/******************************************************************************
 * 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.
 *****************************************************************************/

#if UNITY_2018_3 || UNITY_2019 || UNITY_2018_3_OR_NEWER
#define NEW_PREFAB_SYSTEM
#endif

using System;
using UnityEngine;

namespace Spine.Unity {

	/// <summary>Sets a GameObject's transform to match a bone on a Spine skeleton.</summary>
	#if NEW_PREFAB_SYSTEM
	[ExecuteAlways]
	#else
	[ExecuteInEditMode]
	#endif
	[AddComponentMenu("Spine/BoneFollower")]
	[HelpURL("http://esotericsoftware.com/spine-unity#BoneFollower")]
	public class BoneFollower : MonoBehaviour {

		#region Inspector
		public SkeletonRenderer skeletonRenderer;
		public SkeletonRenderer SkeletonRenderer {
			get { return skeletonRenderer; }
			set {
				skeletonRenderer = value;
				Initialize();
			}
		}

		/// <summary>If a bone isn't set in code, boneName is used to find the bone at the beginning. For runtime switching by name, use SetBoneByName. You can also set the BoneFollower.bone field directly.</summary>
		[SpineBone(dataField: "skeletonRenderer")]
		public string boneName;

		public bool followXYPosition = true;
		public bool followZPosition = true;
		public bool followBoneRotation = true;

		[Tooltip("Follows the skeleton's flip state by controlling this Transform's local scale.")]
		public bool followSkeletonFlip = true;

		[Tooltip("Follows the target bone's local scale. BoneFollower cannot inherit world/skewed scale because of UnityEngine.Transform property limitations.")]
		public bool followLocalScale = false;

		public enum AxisOrientation {
			XAxis = 1,
			YAxis
		}
		[Tooltip("Applies when 'Follow Skeleton Flip' is disabled but 'Follow Bone Rotation' is enabled."
			+ " When flipping the skeleton by scaling its Transform, this follower's rotation is adjusted"
			+ " instead of its scale to follow the bone orientation. When one of the axes is flipped, "
			+ " only one axis can be followed, either the X or the Y axis, which is selected here.")]
		public AxisOrientation maintainedAxisOrientation = AxisOrientation.XAxis;

		[UnityEngine.Serialization.FormerlySerializedAs("resetOnAwake")]
		public bool initializeOnAwake = true;
		#endregion

		[NonSerialized] public bool valid;
		[NonSerialized] public Bone bone;

		Transform skeletonTransform;
		bool skeletonTransformIsParent;

		/// <summary>
		/// Sets the target bone by its bone name. Returns false if no bone was found. To set the bone by reference, use BoneFollower.bone directly.</summary>
		public bool SetBone (string name) {
			bone = skeletonRenderer.skeleton.FindBone(name);
			if (bone == null) {
				Debug.LogError("Bone not found: " + name, this);
				return false;
			}
			boneName = name;
			return true;
		}

		public void Awake () {
			if (initializeOnAwake) Initialize();
		}

		public void HandleRebuildRenderer (SkeletonRenderer skeletonRenderer) {
			Initialize();
		}

		public void Initialize () {
			bone = null;
			valid = skeletonRenderer != null && skeletonRenderer.valid;
			if (!valid) return;

			skeletonTransform = skeletonRenderer.transform;
			skeletonRenderer.OnRebuild -= HandleRebuildRenderer;
			skeletonRenderer.OnRebuild += HandleRebuildRenderer;
			skeletonTransformIsParent = Transform.ReferenceEquals(skeletonTransform, transform.parent);

			if (!string.IsNullOrEmpty(boneName))
				bone = skeletonRenderer.skeleton.FindBone(boneName);

			#if UNITY_EDITOR
			if (Application.isEditor)
				LateUpdate();
			#endif
		}

		void OnDestroy () {
			if (skeletonRenderer != null)
				skeletonRenderer.OnRebuild -= HandleRebuildRenderer;
		}

		public void LateUpdate () {
			if (!valid) {
				Initialize();
				return;
			}

			#if UNITY_EDITOR
			if (!Application.isPlaying)
				skeletonTransformIsParent = Transform.ReferenceEquals(skeletonTransform, transform.parent);
			#endif

			if (bone == null) {
				if (string.IsNullOrEmpty(boneName)) return;
				bone = skeletonRenderer.skeleton.FindBone(boneName);
				if (!SetBone(boneName)) return;
			}

			Transform thisTransform = this.transform;
			float additionalFlipScale = 1;
			if (skeletonTransformIsParent) {
				// Recommended setup: Use local transform properties if Spine GameObject is the immediate parent
				thisTransform.localPosition = new Vector3(followXYPosition ? bone.worldX : thisTransform.localPosition.x,
														followXYPosition ? bone.worldY : thisTransform.localPosition.y,
														followZPosition ? 0f : thisTransform.localPosition.z);
				if (followBoneRotation) {
					float halfRotation = Mathf.Atan2(bone.c, bone.a) * 0.5f;
					if (followLocalScale && bone.scaleX < 0) // Negate rotation from negative scaleX. Don't use negative determinant. local scaleY doesn't factor into used rotation.
						halfRotation += Mathf.PI * 0.5f;

					var q = default(Quaternion);
					q.z = Mathf.Sin(halfRotation);
					q.w = Mathf.Cos(halfRotation);
					thisTransform.localRotation = q;
				}
			} else {
				// For special cases: Use transform world properties if transform relationship is complicated
				Vector3 targetWorldPosition = skeletonTransform.TransformPoint(new Vector3(bone.worldX, bone.worldY, 0f));
				if (!followZPosition) targetWorldPosition.z = thisTransform.position.z;
				if (!followXYPosition) {
					targetWorldPosition.x = thisTransform.position.x;
					targetWorldPosition.y = thisTransform.position.y;
				}

				Vector3 skeletonLossyScale = skeletonTransform.lossyScale;
				Transform transformParent = thisTransform.parent;
				Vector3 parentLossyScale = transformParent != null ? transformParent.lossyScale : Vector3.one;
				if (followBoneRotation) {
					float boneWorldRotation = bone.WorldRotationX;

					if ((skeletonLossyScale.x * skeletonLossyScale.y) < 0)
						boneWorldRotation = -boneWorldRotation;

					if (followSkeletonFlip || maintainedAxisOrientation == AxisOrientation.XAxis) {
						if ((skeletonLossyScale.x * parentLossyScale.x < 0))
							boneWorldRotation += 180f;
					}
					else {
						if ((skeletonLossyScale.y * parentLossyScale.y < 0))
							boneWorldRotation += 180f;
					}

					Vector3 worldRotation = skeletonTransform.rotation.eulerAngles;
					if (followLocalScale && bone.scaleX < 0) boneWorldRotation += 180f;
					thisTransform.SetPositionAndRotation(targetWorldPosition, Quaternion.Euler(worldRotation.x, worldRotation.y, worldRotation.z + boneWorldRotation));
				} else {
					thisTransform.position = targetWorldPosition;
				}

				additionalFlipScale = Mathf.Sign(skeletonLossyScale.x * parentLossyScale.x
												* skeletonLossyScale.y * parentLossyScale.y);
			}

			Vector3 localScale = followLocalScale ? new Vector3(bone.scaleX, bone.scaleY, 1f) : new Vector3(1f, 1f, 1f);
			if (followSkeletonFlip)
				localScale.y *= Mathf.Sign(bone.skeleton.ScaleX * bone.skeleton.ScaleY) * additionalFlipScale;

			thisTransform.localScale = localScale;
		}
	}

}
