import sqlite3
import contextlib
from typing import Generator
from app import config


def get_db_connection() -> sqlite3.Connection:
    conn = sqlite3.connect(config.DB_PATH, timeout=15.0)
    conn.row_factory = sqlite3.Row
    conn.execute("PRAGMA journal_mode=WAL;")
    conn.execute("PRAGMA synchronous=NORMAL;")
    conn.execute("PRAGMA foreign_keys=ON;")
    return conn


@contextlib.contextmanager
def get_db() -> Generator[sqlite3.Connection, None, None]:
    conn = get_db_connection()
    try:
        yield conn
        conn.commit()
    except Exception:
        conn.rollback()
        raise
    finally:
        conn.close()


def _migrate(conn: sqlite3.Connection):
    """Safe schema migrations: add new columns/tables without touching existing data."""
    # --- vocabulary_cards new columns ---
    existing_cols = {
        row[1] for row in conn.execute("PRAGMA table_info(vocabulary_cards)").fetchall()
    }
    card_migrations = [
        ("collection", "TEXT NOT NULL DEFAULT 'General'"),
        ("srs_reps", "INTEGER DEFAULT 0"),
        ("srs_interval", "INTEGER DEFAULT 0"),
        ("srs_ease", "REAL DEFAULT 2.5"),
        ("srs_next_review", "TIMESTAMP DEFAULT CURRENT_TIMESTAMP"),
        ("srs_last_review", "TIMESTAMP"),
        ("srs_state", "TEXT DEFAULT 'new'"),
        ("error_count", "INTEGER DEFAULT 0"),
    ]
    for col, definition in card_migrations:
        if col not in existing_cols:
            conn.execute(f"ALTER TABLE vocabulary_cards ADD COLUMN {col} {definition}")

    # Ensure srs_logs table exists
    conn.execute("""
    CREATE TABLE IF NOT EXISTS srs_logs (
        id INTEGER PRIMARY KEY AUTOINCREMENT,
        user_id INTEGER NOT NULL,
        card_id INTEGER NOT NULL,
        rating INTEGER NOT NULL,
        interval INTEGER NOT NULL,
        ease REAL NOT NULL,
        reviewed_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
        FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE,
        FOREIGN KEY (card_id) REFERENCES vocabulary_cards(id) ON DELETE CASCADE
    );
    """)

    conn.execute("CREATE INDEX IF NOT EXISTS idx_srs_user ON srs_logs(user_id);")
    conn.execute("CREATE INDEX IF NOT EXISTS idx_srs_reviewed ON srs_logs(user_id, reviewed_at);")


def init_db():
    config.DB_PATH.parent.mkdir(parents=True, exist_ok=True)
    with get_db() as conn:
        conn.executescript("""
        CREATE TABLE IF NOT EXISTS users (
            id INTEGER PRIMARY KEY AUTOINCREMENT,
            username TEXT UNIQUE NOT NULL COLLATE NOCASE,
            password_hash TEXT NOT NULL,
            salt TEXT NOT NULL,
            created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
        );

        CREATE TABLE IF NOT EXISTS sessions (
            token TEXT PRIMARY KEY,
            user_id INTEGER NOT NULL,
            created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
            expires_at TIMESTAMP NOT NULL,
            user_agent TEXT,
            ip TEXT,
            FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE
        );

        CREATE TABLE IF NOT EXISTS vocabulary_cards (
            id INTEGER PRIMARY KEY AUTOINCREMENT,
            user_id INTEGER NOT NULL,
            term TEXT NOT NULL,
            translation TEXT NOT NULL,
            context_sentence TEXT DEFAULT '',
            phonetic TEXT DEFAULT '',
            audio_url TEXT DEFAULT '',
            part_of_speech TEXT DEFAULT '',
            definition_en TEXT DEFAULT '',
            tags TEXT DEFAULT 'general',
            notes TEXT DEFAULT '',
            collection TEXT NOT NULL DEFAULT 'General',
            srs_reps INTEGER DEFAULT 0,
            srs_interval INTEGER DEFAULT 0,
            srs_ease REAL DEFAULT 2.5,
            srs_next_review TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
            srs_last_review TIMESTAMP,
            srs_state TEXT DEFAULT 'new',
            error_count INTEGER DEFAULT 0,
            created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
            updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
            FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE
        );

        CREATE INDEX IF NOT EXISTS idx_vocab_user ON vocabulary_cards(user_id);
        CREATE INDEX IF NOT EXISTS idx_vocab_term ON vocabulary_cards(term);
        CREATE INDEX IF NOT EXISTS idx_vocab_created ON vocabulary_cards(created_at DESC);
        CREATE INDEX IF NOT EXISTS idx_vocab_collection ON vocabulary_cards(user_id, collection);
        CREATE INDEX IF NOT EXISTS idx_vocab_srs_queue ON vocabulary_cards(user_id, srs_next_review, srs_state);

        CREATE TABLE IF NOT EXISTS srs_logs (
            id INTEGER PRIMARY KEY AUTOINCREMENT,
            user_id INTEGER NOT NULL,
            card_id INTEGER NOT NULL,
            rating INTEGER NOT NULL,
            interval INTEGER NOT NULL,
            ease REAL NOT NULL,
            reviewed_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
            FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE,
            FOREIGN KEY (card_id) REFERENCES vocabulary_cards(id) ON DELETE CASCADE
        );

        CREATE INDEX IF NOT EXISTS idx_srs_user ON srs_logs(user_id);
        CREATE INDEX IF NOT EXISTS idx_srs_reviewed ON srs_logs(user_id, reviewed_at);

        CREATE TABLE IF NOT EXISTS dictionary_cache (
            query TEXT PRIMARY KEY COLLATE NOCASE,
            response_json TEXT NOT NULL,
            cached_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
        );
        """)
        # Apply migrations for pre-existing databases
        _migrate(conn)