Add live eBay Browse API price lookup to photo analysis

After photo analysis completes, fires a background request to the
eBay Browse API (app-level auth, no user login needed) to fetch
current Buy It Now prices for similar items on eBay UK.

- EbayAuthService.GetAppTokenAsync(): client credentials OAuth flow,
  cached for the token lifetime
- EbayPriceResearchService: searches /buy/browse/v1/item_summary/search
  filtered to FIXED_PRICE + EBAY_GB, returns min/max/median/suggested
  (suggested = 40th percentile — competitive but not cheapest)
- PhotoAnalysisView: shows spinner + "Checking live eBay UK prices…",
  then updates price badge, range bar and PriceOverride with real data,
  plus a "Based on N live listings (£X – £Y)" label

Silently degrades if eBay credentials are not configured.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

EbayListingTool/Services/EbayAuthService.cs

@@ -15,6 +15,10 @@ public class EbayAuthService
     private readonly string _tokenPath;
     private EbayToken? _token;
 
+    // App-level (client credentials) token — no user login needed, used for Browse API
+    private string? _appToken;
+    private DateTime _appTokenExpiry = DateTime.MinValue;
+
     private static readonly string[] Scopes =
     [
         "https://api.ebay.com/oauth/api_scope",
@@ -191,6 +195,47 @@ public class EbayAuthService
         }
     }
 
+    /// <summary>
+    /// Returns an application-level OAuth token (client credentials grant).
+    /// Does NOT require the user to be logged in — uses Client ID + Secret only.
+    /// Cached for the token lifetime minus a 5-minute safety margin.
+    /// </summary>
+    public async Task<string> GetAppTokenAsync()
+    {
+        if (_appToken != null && DateTime.UtcNow < _appTokenExpiry)
+            return _appToken;
+
+        if (string.IsNullOrEmpty(_settings.ClientId) || string.IsNullOrEmpty(_settings.ClientSecret))
+            throw new InvalidOperationException("eBay Client ID / Secret not configured in appsettings.json.");
+
+        var tokenUrl = _settings.Sandbox
+            ? "https://api.sandbox.ebay.com/identity/v1/oauth2/token"
+            : "https://api.ebay.com/identity/v1/oauth2/token";
+
+        using var http = new HttpClient();
+        var credentials = Convert.ToBase64String(
+            Encoding.UTF8.GetBytes($"{_settings.ClientId}:{_settings.ClientSecret}"));
+        http.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic", credentials);
+
+        var body = new FormUrlEncodedContent(new Dictionary<string, string>
+        {
+            ["grant_type"] = "client_credentials",
+            ["scope"]      = "https://api.ebay.com/oauth/api_scope"
+        });
+
+        var response = await http.PostAsync(tokenUrl, body);
+        var json     = await response.Content.ReadAsStringAsync();
+
+        if (!response.IsSuccessStatusCode)
+            throw new HttpRequestException($"App token request failed: {json}");
+
+        var obj = JObject.Parse(json);
+        _appToken       = obj["access_token"]!.ToString();
+        var expiresIn   = obj["expires_in"]?.Value<int>() ?? 7200;
+        _appTokenExpiry = DateTime.UtcNow.AddSeconds(expiresIn - 300); // 5-min buffer
+        return _appToken;
+    }
+
     public void Disconnect()
     {
         _token = null;

EbayListingTool/Services/EbayPriceResearchService.cs

@@ -0,0 +1,80 @@
+using System.Net.Http.Headers;
+using Newtonsoft.Json.Linq;
+
+namespace EbayListingTool.Services;
+
+public class LivePriceResult
+{
+    public List<decimal> Prices     { get; init; } = new();
+    public int           Count      => Prices.Count;
+    public decimal       Min        => Prices.Count > 0 ? Prices.Min()    : 0;
+    public decimal       Max        => Prices.Count > 0 ? Prices.Max()    : 0;
+    public decimal       Median     => Prices.Count > 0 ? Percentile(50)  : 0;
+    public decimal       Suggested  => Prices.Count > 0 ? Percentile(40)  : 0; // 40th pct: competitive but not lowest
+
+    private decimal Percentile(int pct)
+    {
+        var sorted = Prices.OrderBy(p => p).ToList();
+        int idx = (int)Math.Round((pct / 100.0) * (sorted.Count - 1));
+        return sorted[Math.Clamp(idx, 0, sorted.Count - 1)];
+    }
+}
+
+/// <summary>
+/// Uses the eBay Browse API (app-level token, no user login required) to fetch
+/// current Buy It Now prices for similar items on eBay UK.
+/// </summary>
+public class EbayPriceResearchService
+{
+    private readonly EbayAuthService _auth;
+    private static readonly HttpClient _http = new();
+
+    public EbayPriceResearchService(EbayAuthService auth)
+    {
+        _auth = auth;
+    }
+
+    public async Task<LivePriceResult> GetLivePricesAsync(string query, int limit = 20)
+    {
+        if (string.IsNullOrWhiteSpace(query))
+            return new LivePriceResult();
+
+        var token   = await _auth.GetAppTokenAsync();
+        var baseUrl = _auth.BaseUrl;
+
+        using var request = new HttpRequestMessage(HttpMethod.Get,
+            $"{baseUrl}/buy/browse/v1/item_summary/search" +
+            $"?q={Uri.EscapeDataString(query)}" +
+            $"&filter=buyingOptions%3A%7BFIXED_PRICE%7D" +
+            $"&limit={limit}" +
+            $"&sort=price");
+
+        request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", token);
+        request.Headers.Add("X-EBAY-C-MARKETPLACE-ID", "EBAY_GB");
+
+        var response = await _http.SendAsync(request);
+        var json     = await response.Content.ReadAsStringAsync();
+
+        if (!response.IsSuccessStatusCode)
+            throw new HttpRequestException($"eBay Browse API error ({(int)response.StatusCode}): {json}");
+
+        var obj    = JObject.Parse(json);
+        var items  = obj["itemSummaries"] as JArray ?? new JArray();
+        var prices = new List<decimal>();
+
+        foreach (var item in items)
+        {
+            var priceVal = item["price"]?["value"]?.ToString();
+            var currency = item["price"]?["currency"]?.ToString();
+            if (currency == "GBP" && decimal.TryParse(priceVal,
+                    System.Globalization.NumberStyles.Any,
+                    System.Globalization.CultureInfo.InvariantCulture,
+                    out var p) && p > 0)
+            {
+                prices.Add(p);
+            }
+        }
+
+        return new LivePriceResult { Prices = prices };
+    }
+}

EbayListingTool/Views/MainWindow.xaml.cs

@@ -14,6 +14,7 @@ public partial class MainWindow : MetroWindow
     private readonly AiAssistantService _aiService;
     private readonly BulkImportService _bulkService;
     private readonly SavedListingsService _savedService;
+    private readonly EbayPriceResearchService _priceService;
 
     public MainWindow()
     {
@@ -26,9 +27,10 @@ public partial class MainWindow : MetroWindow
         _aiService       = new AiAssistantService(config);
         _bulkService     = new BulkImportService();
         _savedService    = new SavedListingsService();
+        _priceService    = new EbayPriceResearchService(_auth);
 
         // Photo Analysis tab — no eBay needed
-        PhotoView.Initialise(_aiService, _savedService);
+        PhotoView.Initialise(_aiService, _savedService, _priceService);
         PhotoView.UseDetailsRequested += OnUseDetailsRequested;
 
         // Saved Listings tab

EbayListingTool/Views/PhotoAnalysisView.xaml

@@ -490,6 +490,18 @@
                                                    StringFormat="F2" Interval="0.5"/>
                             </StackPanel>
 
+
+                            <!-- Live eBay price status -->
+                            <StackPanel x:Name="LivePriceRow" Orientation="Horizontal"
+                                        Margin="0,6,0,0" Visibility="Collapsed">
+                                <mah:ProgressRing x:Name="LivePriceSpinner"
+                                                  Width="11" Height="11" Margin="0,0,6,0"/>
+                                <TextBlock x:Name="LivePriceStatus"
+                                           FontSize="10"
+                                           Foreground="{DynamicResource MahApps.Brushes.Gray5}"
+                                           VerticalAlignment="Center"
+                                           TextWrapping="Wrap"/>
+                            </StackPanel>
                             <!-- Price reasoning -->
                             <TextBlock x:Name="PriceReasoningText"
                                        FontSize="11" FontStyle="Italic"

EbayListingTool/Views/PhotoAnalysisView.xaml.cs

@@ -14,6 +14,7 @@ public partial class PhotoAnalysisView : UserControl
 {
     private AiAssistantService?       _aiService;
     private SavedListingsService?     _savedService;
+    private EbayPriceResearchService? _priceService;
     private List<string>            _currentImagePaths = new();
     private PhotoAnalysisResult?    _lastResult;
     private int                     _activePhotoIndex  = 0;
@@ -50,10 +51,12 @@ public partial class PhotoAnalysisView : UserControl
         PhotoPreviewContainer.SizeChanged += PhotoPreviewContainer_SizeChanged;
     }
 
-    public void Initialise(AiAssistantService aiService, SavedListingsService savedService)
+    public void Initialise(AiAssistantService aiService, SavedListingsService savedService,
+                           EbayPriceResearchService priceService)
     {
         _aiService    = aiService;
         _savedService = savedService;
+        _priceService = priceService;
     }
 
     // ---- Photo clip geometry sync ----
@@ -204,6 +207,8 @@ public partial class PhotoAnalysisView : UserControl
             var result = await _aiService.AnalyseItemFromPhotosAsync(_currentImagePaths);
             _lastResult = result;
             ShowResults(result);
+            // Fire live price lookup in background — updates price display when ready
+            _ = UpdateLivePricesAsync(result.Title);
         }
         catch (Exception ex)
         {
@@ -344,11 +349,58 @@ public partial class PhotoAnalysisView : UserControl
         TitleBox.Text       = r.Title;
         DescriptionBox.Text = r.Description;
 
+        // Reset live price row until lookup completes
+        LivePriceRow.Visibility = Visibility.Collapsed;
+
         // Animate results in
         var sb = (Storyboard)FindResource("ResultsReveal");
         sb.Begin(this);
     }
 
+    private async Task UpdateLivePricesAsync(string query)
+    {
+        if (_priceService == null) return;
+
+        // Show spinner
+        LivePriceRow.Visibility     = Visibility.Visible;
+        LivePriceSpinner.Visibility = Visibility.Visible;
+        LivePriceStatus.Text        = "Checking live eBay UK prices…";
+
+        try
+        {
+            var live = await _priceService.GetLivePricesAsync(query);
+
+            if (live.Count == 0)
+            {
+                LivePriceStatus.Text        = "No matching live listings found.";
+                LivePriceSpinner.Visibility = Visibility.Collapsed;
+                return;
+            }
+
+            // Update range bar with real data
+            PriceMinText.Text        = $"£{live.Min:F2}";
+            PriceMaxText.Text        = $"£{live.Max:F2}";
+            PriceRangeBar.Visibility = Visibility.Visible;
+
+            // Update suggested price to 40th percentile (competitive but not cheapest)
+            var suggested = live.Suggested;
+            PriceSuggestedText.Text = $"£{suggested:F2}";
+            PriceOverride.Value     = (double)suggested;
+            if (_lastResult != null) _lastResult.PriceSuggested = suggested;
+
+            // Update status label
+            LivePriceSpinner.Visibility = Visibility.Collapsed;
+            LivePriceStatus.Text =
+                $"Based on {live.Count} live eBay UK listing{(live.Count == 1 ? "" : "s")} " +
+                $"(range £{live.Min:F2} – £{live.Max:F2})";
+        }
+        catch (Exception ex)
+        {
+            LivePriceSpinner.Visibility = Visibility.Collapsed;
+            LivePriceStatus.Text        = $"Live price lookup unavailable: {ex.Message}";
+        }
+    }
+
     private void TitleBox_TextChanged(object sender, TextChangedEventArgs e)
     {
         var len = TitleBox.Text.Length;