using OpenTK.Mathematics;

namespace VoxelEngine.Rendering;

public sealed class Camera
{
    private static readonly Vector3 WorldUp = Vector3.UnitY;

    public Vector3 Position { get; private set; }
    public float Yaw { get; private set; } = -90f;   // degrees; -90 looks down -Z
    public float Pitch { get; private set; }         // degrees
    public float Fov { get; set; } = 60f;            // degrees
    public float FarPlane { get; set; } = 100f;      // world units
    public float AspectRatio { get; set; }

    public Vector3 Front { get; private set; } = -Vector3.UnitZ;
    public Vector3 Right { get; private set; } = Vector3.UnitX;
    public Vector3 Up { get; private set; } = Vector3.UnitY;

    public Camera(Vector3 position, float aspectRatio)
    {
        this.Position = position;
        this.AspectRatio = aspectRatio;
        this.UpdateVectors();
    }

    public void Move(Vector3 delta) => this.Position += delta;

    public void AddRotation(float yawDelta, float pitchDelta)
    {
        this.Yaw += yawDelta;
        this.Pitch = MathHelper.Clamp(this.Pitch + pitchDelta, -89f, 89f);
        this.UpdateVectors();
    }

    public Matrix4 GetViewMatrix() => Matrix4.LookAt(this.Position, this.Position + this.Front, this.Up);

    public Matrix4 GetProjectionMatrix() =>
        Matrix4.CreatePerspectiveFieldOfView(
            MathHelper.DegreesToRadians(this.Fov), this.AspectRatio, 0.1f, this.FarPlane);

    private void UpdateVectors()
    {
        float yaw = MathHelper.DegreesToRadians(this.Yaw);
        float pitch = MathHelper.DegreesToRadians(this.Pitch);

        this.Front = Vector3.Normalize(new Vector3(
            MathF.Cos(yaw) * MathF.Cos(pitch),
            MathF.Sin(pitch),
            MathF.Sin(yaw) * MathF.Cos(pitch)));

        this.Right = Vector3.Normalize(Vector3.Cross(this.Front, Camera.WorldUp));
        this.Up = Vector3.Normalize(Vector3.Cross(this.Right, this.Front));
    }
}