#if UNITY_EDITOR
using System.Collections.Generic;
using System.IO;
using System.Linq;
using UnityEditor;
using UnityEditor.Animations;
using UnityEngine;

public static class AnimatorSingleLayerizer
{
    [MenuItem("Tools/Animator/Make Single-Layer Copy (Selected Controller)")]
    public static void MakeSingleLayerCopy()
    {
        var srcCtrl = Selection.activeObject as AnimatorController;
        if (!srcCtrl)
        {
            EditorUtility.DisplayDialog("Select AnimatorController",
                "Select an AnimatorController in the Project view first.", "OK");
            return;
        }

        var srcPath = AssetDatabase.GetAssetPath(srcCtrl);
        var dir = Path.GetDirectoryName(srcPath).Replace('\\','/');
        var nameNoExt = Path.GetFileNameWithoutExtension(srcPath);
        var dstPath = AssetDatabase.GenerateUniqueAssetPath($"{dir}/{nameNoExt}_SingleLayer.controller");

        if (!AssetDatabase.CopyAsset(srcPath, dstPath))
        {
            EditorUtility.DisplayDialog("Copy failed", "Could not duplicate controller.", "OK");
            return;
        }

        AssetDatabase.SaveAssets();
        AssetDatabase.Refresh();

        var dstCtrl = AssetDatabase.LoadAssetAtPath<AnimatorController>(dstPath);
        if (!dstCtrl)
        {
            EditorUtility.DisplayDialog("Load failed", "Could not load duplicated controller.", "OK");
            return;
        }

        // Base layer to keep
        var baseLayer = dstCtrl.layers[0];
        var baseSM = baseLayer.stateMachine;

        // Migrate all extra layers into Base as sub state machines
        var layers = dstCtrl.layers;
        var migrated = 0;
        for (int i = 1; i < layers.Length; i++)
        {
            var srcLayer = layers[i];
            var sub = baseSM.AddStateMachine($"L_{srcLayer.name}");
            CopyStateMachineRecursively(srcLayer.stateMachine, sub);
            migrated++;
        }

        // Remove extra layers (only Base remains)
        dstCtrl.layers = new[] { baseLayer };

        EditorUtility.SetDirty(dstCtrl);
        AssetDatabase.SaveAssets();
        Debug.Log($"[SingleLayerizer] Created: {dstPath}\nMigrated layers: {migrated}\nBase layer kept: {baseLayer.name}");
        EditorGUIUtility.PingObject(dstCtrl);
    }

    // --------- Copy helpers ---------

    static void CopyStateMachineRecursively(AnimatorStateMachine src, AnimatorStateMachine dst)
    {
        // Maps to reconnect transitions
        var stateMap = new Dictionary<AnimatorState, AnimatorState>();
        var smMap    = new Dictionary<AnimatorStateMachine, AnimatorStateMachine> { { src, dst } };

        // Copy child states
        foreach (var cs in src.states)
        {
            var s = cs.state;
            var newS = dst.AddState(s.name);
            newS.motion = s.motion;
            newS.speed = s.speed;
            newS.speedParameter = s.speedParameter;
            newS.speedParameterActive = s.speedParameterActive;
            newS.writeDefaultValues = s.writeDefaultValues;
            newS.mirror = s.mirror;
            newS.mirrorParameter = s.mirrorParameter;
            newS.mirrorParameterActive = s.mirrorParameterActive;
#if UNITY_2021_2_OR_NEWER
            newS.timeParameter = s.timeParameter;
            newS.timeParameterActive = s.timeParameterActive;
#endif
            stateMap[s] = newS;
        }

        // Copy child state machines (recursive)
        foreach (var csm in src.stateMachines)
        {
            var newSM = dst.AddStateMachine(csm.stateMachine.name);
            smMap[csm.stateMachine] = newSM;
            CopyStateMachineRecursively(csm.stateMachine, newSM);
        }

        // Default state
        if (src.defaultState && stateMap.TryGetValue(src.defaultState, out var mappedDefault))
            dst.defaultState = mappedDefault;

        // AnyState transitions (only to states; ignore to sub-SMs)
        foreach (var t in src.anyStateTransitions)
        {
            if (t.destinationState && stateMap.TryGetValue(t.destinationState, out var to))
            {
                var nt = dst.AddAnyStateTransition(to);
                CopyTransitionSettings(t, nt);
            }
        }

        // State → State transitions
        foreach (var cs in src.states)
        {
            var from = cs.state;
            if (!stateMap.TryGetValue(from, out var mappedFrom)) continue;

            foreach (var t in from.transitions)
            {
                if (t.destinationState && stateMap.TryGetValue(t.destinationState, out var to))
                {
                    var nt = mappedFrom.AddTransition(to);
                    CopyTransitionSettings(t, nt);
                }
            }
        }

        // NOTE: Entry transitions and StateMachine → StateMachine transitions are skipped
        // because AnimatorTransition doesn't expose the same API surface.
        // DefaultState should cover standard entry behavior.
    }

    static void CopyTransitionSettings(AnimatorStateTransition src, AnimatorStateTransition dst)
    {
        dst.hasExitTime = src.hasExitTime;
        dst.exitTime = src.exitTime;
        dst.hasFixedDuration = src.hasFixedDuration;
        dst.duration = src.duration;
        dst.offset = src.offset;
        dst.interruptionSource = src.interruptionSource;
        dst.orderedInterruption = src.orderedInterruption;
        dst.canTransitionToSelf = src.canTransitionToSelf;

        // Conditions
        foreach (var c in src.conditions)
            dst.AddCondition(c.mode, c.threshold, c.parameter);
    }
}
#endif