Add ambientCG importer and extract shared web-asset import framework

New Tools/ambientCG Importer window (catalog browser, ZIP download with
selective map extraction, URP/Lit material build). Generic pieces moved
from the PolyHaven tool into Editor/WebAssets (EditorWebRequest,
PbrMapType, PbrMaterialBuilder, ImportUtil, AssetBrowserGrid); PolyHaven
API/window now delegate to the shared code, behavior unchanged.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Assets/Scripts/Editor/PolyHaven/PolyHavenApi.cs

@@ -1,9 +1,8 @@
 using System;
 using System.Collections.Generic;
+using Chameleon.Editor.WebAssets;
 using Newtonsoft.Json.Linq;
-using UnityEditor;
 using UnityEngine;
-using UnityEngine.Networking;
 
 namespace Chameleon.Editor.PolyHaven
 {
@@ -34,36 +33,25 @@ namespace Chameleon.Editor.PolyHaven
         public string[] Categories = Array.Empty<string>();
     }
 
-    /// <summary>One catalog entry from /assets (lightweight, for the browser grid).</summary>
-    public sealed class PolyHavenAsset
-    {
-        public string Slug;
-        public string Name;
-        public string ThumbnailUrl;
-        public string[] Categories = Array.Empty<string>();
-        public string[] Tags = Array.Empty<string>();
-        public string Search; // pre-lowered "name slug categories tags" haystack
-    }
-
     /// <summary>Parsed /files/{slug}: MapType -> resolution("2k") -> best file.</summary>
     public sealed class PolyHavenFiles
     {
-        public readonly Dictionary<PolyHavenMapType, Dictionary<string, PolyHavenFile>> Maps =
-            new Dictionary<PolyHavenMapType, Dictionary<string, PolyHavenFile>>();
+        public readonly Dictionary<PbrMapType, Dictionary<string, PolyHavenFile>> Maps =
+            new Dictionary<PbrMapType, Dictionary<string, PolyHavenFile>>();
 
         // Every resolution string seen across all maps (e.g. "1k","2k","4k"), sorted low->high.
         public List<string> Resolutions = new List<string>();
 
-        public bool Has(PolyHavenMapType type) => Maps.ContainsKey(type);
+        public bool Has(PbrMapType type) => Maps.ContainsKey(type);
 
-        public bool TryGet(PolyHavenMapType type, string res, out PolyHavenFile file)
+        public bool TryGet(PbrMapType type, string res, out PolyHavenFile file)
         {
             file = default;
             return Maps.TryGetValue(type, out var byRes) && byRes.TryGetValue(res, out file);
         }
 
         /// <summary>Best available file at res, else next-lower resolution of the same map.</summary>
-        public bool TryGetWithFallback(PolyHavenMapType type, string res, out PolyHavenFile file, out string usedRes)
+        public bool TryGetWithFallback(PbrMapType type, string res, out PolyHavenFile file, out string usedRes)
         {
             file = default;
             usedRes = null;
@@ -71,11 +59,11 @@ namespace Chameleon.Editor.PolyHaven
                 return false;
             if (byRes.TryGetValue(res, out file)) { usedRes = res; return true; }
 
-            int target = ResolutionRank(res);
+            int target = ImportUtil.ResolutionRank(res);
             int bestRank = -1;
             foreach (var kv in byRes)
             {
-                int rank = ResolutionRank(kv.Key);
+                int rank = ImportUtil.ResolutionRank(kv.Key);
                 if (rank <= target && rank > bestRank)
                 {
                     bestRank = rank;
@@ -87,7 +75,7 @@ namespace Chameleon.Editor.PolyHaven
             {
                 foreach (var kv in byRes)
                 {
-                    int rank = ResolutionRank(kv.Key);
+                    int rank = ImportUtil.ResolutionRank(kv.Key);
                     if (bestRank == -1 || rank < bestRank)
                     {
                         bestRank = rank;
@@ -98,23 +86,27 @@ namespace Chameleon.Editor.PolyHaven
             }
             return usedRes != null;
         }
-
-        public static int ResolutionRank(string res)
-        {
-            if (string.IsNullOrEmpty(res)) return int.MaxValue;
-            var digits = res.TrimEnd('k', 'K');
-            return int.TryParse(digits, out var n) ? n : int.MaxValue;
-        }
     }
 
     /// <summary>
-    /// Async client for the public Poly Haven API (same endpoints the Blender/UE5 plugins use).
-    /// All requests poll on EditorApplication.update — never blocks the editor.
+    /// Async client for the public Poly Haven API (same endpoints the Blender/UE5
+    /// plugins use). Transport is the shared non-blocking EditorWebRequest.
     /// </summary>
     public static class PolyHavenApi
     {
         private const string ApiBase = "https://api.polyhaven.com";
-        private const string UserAgent = "Chameleon-Unity-PolyHavenImporter/1.0";
+
+        // Poly Haven's dynamic file-tree keys per map type.
+        private static readonly (PbrMapType type, string apiKey)[] ApiKeys =
+        {
+            (PbrMapType.Diffuse,      "Diffuse"),
+            (PbrMapType.NormalGL,     "nor_gl"),
+            (PbrMapType.Rough,        "Rough"),
+            (PbrMapType.AO,           "AO"),
+            (PbrMapType.Metal,        "Metal"),
+            (PbrMapType.Displacement, "Displacement"),
+            (PbrMapType.Arm,          "arm"),
+        };
 
         // Best format preference per map: lossless where it matters, jpg otherwise.
         private static readonly string[] LosslessPref = { "png", "exr", "jpg" };
@@ -147,13 +139,11 @@ namespace Chameleon.Editor.PolyHaven
 
         public static void FetchInfo(string slug, Action<PolyHavenInfo> onDone, Action<string> onError)
         {
-            var req = UnityWebRequest.Get($"{ApiBase}/info/{slug}");
-            req.SetRequestHeader("User-Agent", UserAgent);
-            Send(req, () =>
+            EditorWebRequest.GetText($"{ApiBase}/info/{slug}", text =>
             {
                 try
                 {
-                    var o = JObject.Parse(req.downloadHandler.text);
+                    var o = JObject.Parse(text);
                     var info = new PolyHavenInfo
                     {
                         Slug = slug,
@@ -173,32 +163,29 @@ namespace Chameleon.Editor.PolyHaven
             }, onError);
         }
 
-        /// <summary>Loads the full texture catalog (keyed by slug) for the browser grid.</summary>
-        public static void FetchAssets(string type, Action<List<PolyHavenAsset>> onDone, Action<string> onError)
+        /// <summary>Loads the full texture catalog as browser-grid entries.</summary>
+        public static void FetchAssets(string type, Action<List<AssetBrowserGrid.Entry>> onDone, Action<string> onError)
         {
-            var req = UnityWebRequest.Get($"{ApiBase}/assets?t={type}");
-            req.SetRequestHeader("User-Agent", UserAgent);
-            Send(req, () =>
+            EditorWebRequest.GetText($"{ApiBase}/assets?t={type}", text =>
             {
                 try
                 {
-                    var root = JObject.Parse(req.downloadHandler.text);
-                    var list = new List<PolyHavenAsset>(root.Count);
+                    var root = JObject.Parse(text);
+                    var list = new List<AssetBrowserGrid.Entry>(root.Count);
                     foreach (var prop in root)
                     {
                         if (prop.Value is not JObject o) continue;
-                        var a = new PolyHavenAsset
+                        string name = (string)o["name"] ?? prop.Key;
+                        var e = new AssetBrowserGrid.Entry
                         {
-                            Slug = prop.Key,
-                            Name = (string)o["name"] ?? prop.Key,
+                            Key = prop.Key,
+                            Name = name,
                             ThumbnailUrl = (string)o["thumbnail_url"] ?? ThumbnailUrl(prop.Key),
-                            Categories = ToStringArray(o["categories"]),
-                            Tags = ToStringArray(o["tags"]),
                         };
-                        a.Search = (a.Name + " " + a.Slug + " " +
-                                    string.Join(" ", a.Categories) + " " +
-                                    string.Join(" ", a.Tags)).ToLowerInvariant();
-                        list.Add(a);
+                        e.Search = (name + " " + prop.Key + " " +
+                                    JoinStrings(o["categories"]) + " " +
+                                    JoinStrings(o["tags"])).ToLowerInvariant();
+                        list.Add(e);
                     }
                     list.Sort((x, y) => string.Compare(x.Name, y.Name, StringComparison.OrdinalIgnoreCase));
                     onDone?.Invoke(list);
@@ -209,52 +196,25 @@ namespace Chameleon.Editor.PolyHaven
 
         public static void FetchFiles(string slug, Action<PolyHavenFiles> onDone, Action<string> onError)
         {
-            var req = UnityWebRequest.Get($"{ApiBase}/files/{slug}");
-            req.SetRequestHeader("User-Agent", UserAgent);
-            Send(req, () =>
+            EditorWebRequest.GetText($"{ApiBase}/files/{slug}", text =>
             {
-                try { onDone?.Invoke(ParseFiles(req.downloadHandler.text)); }
+                try { onDone?.Invoke(ParseFiles(text)); }
                 catch (Exception e) { onError?.Invoke($"Files parse failed: {e.Message}"); }
             }, onError);
         }
 
-        public static void FetchThumbnail(string url, Action<Texture2D> onDone, Action<string> onError)
-        {
-            var req = UnityWebRequestTexture.GetTexture(url);
-            req.SetRequestHeader("User-Agent", UserAgent);
-            Send(req, () =>
-            {
-                var tex = DownloadHandlerTexture.GetContent(req);
-                // Survive play-mode enter/exit cleanup — otherwise Unity destroys these
-                // loose runtime textures and the browser previews go blank.
-                if (tex)
-                    tex.hideFlags = HideFlags.HideAndDontSave;
-                onDone?.Invoke(tex);
-            }, onError);
-        }
-
-        /// <summary>Streams a file straight to disk (no RAM peak on big EXR/8K files).</summary>
-        public static void DownloadFile(PolyHavenFile file, string destPath, Action onDone,
-            Action<string> onError, Action<float> onProgress = null)
-        {
-            var req = new UnityWebRequest(file.Url, UnityWebRequest.kHttpVerbGET);
-            req.downloadHandler = new DownloadHandlerFile(destPath) { removeFileOnAbort = true };
-            req.SetRequestHeader("User-Agent", UserAgent);
-            Send(req, () => onDone?.Invoke(), onError, onProgress);
-        }
-
         // ---- Parsing -----------------------------------------------------------
 
-        private static string[] ToStringArray(JToken token)
+        private static string JoinStrings(JToken token)
         {
-            if (token is not JArray arr) return Array.Empty<string>();
+            if (token is not JArray arr) return "";
             var list = new List<string>(arr.Count);
             foreach (var t in arr)
             {
                 var s = (string)t;
                 if (!string.IsNullOrEmpty(s)) list.Add(s);
             }
-            return list.ToArray();
+            return string.Join(" ", list);
         }
 
         private static PolyHavenFiles ParseFiles(string json)
@@ -263,12 +223,13 @@ namespace Chameleon.Editor.PolyHaven
             var result = new PolyHavenFiles();
             var resSet = new HashSet<string>();
 
-            foreach (var meta in PolyHavenMapInfo.All)
+            foreach (var (type, apiKey) in ApiKeys)
             {
-                if (root[meta.ApiKey] is not JObject byRes)
+                if (root[apiKey] is not JObject byRes)
                     continue;
 
-                var pref = (meta.IsNormal || meta.Type == PolyHavenMapType.Displacement)
+                var meta = PbrMapInfo.Get(type);
+                var pref = (meta.IsNormal || type == PbrMapType.Displacement)
                     ? LosslessPref
                     : LossyPref;
 
@@ -298,48 +259,13 @@ namespace Chameleon.Editor.PolyHaven
                 }
 
                 if (perRes.Count > 0)
-                    result.Maps[meta.Type] = perRes;
+                    result.Maps[type] = perRes;
             }
 
             var resList = new List<string>(resSet);
-            resList.Sort((x, y) => PolyHavenFiles.ResolutionRank(x).CompareTo(PolyHavenFiles.ResolutionRank(y)));
+            resList.Sort((x, y) => ImportUtil.ResolutionRank(x).CompareTo(ImportUtil.ResolutionRank(y)));
             result.Resolutions = resList;
             return result;
         }
-
-        // ---- Non-blocking transport -------------------------------------------
-
-        private static void Send(UnityWebRequest req, Action onSuccess, Action<string> onError,
-            Action<float> onProgress = null)
-        {
-            var op = req.SendWebRequest();
-            void Tick()
-            {
-                if (onProgress != null && !op.isDone)
-                    onProgress(req.downloadProgress);
-
-                if (!op.isDone)
-                    return;
-
-                EditorApplication.update -= Tick;
-                try
-                {
-                    if (req.result != UnityWebRequest.Result.Success)
-                    {
-                        onError?.Invoke($"{req.error} ({req.url})");
-                    }
-                    else
-                    {
-                        onProgress?.Invoke(1f);
-                        onSuccess?.Invoke();
-                    }
-                }
-                finally
-                {
-                    req.Dispose();
-                }
-            }
-            EditorApplication.update += Tick;
-        }
     }
 }