from sqlalchemy import create_engine, text, event
from sqlalchemy.orm import sessionmaker, Session
from sqlalchemy.pool import QueuePool
from typing import Generator
from contextlib import contextmanager
import logging
import time

from .config import get_settings
from .models import Base

settings = get_settings()
logger = logging.getLogger(__name__)

# Create engine with connection pool configuration
engine = create_engine(
    settings.database_url,
    pool_pre_ping=True,  # Check connection health before using
    poolclass=QueuePool,
    pool_size=settings.database_pool_size,
    max_overflow=settings.database_max_overflow,
    pool_timeout=settings.database_pool_timeout,
    pool_recycle=settings.database_pool_recycle,
)

SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)


# Connection pool monitoring
@event.listens_for(engine, "checkout")
def receive_checkout(dbapi_connection, connection_record, connection_proxy):
    """Log when a connection is checked out from the pool"""
    logger.debug(f"Connection checked out from pool: {id(dbapi_connection)}")


@event.listens_for(engine, "checkin")
def receive_checkin(dbapi_connection, connection_record):
    """Log when a connection is returned to the pool"""
    logger.debug(f"Connection returned to pool: {id(dbapi_connection)}")


def get_pool_status() -> dict:
    """Get current connection pool status for monitoring"""
    pool = engine.pool
    return {
        "pool_size": pool.size(),
        "checked_out": pool.checkedout(),
        "overflow": pool.overflow(),
        "checked_in": pool.checkedin(),
    }


def init_db():
    """Create all tables and run migrations"""
    Base.metadata.create_all(bind=engine)

    # Run migrations for schema updates
    _run_migrations()


def _run_migrations():
    """Run manual migrations for schema updates"""
    migrations = [
        # Add format_metadata column to artifacts table
        """
        DO $$
        BEGIN
            IF NOT EXISTS (
                SELECT 1 FROM information_schema.columns
                WHERE table_name = 'artifacts' AND column_name = 'format_metadata'
            ) THEN
                ALTER TABLE artifacts ADD COLUMN format_metadata JSONB DEFAULT '{}';
            END IF;
        END $$;
        """,
        # Add format column to packages table
        """
        DO $$
        BEGIN
            IF NOT EXISTS (
                SELECT 1 FROM information_schema.columns
                WHERE table_name = 'packages' AND column_name = 'format'
            ) THEN
                ALTER TABLE packages ADD COLUMN format VARCHAR(50) DEFAULT 'generic' NOT NULL;
                CREATE INDEX IF NOT EXISTS idx_packages_format ON packages(format);
            END IF;
        END $$;
        """,
        # Add platform column to packages table
        """
        DO $$
        BEGIN
            IF NOT EXISTS (
                SELECT 1 FROM information_schema.columns
                WHERE table_name = 'packages' AND column_name = 'platform'
            ) THEN
                ALTER TABLE packages ADD COLUMN platform VARCHAR(50) DEFAULT 'any' NOT NULL;
                CREATE INDEX IF NOT EXISTS idx_packages_platform ON packages(platform);
            END IF;
        END $$;
        """,
        # Add ref_count index and constraints for artifacts
        """
        DO $$
        BEGIN
            -- Add ref_count index
            IF NOT EXISTS (
                SELECT 1 FROM pg_indexes WHERE indexname = 'idx_artifacts_ref_count'
            ) THEN
                CREATE INDEX idx_artifacts_ref_count ON artifacts(ref_count);
            END IF;

            -- Add ref_count >= 0 constraint
            IF NOT EXISTS (
                SELECT 1 FROM pg_constraint WHERE conname = 'check_ref_count_non_negative'
            ) THEN
                ALTER TABLE artifacts ADD CONSTRAINT check_ref_count_non_negative CHECK (ref_count >= 0);
            END IF;
        END $$;
        """,
        # Add composite indexes for packages and tags
        """
        DO $$
        BEGIN
            -- Composite index for package lookup by project and name
            IF NOT EXISTS (
                SELECT 1 FROM pg_indexes WHERE indexname = 'idx_packages_project_name'
            ) THEN
                CREATE UNIQUE INDEX idx_packages_project_name ON packages(project_id, name);
            END IF;

            -- Composite index for tag lookup by package and name
            IF NOT EXISTS (
                SELECT 1 FROM pg_indexes WHERE indexname = 'idx_tags_package_name'
            ) THEN
                CREATE UNIQUE INDEX idx_tags_package_name ON tags(package_id, name);
            END IF;

            -- Composite index for recent tags queries
            IF NOT EXISTS (
                SELECT 1 FROM pg_indexes WHERE indexname = 'idx_tags_package_created_at'
            ) THEN
                CREATE INDEX idx_tags_package_created_at ON tags(package_id, created_at);
            END IF;
        END $$;
        """,
    ]

    with engine.connect() as conn:
        for migration in migrations:
            try:
                conn.execute(text(migration))
                conn.commit()
            except Exception as e:
                logger.warning(f"Migration failed (may already be applied): {e}")


def get_db() -> Generator[Session, None, None]:
    """Dependency for getting database sessions"""
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()


@contextmanager
def transaction(db: Session):
    """
    Context manager for explicit transaction management with savepoint support.

    Usage:
        with transaction(db):
            # operations here
            # automatically commits on success, rolls back on exception
    """
    try:
        yield db
        db.commit()
    except Exception:
        db.rollback()
        raise


@contextmanager
def savepoint(db: Session, name: str = None):
    """
    Create a savepoint for partial rollback support.

    Usage:
        with savepoint(db, "my_savepoint"):
            # operations here
            # rolls back to savepoint on exception, but doesn't rollback whole transaction
    """
    savepoint_obj = db.begin_nested()
    try:
        yield savepoint_obj
        savepoint_obj.commit()
    except Exception:
        savepoint_obj.rollback()
        raise


def retry_on_deadlock(func, max_retries: int = 3, delay: float = 0.1):
    """
    Decorator/wrapper to retry operations on deadlock detection.

    Usage:
        @retry_on_deadlock
        def my_operation(db):
            ...

    Or:
        retry_on_deadlock(lambda: my_operation(db))()
    """
    import functools
    from sqlalchemy.exc import OperationalError

    @functools.wraps(func)
    def wrapper(*args, **kwargs):
        last_exception = None
        for attempt in range(max_retries):
            try:
                return func(*args, **kwargs)
            except OperationalError as e:
                # Check for deadlock error codes (PostgreSQL: 40P01, MySQL: 1213)
                error_str = str(e).lower()
                if "deadlock" in error_str or "40p01" in error_str:
                    last_exception = e
                    logger.warning(f"Deadlock detected, retrying (attempt {attempt + 1}/{max_retries})")
                    time.sleep(delay * (attempt + 1))  # Exponential backoff
                else:
                    raise
        raise last_exception

    return wrapper