"""
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, "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")

        # 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()