import logging
import os
import shutil
from app.logger import log_startup_warning
from utils.install_util import get_missing_requirements_message
from filelock import FileLock, Timeout
from comfy.cli_args import args

_DB_AVAILABLE = False
Session = None


try:
    from alembic import command
    from alembic.config import Config
    from alembic.runtime.migration import MigrationContext
    from alembic.script import ScriptDirectory
    from sqlalchemy import create_engine, event
    from sqlalchemy.orm import sessionmaker

    _DB_AVAILABLE = True
except ImportError as e:
    log_startup_warning(
        f"""
------------------------------------------------------------------------
Error importing dependencies: {e}
{get_missing_requirements_message()}
This error is happening because ComfyUI now uses a local sqlite database.
------------------------------------------------------------------------
""".strip()
    )


def dependencies_available():
    """
    Temporary function to check if the dependencies are available
    """
    return _DB_AVAILABLE


def can_create_session():
    """
    Temporary function to check if the database is available to create a session
    During initial release there may be environmental issues (or missing dependencies) that prevent the database from being created
    """
    return dependencies_available() and Session is not None


def get_alembic_config():
    root_path = os.path.join(os.path.dirname(__file__), "../..")
    config_path = os.path.abspath(os.path.join(root_path, "alembic.ini"))
    scripts_path = os.path.abspath(os.path.join(root_path, "alembic_db"))

    config = Config(config_path)
    config.set_main_option("script_location", scripts_path)
    config.set_main_option("sqlalchemy.url", args.database_url)

    return config


def get_db_path():
    url = args.database_url
    if url.startswith("sqlite:///"):
        return url.split("///")[1]
    else:
        raise ValueError(f"Unsupported database URL '{url}'.")


_db_lock = None

def _acquire_file_lock(db_path):
    """Acquire an OS-level file lock to prevent multi-process access.

    Uses filelock for cross-platform support (macOS, Linux, Windows).
    The OS automatically releases the lock when the process exits, even on crashes.
    """
    global _db_lock
    lock_path = db_path + ".lock"
    _db_lock = FileLock(lock_path)
    try:
        _db_lock.acquire(timeout=0)
    except Timeout:
        raise RuntimeError(
            f"Could not acquire lock on database '{db_path}'. "
            "Another ComfyUI process may already be using it. "
            "Use --database-url to specify a separate database file."
        )


def init_db():
    db_url = args.database_url
    logging.debug(f"Database URL: {db_url}")
    db_path = get_db_path()
    db_exists = os.path.exists(db_path)

    config = get_alembic_config()

    # Check if we need to upgrade
    engine = create_engine(db_url)

    # Enable foreign key enforcement for SQLite
    @event.listens_for(engine, "connect")
    def set_sqlite_pragma(dbapi_connection, connection_record):
        cursor = dbapi_connection.cursor()
        cursor.execute("PRAGMA foreign_keys=ON")
        cursor.close()

    conn = engine.connect()

    context = MigrationContext.configure(conn)
    current_rev = context.get_current_revision()

    script = ScriptDirectory.from_config(config)
    target_rev = script.get_current_head()

    if target_rev is None:
        logging.warning("No target revision found.")
    elif current_rev != target_rev:
        # Backup the database pre upgrade
        backup_path = db_path + ".bkp"
        if db_exists:
            shutil.copy(db_path, backup_path)
        else:
            backup_path = None

        try:
            command.upgrade(config, target_rev)
            logging.info(f"Database upgraded from {current_rev} to {target_rev}")
        except Exception as e:
            if backup_path:
                # Restore the database from backup if upgrade fails
                shutil.copy(backup_path, db_path)
                os.remove(backup_path)
            logging.exception("Error upgrading database: ")
            raise e

    # Acquire an OS-level file lock after migrations are complete.
    # Alembic uses its own connection, so we must wait until it's done
    # before locking — otherwise our own lock blocks the migration.
    conn.close()
    _acquire_file_lock(db_path)

    global Session
    Session = sessionmaker(bind=engine)


def create_session():
    return Session()