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 Camera
    {
        /// <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; private set; }

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

        /// <summary>
        /// The final transformation matrix.
        /// </summary>
        public Matrix TransformationMatrix { get; private set; }

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

        /// <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 Camera(GraphicsDevice graphicsDevice = null)
        {
            this.graphicsDevice = graphicsDevice ?? (Configuration.GraphicsDeviceManager.GraphicsDevice);

            position.Z = 0;
            worldMatrix = Matrix.Identity;
            lookAt = Vector3.Forward;
            upDirection = Vector3.Up;
            Center();
            projectionMatrix = Matrix.CreateOrthographic(graphicsDevice.Viewport.Width, graphicsDevice.Viewport.Height, 0, 1);
            Apply();
        }

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

        /// <summary>
        /// Centers the camera to middle of width and height of game window.
        /// </summary>
        public void Center()
        {
            position.X = this.graphicsDevice.Viewport.Width * 0.5f;
            position.Y = this.graphicsDevice.Viewport.Height * 0.5f;
        }
    }
}