//#define USE_COMMANDS



using System.IO;

using Delta.Engine;

using Delta.InputSystem;

using Delta.InputSystem.Devices;

using Delta.Utilities;

using Delta.Utilities.Datatypes;

using Delta.Utilities.Helpers;

using NUnit.Framework;



namespace Delta.Rendering.Cameras

{

	/// <summary>

	/// 3D camera that support setting of position and target.

	/// </summary>

	/// <remarks>

	/// With this camera you can apply behaviour of looking at given target or

	/// move around given target.

	/// </remarks>

	public class LookAtCamera : BaseCamera

	{

		#region Constants



		#region ImplementationVersion

		/// <summary>

		/// The current version of the implementation of this Camera class.

		/// </summary>

		private const int ImplementationVersion = 1;

		#endregion



		#region MPS

		/// <summary>

		/// The Move speed Per Second.

		/// </summary>

		private const float MPS = 100.0f;

		#endregion



		#region MouseSpeedFactor

		/// <summary>

		/// Speed multiplier for mouse control

		/// </summary>

		private const float MouseSpeedFactor = 2.75f;

		#endregion



		#region KeyboardSpeedFactor

		/// <summary>

		/// Speed multiplier for keyboard control

		/// </summary>

		private const float KeyboardSpeedFactor = 1.0f;

		#endregion



		#region MinPitchRotation

		/// <summary>

		/// Limit for looking down

		/// </summary>

		private const float MinPitchRotation = -90 + 1; //2;

		#endregion



		#region MaxPitchRotation

		/// <summary>

		/// Limit for looking up

		/// </summary>

		private const float MaxPitchRotation = +90 - 1; //2;

		#endregion



		#region DefaultLookAtCamPosition

		/// <summary>

		/// A default position which can be used if the current camera position

		/// value isn't known (in the constructor).

		/// </summary>

		public static readonly Vector DefaultLookAtCamPosition =

			new Vector(0.0f, -5.0f, 5.0f);

		#endregion



		#region DefaultTargetPosition

		/// <summary>

		/// A position to a default target twhich can be used if the current camera

		/// target position value isn't known (in the constructor).

		/// </summary>

		public static readonly Vector DefaultTargetPosition = Vector.Zero;

		#endregion



		#endregion



		#region Public



		#region Position (override)

		/// <summary>

		/// The camera position.

		/// </summary>

		public override Vector Position

		{

			get

			{

				return position;

			}

			set

			{

				// At first directly set the new position

				position = value;

				SetPositionValues();

			}

		}

		#endregion



		#region Target (override)

		/// <summary>

		/// Target

		/// </summary>

		public override Vector Target

		{

			get

			{

				return target;

			}

			set

			{

				// Set the new target (position)

				target = value;

				SetPositionValues();

			}

		}

		#endregion



		#region Distance (override)

		/// <summary>

		/// The distance between target position and camera position

		/// </summary>

		public override float Distance

		{

			get

			{

				return base.Distance;

			}

			set

			{

				base.Distance = value;

				UpdatePosition();

			} // set

		}



		// Distance

		#endregion



		#endregion



		#region Private

		/// <summary>

		/// Used to be able to reset the position to constructor time

		/// </summary>

		private Vector defaultPosition;



		/// <summary>

		/// Used to be able to reset the target to constructor time

		/// </summary>

		private Vector defaultTarget;



		/// <summary>

		/// Flag determining if shift is pressed.

		/// Used to make the speed multiplier slower.

		/// </summary>

		private bool shiftPressed;



		/// <summary>

		/// Flag determining if control is pressed.

		/// Used to make the speed multiplier faster.

		/// </summary>

		private bool ctrlPressed;



		#region SpeedMultiplier

		/// <summary>

		/// Speed multiplier for every movement

		/// </summary>

		private float SpeedMultiplier

		{

			get

			{

				return shiftPressed

				       	? SlowMultiplier

				       	: (ctrlPressed

				       	   	? FastMultiplier

				       	   	: 1.0f);

			}

		}

		#endregion



		#region MoveSpeed

		/// <summary>

		/// Movespeed per second over time.

		/// </summary>

		private static float MoveSpeed

		{

			get

			{

				return MPS * Time.Delta;

			} // get

		}

		#endregion



		#endregion



		#region Constructor

		/// <summary>

		/// Create look at camera

		/// </summary>

		/// <param name="setPosition">Camera initial position.</param>

		public LookAtCamera(Vector setPosition)

			: this(setPosition, DefaultTargetPosition)

		{

		}



		/// <summary>

		/// Create look at camera

		/// </summary>

		/// <param name="setPosition">Camera initial position.</param>

		/// <param name="setTarget">Camera initial target.</param>

		public LookAtCamera(Vector setPosition, Vector setTarget)

			: base(setPosition)

		{

			target = setTarget;

			SetPositionValues();



			// Store defaults

			defaultPosition = setPosition;

			defaultTarget = setTarget;

			shiftPressed = false;

			ctrlPressed = false;

		}

		#endregion



		#region UpdateViewMatrix (override)

		/// <summary>

		/// Update view matrix

		/// </summary>

		protected override void UpdateViewMatrix()

		{

			// Create a standard look at matrix

			viewMatrix = Matrix.CreateLookAt(Position, Target, UpVector);

		}

		#endregion



		#region SetupInputCommands (override)

		/// <summary>

		/// Setup the connection between input commands and camera movement.

		/// </summary>

		protected override void SetupInputCommands()

		{

			// Make sure the commands are used (to allow quitting with Escape)

			if (Input.Commands == null)

			{

				return;

			}



		}

		#endregion



		#region Zoom

		/// <summary>

		/// Zoom in or out. if respectFPS is set to true, Time.Delta will be taken

		/// into account. E.g.: set this to true for hold-able buttons.

		/// </summary>

		/// <param name="zoomIn">if set to <c>true</c> [zoom in].</param>

		public void Zoom(bool zoomIn, bool respectFps)

		{

			if (IsLocked)

			{

				return;

			}

			float zoomSpeed = MathHelper.Max(Distance, 0.1f) * 0.1f *

			                  SpeedMultiplier * (respectFps

			                                     	? (Time.Delta * 10f)

			                                     	: 1f);

			// Limit zoomSpeed, else we get into millions too quickly

			zoomSpeed = MathHelper.Min(zoomSpeed, 100000 * Time.Delta);

			Distance += zoomIn

			            	? -zoomSpeed

			            	: zoomSpeed;

		}

		#endregion





		#region RotateHorizontal

		/// <summary>

		/// Rotate horizontal

		/// </summary>

		/// <param name="left">if set to <c>true</c> [left].</param>

		public void RotateHorizontal(bool left)

		{

			if (IsLocked)

			{

				return;

			}

			rotation.X +=

				MPS * 0.05f * KeyboardSpeedFactor *

				(left

				 	? -SpeedMultiplier

				 	: SpeedMultiplier) * (Time.Delta * 10f);

			UpdatePosition();

		}

		#endregion



		#region RotateVertical

		/// <summary>

		/// Rotate vertical

		/// </summary>

		/// <param name="up">if set to <c>true</c> [up].</param>

		public void RotateVertical(bool up)

		{

			if (IsLocked)

			{

				return;

			}

			rotation.Y +=

				MPS * 0.05f * KeyboardSpeedFactor *

				(up

				 	? SpeedMultiplier

				 	: -SpeedMultiplier) * (Time.Delta * 10f);

			UpdatePosition();

		}

		#endregion



		#region ResetCamera

		/// <summary>

		/// Resets camera position/rotation to values at constructor time

		/// </summary>

		public void ResetCamera()

		{

			position = defaultPosition;

			target = defaultTarget;

			SetPositionValues();



			UpdatePosition();

		}

		#endregion



		#region UpdatePosition

		/// <summary>

		/// Update position

		/// </summary>

		private void UpdatePosition()

		{

			// Always clamp the up-down rotation so we don't rotate "over" the

			// up-vector to avoid the "flipping problem"

			rotation.Y = MathHelper.Clamp(rotation.Y, MinPitchRotation,

				MaxPitchRotation);



			Matrix rotationMatrix = Matrix.Identity;

			// Matrix.CreateRotationY(Z) - We don't need here the "Roll" rotation

			Matrix xRotation = Matrix.CreateRotationX(rotation.Y);

			Matrix zRotation = Matrix.CreateRotationZ(rotation.X);

			Matrix.Multiply(ref xRotation, ref zRotation, ref rotationMatrix);



			// We have to invert here the look vector, because to compute the

			// position we have to "go" from the target to the position instead of

			// "looking" case which is the other case (-> look from position to the

			// target)

			Vector lookVector = new Vector(0f, Distance, 0f);

			Vector.TransformNormal(ref lookVector, ref rotationMatrix, ref position);

			Vector.Add(ref position, ref target, out position);

		}

		#endregion



		#region SetPositionValues

		/// <summary>

		/// Set position values

		/// Used by the Position and Target properties.

		/// </summary>

		private void SetPositionValues()

		{

			// and we have to clear the current rotation now, because the new

			// position is already "final"



			// Now we still need to know the new direction we have to look to the

			// (old) target

			Vector.Subtract(ref target, ref position, out lookDirection);

			// and store the new distance to (in base because we want to avoid the

			// unnecessary UpdatePosition() call from Distance here)

			distance = lookDirection.Length;

			lookDirection.Normalize();



			// Position.Z = sin(Rotation.X) -> see trigonometrical functions

			// Note: we consider at the moment only the x rotation, because we don't

			// have any rotation on y or z (with default values)

			rotation.Y = MathHelper.Asin(-LookDirection.Z);

			rotation.X = -MathHelper.Atan(-LookDirection.X, -lookDirection.Y);

		}

		#endregion



		#region ISaveLoadBinary Members



		#region Save (override)

		/// <summary>

		/// Override saving data from BinaryStream.

		/// </summary>

		/// <param name="dataWriter">Binary writer used for writing data.</param>

		public override void Save(BinaryWriter dataWriter)

		{

			base.Save(dataWriter);



			// Save the implementation version first

			dataWriter.Write(ImplementationVersion);



			// and then all required values

			defaultPosition.Save(dataWriter);

			defaultTarget.Save(dataWriter);

		}

		#endregion



		#region Load (override)

		/// <summary>

		/// Override loading data from BinaryStream.

		/// </summary>

		/// <param name="reader">Binary reader used for reading data.</param>

		public override void Load(BinaryReader reader)

		{

			base.Load(reader);



			// First read the implementation version

			int version = reader.ReadInt32();

			switch (version)

			{

					// Version 1

				case 1:

					// Now just read the saved values

					defaultPosition = new Vector(reader);

					defaultTarget = new Vector(reader);

					break;



				default:

					Log.InvalidVersionWarning(GetType().Name + ": " + Name,

						version, ImplementationVersion);

					break;

			} // switch

		}

		#endregion



		#endregion



		#region Tests

		/// <summary>

		/// Tests

		/// </summary>

		internal class LookAtCameraTests

		{

			#region TestSaveAndLoad (LongRunning)

			/// <summary>

			/// Test save and load functionality of the Graph class

			/// </summary>

			[Test, Category("LongRunning")]

			public void TestSaveAndLoad()

			{

				// Creation of the graph

				LookAtCamera lookAtCamera = new LookAtCamera(new Vector(3, -6, 8))

				{

					// BaseCamera

					LookDirection = new Vector(-1, 2, -1),

					Target = new Vector(3, 4, 1),

					Rotation = new Vector(3, 1, 0),

					FieldOfView = 65,

					FarPlane = 205,

					NearPlane = 0.15f,

					AlwaysNeedsUpdate = true,

					IsLocked = true,

					// LookAtCamera

					defaultPosition = new Vector(0, -5, 9),

					defaultTarget = new Vector(3, 3, 1),

				};



				// Saving

				MemoryStream savedStream = new MemoryStream();

				BinaryWriter writer = new BinaryWriter(savedStream);

				lookAtCamera.Save(writer);

				writer.Flush();

				writer = null;



				// Loading

				savedStream.Position = 0;

				BinaryReader reader = new BinaryReader(savedStream);

				LookAtCamera loadedCamera = new LookAtCamera(Vector.Zero);

				loadedCamera.Load(reader);



				// Checking

				// BaseCamera values

				Assert.Equal(loadedCamera.LookDirection, lookAtCamera.LookDirection);

				Assert.Equal(loadedCamera.Target, lookAtCamera.Target);

				Assert.Equal(loadedCamera.Rotation, lookAtCamera.Rotation);

				Assert.Equal(loadedCamera.FieldOfView, lookAtCamera.FieldOfView);

				Assert.Equal(loadedCamera.FarPlane, lookAtCamera.FarPlane);

				Assert.Equal(loadedCamera.NearPlane, lookAtCamera.NearPlane);

				Assert.Equal(loadedCamera.AlwaysNeedsUpdate,

					lookAtCamera.AlwaysNeedsUpdate);

				Assert.Equal(loadedCamera.IsLocked, lookAtCamera.IsLocked);

				// LookAtCamera values

				Assert.Equal(loadedCamera.defaultPosition,

					lookAtCamera.defaultPosition);

				Assert.Equal(loadedCamera.defaultTarget, lookAtCamera.defaultTarget);

			}

			#endregion

		}

		#endregion

	}

}