// ClassicalSharp copyright 2014-2016 UnknownShadow200 | Licensed under MIT
using System;
using ClassicalSharp.Model;
using OpenTK;

namespace ClassicalSharp {

	/// <summary> Entity component that performs model animation depending on movement speed and time. </summary>
	public sealed class AnimatedComponent {
		
		Game game;
		Entity entity;
		public AnimatedComponent( Game game, Entity entity ) {
			this.game = game;
			this.entity = entity;
		}
		
		public float legXRot, armXRot, armZRot;
		public float bobYOffset, tilt, walkTime, swing;
		internal float walkTimeO, walkTimeN, swingO, swingN;
		internal float leftXRot, leftZRot, rightXRot, rightZRot;
		
		/// <summary> Calculates the next animation state based on old and new position. </summary>
		public void UpdateAnimState( Vector3 oldPos, Vector3 newPos, double delta ) {
			walkTimeO = walkTimeN;
			swingO = swingN;
			float dx = newPos.X - oldPos.X;
			float dz = newPos.Z - oldPos.Z;
			double distance = Math.Sqrt( dx * dx + dz * dz );

			if( distance > 0.05 ) {
				float walkDelta = (float)distance * 2 * (float)(20 * delta);
				walkTimeN += walkDelta;
				swingN += (float)delta * 3;
			} else {
				swingN -= (float)delta * 3;
			}
			Utils.Clamp( ref swingN, 0, 1 );
		}
		
		const float armMax = 60 * Utils.Deg2Rad;
		const float legMax = 80 * Utils.Deg2Rad;
		const float idleMax = 3 * Utils.Deg2Rad;
		const float idleXPeriod = (float)(2 * Math.PI / 5.0f);
		const float idleZPeriod = (float)(2 * Math.PI / 3.5f);
		
		/// <summary> Calculates the interpolated state between the last and next animation state. </summary>
		public void GetCurrentAnimState( float t ) {
			swing = Utils.Lerp( swingO, swingN, t );
			walkTime = Utils.Lerp( walkTimeO, walkTimeN, t );
			float idleTime = (float)game.accumulator;
			float idleXRot = (float)(Math.Sin( idleTime * idleXPeriod ) * idleMax);
			float idleZRot = (float)(idleMax + Math.Cos(idleTime * idleZPeriod) * idleMax);
			
			armXRot = (float)(Math.Cos( walkTime ) * swing * armMax) - idleXRot;
			legXRot = -(float)(Math.Cos( walkTime ) * swing * legMax);
			armZRot = -idleZRot;
			
			bobYOffset = (float)(Math.Abs( Math.Cos( walkTime ) ) * swing * (2.5f/16f));
			tilt = (float)Math.Cos( walkTime ) * swing * (0.15f * Utils.Deg2Rad);		
			if( entity.Model is HumanoidModel || entity.Model is ChibiModel )
				CalcHumanAnim( idleXRot, idleZRot );
		}
		
		void CalcHumanAnim( float idleXRot, float idleZRot ) {
			if( game.SimpleArmsAnim ) {
				leftXRot = armXRot; leftZRot = armZRot;
				rightXRot = -armXRot; rightZRot = -armZRot;
			} else {
				PerpendicularAnim( 0.23f, idleXRot, idleZRot, out leftXRot, out leftZRot );
				PerpendicularAnim( 0.28f, idleXRot, idleZRot, out rightXRot, out rightZRot );
				rightXRot = -rightXRot; rightZRot = -rightZRot;
			}
		}
		
		const float maxAngle = 110 * Utils.Deg2Rad;
		void PerpendicularAnim( float flapSpeed, float idleXRot, float idleZRot,
		                       out float xRot, out float zRot ) {
			float verAngle = (float)(0.5 + 0.5 * Math.Sin( walkTime * flapSpeed ) );
			zRot = -idleZRot - verAngle * swing * maxAngle;
			float horAngle = (float)(Math.Cos( walkTime ) * swing * armMax * 1.5f);
			xRot = idleXRot + horAngle;
		}
	}
}