"""
Database connection setup using SQLAlchemy.
"""

from datetime import datetime
from typing import Optional

from sqlalchemy import create_engine, inspect
from sqlalchemy.orm import sessionmaker, declarative_base
from contextlib import contextmanager

from .config import settings

# Create engine
engine = create_engine(
    settings.database_url,
    pool_size=10,
    max_overflow=20,
    pool_pre_ping=True,  # Verify connections before use
    echo=False,  # Set to True for SQL debugging
)

# Session factory
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)

# Base class for models
Base = declarative_base()


def get_db():
    """
    Dependency for FastAPI routes to get a database session.
    """
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()


@contextmanager
def get_db_session():
    """
    Context manager for database sessions.
    Use in non-FastAPI contexts (scripts, etc).
    """
    db = SessionLocal()
    try:
        yield db
        db.commit()
    except Exception:
        db.rollback()
        raise
    finally:
        db.close()


def init_db():
    """
    Initialize database - create all tables.
    """
    Base.metadata.create_all(bind=engine)


def drop_db():
    """
    Drop all tables - use with caution!
    """
    Base.metadata.drop_all(bind=engine)


def get_db_schema_version() -> Optional[int]:
    """
    Get the current schema version from the database.
    Returns None if table doesn't exist or no version is set.
    """
    from .models import SchemaVersion  # Import here to avoid circular imports

    # Check if schema_version table exists
    inspector = inspect(engine)
    if "schema_version" not in inspector.get_table_names():
        return None

    try:
        with get_db_session() as db:
            row = db.query(SchemaVersion).first()
            return row.version if row else None
    except Exception:
        return None


def set_db_schema_version(version: int):
    """
    Set/update the schema version in the database.
    Creates the row if it doesn't exist.
    """
    from .models import SchemaVersion

    with get_db_session() as db:
        row = db.query(SchemaVersion).first()
        if row:
            row.version = version
            row.migrated_at = datetime.utcnow()
        else:
            db.add(SchemaVersion(id=1, version=version, migrated_at=datetime.utcnow()))


def check_and_migrate_if_needed():
    """
    Check schema version and run migration if needed.
    Called during application startup.
    """
    from .version import SCHEMA_VERSION
    from .migration import run_full_migration

    db_version = get_db_schema_version()

    if db_version == SCHEMA_VERSION:
        print(f"Schema version {SCHEMA_VERSION} matches. Fast startup.")
        # Still ensure tables exist (they should if version matches)
        init_db()
        return

    if db_version is None:
        print(f"No schema version found. Running initial migration (v{SCHEMA_VERSION})...")
    else:
        print(f"Schema mismatch: DB has v{db_version}, code expects v{SCHEMA_VERSION}")
        print("Running full migration...")

    try:
        success = run_full_migration(geocode=False)

        if success:
            # Ensure schema_version table exists before writing
            init_db()
            set_db_schema_version(SCHEMA_VERSION)
            print(f"Migration complete. Schema version set to {SCHEMA_VERSION}")
        else:
            print("Warning: Migration completed but no data was imported.")
            init_db()
            set_db_schema_version(SCHEMA_VERSION)

    except Exception as e:
        print(f"FATAL: Migration failed: {e}")
        print("Application cannot start. Please check database and CSV files.")
        raise