//---------------------------------------------------------------------------------------------------------------------------------------------------
// <copyright file="Camera.cs" company="DarkWynter Studios">
//     Copyright (C)2007 DarkWynter Studios.  All rights reserved.
// </copyright>
//---------------------------------------------------------------------------------------------------------------------------------------------------
// {Contact : darkwynter.com for licensing information
//---------------------------------------------------------------------------------------------------------------------------------------------------

namespace DarkWynter.Stream
{
    #region Using Statements
    using System;
    using System.Collections;
    using System.Collections.Generic;
    using Microsoft.Xna.Framework;
    using Microsoft.Xna.Framework.Content;
    using Microsoft.Xna.Framework.Graphics;
    using Microsoft.Xna.Framework.Input;
    using Microsoft.Xna.Framework.Storage;
    #endregion

    /// <summary>
    /// Camera class
    /// </summary>
    public class Camera
    {
        /// <summary>
        /// Viewport associated with this Camera
        /// </summary>
        public Viewport viewport;

        /// <summary>
        /// Allows user to move camera around relative the Mass's currentPosition 
        /// </summary>
        public static Vector3 offset = new Vector3(700, 1400, 700);
        private Vector3 firstPersonOffset = new Vector3(0, 0, 0);
        private Vector3 thirdPersonOffset = new Vector3(700, 1400, 700);

        /// <summary>
        /// Constructor
        /// </summary>
        public Camera()
        {
            viewport = new Viewport();
        }

        private void GetOffset(bool fpvEnabled)
        {
            // First person view
            if (fpvEnabled)
            {
                if (offset.Length() > firstPersonOffset.Length())
                {
                    offset -= thirdPersonOffset / 100;
                }
            }
            // Third person view
            else
            {
                if (offset.Length() < thirdPersonOffset.Length())
                {
                    offset += thirdPersonOffset / 100;
                }
            }
        }

        /// <summary>
        /// Set the 3rd person camera max distance,
        /// </summary>
        /// <param name="cameraLocation"></param>
        public static void SetCameraLocation(Vector3 cameraLocation)
        {
            offset = cameraLocation;
        }
        /// <summary>
        /// Generates the View Matrix based on the mass's position and the camera offset
        /// </summary>
        /// <param name="currentPosition">Player's current position</param>
        /// <param name="normalVector">Player's normal Vector</param>
        /// <param name="upVector">Player's up vector</param>
        /// <param name="fpvEnabled">First Person View enabled/disabled</param>
        /// <returns>View Matrix</returns>
        public Matrix GetViewMatrix(Vector3 currentPosition, Vector3 normalVector, Vector3 upVector, bool fpvEnabled)
        {
            GetOffset(fpvEnabled);

            // Calculate new camera position relative to current position
            Vector3 cameraPosition = currentPosition - (offset * normalVector);

            // Calculate new lookAtPosition in the opposite direction of cameraPosition relative to current position
            Vector3 lookAtPosition = currentPosition + normalVector + (offset * normalVector);

            // Use just the height value or camera goes wobbly sideways
            Vector3 upVec = upVector + new Vector3(0, offset.Y, 0);

            // Make sure camera doesn't go below player position (clipping)
            float buffer = 50;
            if(cameraPosition.Y < currentPosition.Y + buffer)
                cameraPosition.Y = currentPosition.Y + buffer;

            // return final view matrix
            return Matrix.CreateLookAt(
                    cameraPosition,
                    lookAtPosition,
                    upVec
                );
        }

        /// <summary>
        /// Generates the projection matrix
        /// </summary>
        /// <returns>Projection matrix</returns>
        public Matrix GetProjectionMatrix()
        {
            return

            Matrix.CreatePerspectiveFieldOfView(
                    (float)Math.PI / 4,
                    viewport.Width / viewport.Height,
                    0.3f, 100000f
                );
        }
    }
}