"""
Database configuration and session management
"""
from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine, async_sessionmaker
from sqlalchemy.orm import declarative_base
from sqlalchemy import event, text
import logging
import os
from pathlib import Path

from app.config import settings

logger = logging.getLogger(__name__)

# Create database directory if it doesn't exist
db_path = Path(settings.database_url.replace("sqlite+aiosqlite:///", ""))
db_path.parent.mkdir(parents=True, exist_ok=True)

# Create async engine
# SQLite doesn't support pool configuration
if "sqlite" in settings.database_url:
    engine = create_async_engine(
        settings.database_url,
        echo=False,  # Set to True for SQL debugging
        connect_args={
            "check_same_thread": False,  # SQLite specific
            "timeout": 30
        }
    )
else:
    engine = create_async_engine(
        settings.database_url,
        echo=False,  # Set to True for SQL debugging
        pool_size=settings.performance.db_pool_size,
        pool_recycle=settings.performance.db_pool_recycle
    )

# Create async session factory
AsyncSessionLocal = async_sessionmaker(
    engine,
    class_=AsyncSession,
    expire_on_commit=False
)

# Base class for models
Base = declarative_base()

async def get_db() -> AsyncSession:
    """Dependency to get database session"""
    async with AsyncSessionLocal() as session:
        try:
            yield session
        finally:
            await session.close()

async def init_db():
    """Initialize database, create tables if they don't exist"""
    async with engine.begin() as conn:
        # Import all models to register them with Base
        from app.models import Photo, Folder, SourceRoot, Tag, PhotoTag, Heap, HeapPhoto, Embedding

        # Create all tables. Note: create_all only creates *missing* tables —
        # it does NOT add new columns to existing tables when the model gains
        # them. Anything new on an existing table needs an explicit ALTER
        # below.
        await conn.run_sync(Base.metadata.create_all)

        # Enable WAL mode for SQLite (better concurrency)
        if "sqlite" in settings.database_url:
            await conn.execute(text("PRAGMA journal_mode=WAL"))
            await conn.execute(text("PRAGMA synchronous=NORMAL"))
            await conn.execute(text("PRAGMA cache_size=10000"))
            await conn.execute(text("PRAGMA temp_store=MEMORY"))

        # ── Idempotent column adds ────────────────────────────────────────
        # The project does not use Alembic; we lean on create_all + a small
        # set of inline ALTER TABLE statements for the columns we've added
        # post-launch. SQLite supports ADD COLUMN but not "IF NOT EXISTS"
        # for columns, so introspect via PRAGMA first. Each entry is
        # (column_name, ALTER statement). Add new columns at the bottom.
        if "sqlite" in settings.database_url:
            existing_cols = {
                row[1]
                for row in (
                    await conn.execute(text("PRAGMA table_info(photos)"))
                ).fetchall()
            }
            pending_alters: list[tuple[str, str]] = [
                ("phash", "ALTER TABLE photos ADD COLUMN phash VARCHAR(16)"),
                (
                    "duplicate_group_id",
                    "ALTER TABLE photos ADD COLUMN duplicate_group_id VARCHAR",
                ),
            ]
            for col_name, alter_sql in pending_alters:
                if col_name not in existing_cols:
                    logger.info(f"Adding photos.{col_name} column")
                    await conn.execute(text(alter_sql))
            # Indexes for the new duplicate-detection columns. CREATE INDEX
            # IF NOT EXISTS is supported on SQLite so this is safe to run
            # every startup.
            await conn.execute(
                text("CREATE INDEX IF NOT EXISTS ix_photos_phash ON photos(phash)")
            )
            await conn.execute(
                text(
                    "CREATE INDEX IF NOT EXISTS ix_photos_duplicate_group_id "
                    "ON photos(duplicate_group_id)"
                )
            )

        logger.info("Database initialized successfully")

async def create_fts_table():
    """Create Full-Text Search table for SQLite"""
    if "sqlite" in settings.database_url:
        async with engine.begin() as conn:
            # Create FTS5 virtual table for full-text search
            await conn.execute(text("""
                CREATE VIRTUAL TABLE IF NOT EXISTS photos_fts USING fts5(
                    photo_id UNINDEXED,
                    filename,
                    user_title,
                    user_notes,
                    exif_text,
                    tokenize='unicode61'
                )
            """))
            logger.info("FTS5 table created successfully")