using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace RecrownedAthenaeum.Camera
{
    /// <summary>
    /// A generic 3D camera.
    /// </summary>
    public class Camera3D
    {
        /// <summary>
        /// The zoom of the camera.
        /// </summary>
        public float worldScale = 1f;

        /// <summary>
        /// Current position in the world.
        /// </summary>
        public Vector3 position;

        /// <summary>
        /// The place the 3D camera is looking at.
        /// </summary>
        public Vector3 lookAt;

        /// <summary>
        /// The direction up is for the 3D camera.
        /// </summary>
        public Vector3 upDirection;

        /// <summary>
        /// The transform matrix representing the world (rotation and translations of the original world).
        /// </summary>
        public Matrix worldMatrix;

        /// <summary>
        /// The view matrix that describes where the camera looks.
        /// </summary>
        public Matrix ViewMatrix { get; protected set; }

        /// <summary>
        /// The projection matrix.
        /// </summary>
        public Matrix projectionMatrix;

        /// <summary>
        /// The graphics device used 
        /// </summary>
        protected GraphicsDevice graphicsDevice;

        /// <summary>
        /// The basic effect that contains the transformations.
        /// </summary>
        public BasicEffect BasicEffect { get; protected set; }

        /// <summary>
        /// Constructs 3D camera with an orthographic projection matrix with dimensions of graphics devices viewport. All changes to matrices should have apply called after changes.
        /// </summary>
        /// <param name="graphicsDevice">The graphics device to use. Will use graphics device from <see cref="Configuration"/>'s graphics device manager if this is null which it is by default.</param>
        public Camera3D(GraphicsDevice graphicsDevice = null)
        {
            graphicsDevice = graphicsDevice ?? (Configuration.GraphicsDeviceManager.GraphicsDevice);
            this.graphicsDevice = graphicsDevice;
            worldMatrix = Matrix.Identity;
            lookAt = Vector3.Forward;
            upDirection = Vector3.Up;

            projectionMatrix = Matrix.Identity;

            BasicEffect = new BasicEffect(graphicsDevice);
            BasicEffect.TextureEnabled = true;
            BasicEffect.VertexColorEnabled = true;
            Apply();
        }

        /// <summary>
        /// Applies the changes to the fields and properties of the camera.
        /// </summary>
        public virtual void Apply()
        {
            ViewMatrix = Matrix.CreateLookAt(position, lookAt, upDirection);
            worldMatrix *= Matrix.CreateScale(worldScale);

            BasicEffect.World = worldMatrix;
            BasicEffect.View = ViewMatrix;
            BasicEffect.Projection = projectionMatrix;
        }

        /// <summary>
        /// Moves camera by the given amount.
        /// </summary>
        /// <param name="move">A <see cref="Vector3"/> that contains how much in each direction to move.</param>
        public void MoveCamera(Vector3 move)
        {
            position += move;
            Apply();
        }
    }
}