from sqlalchemy import create_engine, event, text
from sqlalchemy.orm import sessionmaker, DeclarativeBase
from .config import settings


engine = create_engine(
    settings.database_url,
    connect_args={"check_same_thread": False},
    echo=False,
)


@event.listens_for(engine, "connect")
def set_sqlite_pragma(dbapi_conn, _):
    cursor = dbapi_conn.cursor()
    cursor.execute("PRAGMA journal_mode=WAL")
    cursor.execute("PRAGMA foreign_keys=ON")
    cursor.execute("PRAGMA busy_timeout=5000")
    cursor.execute("PRAGMA synchronous=NORMAL")
    cursor.close()


SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)


class Base(DeclarativeBase):
    pass


FTS_SETUP_SQL = """
CREATE VIRTUAL TABLE IF NOT EXISTS videos_fts USING fts5(
    title, description, content=videos, content_rowid=id
);

CREATE VIRTUAL TABLE IF NOT EXISTS channels_fts USING fts5(
    name, description, content=channels, content_rowid=id
);

CREATE TRIGGER IF NOT EXISTS videos_ai AFTER INSERT ON videos BEGIN
    INSERT INTO videos_fts(rowid, title, description)
    VALUES (new.id, new.title, COALESCE(new.description, ''));
END;

CREATE TRIGGER IF NOT EXISTS videos_ad AFTER DELETE ON videos BEGIN
    INSERT INTO videos_fts(videos_fts, rowid, title, description)
    VALUES ('delete', old.id, old.title, COALESCE(old.description, ''));
END;

CREATE TRIGGER IF NOT EXISTS videos_au AFTER UPDATE ON videos BEGIN
    INSERT INTO videos_fts(videos_fts, rowid, title, description)
    VALUES ('delete', old.id, old.title, COALESCE(old.description, ''));
    INSERT INTO videos_fts(rowid, title, description)
    VALUES (new.id, new.title, COALESCE(new.description, ''));
END;

CREATE TRIGGER IF NOT EXISTS channels_ai AFTER INSERT ON channels BEGIN
    INSERT INTO channels_fts(rowid, name, description)
    VALUES (new.id, new.name, COALESCE(new.description, ''));
END;

CREATE TRIGGER IF NOT EXISTS channels_ad AFTER DELETE ON channels BEGIN
    INSERT INTO channels_fts(channels_fts, rowid, name, description)
    VALUES ('delete', old.id, old.name, COALESCE(old.description, ''));
END;

CREATE TRIGGER IF NOT EXISTS channels_au AFTER UPDATE ON channels BEGIN
    INSERT INTO channels_fts(channels_fts, rowid, name, description)
    VALUES ('delete', old.id, old.name, COALESCE(old.description, ''));
    INSERT INTO channels_fts(rowid, name, description)
    VALUES (new.id, new.name, COALESCE(new.description, ''));
END;
"""


def _add_column_if_missing(raw_conn, table: str, column: str, definition: str):
    existing = {row[1] for row in raw_conn.execute(f"PRAGMA table_info({table})")}
    if column not in existing:
        raw_conn.execute(f"ALTER TABLE {table} ADD COLUMN {column} {definition}")


def init_db():
    from . import models  # noqa: F401

    Base.metadata.create_all(bind=engine)
    raw_conn = engine.raw_connection()
    try:
        # Column migrations — safe to run on every startup
        _add_column_if_missing(raw_conn, "videos", "view_count", "INTEGER")
        _add_column_if_missing(raw_conn, "videos", "like_count", "INTEGER")
        _add_column_if_missing(raw_conn, "videos", "dislike_count", "INTEGER")
        raw_conn.commit()
        # executescript handles multi-statement SQL including trigger BEGIN...END blocks
        raw_conn.executescript(FTS_SETUP_SQL)
    finally:
        raw_conn.close()


def get_db():
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()