("DROP TABLE variant_packs")
            cursor.execute("ALTER TABLE variant_packs_new RENAME TO variant_packs")
            cursor.execute("CREATE INDEX ix_variant_packs_drug_variant_id ON variant_packs (drug_variant_id)")
            print("Dropped label column from variant_packs")
        else:
            print("variant_packs.label already absent, skipping")

        conn.commit()
    finally:
        conn.close()