/******************************************************************************
 * Spine Runtimes License Agreement
 * Last updated January 1, 2020. Replaces all prior versions.
 *
 * Copyright (c) 2013-2020, Esoteric Software LLC
 *
 * Integration of the Spine Runtimes into software or otherwise creating
 * derivative works of the Spine Runtimes is permitted under the terms and
 * conditions of Section 2 of the Spine Editor License Agreement:
 * http://esotericsoftware.com/spine-editor-license
 *
 * Otherwise, it is permitted to integrate the Spine Runtimes into software
 * or otherwise create derivative works of the Spine Runtimes (collectively,
 * "Products"), provided that each user of the Products must obtain their own
 * Spine Editor license and redistribution of the Products in any form must
 * include this license and copyright notice.
 *
 * THE SPINE RUNTIMES ARE PROVIDED BY ESOTERIC SOFTWARE LLC "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 LLC 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
 * THE SPINE RUNTIMES, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *****************************************************************************/

using UnityEngine;

namespace Spine.Unity {

	/// <summary>
	/// Utility component to support flipping of hinge chains (chains of HingeJoint objects) along with the parent skeleton.
	/// Note that flipping needs to be performed by 180 degree rotation at <see cref="SkeletonUtility"/>,
	/// by setting <see cref="SkeletonUtility.flipBy180DegreeRotation"/> to true, not via negative scale.
	///
	/// Note: This component is automatically attached when calling "Create Hinge Chain" at <see cref="SkeletonUtilityBone"/>,
	/// do not attempt to use this component for other purposes.
	/// </summary>
	public class FollowSkeletonUtilityRootRotation : MonoBehaviour {

		const float FLIP_ANGLE_THRESHOLD = 100.0f;

		public Transform reference;
		Vector3 prevLocalEulerAngles;

		private void Start () {
			prevLocalEulerAngles = this.transform.localEulerAngles;
		}

		void FixedUpdate () {
			this.transform.rotation = reference.rotation;

			bool wasFlippedAroundY = Mathf.Abs(this.transform.localEulerAngles.y - prevLocalEulerAngles.y) > FLIP_ANGLE_THRESHOLD;
			bool wasFlippedAroundX = Mathf.Abs(this.transform.localEulerAngles.x - prevLocalEulerAngles.x) > FLIP_ANGLE_THRESHOLD;
			if (wasFlippedAroundY)
				CompensatePositionToYRotation();
			if (wasFlippedAroundX)
				CompensatePositionToXRotation();

			prevLocalEulerAngles = this.transform.localEulerAngles;
		}

		/// <summary>
		/// Compensates the position so that a child at the reference position remains in the same place,
		/// to counter any movement that occurred by rotation.
		/// </summary>
		void CompensatePositionToYRotation () {
			Vector3 newPosition = reference.position + (reference.position - this.transform.position);
			newPosition.y = this.transform.position.y;
			this.transform.position = newPosition;
		}

		/// <summary>
		/// Compensates the position so that a child at the reference position remains in the same place,
		/// to counter any movement that occurred by rotation.
		/// </summary>
		void CompensatePositionToXRotation () {
			Vector3 newPosition = reference.position + (reference.position - this.transform.position);
			newPosition.x = this.transform.position.x;
			this.transform.position = newPosition;
		}
	}
}
