using Godot;

namespace Pong.Scripts;

public partial class Ball : CharacterBody2D
{
	[Export] private double _ballSpeed;
	[Export] private double _maxRandomAngle;
	
	private Vector2 _velocity;

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

	public override void _Ready()
	{
		// 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.
		_velocity = GetRandomStartingDirection() * BallSpeed + new Vector2(0, rng.RandfRange(-_maxRandomAngle, _maxRandomAngle) * BallSpeed);
	}

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

	/// <summary>
	/// this method moves the ball and bounces if it collides with something.
	/// </summary>
	/// <param name="delta">delta time from the _PhysicsProcess 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 Vector2.Left or Vector2.Right based on that number.
	/// </summary>
	private Vector2 GetRandomStartingDirection() {
		using var rng = new RandomNumberGenerator();
		rng.Randomize();
		var range = rng.RandiRange(0,1);

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

		return Vector2.Right;
	}
}