"""DuckDB singleton connection with asyncio write lock and schema migrations."""
import asyncio
import os
import duckdb

_conn: duckdb.DuckDBPyConnection | None = None
_write_lock = asyncio.Lock()


def get_db_path() -> str:
    return os.getenv("DB_PATH", "data/app.db")


def init_db(path: str | None = None) -> duckdb.DuckDBPyConnection:
    """Open (or reuse) the DuckDB connection and run schema migrations."""
    global _conn
    if _conn is not None:
        return _conn
    db_path = path or get_db_path()
    if db_path != ":memory:":
        os.makedirs(os.path.dirname(db_path), exist_ok=True)
    _conn = duckdb.connect(db_path)
    _run_migrations(_conn)
    return _conn


def get_conn() -> duckdb.DuckDBPyConnection:
    """Return the active connection; raises if not yet initialised."""
    if _conn is None:
        raise RuntimeError("Database not initialised. Call init_db() first.")
    return _conn


def close_db() -> None:
    """Close the connection (called on app shutdown)."""
    global _conn
    if _conn is not None:
        _conn.close()
        _conn = None


def get_write_lock() -> asyncio.Lock:
    """Return the asyncio lock that serialises write operations."""
    return _write_lock


def _run_migrations(conn: duckdb.DuckDBPyConnection) -> None:
    conn.execute("""
        CREATE TABLE IF NOT EXISTS users (
            id          UUID      DEFAULT uuid() PRIMARY KEY,
            email       VARCHAR   NOT NULL UNIQUE,
            password_hash VARCHAR NOT NULL,
            role        VARCHAR   DEFAULT 'user',
            created_at  TIMESTAMP DEFAULT now(),
            updated_at  TIMESTAMP DEFAULT now()
        )
    """)
    conn.execute("""
        CREATE TABLE IF NOT EXISTS refresh_tokens (
            jti         UUID      DEFAULT uuid() PRIMARY KEY,
            user_id     UUID      NOT NULL,
            issued_at   TIMESTAMP DEFAULT now(),
            expires_at  TIMESTAMP NOT NULL,
            revoked     BOOLEAN   DEFAULT false
        )
    """)
    conn.execute("""
        CREATE TABLE IF NOT EXISTS uploaded_images (
            id           UUID      DEFAULT uuid() PRIMARY KEY,
            user_id      UUID      NOT NULL,
            filename     VARCHAR   NOT NULL,
            content_type VARCHAR   NOT NULL,
            file_path    VARCHAR   NOT NULL,
            size_bytes   BIGINT    NOT NULL,
            created_at   TIMESTAMP DEFAULT now()
        )
    """)