/*
 * MIT License
 * 
 * Copyright (c) 2022 bd_
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

using System.Collections.Generic;
using System.Linq;
using UnityEditor;
using UnityEngine;
using VRC.SDKBase.Editor.BuildPipeline;

namespace nadena.dev.modular_avatar.core.editor
{
    internal static class BoneDatabase
    {
        private static Dictionary<Transform, bool> IsRetargetable = new Dictionary<Transform, bool>();

        internal static void ResetBones()
        {
            IsRetargetable.Clear();
        }

        internal static void AddMergedBone(Transform bone)
        {
            IsRetargetable[bone] = true;
        }

        internal static void MarkNonRetargetable(Transform bone)
        {
            if (IsRetargetable.ContainsKey(bone)) IsRetargetable[bone] = false;
        }

        internal static Transform GetRetargetedBone(Transform bone)
        {
            if (bone == null || !IsRetargetable.ContainsKey(bone)) return null;

            while (bone != null && IsRetargetable.ContainsKey(bone) && IsRetargetable[bone]) bone = bone.parent;

            if (IsRetargetable.ContainsKey(bone)) return null;
            return bone;
        }

        internal static IEnumerable<KeyValuePair<Transform, Transform>> GetRetargetedBones()
        {
            return IsRetargetable.Where((kvp) => kvp.Value)
                .Select(kvp => new KeyValuePair<Transform, Transform>(kvp.Key, GetRetargetedBone(kvp.Key)))
                .Where(kvp => kvp.Value != null);
        }

        public static Transform GetRetargetedBone(Transform bone, bool fallbackToOriginal)
        {
            Transform retargeted = GetRetargetedBone(bone);

            return retargeted ? retargeted : (fallbackToOriginal ? bone : null);
        }
    }

    internal class RetargetMeshes
    {
        internal void OnPreprocessAvatar(GameObject avatarGameObject)
        {
            foreach (var renderer in avatarGameObject.GetComponentsInChildren<SkinnedMeshRenderer>(true))
            {
                bool isRetargetable = false;
                foreach (var bone in renderer.bones)
                {
                    if (BoneDatabase.GetRetargetedBone(bone) != null)
                    {
                        isRetargetable = true;
                        break;
                    }
                }

                if (isRetargetable)
                {
                    new MeshRetargeter(renderer).Retarget();
                }
            }

            // Now remove retargeted bones
            if (true)
            {
                foreach (var bonePair in BoneDatabase.GetRetargetedBones())
                {
                    if (BoneDatabase.GetRetargetedBone(bonePair.Key) == null) continue;

                    var sourceBone = bonePair.Key;
                    var destBone = bonePair.Value;

                    var children = new List<Transform>();
                    foreach (Transform child in sourceBone)
                    {
                        children.Add(child);
                    }

                    foreach (Transform child in children)
                    {
                        child.SetParent(destBone, true);
                    }

                    UnityEngine.Object.DestroyImmediate(sourceBone.gameObject);
                }
            }
        }
    }

    /**
     * This class processes a given mesh, adjusting the bind poses for any bones that are to be merged to instead match
     * the bind pose of the original avatar's bone.
     */
    public class MeshRetargeter
    {
        private readonly SkinnedMeshRenderer renderer;
        private Mesh src, dst;

        struct BindInfo
        {
            public Matrix4x4 priorLocalToBone;
            public Matrix4x4 localToBone;
            public Matrix4x4 priorToNew;
        }

        public MeshRetargeter(SkinnedMeshRenderer renderer)
        {
            this.renderer = renderer;
        }

        public void Retarget()
        {
            var avatar = RuntimeUtil.FindAvatarInParents(renderer.transform);
            if (avatar == null) throw new System.Exception("Could not find avatar in parents of " + renderer.name);
            var avatarTransform = avatar.transform;

            var avPos = avatarTransform.position;
            var avRot = avatarTransform.rotation;
            var avScale = avatarTransform.lossyScale;

            avatarTransform.position = Vector3.zero;
            avatarTransform.rotation = Quaternion.identity;
            avatarTransform.localScale = Vector3.one;

            src = renderer.sharedMesh;
            dst = Mesh.Instantiate(src);
            dst.name = "RETARGETED: " + src.name;

            RetargetBones();
            AdjustShapeKeys();

            avatarTransform.position = avPos;
            avatarTransform.rotation = avRot;
            avatarTransform.localScale = avScale;

            AssetDatabase.CreateAsset(dst, Util.GenerateAssetPath());
        }

        private void AdjustShapeKeys()
        {
            // TODO
        }

        private void RetargetBones()
        {
            var originalBindPoses = src.bindposes;
            var originalBones = renderer.bones;

            var newBones = (Transform[]) originalBones.Clone();
            var newBindPoses = (Matrix4x4[]) originalBindPoses.Clone();

            for (int i = 0; i < originalBones.Length; i++)
            {
                Transform newBindTarget = BoneDatabase.GetRetargetedBone(originalBones[i]);
                if (newBindTarget == null) continue;

                Matrix4x4 Bp = newBindTarget.worldToLocalMatrix * originalBones[i].localToWorldMatrix *
                               originalBindPoses[i];

                newBones[i] = newBindTarget;
                newBindPoses[i] = Bp;
            }

            dst.bindposes = newBindPoses;
            renderer.bones = newBones;
            renderer.sharedMesh = dst;
            renderer.rootBone = BoneDatabase.GetRetargetedBone(renderer.rootBone, true);
            renderer.probeAnchor = BoneDatabase.GetRetargetedBone(renderer.probeAnchor, true);
        }
    }
}