import sqlite3
from flask import g

DATABASE = 'sqlite.db'

def connect_db():
    db = sqlite3.connect(DATABASE)
    db.row_factory = sqlite3.Row
    db.execute("PRAGMA foreign_keys=ON;")
    return db

def get_db():
    if 'db' not in g:
        g.db = connect_db()
    return g.db

def close_db(e=None):
    db = g.pop('db', None)

    if db is not None:
        db.close()

def init_db(app):
    with app.app_context():
        db = get_db()
        db.execute("PRAGMA journal_mode=WAL;")
        db.execute("PRAGMA foreign_keys=ON;")

        # create inital tables
        db.executescript("""
        CREATE TABLE IF NOT EXISTS users (
            id INTEGER PRIMARY KEY AUTOINCREMENT,username TEXT UNIQUE NOT NULL,
            password_hash TEXT NOT NULL,
            created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
        );
                   
        CREATE TABLE IF NOT EXISTS games (
            id INTEGER PRIMARY KEY AUTOINCREMENT,
            created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
            final_fen TEXT,
            termination TEXT CHECK(termination IN ('checkmate', 'resignation', 'timeout', 'draw', 'other')),
            termination_detail TEXT,
            winner_color TEXT CHECK(winner_color IN ('white', 'black', 'draw')),
            move_history TEXT NOT NULL DEFAULT '[]',
            time_mode TEXT,
            started_at TIMESTAMP,
            ended_at TIMESTAMP
        );

        CREATE TABLE IF NOT EXISTS game_players (
            game_id INTEGER NOT NULL,
            player_id INTEGER NOT NULL,
            color TEXT NOT NULL CHECK(color IN ('white', 'black')),

            PRIMARY KEY (game_id, player_id),
            UNIQUE (game_id, color),

            FOREIGN KEY (game_id) REFERENCES games(id) ON DELETE CASCADE,
            FOREIGN KEY (player_id) REFERENCES users(id) ON DELETE CASCADE
        );

        CREATE INDEX IF NOT EXISTS idx_game_players_game_id
        ON game_players(game_id);

        CREATE INDEX IF NOT EXISTS idx_game_players_player_id
        ON game_players(player_id);
                         
        CREATE TABLE IF NOT EXISTS friendships (
            requester_id INTEGER NOT NULL,
            addressee_id INTEGER NOT NULL,
            status TEXT NOT NULL CHECK(status IN ('pending','accepted','blocked')),

            PRIMARY KEY (requester_id, addressee_id),

            FOREIGN KEY (requester_id) REFERENCES users(id) ON DELETE CASCADE,
            FOREIGN KEY (addressee_id) REFERENCES users(id) ON DELETE CASCADE
        );
        """
        )

        # Lightweight migration support for existing databases.
        user_columns = {
            row["name"]
            for row in db.execute("PRAGMA table_info(users)").fetchall()
        }
        if "last_seen_at" not in user_columns:
            db.execute("ALTER TABLE users ADD COLUMN last_seen_at TIMESTAMP")

        game_columns = {
            row["name"]
            for row in db.execute("PRAGMA table_info(games)").fetchall()
        }
        if "termination_detail" not in game_columns:
            db.execute("ALTER TABLE games ADD COLUMN termination_detail TEXT")
        if "winner_color" not in game_columns:
            db.execute(
                "ALTER TABLE games ADD COLUMN winner_color TEXT "
                "CHECK(winner_color IN ('white', 'black', 'draw'))"
            )
        if "move_history" not in game_columns:
            db.execute(
                "ALTER TABLE games ADD COLUMN move_history TEXT NOT NULL DEFAULT '[]'"
            )
        if "time_mode" not in game_columns:
            db.execute("ALTER TABLE games ADD COLUMN time_mode TEXT")
        if "started_at" not in game_columns:
            db.execute("ALTER TABLE games ADD COLUMN started_at TIMESTAMP")
        if "ended_at" not in game_columns:
            db.execute("ALTER TABLE games ADD COLUMN ended_at TIMESTAMP")

        db.commit()