namespace Pong.Scripts.Objects;

public partial class Ball : CharacterBody2D
{
	[Export] private double _ballSpeed;
	[Export] private double _maxRandomAngle;

	/// <summary>
	/// this property multiples the ballSpeed by the <see cref="Constants.Meter">Meter</see> constant.
	/// </summary>
	private double BallSpeed => _ballSpeed * Constants.Meter;

	public override void _Ready()
	{
		FlickBall();
	}

	/// <summary>
	/// flick the ball in a direction.
	/// </summary>
	internal void FlickBall()
	{
		// this should dispose when this method goes out of scope (this means after the velocity variable is assigned)
		using var rng = new RandomNumberGenerator();
		rng.Randomize();
		// set the velocity currently to the left of the screen with a random y angle.
		var randomAngle = new Vector2 { Y = rng.RandfRange(-_maxRandomAngle, _maxRandomAngle) * BallSpeed };
		
		Velocity = GetRandomStartingDirection() * BallSpeed + randomAngle;
	}

	public override void _PhysicsProcess(double delta)
	{
		CollisionCheck(delta);
	}

	/// <summary>
	/// this method moves the ball and bounces if it collides with something.
	/// </summary>
	/// <param name="delta">delta time from the <see cref="_PhysicsProcess">_PhysicsProcess</see> method.</param>
	private void CollisionCheck(double delta)
	{
		var collision = MoveAndCollide(Velocity * delta);
		if (collision == null) return;
		Velocity = Velocity.Bounce(collision.GetNormal());
	}

	/// <summary>
	/// this method generates a random number between 0 and 1 and
	/// either returns <see cref="Vector2.Left">Vector2.Left</see> or <see cref="Vector2.Right">Vector2.Right</see>
	/// based on that number.
	/// </summary>
	private static Vector2 GetRandomStartingDirection()
	{
		using var rng = new RandomNumberGenerator();
		rng.Randomize();
		var range = rng.RandiRange(0, 1);

		if (range == 0)
		{
			return Vector2.Left;
		}

		return Vector2.Right;
	}
}