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

namespace Test3D.Objects
{
    public class Camera
    {
        // We need this to calculate the aspectRatio in the ProjectionMatrix property.
        GraphicsDevice graphicsDevice;

        Vector3 position = new Vector3();
        Vector3 rotation = new Vector3();

        Vector3 up;
        Vector3 right;
        Vector3 look;

        public enum CameraRotations
        {
            YawLeft,
            YawRight,
            PitchUp,
            PitchDown,
            RollClockwise,
            RollAntiClockwise,
        }

        public enum CameraMovements
        {
            StrafeLeft,
            StrafeRight,
            ThrustForward,
            ThrustBackward,

        }

        public Matrix ViewMatrix
        {
            get
            {
                /* To apply Roll (Z rotation) we rotate up and right around the look vector: */
                Matrix rollMatrix = Matrix.CreateFromAxisAngle(look, rotation.Z);
                up = Vector3.Transform(up, rollMatrix);
                right = Vector3.Transform(right, rollMatrix);

                /* To apply Yaw (Y rotation) we rotate the look and right vectors around the up vector: */
                Matrix yawMatrix = Matrix.CreateFromAxisAngle(up, rotation.Y);
                look = Vector3.Transform(look, yawMatrix);
                right = Vector3.Transform(right, yawMatrix);

                /* To apply Pitch (X rotation) we rotate look and up around the right vector: */
                Matrix pitchMatrix = Matrix.CreateFromAxisAngle(right, rotation.X);
                look = Vector3.Transform(look, pitchMatrix);
                up = Vector3.Transform(up, pitchMatrix);

                /* The CreateLookAt function requires a camera position, a target and an up direction.
                 * We know the camera position and the up vector but we do not know the target.
                 * However the look vector points in the direction the camera is facing so we can use that to create a target by adding it to the position.
                 */
                Vector3 target = position + look;

                return Matrix.CreateLookAt(position, target, up);
            }
        }

        public Matrix ProjectionMatrix
        {
            get
            {
                float fieldOfView = Microsoft.Xna.Framework.MathHelper.PiOver4;
                float nearClipPlane = 1;
                float farClipPlane = 200;
                float aspectRatio = graphicsDevice.Viewport.Width / (float)graphicsDevice.Viewport.Height;

                return Matrix.CreatePerspectiveFieldOfView(fieldOfView, aspectRatio, nearClipPlane, farClipPlane);
            }
        }

        public Camera(GraphicsDevice graphicsDevice)
        {
            this.graphicsDevice = graphicsDevice;
        }

        public void SetPosition(Vector3 pos)
        {
            position = pos;
        }

        public void SetRotation(Vector3 rot)
        {
            rotation = rot;
        }

        public void Rotate(CameraRotations rot, float angle)
        {
            switch (rot)
            {
                case CameraRotations.YawLeft:
                    RotateAroundY(angle);
                    break;
                case CameraRotations.YawRight:
                    RotateAroundY(-angle);
                    break;
                case CameraRotations.PitchUp:
                    RotateAroundX(angle);
                    break;
                case CameraRotations.PitchDown:
                    RotateAroundX(-angle);
                    break;
                case CameraRotations.RollClockwise:
                    RotateAroundZ(angle);
                    break;
                case CameraRotations.RollAntiClockwise:
                    RotateAroundZ(-angle);
                    break;
                default:
                    break;
            }
        }

        public void Move(CameraMovements mov, float speed)
        {
            const float unitsPerSecond = 10;

            switch (mov)
            {
                case CameraMovements.StrafeLeft:
                    position += right * unitsPerSecond * speed;
                    break;
                case CameraMovements.StrafeRight:
                    position -= right * unitsPerSecond * speed;
                    break;
                case CameraMovements.ThrustForward:
                    position += look * unitsPerSecond * speed;
                    break;
                case CameraMovements.ThrustBackward:
                    position -= look * unitsPerSecond * speed;
                    break;
                default:
                    break;
            }
        }

        private void RotateAroundY(float angle)
        {
            rotation.Y += angle;

            // keep the value in the range 0-360 (0 - 2 PI radians)
            if (rotation.Y > Math.PI * 2)
                rotation.Y -= MathHelper.Pi * 2;
            else if (rotation.Y < 0)
                rotation.Y += MathHelper.Pi * 2;
        }

        private void RotateAroundX(float angle)
        {
            rotation.X += angle;

            // keep the value in the range 0-360 (0 - 2 PI radians)
            if (rotation.X > Math.PI * 2)
                rotation.X -= MathHelper.Pi * 2;
            else if (rotation.X < 0)
                rotation.X += MathHelper.Pi * 2;
        }

        private void RotateAroundZ(float angle)
        {
            rotation.Z += angle;

            // keep the value in the range 0-360 (0 - 2 PI radians)
            if (rotation.Z > Math.PI * 2)
                rotation.Z -= MathHelper.Pi * 2;
            else if (rotation.Z < 0)
                rotation.Z += MathHelper.Pi * 2;
        }

        public void Update(GameTime gameTime)
        {
            float unit = (float)gameTime.ElapsedGameTime.TotalSeconds;

            // Rotation
            if (Keyboard.GetState().IsKeyDown(Keys.NumPad4))
            {
                Rotate(CameraRotations.YawRight, unit);
            }
            else if (Keyboard.GetState().IsKeyDown(Keys.NumPad6))
            {
                Rotate(CameraRotations.YawLeft, unit);
            }

            if (Keyboard.GetState().IsKeyDown(Keys.PageDown))
            {
                Rotate(CameraRotations.PitchDown, unit);
            }
            else if (Keyboard.GetState().IsKeyDown(Keys.PageUp))
            {
                Rotate(CameraRotations.PitchUp, unit);
            }

            if (Keyboard.GetState().IsKeyDown(Keys.NumPad1))
            {
                Rotate(CameraRotations.RollAntiClockwise, unit);
            }
            else if (Keyboard.GetState().IsKeyDown(Keys.NumPad3))
            {
                Rotate(CameraRotations.RollClockwise, unit);
            }

            // Movement
            if (Keyboard.GetState().IsKeyDown(Keys.Left))
            {
                Move(CameraMovements.StrafeLeft, unit);
            }
            else if (Keyboard.GetState().IsKeyDown(Keys.Right))
            {
                Move(CameraMovements.StrafeRight, unit);
            }

            if (Keyboard.GetState().IsKeyDown(Keys.Up))
            {
                Move(CameraMovements.ThrustForward, unit);
            }
            else if (Keyboard.GetState().IsKeyDown(Keys.Down))
            {
                Move(CameraMovements.ThrustBackward, unit);
            }
        }
    }
}