#if UNITY_EDITOR
using System;
using System.IO;
using System.Linq;
using UnityEditor;
using UnityEngine;
using Object = UnityEngine.Object;

/// <summary>Bake an upright, grounded, periodic in-place gait onto this exact bind.</summary>
public static class FinalizeAnimalWalk
{
    const string Root = "Assets/Bundles/Characters/Animal/RockBall";
    sealed class Pose
    {
        public Vector3[] p, s;
        public Quaternion[] q;
    }
    static Pose Read(Transform[] bones) => new Pose {
        p=bones.Select(t=>t.localPosition).ToArray(), s=bones.Select(t=>t.localScale).ToArray(),
        q=bones.Select(t=>t.localRotation).ToArray() };
    static void Write(Transform[] bones, Pose pose)
    {
        for(int i=0;i<bones.Length;i++) { bones[i].localPosition=pose.p[i]; bones[i].localRotation=pose.q[i]; bones[i].localScale=pose.s[i]; }
    }
    static Vector3[] Vertices(SkinnedMeshRenderer skin)
    {
        var m=skin.sharedMesh;
        var bind=m.bindposes;
        var matrices=skin.bones.Select((b,i)=>b.localToWorldMatrix*bind[i]).ToArray();
        var weights=m.boneWeights;
        return m.vertices.Select((v,i)=> {
            var w=weights[i];
            return matrices[w.boneIndex0].MultiplyPoint3x4(v)*w.weight0
                +matrices[w.boneIndex1].MultiplyPoint3x4(v)*w.weight1
                +matrices[w.boneIndex2].MultiplyPoint3x4(v)*w.weight2
                +matrices[w.boneIndex3].MultiplyPoint3x4(v)*w.weight3;
        }).ToArray();
    }
    static float Bottom(GameObject model) => model.GetComponentsInChildren<SkinnedMeshRenderer>().SelectMany(Vertices).Min(v=>v.y);
    static float Difference(Pose a,Pose b)
    {
        float sum=0;
        for(int i=0;i<a.q.Length;i++) sum+=Mathf.Pow(Quaternion.Angle(a.q[i],b.q[i]),2)+10000*(a.p[i]-b.p[i]).sqrMagnitude;
        return Mathf.Sqrt(sum/a.q.Length);
    }
    public static string Run(float strideMeters = .06f, float liftMeters = .018f, float cycleSeconds = 1.1f)
        => RunFor(Root,"RockBall",.55f,"bone_0","bone_8","bone_10",strideMeters,liftMeters,cycleSeconds,"Tools/output/rockball_walk_audit");

    public static string RunFor(string assetRoot,string actor,float height,string rootBone,string rightFoot,string leftFoot,
        float strideMeters,float liftMeters,float cycleSeconds,string reportDirectory,bool calibrateBind=false,float sourceWeight=1f)
    {
        var asset=AssetDatabase.LoadAssetAtPath<GameObject>(assetRoot+"/Rigged/"+actor+"_Rigged.fbx");
        var model=Object.Instantiate(asset);
        try
        {
            var animator=model.GetComponent<Animator>();
            if(animator!=null) animator.enabled=false;
            var bones=model.GetComponentsInChildren<Transform>().Where(t=>t!=model.transform && (t.name=="Armature" || t.name.StartsWith("bone_"))).ToArray();
            var root=bones.First(t=>t.name==rootBone);
            var feet=new[] { bones.First(t=>t.name==rightFoot),bones.First(t=>t.name==leftFoot) };
            var bindPose=Read(bones);
            var bindRotation=root.rotation;
            var bindPosition=root.position;
            float bindBottom=Bottom(model);
            float bindHeight=model.GetComponentsInChildren<SkinnedMeshRenderer>().SelectMany(Vertices).Max(v=>v.y)-bindBottom;
            float metersToBind=bindHeight/height;
            var src=AssetDatabase.LoadAllAssetsAtPath(assetRoot+"/Anims/"+actor+"_Walk.fbx").OfType<AnimationClip>().First(c=>!c.name.StartsWith("__preview__"));
            int count=Mathf.RoundToInt(src.length*30)+1;
            var poses=new Pose[count];
            Quaternion reference=Quaternion.identity;
            Pose referencePose=null;
            float referenceTilt=0;
            for(int f=0;f<count;f++)
            {
                Write(bones,bindPose);
                src.SampleAnimation(model,f/30f);
                if(f==0) { reference=root.rotation; referenceTilt=Vector3.Angle(root.up,Vector3.up); referencePose=Read(bones); }
                // Root policy is authored into the clip, never counter-rotated at runtime.
                // Remove the generated initial pitch/roll offset, retain gait deltas.
                if(calibrateBind)
                {
                    var raw=Read(bones);
                    for(int b=0;b<bones.Length;b++)
                    {
                        bones[b].localPosition=bindPose.p[b]+(raw.p[b]-referencePose.p[b])*sourceWeight;
                        bones[b].localRotation=Quaternion.Slerp(bindPose.q[b],bindPose.q[b]*Quaternion.Inverse(referencePose.q[b])*raw.q[b],sourceWeight);
                        bones[b].localScale=bindPose.s[b];
                    }
                }
                else root.rotation=bindRotation*Quaternion.Inverse(reference)*root.rotation;
                root.position=new Vector3(bindPosition.x,root.position.y,bindPosition.z);
                root.position+=Vector3.up*(bindBottom-Bottom(model));
                poses[f]=Read(bones);
            }
            // Select repeated gait phases, not an arbitrary first/last truncation.
            int first=0,last=count-1;
            float error=float.MaxValue;
            for(int a=0;a<count/4;a++)
                for(int b=Mathf.Max(a+21,count*2/3);b<count;b++)
                {
                    float d=Difference(poses[a],poses[b]);
                    if(d<error) { error=d; first=a; last=b; }
                }
            if(error>15) throw new InvalidOperationException($"No usable repeated gait phase (RMS={error:F2}). Generate a better walk.");
            int frames=last-first+1;
            var loop=new Pose[frames];
            for(int f=0;f<frames;f++)
            {
                float t=(float)f/(frames-1);
                float blend=t*t*t*(t*(6*t-15)+10); // smooth residual closure, zero derivative at ends
                var a=poses[first+f]; var begin=poses[first]; var end=poses[last];
                var p=new Pose { p=new Vector3[bones.Length],s=new Vector3[bones.Length],q=new Quaternion[bones.Length] };
                for(int i=0;i<bones.Length;i++)
                {
                    p.p[i]=a.p[i]+blend*(begin.p[i]-end.p[i]);
                    p.s[i]=a.s[i]+blend*(begin.s[i]-end.s[i]);
                    p.q[i]=a.q[i]*Quaternion.Slerp(Quaternion.identity,Quaternion.Inverse(end.q[i])*begin.q[i],blend);
                }
                Write(bones,p);
                // Author an explicit alternating short step in the OFFLINE clip bake.
                // Bone mapping and dimensions belong to this character's recipe.
                for(int foot=0;foot<feet.Length;foot++)
                {
                    float phase=2*Mathf.PI*t+foot*Mathf.PI;
                    float swing=Mathf.Max(0,Mathf.Cos(phase));
                    feet[foot].position+=Vector3.back*(Mathf.Sin(phase)*strideMeters*.5f*metersToBind)
                        +Vector3.up*(swing*swing*liftMeters*metersToBind);
                }
                root.position+=Vector3.up*(bindBottom-Bottom(model));
                loop[f]=Read(bones);
            }
            // Force identical quaternion representatives on the seam.
            for(int f=1;f<frames;f++) for(int b=0;b<bones.Length;b++)
                if(Quaternion.Dot(loop[f-1].q[b],loop[f].q[b])<0) {
                    var q=loop[f].q[b]; loop[f].q[b]=new Quaternion(-q.x,-q.y,-q.z,-q.w);
                }
            loop[frames-1]=loop[0];
            var clip=AssetDatabase.LoadAssetAtPath<AnimationClip>(assetRoot+"/Clips/Walk.anim");
            Undo.RecordObject(clip,"Bake verified in-place Walk");
            clip.ClearCurves();
            clip.frameRate=30;
            for(int b=0;b<bones.Length;b++)
            {
                string path=AnimationUtility.CalculateTransformPath(bones[b],model.transform);
                for(int component=0;component<10;component++)
                {
                    int c=component;
                    var keys=Enumerable.Range(0,frames).Select(f=>new Keyframe(cycleSeconds*f/(frames-1),
                        c<3 ? loop[f].p[b][c] : c<7 ? loop[f].q[b][c-3] : loop[f].s[b][c-7])).ToArray();
                    for(int k=0;k<frames;k++)
                    {
                        int prev=k==0 ? frames-2 : k-1, next=k==frames-1 ? 1 : k+1;
                        float tangent=(keys[next].value-keys[prev].value)*(frames-1)/(2*cycleSeconds);
                        keys[k].inTangent=tangent; keys[k].outTangent=tangent;
                    }
                    string prop=c<3 ? "m_LocalPosition."+"xyz"[c] : c<7 ? "m_LocalRotation."+"xyzw"[c-3] : "m_LocalScale."+"xyz"[c-7];
                    AnimationUtility.SetEditorCurve(clip,EditorCurveBinding.FloatCurve(path,typeof(Transform),prop),new AnimationCurve(keys));
                }
            }
            var settings=AnimationUtility.GetAnimationClipSettings(clip);
            settings.startTime=0; settings.stopTime=cycleSeconds; settings.loopTime=true; settings.loopBlend=false;
            AnimationUtility.SetAnimationClipSettings(clip,settings);
            EditorUtility.SetDirty(clip);
            AssetDatabase.SaveAssets();
            string report=$"frames={first}..{last} length={clip.length:F4} phaseRms={error:F3} sourceInitialRootTilt={referenceTilt:F3}; allBoneBindCalibration={calibrateBind} sourceWeight={sourceWeight:F3}; root bind calibration + in-place XZ + per-frame grounded skin + periodic closure; authored short-foot stride={strideMeters:F3}m lift={liftMeters:F3}m cycle={cycleSeconds:F3}s";
            string outPath=Path.GetFullPath(Path.Combine(Application.dataPath,"../../",reportDirectory,"walk_processing.txt"));
            Directory.CreateDirectory(Path.GetDirectoryName(outPath));
            File.WriteAllText(outPath,report);
            return report;
        }
        finally { Object.DestroyImmediate(model); }
    }
}
#endif