import sqlite3


LATEST_SCHEMA_VERSION = 2

INITIAL_SCHEMA = """
    CREATE TABLE IF NOT EXISTS user_settings (
        user_id INTEGER PRIMARY KEY,
        ollama_model TEXT,
        updated_at TEXT NOT NULL
    );

    CREATE TABLE IF NOT EXISTS authorized_users (
        user_id INTEGER PRIMARY KEY,
        authorized_at TEXT NOT NULL
    );

    CREATE TABLE IF NOT EXISTS memories (
        id INTEGER PRIMARY KEY AUTOINCREMENT,
        user_id INTEGER NOT NULL,
        text TEXT NOT NULL,
        created_at TEXT NOT NULL
    );

    CREATE TABLE IF NOT EXISTS notes (
        id INTEGER PRIMARY KEY AUTOINCREMENT,
        user_id INTEGER NOT NULL,
        text TEXT NOT NULL,
        created_at TEXT NOT NULL
    );

    CREATE TABLE IF NOT EXISTS reminders (
        id INTEGER PRIMARY KEY AUTOINCREMENT,
        user_id INTEGER NOT NULL,
        chat_id INTEGER NOT NULL,
        text TEXT NOT NULL,
        remind_at TEXT NOT NULL,
        status TEXT NOT NULL DEFAULT 'pending',
        created_at TEXT NOT NULL,
        sent_at TEXT
    );

    CREATE TABLE IF NOT EXISTS tracked_items (
        id INTEGER PRIMARY KEY AUTOINCREMENT,
        user_id INTEGER NOT NULL,
        title TEXT NOT NULL,
        status TEXT NOT NULL,
        created_at TEXT NOT NULL,
        updated_at TEXT NOT NULL
    );

    CREATE TABLE IF NOT EXISTS conversation_messages (
        id INTEGER PRIMARY KEY AUTOINCREMENT,
        user_id INTEGER NOT NULL,
        chat_id INTEGER NOT NULL,
        role TEXT NOT NULL CHECK(role IN ('user', 'assistant')),
        content TEXT NOT NULL,
        created_at TEXT NOT NULL
    );

    CREATE TABLE IF NOT EXISTS conversation_contexts (
        user_id INTEGER NOT NULL,
        chat_id INTEGER NOT NULL,
        started_after_id INTEGER NOT NULL DEFAULT 0,
        updated_at TEXT NOT NULL,
        PRIMARY KEY (user_id, chat_id)
    );

    CREATE INDEX IF NOT EXISTS idx_memories_user_created
        ON memories(user_id, created_at DESC);
    CREATE INDEX IF NOT EXISTS idx_notes_user_created
        ON notes(user_id, created_at DESC);
    CREATE INDEX IF NOT EXISTS idx_reminders_due
        ON reminders(status, remind_at);
    CREATE INDEX IF NOT EXISTS idx_tracked_user_updated
        ON tracked_items(user_id, updated_at DESC);
    CREATE INDEX IF NOT EXISTS idx_conversation_chat_id
        ON conversation_messages(user_id, chat_id, id DESC);
"""


def _schema_version(connection: sqlite3.Connection) -> int:
    row = connection.execute("PRAGMA user_version").fetchone()
    return int(row[0])


def _has_column(
    connection: sqlite3.Connection,
    table: str,
    column: str,
) -> bool:
    return any(
        str(row["name"]) == column
        for row in connection.execute(f"PRAGMA table_info({table})")
    )


def migrate_database(connection: sqlite3.Connection) -> None:
    """Bring a new or existing database to the latest known schema."""
    connection.execute("PRAGMA journal_mode=WAL")
    version = _schema_version(connection)

    if version < 1:
        connection.executescript(INITIAL_SCHEMA)
        connection.execute("PRAGMA user_version = 1")
        version = 1

    if version < 2:
        if not _has_column(connection, "user_settings", "yandex_model"):
            connection.execute(
                "ALTER TABLE user_settings ADD COLUMN yandex_model TEXT"
            )
        connection.execute("PRAGMA user_version = 2")