/******************************************************************************
 * Spine Runtimes Software License v2.5
 *
 * Copyright (c) 2013-2016, Esoteric Software
 * All rights reserved.
 *
 * You are granted a perpetual, non-exclusive, non-sublicensable, and
 * non-transferable license to use, install, execute, and perform the Spine
 * Runtimes software and derivative works solely for personal or internal
 * use. Without the written permission of Esoteric Software (see Section 2 of
 * the Spine Software License Agreement), you may not (a) modify, translate,
 * adapt, or develop new applications using the Spine Runtimes or otherwise
 * create derivative works or improvements of the Spine Runtimes or (b) remove,
 * delete, alter, or obscure any trademarks or any copyright, trademark, patent,
 * or other intellectual property or proprietary rights notices on or in the
 * Software, including any copy thereof. Redistributions in binary or source
 * form must include this license and terms.
 *
 * THIS SOFTWARE IS PROVIDED BY ESOTERIC SOFTWARE "AS IS" AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
 * EVENT SHALL ESOTERIC SOFTWARE BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES, BUSINESS INTERRUPTION, OR LOSS OF
 * USE, DATA, OR PROFITS) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
 * IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *****************************************************************************/
using UnityEngine;

namespace Spine.Unity {
	[DisallowMultipleComponent]
	public sealed class SkeletonAnimationFixedTimestep : MonoBehaviour {
		#region Inspector
		public SkeletonAnimation skeletonAnimation;

		[Tooltip("The duration of each frame in seconds. For 12fps: enter '1/12' in the Unity inspector.")]
		public float frameDeltaTime = 1 / 15f;

		[Header("Advanced")]
		[Tooltip("The maximum number of fixed timesteps. If the game framerate drops below the If the framerate is consistently faster than the limited frames, this does nothing.")]
		public int maxFrameSkip = 4;

		[Tooltip("If enabled, the Skeleton mesh will be updated only on the same frame when the animation is updated./n/nDisable this or call SkeletonAnimation.LateUpdate yourself if you are modifying the Skeleton using other components that don't run in the same fixed timestep.")]
		public bool frameskipMeshUpdate = true;

		[Tooltip("This is the amount the internal accumulator starts with. Set it to some fraction of your frame delta time if you want to stagger updates between multiple skeletons.")]
		public float timeOffset;
		#endregion

		float accumulatedTime = 0;
		bool requiresNewMesh;

		void OnValidate () {
			skeletonAnimation = GetComponent<SkeletonAnimation>();
			if (frameDeltaTime <= 0) frameDeltaTime = 1 / 60f;
			if (maxFrameSkip <= 1) maxFrameSkip = 1;
		}

		void Awake () {
			requiresNewMesh = true;
			accumulatedTime = timeOffset;
		}

		void Update () {
			if (skeletonAnimation.enabled)
				skeletonAnimation.enabled = false;

			accumulatedTime += Time.deltaTime;

			float frames = 0;
			while (accumulatedTime >= frameDeltaTime) {
				frames++;
				if (frames > maxFrameSkip) break;
				accumulatedTime -= frameDeltaTime;
			}

			if (frames > 0) {
				skeletonAnimation.Update(frames * frameDeltaTime);
				requiresNewMesh = true;
			}	
		}

		void LateUpdate () {
			if (frameskipMeshUpdate && !requiresNewMesh) return;

			skeletonAnimation.LateUpdate();
			requiresNewMesh = false;
		}
	}
}