using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using MCPForUnity.Editor.Helpers;
using Newtonsoft.Json.Linq;
using UnityEditor;
using UnityEditor.SceneManagement;
using UnityEngine;
using UnityEngine.SceneManagement;
using MCPForUnity.Runtime.Helpers;

namespace MCPForUnity.Editor.Tools.Prefabs
{
    [McpForUnityTool("manage_prefabs", AutoRegister = false)]
    /// <summary>
    /// Tool to manage Unity Prefabs: create, inspect, modify, and open/save/close prefab stage.
    /// Supports both headless editing (modify_contents) and interactive prefab stage workflows.
    /// </summary>
    public static class ManagePrefabs
    {
        // Action constants
        private const string ACTION_CREATE_FROM_GAMEOBJECT = "create_from_gameobject";
        private const string ACTION_GET_INFO = "get_info";
        private const string ACTION_GET_HIERARCHY = "get_hierarchy";
        private const string ACTION_MODIFY_CONTENTS = "modify_contents";
        private const string ACTION_OPEN_PREFAB_STAGE = "open_prefab_stage";
        private const string ACTION_SAVE_PREFAB_STAGE = "save_prefab_stage";
        private const string ACTION_CLOSE_PREFAB_STAGE = "close_prefab_stage";
        private const string SupportedActions = ACTION_CREATE_FROM_GAMEOBJECT + ", " + ACTION_GET_INFO + ", " + ACTION_GET_HIERARCHY + ", " + ACTION_MODIFY_CONTENTS + ", " + ACTION_OPEN_PREFAB_STAGE + ", " + ACTION_SAVE_PREFAB_STAGE + ", " + ACTION_CLOSE_PREFAB_STAGE;

        public static object HandleCommand(JObject @params)
        {
            if (@params == null)
            {
                return new ErrorResponse("Parameters cannot be null.");
            }

            string action = @params["action"]?.ToString()?.ToLowerInvariant();
            if (string.IsNullOrEmpty(action))
            {
                return new ErrorResponse($"Action parameter is required. Valid actions are: {SupportedActions}.");
            }

            try
            {
                switch (action)
                {
                    case ACTION_CREATE_FROM_GAMEOBJECT:
                        return CreatePrefabFromGameObject(@params);
                    case ACTION_GET_INFO:
                        return GetInfo(@params);
                    case ACTION_GET_HIERARCHY:
                        return GetHierarchy(@params);
                    case ACTION_MODIFY_CONTENTS:
                        return ModifyContents(@params);
                    case ACTION_OPEN_PREFAB_STAGE:
                    {
                        string prefabPath = @params["prefabPath"]?.ToString() ?? @params["path"]?.ToString();
                        return OpenPrefabStage(prefabPath);
                    }
                    case ACTION_SAVE_PREFAB_STAGE:
                        return SavePrefabStage();
                    case ACTION_CLOSE_PREFAB_STAGE:
                    {
                        bool saveBeforeClose = @params["saveBeforeClose"]?.ToObject<bool>() ?? false;
                        return ClosePrefabStage(saveBeforeClose);
                    }
                    default:
                        return new ErrorResponse($"Unknown action: '{action}'. Valid actions are: {SupportedActions}.");
                }
            }
            catch (Exception e)
            {
                McpLog.Error($"[ManagePrefabs] Action '{action}' failed: {e}");
                return new ErrorResponse($"Internal error: {e.Message}");
            }
        }

        #region Create Prefab from GameObject

        /// <summary>
        /// Creates a prefab asset from a GameObject in the scene.
        /// </summary>
        private static object CreatePrefabFromGameObject(JObject @params)
        {
            // 1. Validate and parse parameters
            var validation = ValidateCreatePrefabParams(@params);
            if (!validation.isValid)
            {
                return new ErrorResponse(validation.errorMessage);
            }

            string targetName = validation.targetName;
            string finalPath = validation.finalPath;
            bool includeInactive = validation.includeInactive;
            bool replaceExisting = validation.replaceExisting;
            bool unlinkIfInstance = validation.unlinkIfInstance;

            // 2. Find the source object
            GameObject sourceObject = FindSceneObjectByName(targetName, includeInactive);
            if (sourceObject == null)
            {
                return new ErrorResponse($"GameObject '{targetName}' not found in the active scene or prefab stage{(includeInactive ? " (including inactive objects)" : "")}.");
            }

            // 3. Validate source object state
            var objectValidation = ValidateSourceObjectForPrefab(sourceObject, unlinkIfInstance);
            if (!objectValidation.isValid)
            {
                return new ErrorResponse(objectValidation.errorMessage);
            }

            // 4. Check for path conflicts and track if file will be replaced
            bool fileExistedAtPath = AssetDatabase.LoadAssetAtPath<UnityEngine.Object>(finalPath) != null;

            if (!replaceExisting && fileExistedAtPath)
            {
                finalPath = AssetDatabase.GenerateUniqueAssetPath(finalPath);
                McpLog.Info($"[ManagePrefabs] Generated unique path: {finalPath}");
            }

            // 5. Ensure directory exists
            EnsureAssetDirectoryExists(finalPath);

            // 6. Unlink from existing prefab if needed
            if (unlinkIfInstance && objectValidation.shouldUnlink)
            {
                try
                {
                    // UnpackPrefabInstance requires the prefab instance root, not a child object
                    GameObject rootToUnlink = PrefabUtility.GetOutermostPrefabInstanceRoot(sourceObject);
                    if (rootToUnlink != null)
                    {
                        PrefabUtility.UnpackPrefabInstance(rootToUnlink, PrefabUnpackMode.Completely, InteractionMode.AutomatedAction);
                        McpLog.Info($"[ManagePrefabs] Unpacked prefab instance '{rootToUnlink.name}' before creating new prefab.");
                    }
                }
                catch (Exception e)
                {
                    return new ErrorResponse($"Failed to unlink prefab instance: {e.Message}");
                }
            }

            // 7. Persist any runtime-only materials so they survive prefab serialization
            var persistResult = PersistRuntimeMaterials(sourceObject, finalPath);

            // 8. Create the prefab
            try
            {
                GameObject result = CreatePrefabAsset(sourceObject, finalPath, replaceExisting);

                if (result == null)
                {
                    return new ErrorResponse($"Failed to create prefab asset at '{finalPath}'.");
                }

                // 9. Select the newly created instance
                Selection.activeGameObject = result;

                return new SuccessResponse(
                    $"Prefab created at '{finalPath}' and instance linked.",
                    new
                    {
                        prefabPath = finalPath,
                        instanceId = result.GetInstanceIDCompat(),
                        instanceName = result.name,
                        wasUnlinked = unlinkIfInstance && objectValidation.shouldUnlink,
                        wasReplaced = replaceExisting && fileExistedAtPath,
                        componentCount = result.GetComponents<Component>().Length,
                        childCount = result.transform.childCount,
                        materialsPersisted = persistResult.count
                    }
                );
            }
            catch (Exception e)
            {
                McpLog.Error($"[ManagePrefabs] Error creating prefab at '{finalPath}': {e}");
                return new ErrorResponse($"Error saving prefab asset: {e.Message}");
            }
        }

        /// <summary>
        /// Validates parameters for creating a prefab from GameObject.
        /// </summary>
        private static (bool isValid, string errorMessage, string targetName, string finalPath, bool includeInactive, bool replaceExisting, bool unlinkIfInstance)
        ValidateCreatePrefabParams(JObject @params)
        {
            string targetName = @params["target"]?.ToString() ?? @params["name"]?.ToString();
            if (string.IsNullOrEmpty(targetName))
            {
                return (false, "'target' parameter is required for create_from_gameobject.", null, null, false, false, false);
            }

            string requestedPath = @params["prefabPath"]?.ToString();
            if (string.IsNullOrWhiteSpace(requestedPath))
            {
                return (false, "'prefabPath' parameter is required for create_from_gameobject.", targetName, null, false, false, false);
            }

            string sanitizedPath = AssetPathUtility.SanitizeAssetPath(requestedPath);
            if (sanitizedPath == null)
            {
                return (false, $"Invalid prefab path (path traversal detected): '{requestedPath}'", targetName, null, false, false, false);
            }
            if (string.IsNullOrEmpty(sanitizedPath))
            {
                return (false, $"Invalid prefab path '{requestedPath}'. Path cannot be empty.", targetName, null, false, false, false);
            }
            if (!sanitizedPath.EndsWith(".prefab", StringComparison.OrdinalIgnoreCase))
            {
                sanitizedPath += ".prefab";
            }

            // Validate path is within Assets folder
            if (!sanitizedPath.StartsWith("Assets/", StringComparison.OrdinalIgnoreCase))
            {
                return (false, $"Prefab path must be within the Assets folder. Got: '{sanitizedPath}'", targetName, null, false, false, false);
            }

            bool includeInactive = @params["searchInactive"]?.ToObject<bool>() ?? false;
            bool replaceExisting = @params["allowOverwrite"]?.ToObject<bool>() ?? false;
            bool unlinkIfInstance = @params["unlinkIfInstance"]?.ToObject<bool>() ?? false;

            return (true, null, targetName, sanitizedPath, includeInactive, replaceExisting, unlinkIfInstance);
        }

        /// <summary>
        /// Validates source object can be converted to prefab.
        /// </summary>
        private static (bool isValid, string errorMessage, bool shouldUnlink, string existingPrefabPath)
            ValidateSourceObjectForPrefab(GameObject sourceObject, bool unlinkIfInstance)
        {
            // Check if this is a Prefab Asset (the .prefab file itself in the editor)
            if (PrefabUtility.IsPartOfPrefabAsset(sourceObject))
            {
                return (false,
                    $"GameObject '{sourceObject.name}' is part of a prefab asset. " +
                    "Open the prefab stage to save changes instead.",
                    false, null);
            }

            // Check if this is already a Prefab Instance
            PrefabInstanceStatus status = PrefabUtility.GetPrefabInstanceStatus(sourceObject);
            if (status != PrefabInstanceStatus.NotAPrefab)
            {
                string existingPath = PrefabUtility.GetPrefabAssetPathOfNearestInstanceRoot(sourceObject);

                if (!unlinkIfInstance)
                {
                    return (false,
                        $"GameObject '{sourceObject.name}' is already linked to prefab '{existingPath}'. " +
                        "Set 'unlinkIfInstance' to true to unlink it first, or modify the existing prefab instead.",
                        false, existingPath);
                }

                // Needs to be unlinked
                return (true, null, true, existingPath);
            }

            return (true, null, false, null);
        }

        /// <summary>
        /// Creates a prefab asset from a GameObject.
        /// </summary>
        private static GameObject CreatePrefabAsset(GameObject sourceObject, string path, bool replaceExisting)
        {
            GameObject result = PrefabUtility.SaveAsPrefabAssetAndConnect(
                sourceObject,
                path,
                InteractionMode.AutomatedAction
            );

            string action = replaceExisting ? "Replaced existing" : "Created new";
            McpLog.Info($"[ManagePrefabs] {action} prefab at '{path}'.");

            if (result != null)
            {
                AssetDatabase.SaveAssets();
                AssetDatabase.Refresh();
            }

            return result;
        }

        /// <summary>
        /// Scans all Renderers in the hierarchy and persists any runtime-only materials
        /// (MaterialPropertyBlock overrides or in-memory instances from renderer.material)
        /// as .mat assets so they survive prefab serialization.
        /// </summary>
        private static (int count, List<string> paths) PersistRuntimeMaterials(GameObject root, string prefabPath)
        {
            var renderers = root.GetComponentsInChildren<Renderer>(true);
            var persistedPaths = new List<string>();
            string prefabDir = Path.GetDirectoryName(prefabPath).Replace("\\", "/");
            string materialsFolder = $"{prefabDir}/Materials";

            foreach (var renderer in renderers)
            {
                Material[] sharedMats = renderer.sharedMaterials;
                bool changed = false;

                for (int slot = 0; slot < sharedMats.Length; slot++)
                {
                    Material mat = sharedMats[slot];

                    // Case 1: Material is null but a property block has color data —
                    // this happens after instance mode severs the asset link.
                    // Case 2: Material exists but is not a persistent asset (runtime instance).
                    bool isRuntimeInstance = mat != null && !EditorUtility.IsPersistent(mat);
                    bool isNullWithPropertyBlock = mat == null && HasPropertyBlockColors(renderer, slot);
                    bool isNullMaterial = mat == null && !isNullWithPropertyBlock;

                    if (!isRuntimeInstance && !isNullWithPropertyBlock)
                        continue;

                    // Derive a unique asset path from the GameObject name and slot
                    string goName = renderer.gameObject.name.Replace(" ", "_");
                    string suffix = slot > 0 ? $"_slot{slot}" : "";
                    string matPath = $"{materialsFolder}/{goName}{suffix}_mat.mat";
                    matPath = AssetPathUtility.SanitizeAssetPath(matPath);
                    if (matPath == null)
                    {
                        McpLog.Warn($"[ManagePrefabs] Could not build safe material path for '{renderer.gameObject.name}', skipping.");
                        continue;
                    }

                    // Ensure the Materials directory exists (recursive)
                    EnsureAssetFolderExists(materialsFolder);

                    Material persisted = AssetDatabase.LoadAssetAtPath<Material>(matPath);
                    if (persisted == null)
                    {
                        // Create a new material with the correct shader for the active pipeline
                        Shader shader = isRuntimeInstance && mat.shader != null
                            ? mat.shader
                            : RenderPipelineUtility.ResolveShader("Standard");
                        persisted = new Material(shader);
                        AssetDatabase.CreateAsset(persisted, matPath);
                    }

                    // Copy properties from the runtime instance if available
                    if (isRuntimeInstance)
                    {
                        persisted.CopyPropertiesFromMaterial(mat);
                        EditorUtility.SetDirty(persisted);
                    }
                    else if (isNullWithPropertyBlock)
                    {
                        // Extract color from the property block and apply to the new material
                        ApplyPropertyBlockToMaterial(renderer, slot, persisted);
                        EditorUtility.SetDirty(persisted);
                    }

                    sharedMats[slot] = persisted;
                    changed = true;
                    persistedPaths.Add(matPath);
                    McpLog.Info($"[ManagePrefabs] Persisted runtime material for '{renderer.gameObject.name}' slot {slot} → {matPath}");
                }

                if (changed)
                {
                    Undo.RecordObject(renderer, "Persist runtime materials for prefab");
                    renderer.sharedMaterials = sharedMats;
                    // Clear any property blocks now that the material is persisted
                    for (int slot = 0; slot < sharedMats.Length; slot++)
                    {
                        renderer.SetPropertyBlock(null, slot);
                    }
                    EditorUtility.SetDirty(renderer);
                }
            }

            if (persistedPaths.Count > 0)
            {
                AssetDatabase.SaveAssets();
                McpLog.Info($"[ManagePrefabs] Persisted {persistedPaths.Count} runtime material(s) before prefab save.");
            }

            return (persistedPaths.Count, persistedPaths);
        }

        /// <summary>
        /// Recursively creates the folder hierarchy for the given asset path if it doesn't exist.
        /// </summary>
        private static void EnsureAssetFolderExists(string assetFolderPath)
        {
            if (AssetDatabase.IsValidFolder(assetFolderPath))
                return;

            string[] parts = assetFolderPath.Replace('\\', '/').Split('/');
            string current = parts[0]; // "Assets"
            for (int i = 1; i < parts.Length; i++)
            {
                string next = current + "/" + parts[i];
                if (!AssetDatabase.IsValidFolder(next))
                    AssetDatabase.CreateFolder(current, parts[i]);
                current = next;
            }
        }

        private static bool HasPropertyBlockColors(Renderer renderer, int slot)
        {
            MaterialPropertyBlock block = new MaterialPropertyBlock();
            renderer.GetPropertyBlock(block, slot);
            return !block.isEmpty;
        }

        /// <summary>
        /// Extracts color properties from a MaterialPropertyBlock and applies them to a material.
        /// </summary>
        private static void ApplyPropertyBlockToMaterial(Renderer renderer, int slot, Material mat)
        {
            MaterialPropertyBlock block = new MaterialPropertyBlock();
            renderer.GetPropertyBlock(block, slot);

            // Try the standard color property names
            string[] colorProps = { "_BaseColor", "_Color" };
            foreach (string prop in colorProps)
            {
                if (mat.HasProperty(prop) && block.HasColor(prop))
                {
                    mat.SetColor(prop, block.GetColor(prop));
                }
            }
        }

        #endregion

        /// <summary>
        /// Ensures the directory for an asset path exists, creating it if necessary.
        /// </summary>
        private static void EnsureAssetDirectoryExists(string assetPath)
        {
            string directory = Path.GetDirectoryName(assetPath);
            if (string.IsNullOrEmpty(directory))
            {
                return;
            }

            // Use Application.dataPath for more reliable path resolution
            // Application.dataPath points to the Assets folder (e.g., ".../ProjectName/Assets")
            string assetsPath = Application.dataPath;
            string projectRoot = Path.GetDirectoryName(assetsPath);
            string fullDirectory = Path.Combine(projectRoot, directory);

            if (!Directory.Exists(fullDirectory))
            {
                Directory.CreateDirectory(fullDirectory);
                AssetDatabase.Refresh(ImportAssetOptions.ForceSynchronousImport);
                McpLog.Info($"[ManagePrefabs] Created directory: {directory}");
            }
        }

        /// <summary>
        /// Finds a GameObject by name in the active scene or current prefab stage.
        /// </summary>
        private static GameObject FindSceneObjectByName(string name, bool includeInactive)
        {
            // First check if we're in Prefab Stage
            PrefabStage stage = PrefabStageUtility.GetCurrentPrefabStage();
            if (stage?.prefabContentsRoot != null)
            {
                foreach (Transform transform in stage.prefabContentsRoot.GetComponentsInChildren<Transform>(includeInactive))
                {
                    if (transform.name == name && (includeInactive || transform.gameObject.activeSelf))
                    {
                        return transform.gameObject;
                    }
                }
            }

            // Search in the active scene
            Scene activeScene = SceneManager.GetActiveScene();
            foreach (GameObject root in activeScene.GetRootGameObjects())
            {
                // Check the root object itself
                if (root.name == name && (includeInactive || root.activeSelf))
                {
                    return root;
                }

                // Check children
                foreach (Transform transform in root.GetComponentsInChildren<Transform>(includeInactive))
                {
                    if (transform.name == name && (includeInactive || transform.gameObject.activeSelf))
                    {
                        return transform.gameObject;
                    }
                }
            }

            return null;
        }

        #region Read Operations

        /// <summary>
        /// Gets basic metadata information about a prefab asset.
        /// </summary>
        private static object GetInfo(JObject @params)
        {
            string prefabPath = @params["prefabPath"]?.ToString() ?? @params["path"]?.ToString();
            if (string.IsNullOrEmpty(prefabPath))
            {
                return new ErrorResponse("'prefabPath' parameter is required for get_info.");
            }

            string sanitizedPath = AssetPathUtility.SanitizeAssetPath(prefabPath);
            if (string.IsNullOrEmpty(sanitizedPath))
            {
                return new ErrorResponse($"Invalid prefab path: '{prefabPath}'.");
            }
            GameObject prefabAsset = AssetDatabase.LoadAssetAtPath<GameObject>(sanitizedPath);
            if (prefabAsset == null)
            {
                return new ErrorResponse($"No prefab asset found at path '{sanitizedPath}'.");
            }

            string guid = PrefabUtilityHelper.GetPrefabGUID(sanitizedPath);
            PrefabAssetType assetType = PrefabUtility.GetPrefabAssetType(prefabAsset);
            string prefabTypeString = assetType.ToString();
            var componentTypes = PrefabUtilityHelper.GetComponentTypeNames(prefabAsset);
            int childCount = PrefabUtilityHelper.CountChildrenRecursive(prefabAsset.transform);
            var (isVariant, parentPrefab, _) = PrefabUtilityHelper.GetVariantInfo(prefabAsset);

            return new SuccessResponse(
                $"Successfully retrieved prefab info.",
                new
                {
                    assetPath = sanitizedPath,
                    guid = guid,
                    prefabType = prefabTypeString,
                    rootObjectName = prefabAsset.name,
                    rootComponentTypes = componentTypes,
                    childCount = childCount,
                    isVariant = isVariant,
                    parentPrefab = parentPrefab
                }
            );
        }

        /// <summary>
        /// Gets the hierarchical structure of a prefab asset.
        /// Returns all objects in the prefab for full client-side filtering and search.
        /// </summary>
        private static object GetHierarchy(JObject @params)
        {
            string prefabPath = @params["prefabPath"]?.ToString() ?? @params["path"]?.ToString();
            if (string.IsNullOrEmpty(prefabPath))
            {
                return new ErrorResponse("'prefabPath' parameter is required for get_hierarchy.");
            }

            string sanitizedPath = AssetPathUtility.SanitizeAssetPath(prefabPath);
            if (string.IsNullOrEmpty(sanitizedPath))
            {
                return new ErrorResponse($"Invalid prefab path '{prefabPath}'. Path traversal sequences are not allowed.");
            }

            // Load prefab contents in background (without opening stage UI)
            GameObject prefabContents = PrefabUtility.LoadPrefabContents(sanitizedPath);
            if (prefabContents == null)
            {
                return new ErrorResponse($"Failed to load prefab contents from '{sanitizedPath}'.");
            }

            try
            {
                // Build complete hierarchy items (no pagination)
                var allItems = BuildHierarchyItems(prefabContents.transform, sanitizedPath);

                return new SuccessResponse(
                    $"Successfully retrieved prefab hierarchy. Found {allItems.Count} objects.",
                    new
                    {
                        prefabPath = sanitizedPath,
                        total = allItems.Count,
                        items = allItems
                    }
                );
            }
            finally
            {
                // Always unload prefab contents to free memory
                PrefabUtility.UnloadPrefabContents(prefabContents);
            }
        }

        #endregion

        #region Headless Prefab Editing

        /// <summary>
        /// Modifies a prefab's contents directly without opening the prefab stage.
        /// This is ideal for automated/agentic workflows as it avoids UI, dirty flags, and dialogs.
        /// </summary>
        private static object ModifyContents(JObject @params)
        {
            string prefabPath = @params["prefabPath"]?.ToString() ?? @params["path"]?.ToString();
            if (string.IsNullOrEmpty(prefabPath))
            {
                return new ErrorResponse("'prefabPath' parameter is required for modify_contents.");
            }

            string sanitizedPath = AssetPathUtility.SanitizeAssetPath(prefabPath);
            if (string.IsNullOrEmpty(sanitizedPath))
            {
                return new ErrorResponse($"Invalid prefab path '{prefabPath}'. Path traversal sequences are not allowed.");
            }

            // Load prefab contents in isolated context (no UI)
            GameObject prefabContents = PrefabUtility.LoadPrefabContents(sanitizedPath);
            if (prefabContents == null)
            {
                return new ErrorResponse($"Failed to load prefab contents from '{sanitizedPath}'.");
            }

            try
            {
                // Find target object within the prefab (defaults to root)
                string targetName = @params["target"]?.ToString();
                GameObject targetGo = FindInPrefabContents(prefabContents, targetName);

                if (targetGo == null)
                {
                    string searchedFor = string.IsNullOrEmpty(targetName) ? "root" : $"'{targetName}'";
                    return new ErrorResponse($"Target {searchedFor} not found in prefab '{sanitizedPath}'.");
                }

                // Apply modifications
                var modifyResult = ApplyModificationsToPrefabObject(targetGo, @params, prefabContents, sanitizedPath);
                if (modifyResult.error != null)
                {
                    return modifyResult.error;
                }

                // Skip saving when no modifications were made to avoid unnecessary asset writes
                if (!modifyResult.modified)
                {
                    return new SuccessResponse(
                        $"Prefab '{sanitizedPath}' is already up to date; no changes were applied.",
                        new
                        {
                            prefabPath = sanitizedPath,
                            targetName = targetGo.name,
                            modified = false
                        }
                    );
                }

                // Save the prefab
                bool success;
                PrefabUtility.SaveAsPrefabAsset(prefabContents, sanitizedPath, out success);

                if (!success)
                {
                    return new ErrorResponse($"Failed to save prefab asset at '{sanitizedPath}'.");
                }

                AssetDatabase.Refresh();

                McpLog.Info($"[ManagePrefabs] Successfully modified and saved prefab '{sanitizedPath}' (headless).");

                return new SuccessResponse(
                    $"Prefab '{sanitizedPath}' modified and saved successfully.",
                    new
                    {
                        prefabPath = sanitizedPath,
                        targetName = targetGo.name,
                        modified = modifyResult.modified,
                        transform = new
                        {
                            position = new { x = targetGo.transform.localPosition.x, y = targetGo.transform.localPosition.y, z = targetGo.transform.localPosition.z },
                            rotation = new { x = targetGo.transform.localEulerAngles.x, y = targetGo.transform.localEulerAngles.y, z = targetGo.transform.localEulerAngles.z },
                            scale = new { x = targetGo.transform.localScale.x, y = targetGo.transform.localScale.y, z = targetGo.transform.localScale.z }
                        },
                        componentTypes = PrefabUtilityHelper.GetComponentTypeNames(targetGo)
                    }
                );
            }
            finally
            {
                // Always unload prefab contents to free memory
                PrefabUtility.UnloadPrefabContents(prefabContents);
            }
        }

        /// <summary>
        /// Finds a GameObject within loaded prefab contents by name or path.
        /// </summary>
        private static GameObject FindInPrefabContents(GameObject prefabContents, string target)
        {
            if (string.IsNullOrEmpty(target))
            {
                // Return root if no target specified
                return prefabContents;
            }

            // Try to find by path first (e.g., "Parent/Child/Target")
            if (target.Contains("/"))
            {
                Transform found = prefabContents.transform.Find(target);
                if (found != null)
                {
                    return found.gameObject;
                }

                // If path starts with root name, try without it
                if (target.StartsWith(prefabContents.name + "/"))
                {
                    string relativePath = target.Substring(prefabContents.name.Length + 1);
                    found = prefabContents.transform.Find(relativePath);
                    if (found != null)
                    {
                        return found.gameObject;
                    }
                }
            }

            // Check if target matches root name
            if (prefabContents.name == target)
            {
                return prefabContents;
            }

            // Search by name in hierarchy
            foreach (Transform t in prefabContents.GetComponentsInChildren<Transform>(true))
            {
                if (t.gameObject.name == target)
                {
                    return t.gameObject;
                }
            }

            return null;
        }

        /// <summary>
        /// Applies modifications to a GameObject within loaded prefab contents.
        /// Returns (modified: bool, error: ErrorResponse or null).
        /// </summary>
        private static (bool modified, ErrorResponse error) ApplyModificationsToPrefabObject(GameObject targetGo, JObject @params, GameObject prefabRoot, string editingPrefabPath)
        {
            bool modified = false;

            // Name change
            string newName = @params["name"]?.ToString();
            if (!string.IsNullOrEmpty(newName) && targetGo.name != newName)
            {
                // If renaming the root, this will affect the prefab asset name on save
                targetGo.name = newName;
                modified = true;
            }

            // Active state
            bool? setActive = @params["setActive"]?.ToObject<bool?>();
            if (setActive.HasValue && targetGo.activeSelf != setActive.Value)
            {
                targetGo.SetActive(setActive.Value);
                modified = true;
            }

            // Tag
            string tag = @params["tag"]?.ToString();
            if (tag != null && targetGo.tag != tag)
            {
                string tagToSet = string.IsNullOrEmpty(tag) ? "Untagged" : tag;
                try
                {
                    targetGo.tag = tagToSet;
                    modified = true;
                }
                catch (Exception ex)
                {
                    return (false, new ErrorResponse($"Failed to set tag to '{tagToSet}': {ex.Message}"));
                }
            }

            // Layer
            string layerName = @params["layer"]?.ToString();
            if (!string.IsNullOrEmpty(layerName))
            {
                int layerId = LayerMask.NameToLayer(layerName);
                if (layerId == -1)
                {
                    return (false, new ErrorResponse($"Invalid layer specified: '{layerName}'. Use a valid layer name."));
                }
                if (targetGo.layer != layerId)
                {
                    targetGo.layer = layerId;
                    modified = true;
                }
            }

            // Transform: position, rotation, scale
            Vector3? position = VectorParsing.ParseVector3(@params["position"]);
            Vector3? rotation = VectorParsing.ParseVector3(@params["rotation"]);
            Vector3? scale = VectorParsing.ParseVector3(@params["scale"]);

            if (position.HasValue && targetGo.transform.localPosition != position.Value)
            {
                targetGo.transform.localPosition = position.Value;
                modified = true;
            }
            if (rotation.HasValue && targetGo.transform.localEulerAngles != rotation.Value)
            {
                targetGo.transform.localEulerAngles = rotation.Value;
                modified = true;
            }
            if (scale.HasValue && targetGo.transform.localScale != scale.Value)
            {
                targetGo.transform.localScale = scale.Value;
                modified = true;
            }

            // Parent change (within prefab hierarchy)
            JToken parentToken = @params["parent"];
            if (parentToken != null)
            {
                string parentTarget = parentToken.ToString();
                Transform newParent = null;

                if (!string.IsNullOrEmpty(parentTarget))
                {
                    GameObject parentGo = FindInPrefabContents(prefabRoot, parentTarget);
                    if (parentGo == null)
                    {
                        return (false, new ErrorResponse($"Parent '{parentTarget}' not found in prefab."));
                    }
                    if (parentGo.transform.IsChildOf(targetGo.transform))
                    {
                        return (false, new ErrorResponse($"Cannot parent '{targetGo.name}' to '{parentGo.name}' as it would create a hierarchy loop."));
                    }
                    newParent = parentGo.transform;
                }

                if (targetGo.transform.parent != newParent)
                {
                    targetGo.transform.SetParent(newParent, true);
                    modified = true;
                }
            }

            // Components to add
            if (@params["componentsToAdd"] is JArray componentsToAdd)
            {
                foreach (var compToken in componentsToAdd)
                {
                    string typeName = compToken.Type == JTokenType.String
                        ? compToken.ToString()
                        : (compToken as JObject)?["typeName"]?.ToString();

                    if (!string.IsNullOrEmpty(typeName))
                    {
                        if (!ComponentResolver.TryResolve(typeName, out Type componentType, out string error))
                        {
                            return (false, new ErrorResponse($"Component type '{typeName}' not found: {error}"));
                        }
                        targetGo.AddComponent(componentType);
                        modified = true;
                    }
                }
            }

            // Components to remove
            if (@params["componentsToRemove"] is JArray componentsToRemove)
            {
                foreach (var compToken in componentsToRemove)
                {
                    string typeName = compToken.ToString();
                    if (!string.IsNullOrEmpty(typeName))
                    {
                        if (!ComponentResolver.TryResolve(typeName, out Type componentType, out string error))
                        {
                            return (false, new ErrorResponse($"Component type '{typeName}' not found: {error}"));
                        }
                        Component comp = targetGo.GetComponent(componentType);
                        if (comp != null)
                        {
                            UnityEngine.Object.DestroyImmediate(comp);
                            modified = true;
                        }
                    }
                }
            }

            // Create child GameObjects (supports single object or array)
            JToken createChildToken = @params["createChild"] ?? @params["create_child"];
            if (createChildToken != null)
            {
                // Handle array of children
                if (createChildToken is JArray childArray)
                {
                    foreach (var childToken in childArray)
                    {
                        var childResult = CreateSingleChildInPrefab(childToken, targetGo, prefabRoot, editingPrefabPath);
                        if (childResult.error != null)
                        {
                            return (false, childResult.error);
                        }
                        if (childResult.created)
                        {
                            modified = true;
                        }
                    }
                }
                else
                {
                    // Handle single child object
                    var childResult = CreateSingleChildInPrefab(createChildToken, targetGo, prefabRoot, editingPrefabPath);
                    if (childResult.error != null)
                    {
                        return (false, childResult.error);
                    }
                    if (childResult.created)
                    {
                        modified = true;
                    }
                }
            }

            // Delete child GameObjects (supports single string or array of paths/names)
            JToken deleteChildToken = @params["deleteChild"] ?? @params["delete_child"];
            if (deleteChildToken != null)
            {
                var deleteResult = RemoveChildren(deleteChildToken, targetGo, prefabRoot);
                if (deleteResult.error != null)
                {
                    return (false, deleteResult.error);
                }
                if (deleteResult.removedCount > 0)
                {
                    modified = true;
                }
            }

            // Set properties on existing components
            JObject componentProperties = @params["componentProperties"] as JObject ?? @params["component_properties"] as JObject;
            if (componentProperties != null && componentProperties.Count > 0)
            {
                var errors = new List<string>();

                foreach (var entry in componentProperties.Properties())
                {
                    string typeName = entry.Name;
                    if (!ComponentResolver.TryResolve(typeName, out Type componentType, out string resolveError))
                    {
                        errors.Add($"{typeName}: type not found — {resolveError}");
                        continue;
                    }

                    Component component = targetGo.GetComponent(componentType);
                    if (component == null)
                    {
                        errors.Add($"{typeName}: not found on '{targetGo.name}'");
                        continue;
                    }

                    if (entry.Value is not JObject props || !props.HasValues)
                    {
                        continue;
                    }

                    foreach (var prop in props.Properties())
                    {
                        if (!ComponentOps.SetProperty(component, prop.Name, prop.Value, out string setError))
                        {
                            errors.Add($"{typeName}.{prop.Name}: {setError}");
                        }
                        else
                        {
                            modified = true;
                        }
                    }
                }

                if (errors.Count > 0)
                {
                    return (false, new ErrorResponse($"Failed to set component properties (no changes saved): {string.Join("; ", errors)}"));
                }
            }

            return (modified, null);
        }

        /// <summary>
        /// Creates a single child GameObject within the prefab contents.
        /// </summary>
        private static (bool created, ErrorResponse error) CreateSingleChildInPrefab(JToken createChildToken, GameObject defaultParent, GameObject prefabRoot, string editingPrefabPath)
        {
            JObject childParams;
            if (createChildToken is JObject obj)
            {
                childParams = obj;
            }
            else
            {
                return (false, new ErrorResponse("'create_child' must be an object with child properties."));
            }

            // Required: name
            string childName = childParams["name"]?.ToString();
            if (string.IsNullOrEmpty(childName))
            {
                return (false, new ErrorResponse("'create_child.name' is required."));
            }

            // Optional: parent (defaults to the target object)
            string parentName = childParams["parent"]?.ToString();
            Transform parentTransform = defaultParent.transform;
            if (!string.IsNullOrEmpty(parentName))
            {
                GameObject parentGo = FindInPrefabContents(prefabRoot, parentName);
                if (parentGo == null)
                {
                    return (false, new ErrorResponse($"Parent '{parentName}' not found in prefab for create_child."));
                }
                parentTransform = parentGo.transform;
            }

            // Create the GameObject
            GameObject newChild;
            string sourcePrefabPath = childParams["sourcePrefabPath"]?.ToString() ?? childParams["source_prefab_path"]?.ToString();
            string primitiveType = childParams["primitiveType"]?.ToString() ?? childParams["primitive_type"]?.ToString();

            if (!string.IsNullOrEmpty(sourcePrefabPath) && !string.IsNullOrEmpty(primitiveType))
            {
                return (false, new ErrorResponse("'source_prefab_path' and 'primitive_type' are mutually exclusive in create_child."));
            }

            if (!string.IsNullOrEmpty(sourcePrefabPath))
            {
                string sanitizedSourcePath = AssetPathUtility.SanitizeAssetPath(sourcePrefabPath);
                if (string.IsNullOrEmpty(sanitizedSourcePath))
                {
                    return (false, new ErrorResponse($"Invalid source_prefab_path '{sourcePrefabPath}'. Path traversal sequences are not allowed."));
                }

                if (!string.IsNullOrEmpty(editingPrefabPath) &&
                    sanitizedSourcePath.Equals(editingPrefabPath, StringComparison.OrdinalIgnoreCase))
                {
                    return (false, new ErrorResponse($"Cannot nest prefab '{sanitizedSourcePath}' inside itself. This would create a circular reference."));
                }

                GameObject sourcePrefabAsset = AssetDatabase.LoadAssetAtPath<GameObject>(sanitizedSourcePath);
                if (sourcePrefabAsset == null)
                {
                    return (false, new ErrorResponse($"Source prefab not found at path: '{sanitizedSourcePath}'."));
                }

                newChild = PrefabUtility.InstantiatePrefab(sourcePrefabAsset, parentTransform) as GameObject;
                if (newChild == null)
                {
                    return (false, new ErrorResponse($"Failed to instantiate prefab from '{sanitizedSourcePath}' as nested child."));
                }
                newChild.name = childName;
            }
            else if (!string.IsNullOrEmpty(primitiveType))
            {
                try
                {
                    PrimitiveType type = (PrimitiveType)Enum.Parse(typeof(PrimitiveType), primitiveType, true);
                    newChild = GameObject.CreatePrimitive(type);
                    newChild.name = childName;
                }
                catch (ArgumentException)
                {
                    return (false, new ErrorResponse($"Invalid primitive type: '{primitiveType}'. Valid types: {string.Join(", ", Enum.GetNames(typeof(PrimitiveType)))}"));
                }
            }
            else
            {
                newChild = new GameObject(childName);
            }

            // Ensure local-space transform (worldPositionStays=false) for all creation modes
            newChild.transform.SetParent(parentTransform, false);

            // Apply transform properties
            Vector3? position = VectorParsing.ParseVector3(childParams["position"]);
            Vector3? rotation = VectorParsing.ParseVector3(childParams["rotation"]);
            Vector3? scale = VectorParsing.ParseVector3(childParams["scale"]);

            if (position.HasValue)
            {
                newChild.transform.localPosition = position.Value;
            }
            if (rotation.HasValue)
            {
                newChild.transform.localEulerAngles = rotation.Value;
            }
            if (scale.HasValue)
            {
                newChild.transform.localScale = scale.Value;
            }

            // Add components
            JArray componentsToAdd = childParams["componentsToAdd"] as JArray ?? childParams["components_to_add"] as JArray;
            if (componentsToAdd != null)
            {
                for (int i = 0; i < componentsToAdd.Count; i++)
                {
                    var compToken = componentsToAdd[i];
                    string typeName = compToken.Type == JTokenType.String
                        ? compToken.ToString()
                        : (compToken as JObject)?["typeName"]?.ToString();

                    if (string.IsNullOrEmpty(typeName))
                    {
                        // Clean up partially created child
                        UnityEngine.Object.DestroyImmediate(newChild);
                        return (false, new ErrorResponse($"create_child.components_to_add[{i}] must be a string or object with 'typeName' field, got {compToken.Type}"));
                    }

                    if (!ComponentResolver.TryResolve(typeName, out Type componentType, out string error))
                    {
                        // Clean up partially created child
                        UnityEngine.Object.DestroyImmediate(newChild);
                        return (false, new ErrorResponse($"Component type '{typeName}' not found for create_child: {error}"));
                    }
                    newChild.AddComponent(componentType);
                }
            }

            // Set tag if specified
            string tag = childParams["tag"]?.ToString();
            if (!string.IsNullOrEmpty(tag))
            {
                try
                {
                    newChild.tag = tag;
                }
                catch (Exception ex)
                {
                    UnityEngine.Object.DestroyImmediate(newChild);
                    return (false, new ErrorResponse($"Failed to set tag '{tag}' on child '{childName}': {ex.Message}"));
                }
            }

            // Set layer if specified
            string layerName = childParams["layer"]?.ToString();
            if (!string.IsNullOrEmpty(layerName))
            {
                int layerId = LayerMask.NameToLayer(layerName);
                if (layerId == -1)
                {
                    UnityEngine.Object.DestroyImmediate(newChild);
                    return (false, new ErrorResponse($"Invalid layer '{layerName}' for child '{childName}'. Use a valid layer name."));
                }
                newChild.layer = layerId;
            }

            // Set active state
            bool? setActive = childParams["setActive"]?.ToObject<bool?>() ?? childParams["set_active"]?.ToObject<bool?>();
            if (setActive.HasValue)
            {
                newChild.SetActive(setActive.Value);
            }

            McpLog.Info($"[ManagePrefabs] Created child '{childName}' under '{parentTransform.name}' in prefab.");
            return (true, null);
        }

        /// <summary>
        /// Removes child GameObjects from a prefab.
        /// </summary>
        private static (int removedCount, ErrorResponse error) RemoveChildren(JToken deleteChildToken, GameObject targetGo, GameObject prefabRoot)
        {
            int removedCount = 0;

            // Normalize to array
            JArray childrenToDelete;
            if (deleteChildToken is JArray arr)
            {
                childrenToDelete = arr;
            }
            else
            {
                childrenToDelete = new JArray { deleteChildToken };
            }

            foreach (var childToken in childrenToDelete)
            {
                string childPath = childToken.Type == JTokenType.String ? childToken.ToString() : childToken["name"]?.ToString();
                if (string.IsNullOrEmpty(childPath))
                {
                    return (removedCount, new ErrorResponse("'deleteChild'/'delete_child' entries must be a string or object with 'name' field."));
                }

                // Find the child to remove
                Transform childToRemove = targetGo.transform.Find(childPath);
                if (childToRemove == null)
                {
                    return (removedCount, new ErrorResponse($"Child '{childPath}' not found under '{targetGo.name}'."));
                }

                UnityEngine.Object.DestroyImmediate(childToRemove.gameObject);
                removedCount++;
                McpLog.Info($"[ManagePrefabs] Removed child '{childPath}' under '{targetGo.name}' in prefab.");
            }

            return (removedCount, null);
        }

        #endregion

        #region Hierarchy Builder

        /// <summary>
        /// Builds a flat list of hierarchy items from a transform root.
        /// </summary>
        /// <param name="root">The root transform of the prefab.</param>
        /// <param name="mainPrefabPath">Asset path of the main prefab.</param>
        /// <returns>List of hierarchy items with prefab information.</returns>
        private static List<object> BuildHierarchyItems(Transform root, string mainPrefabPath)
        {
            var items = new List<object>();
            BuildHierarchyItemsRecursive(root, root, mainPrefabPath, "", items);
            return items;
        }

        /// <summary>
        /// Recursively builds hierarchy items.
        /// </summary>
        /// <param name="transform">Current transform being processed.</param>
        /// <param name="mainPrefabRoot">Root transform of the main prefab asset.</param>
        /// <param name="mainPrefabPath">Asset path of the main prefab.</param>
        /// <param name="parentPath">Parent path for building full hierarchy path.</param>
        /// <param name="items">List to accumulate hierarchy items.</param>
        private static void BuildHierarchyItemsRecursive(Transform transform, Transform mainPrefabRoot, string mainPrefabPath, string parentPath, List<object> items)
        {
            if (transform == null) return;

            string name = transform.gameObject.name;
            string path = string.IsNullOrEmpty(parentPath) ? name : $"{parentPath}/{name}";
            int instanceId = transform.gameObject.GetInstanceIDCompat();
            bool activeSelf = transform.gameObject.activeSelf;
            int childCount = transform.childCount;
            var componentTypes = PrefabUtilityHelper.GetComponentTypeNames(transform.gameObject);

            // Prefab information
            bool isNestedPrefab = PrefabUtility.IsAnyPrefabInstanceRoot(transform.gameObject);
            bool isPrefabRoot = transform == mainPrefabRoot;
            int nestingDepth = isPrefabRoot ? 0 : PrefabUtilityHelper.GetPrefabNestingDepth(transform.gameObject, mainPrefabRoot);
            string parentPrefabPath = isNestedPrefab && !isPrefabRoot
                ? PrefabUtilityHelper.GetParentPrefabPath(transform.gameObject, mainPrefabRoot)
                : null;
            string nestedPrefabPath = isNestedPrefab ? PrefabUtilityHelper.GetNestedPrefabPath(transform.gameObject) : null;

            var item = new
            {
                name = name,
                instanceId = instanceId,
                path = path,
                activeSelf = activeSelf,
                childCount = childCount,
                componentTypes = componentTypes,
                prefab = new
                {
                    isRoot = isPrefabRoot,
                    isNestedRoot = isNestedPrefab,
                    nestingDepth = nestingDepth,
                    assetPath = isNestedPrefab ? nestedPrefabPath : mainPrefabPath,
                    parentPath = parentPrefabPath
                }
            };

            items.Add(item);

            // Recursively process children
            foreach (Transform child in transform)
            {
                BuildHierarchyItemsRecursive(child, mainPrefabRoot, mainPrefabPath, path, items);
            }
        }

        #endregion

        #region Prefab Stage

        private static object OpenPrefabStage(string requestedPath)
        {
            if (string.IsNullOrWhiteSpace(requestedPath))
            {
                return new ErrorResponse("Either 'prefabPath' or 'path' parameter is required for open_prefab_stage.");
            }

            string sanitizedPath = AssetPathUtility.SanitizeAssetPath(requestedPath);
            if (sanitizedPath == null)
            {
                return new ErrorResponse($"Invalid prefab path (path traversal detected): '{requestedPath}'.");
            }

            if (!sanitizedPath.StartsWith("Assets/", StringComparison.OrdinalIgnoreCase))
            {
                return new ErrorResponse($"Prefab path must be within the Assets folder. Got: '{sanitizedPath}'.");
            }

            if (!sanitizedPath.EndsWith(".prefab", StringComparison.OrdinalIgnoreCase))
            {
                return new ErrorResponse($"Prefab path must end with '.prefab'. Got: '{sanitizedPath}'.");
            }

            try
            {
                GameObject prefabAsset = AssetDatabase.LoadAssetAtPath<GameObject>(sanitizedPath);
                if (prefabAsset == null)
                {
                    return new ErrorResponse($"Prefab asset not found at '{sanitizedPath}'.");
                }

                var prefabStage = PrefabStageUtility.OpenPrefab(sanitizedPath);
                bool enteredStage = prefabStage != null
                    && string.Equals(prefabStage.assetPath, sanitizedPath, StringComparison.OrdinalIgnoreCase)
                    && prefabStage.prefabContentsRoot != null;

                if (!enteredStage)
                {
                    return new ErrorResponse($"Failed to open prefab stage for '{sanitizedPath}'. PrefabStageUtility.OpenPrefab did not enter the requested prefab stage.");
                }

                return new SuccessResponse(
                    $"Opened prefab stage for '{sanitizedPath}'.",
                    new
                    {
                        prefabPath = sanitizedPath,
                        openedPrefabPath = prefabStage.assetPath,
                        rootName = prefabStage.prefabContentsRoot.name,
                        enteredPrefabStage = enteredStage
                    }
                );
            }
            catch (Exception e)
            {
                return new ErrorResponse($"Error opening prefab stage: {e.Message}");
            }
        }

        private static object SavePrefabStage()
        {
            try
            {
                var prefabStage = PrefabStageUtility.GetCurrentPrefabStage();
                if (prefabStage == null)
                {
                    return new ErrorResponse("Not currently in prefab editing mode. Open a prefab stage first with open_prefab_stage.");
                }

                if (!TrySavePrefabStage(prefabStage, out string prefabPath, out string errorMessage))
                {
                    return new ErrorResponse(errorMessage);
                }

                return new SuccessResponse($"Saved prefab stage changes for '{prefabPath}'.", new { prefabPath, saved = true });
            }
            catch (Exception e)
            {
                return new ErrorResponse($"Error saving prefab stage: {e.Message}");
            }
        }

        private static object ClosePrefabStage(bool saveBeforeClose = false)
        {
            try
            {
                var prefabStage = PrefabStageUtility.GetCurrentPrefabStage();
                if (prefabStage == null)
                {
                    return new SuccessResponse("Not currently in prefab editing mode.");
                }

                if (saveBeforeClose)
                {
                    if (!TrySavePrefabStage(prefabStage, out _, out string errorMessage))
                    {
                        return new ErrorResponse(errorMessage);
                    }
                }

                string prefabPath = prefabStage.assetPath;
                StageUtility.GoToMainStage();
                return new SuccessResponse($"Exited prefab stage for '{prefabPath}'.", new { prefabPath });
            }
            catch (Exception e)
            {
                return new ErrorResponse($"Error closing prefab stage: {e.Message}");
            }
        }

        private static bool TrySavePrefabStage(PrefabStage prefabStage, out string prefabPath, out string errorMessage)
        {
            prefabPath = prefabStage.assetPath;
            errorMessage = null;

            if (prefabStage.prefabContentsRoot == null)
            {
                errorMessage = $"Failed to save prefab stage for '{prefabPath}'. The prefab contents root is missing.";
                return false;
            }

            bool saved;
            PrefabUtility.SaveAsPrefabAsset(prefabStage.prefabContentsRoot, prefabPath, out saved);
            if (!saved)
            {
                errorMessage = $"Failed to save prefab stage for '{prefabPath}'. The file may be read-only or the disk may be full.";
                return false;
            }

            prefabStage.ClearDirtiness();
            AssetDatabase.SaveAssets();
            AssetDatabase.Refresh();
            return true;
        }

        #endregion
    }
}