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__)

# Build connect_args with query timeout if configured
connect_args = {}
if settings.database_query_timeout > 0:
    # PostgreSQL statement_timeout is in milliseconds
    connect_args["options"] = f"-c statement_timeout={settings.database_query_timeout * 1000}"

# 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,
    connect_args=connect_args,
)

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 $$;
        """,
        # Add package_versions indexes and triggers (007_package_versions.sql)
        """
        DO $$
        BEGIN
            -- Create indexes for package_versions if table exists
            IF EXISTS (SELECT 1 FROM information_schema.tables WHERE table_name = 'package_versions') THEN
                -- Indexes for common queries
                IF NOT EXISTS (SELECT 1 FROM pg_indexes WHERE indexname = 'idx_package_versions_package_id') THEN
                    CREATE INDEX idx_package_versions_package_id ON package_versions(package_id);
                END IF;
                IF NOT EXISTS (SELECT 1 FROM pg_indexes WHERE indexname = 'idx_package_versions_artifact_id') THEN
                    CREATE INDEX idx_package_versions_artifact_id ON package_versions(artifact_id);
                END IF;
                IF NOT EXISTS (SELECT 1 FROM pg_indexes WHERE indexname = 'idx_package_versions_package_version') THEN
                    CREATE INDEX idx_package_versions_package_version ON package_versions(package_id, version);
                END IF;
            END IF;
        END $$;
        """,
        # Create ref_count trigger functions for tags (ensures triggers exist even if initial migration wasn't run)
        """
        CREATE OR REPLACE FUNCTION increment_artifact_ref_count()
        RETURNS TRIGGER AS $$
        BEGIN
            UPDATE artifacts SET ref_count = ref_count + 1 WHERE id = NEW.artifact_id;
            RETURN NEW;
        END;
        $$ LANGUAGE plpgsql;
        """,
        """
        CREATE OR REPLACE FUNCTION decrement_artifact_ref_count()
        RETURNS TRIGGER AS $$
        BEGIN
            UPDATE artifacts SET ref_count = ref_count - 1 WHERE id = OLD.artifact_id;
            RETURN OLD;
        END;
        $$ LANGUAGE plpgsql;
        """,
        """
        CREATE OR REPLACE FUNCTION update_artifact_ref_count()
        RETURNS TRIGGER AS $$
        BEGIN
            IF OLD.artifact_id != NEW.artifact_id THEN
                UPDATE artifacts SET ref_count = ref_count - 1 WHERE id = OLD.artifact_id;
                UPDATE artifacts SET ref_count = ref_count + 1 WHERE id = NEW.artifact_id;
            END IF;
            RETURN NEW;
        END;
        $$ LANGUAGE plpgsql;
        """,
        # Create triggers for tags ref_count management
        """
        DO $$
        BEGIN
            -- Drop and recreate triggers to ensure they're current
            DROP TRIGGER IF EXISTS tags_ref_count_insert_trigger ON tags;
            CREATE TRIGGER tags_ref_count_insert_trigger
                AFTER INSERT ON tags
                FOR EACH ROW
                EXECUTE FUNCTION increment_artifact_ref_count();

            DROP TRIGGER IF EXISTS tags_ref_count_delete_trigger ON tags;
            CREATE TRIGGER tags_ref_count_delete_trigger
                AFTER DELETE ON tags
                FOR EACH ROW
                EXECUTE FUNCTION decrement_artifact_ref_count();

            DROP TRIGGER IF EXISTS tags_ref_count_update_trigger ON tags;
            CREATE TRIGGER tags_ref_count_update_trigger
                AFTER UPDATE ON tags
                FOR EACH ROW
                WHEN (OLD.artifact_id IS DISTINCT FROM NEW.artifact_id)
                EXECUTE FUNCTION update_artifact_ref_count();
        END $$;
        """,
        # Create ref_count trigger functions for package_versions
        """
        CREATE OR REPLACE FUNCTION increment_version_ref_count()
        RETURNS TRIGGER AS $$
        BEGIN
            UPDATE artifacts SET ref_count = ref_count + 1 WHERE id = NEW.artifact_id;
            RETURN NEW;
        END;
        $$ LANGUAGE plpgsql;
        """,
        """
        CREATE OR REPLACE FUNCTION decrement_version_ref_count()
        RETURNS TRIGGER AS $$
        BEGIN
            UPDATE artifacts SET ref_count = ref_count - 1 WHERE id = OLD.artifact_id;
            RETURN OLD;
        END;
        $$ LANGUAGE plpgsql;
        """,
        # Create triggers for package_versions ref_count
        """
        DO $$
        BEGIN
            IF EXISTS (SELECT 1 FROM information_schema.tables WHERE table_name = 'package_versions') THEN
                -- Drop and recreate triggers to ensure they're current
                DROP TRIGGER IF EXISTS package_versions_ref_count_insert ON package_versions;
                CREATE TRIGGER package_versions_ref_count_insert
                    AFTER INSERT ON package_versions
                    FOR EACH ROW
                    EXECUTE FUNCTION increment_version_ref_count();

                DROP TRIGGER IF EXISTS package_versions_ref_count_delete ON package_versions;
                CREATE TRIGGER package_versions_ref_count_delete
                    AFTER DELETE ON package_versions
                    FOR EACH ROW
                    EXECUTE FUNCTION decrement_version_ref_count();
            END IF;
        END $$;
        """,
        # Migrate existing semver tags to package_versions
        r"""
        DO $$
        BEGIN
            IF EXISTS (SELECT 1 FROM information_schema.tables WHERE table_name = 'package_versions') THEN
                -- Migrate tags that look like versions (v1.0.0, 1.2.3, 2.0.0-beta, etc.)
                INSERT INTO package_versions (package_id, artifact_id, version, version_source, created_by, created_at)
                SELECT
                    t.package_id,
                    t.artifact_id,
                    CASE WHEN t.name LIKE 'v%' THEN substring(t.name from 2) ELSE t.name END,
                    'migrated_from_tag',
                    t.created_by,
                    t.created_at
                FROM tags t
                WHERE t.name ~ '^v?[0-9]+\.[0-9]+(\.[0-9]+)?([-.][a-zA-Z0-9]+)?$'
                ON CONFLICT (package_id, version) DO NOTHING;
            END IF;
        END $$;
        """,
        # Teams and multi-tenancy migration (009_teams.sql)
        """
        CREATE TABLE IF NOT EXISTS teams (
            id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
            name VARCHAR(255) NOT NULL,
            slug VARCHAR(255) NOT NULL UNIQUE,
            description TEXT,
            created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW(),
            updated_at TIMESTAMP WITH TIME ZONE DEFAULT NOW(),
            created_by VARCHAR(255) NOT NULL,
            settings JSONB DEFAULT '{}'
        );
        """,
        """
        CREATE TABLE IF NOT EXISTS team_memberships (
            id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
            team_id UUID NOT NULL REFERENCES teams(id) ON DELETE CASCADE,
            user_id UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
            role VARCHAR(50) NOT NULL DEFAULT 'member',
            created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW(),
            invited_by VARCHAR(255),
            CONSTRAINT team_memberships_unique UNIQUE (team_id, user_id),
            CONSTRAINT team_memberships_role_check CHECK (role IN ('owner', 'admin', 'member'))
        );
        """,
        """
        DO $$
        BEGIN
            IF NOT EXISTS (
                SELECT 1 FROM information_schema.columns
                WHERE table_name = 'projects' AND column_name = 'team_id'
            ) THEN
                ALTER TABLE projects ADD COLUMN team_id UUID REFERENCES teams(id) ON DELETE SET NULL;
                CREATE INDEX IF NOT EXISTS idx_projects_team_id ON projects(team_id);
            END IF;
        END $$;
        """,
        """
        DO $$
        BEGIN
            IF NOT EXISTS (SELECT 1 FROM pg_indexes WHERE indexname = 'idx_teams_slug') THEN
                CREATE INDEX idx_teams_slug ON teams(slug);
            END IF;
            IF NOT EXISTS (SELECT 1 FROM pg_indexes WHERE indexname = 'idx_teams_created_by') THEN
                CREATE INDEX idx_teams_created_by ON teams(created_by);
            END IF;
            IF NOT EXISTS (SELECT 1 FROM pg_indexes WHERE indexname = 'idx_team_memberships_team_id') THEN
                CREATE INDEX idx_team_memberships_team_id ON team_memberships(team_id);
            END IF;
            IF NOT EXISTS (SELECT 1 FROM pg_indexes WHERE indexname = 'idx_team_memberships_user_id') THEN
                CREATE INDEX idx_team_memberships_user_id ON team_memberships(user_id);
            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