// direction choosing functions ------------------------------------------------

function getUserDir(keys: Keys, state: SnakeGameState): Vec2 {
    // get direction based on user input
    const { snake } = state;

    let dir = getSnakeDir(snake);
    const keyDirMap = {
        w: vec2(0, -1),
        s: vec2(0, +1),
        a: vec2(-1, 0),
        d: vec2(+1, 0),
    };
    for (const [key, newDir] of Object.entries(keyDirMap)) {
        // vec2.dot === 0 prevents choosing to move backwards
        if (keys.isKeyPressed(key) && Vec2.dot(dir, newDir) === 0) {
            dir = newDir;
            break;
        }
    }

    return dir;
}

function getWallRiderDir(state: SnakeGameState): Vec2 {
    // basic wall rider "AI" that will ride the wall forever
    // as long as it can turn left (note y-axis is flipped)
    const { snake } = state;

    let dir = getSnakeDir(snake);
    const nextSquare = getSnakeNextSquare(snake, dir);

    if (isOutOfBounds(nextSquare)) {
        dir = dir.rot90();
    }

    return dir;
}