feat: add SuggestAspectsAsync to AiAssistantService

EbayListingTool/Services/AiAssistantService.cs

@@ -284,6 +284,59 @@ public class AiAssistantService
         }
     }
 
+    public async Task<Dictionary<string, string>> SuggestAspectsAsync(
+        string title, string description, List<CategoryAspect> aspects)
+    {
+        if (aspects.Count == 0) return new();
+
+        var aspectLines = aspects.Select(a =>
+        {
+            var line = $"- {a.Name} (required: {a.IsRequired})";
+            if (!a.IsFreeText && a.AllowedValues.Count > 0)
+                line += $" — allowed values: {string.Join(", ", a.AllowedValues.Take(10))}";
+            return line;
+        });
+
+        var prompt =
+            "You are an eBay UK listing expert. Based on this listing, suggest values for the " +
+            "eBay item specifics (aspects) listed below.\n\n" +
+            $"Title: {title}\n" +
+            $"Description: {description}\n\n" +
+            "Aspects needed:\n" +
+            string.Join("\n", aspectLines) + "\n\n" +
+            "Rules:\n" +
+            "- For aspects with 'allowed values', you MUST use one of those exact values.\n" +
+            "- If unsure about an aspect, omit it from the response rather than guess.\n" +
+            "- Return ONLY valid JSON — no markdown, no explanation:\n" +
+            "{\n" +
+            "  \"Brand\": \"Apple\",\n" +
+            "  \"Model\": \"iPhone 14\"\n" +
+            "}\n" +
+            "Use the exact aspect name as the key.";
+
+        var json = await CallAsync(prompt);
+
+        try
+        {
+            JObject obj;
+            try { obj = JObject.Parse(json.Trim()); }
+            catch (JsonReaderException)
+            {
+                var m = System.Text.RegularExpressions.Regex.Match(
+                    json, @"```(?:json)?\s*(\{[\s\S]*?\})\s*```");
+                obj = JObject.Parse(m.Success ? m.Groups[1].Value : json.Trim());
+            }
+
+            return obj.Properties()
+                .Where(p => !string.IsNullOrEmpty(p.Value?.ToString()))
+                .ToDictionary(p => p.Name, p => p.Value!.ToString());
+        }
+        catch
+        {
+            return new();
+        }
+    }
+
     private async Task<string> CallWithVisionAsync(IEnumerable<string> imageDataUrls, string textPrompt)
     {
         if (string.IsNullOrEmpty(_apiKey))