using System;
using System.Collections.Generic;
using System.Text;
using Microsoft.DirectX;
using Microsoft.DirectX.Direct3D;

namespace Camera
{
    class Camera
    {
        public Camera()
        {
            cameraUp = new Vector3(0, 1.0f, 0);
            cameraPointAt = new Vector3(0, 0, 1.0f);
        }

        public Camera(Vector3 pos)
        {
            cameraUp = new Vector3(0, 1.0f, 0);
            cameraPointAt = new Vector3(0, 0, 1.0f);

            worldPosition = pos;
            worldUp = cameraUp + pos;
            worldPointAt = cameraPointAt + pos;
        }

        /// <summary>
        /// Sets the position of the camera in world space.
        /// Also updates the worldUp and worldPointAt vectors.
        /// </summary>
        /// <param name="pos">World space position.</param>
        public void SetPosition(Vector3 pos)
        {
            worldPosition = pos;
            worldUp = cameraUp + pos;
            worldPointAt = cameraPointAt + pos;
        }

        /// <summary>
        /// Moves the camera by an offset along the x axis.
        /// Also updates the worldUp and worldPointAt vectors.
        /// </summary>
        /// <param name="m">Offset of movement along x axis.</param>
        public void MoveX(float m)
        {
            worldPosition += new Vector3(m, 0, 0);
            worldUp = cameraUp + worldPosition;
            worldPointAt = cameraPointAt + worldPosition;
        }

        /// <summary>
        /// Moves the camera by an offset along the y axis.
        /// Also updates the worldUp and worldPointAt vectors.
        /// </summary>
        /// <param name="m">Offset of movement along y axis.</param>
        public void MoveY(float m)
        {
            worldPosition += new Vector3(0, m, 0);
            worldUp = cameraUp + worldPosition;
            worldPointAt = cameraPointAt + worldPosition;
        }

        /// <summary>
        /// Moves the camera by an offset along the z axis.
        /// Also updates the worldUp and worldPointAt vectors.
        /// </summary>
        /// <param name="m">Offset of movement along y axis.</param>
        public void MoveZ(float m)
        {
            worldPosition += new Vector3(0, 0, m);
            worldUp += new Vector3(0, 0, m);
            worldPointAt += new Vector3(0, 0, m);
        }

        /// <summary>
        /// Rotates the camera on the x axis by a 
        /// given angle.
        /// </summary>
        /// <param name="theta">Angle of rotation.</param>
        public void RotateX(float theta)
        {
            // Construct Rotation Matrix
            Matrix M = Matrix.RotationX(theta);
            // Transform vectors
            cameraUp.TransformCoordinate(M);
            cameraPointAt.TransformCoordinate(M);
            // Translate vectors
            worldUp = cameraUp + pos;
            worldPointAt = cameraPointAt + pos;
        }

        /// <summary>
        /// Rotates the camera on the y axis by a 
        /// given angle.
        /// </summary>
        /// <param name="theta">Angle of rotation.</param>
        public void RotateY(float theta)
        {
            // Construct Rotation Matrix
            Matrix M = Matrix.RotationY(theta);
            // Transform vectors
            cameraUp.TransformNormal(M);
            cameraPointAt.TransformNormal(M);
            // Translate vectors
            worldUp = cameraUp + worldPosition;
            worldPointAt = cameraPointAt + worldPosition;
        }
        
        /// <summary>
        /// Rotates the camera on the z axis by a 
        /// given angle.
        /// </summary>
        /// <param name="theta">Angle of rotation.</param>
        public void RotateZ(float theta)
        {
            // Construct Rotation Matrix
            Matrix M = Matrix.RotationZ(theta);
            // Transform vectors
            cameraUp.TransformNormal(M);
            cameraPointAt.TransformNormal(M);
            // Translate vectors
            worldUp = cameraUp + worldPosition;
            worldPointAt = cameraPointAt + worldPosition;
        }

        public void LookAtPoint(Vector3 point)
        {
            // Translate point vector to camera space.
            // That way we can easily perform transformations
            // using unit vectors.
            point -= worldPosition;
            point.Normalize();

            float xDisplacement = point.X - cameraPointAt.X;
            float yDisplacement = point.Y - cameraPointAt.Y;

            // Assign point as the PointAt vector and 
            // apply displacement to the Up vector.
            cameraPointAt = point;
            cameraUp.X += xDisplacement;
            cameraUp.Y += yDisplacement;

            // Update the camera in word space.
            worldPointAt = cameraPointAt + worldPosition;
            worldUp = cameraUp + worldPosition;

        }

        public void NormalizeAll()
        {
            worldPointAt.Normalize();
            worldUp.Normalize();
            cameraPointAt.Normalize();
            cameraUp.Normalize();
        }
           
        // These properties describe the camera in world space.
        public Vector3 worldPosition;
        public Vector3 worldUp;
        public Vector3 worldPointAt;

        // These properties describe the camera in its object space.
        // There is no camera position because it is at the origin.
        // Translations of these points can be done based off the worldPosition.
        private Vector3 cameraUp;
        private Vector3 cameraPointAt;
        
    }

}