import os
import json
import logging
from contextlib import asynccontextmanager, contextmanager
from typing import Any, Optional

from open_webui.internal.wrappers import register_connection
from open_webui.env import (
    OPEN_WEBUI_DIR,
    DATABASE_URL,
    DATABASE_SCHEMA,
    DATABASE_POOL_MAX_OVERFLOW,
    DATABASE_POOL_RECYCLE,
    DATABASE_POOL_SIZE,
    DATABASE_POOL_TIMEOUT,
    DATABASE_ENABLE_SQLITE_WAL,
    DATABASE_ENABLE_SESSION_SHARING,
    ENABLE_DB_MIGRATIONS,
)
from peewee_migrate import Router
from sqlalchemy import Dialect, create_engine, MetaData, event, types
from sqlalchemy.ext.asyncio import create_async_engine, AsyncSession, async_sessionmaker
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import scoped_session, sessionmaker, Session
from sqlalchemy.pool import QueuePool, NullPool
from sqlalchemy.sql.type_api import _T
from typing_extensions import Self

log = logging.getLogger(__name__)


class JSONField(types.TypeDecorator):
    impl = types.Text
    cache_ok = True

    def process_bind_param(self, value: Optional[_T], dialect: Dialect) -> Any:
        return json.dumps(value)

    def process_result_value(self, value: Optional[_T], dialect: Dialect) -> Any:
        if value is not None:
            return json.loads(value)

    def copy(self, **kw: Any) -> Self:
        return JSONField(self.impl.length)

    def db_value(self, value):
        return json.dumps(value)

    def python_value(self, value):
        if value is not None:
            return json.loads(value)


# Workaround to handle the peewee migration
# This is required to ensure the peewee migration is handled before the alembic migration
def handle_peewee_migration(DATABASE_URL):
    # db = None
    try:
        # Replace the postgresql:// with postgres:// to handle the peewee migration
        db = register_connection(DATABASE_URL.replace('postgresql://', 'postgres://'))
        migrate_dir = OPEN_WEBUI_DIR / 'internal' / 'migrations'
        router = Router(db, logger=log, migrate_dir=migrate_dir)
        router.run()
        db.close()

    except Exception as e:
        log.error(f'Failed to initialize the database connection: {e}')
        log.warning('Hint: If your database password contains special characters, you may need to URL-encode it.')
        raise
    finally:
        # Properly closing the database connection
        if db and not db.is_closed():
            db.close()

        # Assert if db connection has been closed
        assert db.is_closed(), 'Database connection is still open.'


if ENABLE_DB_MIGRATIONS:
    handle_peewee_migration(DATABASE_URL)


SQLALCHEMY_DATABASE_URL = DATABASE_URL


def _make_async_url(url: str) -> str:
    """Convert a sync database URL to its async driver equivalent."""
    if url.startswith('sqlite+sqlcipher://'):
        # SQLCipher has no async driver — not supported for async
        raise ValueError(
            'sqlite+sqlcipher:// URLs are not supported with async engine. '
            'Use standard sqlite:// or postgresql:// instead.'
        )
    if url.startswith('sqlite:///') or url.startswith('sqlite://'):
        return url.replace('sqlite://', 'sqlite+aiosqlite://', 1)
    if url.startswith('postgresql+psycopg2://'):
        return url.replace('postgresql+psycopg2://', 'postgresql+asyncpg://', 1)
    if url.startswith('postgresql://'):
        return url.replace('postgresql://', 'postgresql+asyncpg://', 1)
    if url.startswith('postgres://'):
        return url.replace('postgres://', 'postgresql+asyncpg://', 1)
    # For other dialects, return as-is and let SQLAlchemy handle it
    return url


# ============================================================
# SYNC ENGINE (used only for: startup migrations, config loading,
#              Alembic, peewee migration, health checks)
# ============================================================

# Handle SQLCipher URLs
if SQLALCHEMY_DATABASE_URL.startswith('sqlite+sqlcipher://'):
    database_password = os.environ.get('DATABASE_PASSWORD')
    if not database_password or database_password.strip() == '':
        raise ValueError('DATABASE_PASSWORD is required when using sqlite+sqlcipher:// URLs')

    # Extract database path from SQLCipher URL
    db_path = SQLALCHEMY_DATABASE_URL.replace('sqlite+sqlcipher://', '')

    # Create a custom creator function that uses sqlcipher3
    def create_sqlcipher_connection():
        import sqlcipher3

        conn = sqlcipher3.connect(db_path, check_same_thread=False)
        conn.execute(f"PRAGMA key = '{database_password}'")
        return conn

    # The dummy "sqlite://" URL would cause SQLAlchemy to auto-select
    # SingletonThreadPool, which non-deterministically closes in-use
    # connections when thread count exceeds pool_size, leading to segfaults
    # in the native sqlcipher3 C library. Use NullPool by default for safety,
    # or QueuePool if DATABASE_POOL_SIZE is explicitly configured.
    if isinstance(DATABASE_POOL_SIZE, int) and DATABASE_POOL_SIZE > 0:
        engine = create_engine(
            'sqlite://',
            creator=create_sqlcipher_connection,
            pool_size=DATABASE_POOL_SIZE,
            max_overflow=DATABASE_POOL_MAX_OVERFLOW,
            pool_timeout=DATABASE_POOL_TIMEOUT,
            pool_recycle=DATABASE_POOL_RECYCLE,
            pool_pre_ping=True,
            poolclass=QueuePool,
            echo=False,
        )
    else:
        engine = create_engine(
            'sqlite://',
            creator=create_sqlcipher_connection,
            poolclass=NullPool,
            echo=False,
        )

    log.info('Connected to encrypted SQLite database using SQLCipher')

elif 'sqlite' in SQLALCHEMY_DATABASE_URL:
    engine = create_engine(SQLALCHEMY_DATABASE_URL, connect_args={'check_same_thread': False})

    def on_connect(dbapi_connection, connection_record):
        cursor = dbapi_connection.cursor()
        if DATABASE_ENABLE_SQLITE_WAL:
            cursor.execute('PRAGMA journal_mode=WAL')
        else:
            cursor.execute('PRAGMA journal_mode=DELETE')
        cursor.close()

    event.listen(engine, 'connect', on_connect)
else:
    if isinstance(DATABASE_POOL_SIZE, int):
        if DATABASE_POOL_SIZE > 0:
            engine = create_engine(
                SQLALCHEMY_DATABASE_URL,
                pool_size=DATABASE_POOL_SIZE,
                max_overflow=DATABASE_POOL_MAX_OVERFLOW,
                pool_timeout=DATABASE_POOL_TIMEOUT,
                pool_recycle=DATABASE_POOL_RECYCLE,
                pool_pre_ping=True,
                poolclass=QueuePool,
            )
        else:
            engine = create_engine(SQLALCHEMY_DATABASE_URL, pool_pre_ping=True, poolclass=NullPool)
    else:
        engine = create_engine(SQLALCHEMY_DATABASE_URL, pool_pre_ping=True)


# Sync session — used ONLY for startup config loading (config.py runs at import time)
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine, expire_on_commit=False)
metadata_obj = MetaData(schema=DATABASE_SCHEMA)
Base = declarative_base(metadata=metadata_obj)
ScopedSession = scoped_session(SessionLocal)


def get_session():
    """Sync session generator — used ONLY for startup/config operations."""
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()


get_db = contextmanager(get_session)


# ============================================================
# ASYNC ENGINE (used for ALL runtime database operations)
# ============================================================

ASYNC_SQLALCHEMY_DATABASE_URL = _make_async_url(SQLALCHEMY_DATABASE_URL)

if 'sqlite' in ASYNC_SQLALCHEMY_DATABASE_URL:
    async_engine = create_async_engine(
        ASYNC_SQLALCHEMY_DATABASE_URL,
        connect_args={'check_same_thread': False},
    )

    if DATABASE_ENABLE_SQLITE_WAL:

        @event.listens_for(async_engine.sync_engine, 'connect')
        def _set_sqlite_wal(dbapi_connection, connection_record):
            cursor = dbapi_connection.cursor()
            cursor.execute('PRAGMA journal_mode=WAL')
            cursor.close()
else:
    if isinstance(DATABASE_POOL_SIZE, int):
        if DATABASE_POOL_SIZE > 0:
            async_engine = create_async_engine(
                ASYNC_SQLALCHEMY_DATABASE_URL,
                pool_size=DATABASE_POOL_SIZE,
                max_overflow=DATABASE_POOL_MAX_OVERFLOW,
                pool_timeout=DATABASE_POOL_TIMEOUT,
                pool_recycle=DATABASE_POOL_RECYCLE,
                pool_pre_ping=True,
            )
        else:
            async_engine = create_async_engine(
                ASYNC_SQLALCHEMY_DATABASE_URL,
                pool_pre_ping=True,
                poolclass=NullPool,
            )
    else:
        async_engine = create_async_engine(
            ASYNC_SQLALCHEMY_DATABASE_URL,
            pool_pre_ping=True,
        )


AsyncSessionLocal = async_sessionmaker(
    bind=async_engine,
    class_=AsyncSession,
    autocommit=False,
    autoflush=False,
    expire_on_commit=False,
)


async def get_async_session():
    """Async session generator for FastAPI Depends()."""
    async with AsyncSessionLocal() as db:
        try:
            yield db
        finally:
            await db.close()


@asynccontextmanager
async def get_async_db():
    """Async context manager for use outside of FastAPI dependency injection."""
    async with AsyncSessionLocal() as db:
        try:
            yield db
        finally:
            await db.close()


@asynccontextmanager
async def get_async_db_context(db: Optional[AsyncSession] = None):
    """Async context manager that reuses an existing session if provided and session sharing is enabled."""
    if isinstance(db, AsyncSession) and DATABASE_ENABLE_SESSION_SHARING:
        yield db
    else:
        async with get_async_db() as session:
            yield session