chore: initial commit

2025-02-04 14:39:54 -06:00
commit a1a682916e
45 changed files with 1736 additions and 0 deletions
@@ -0,0 +1,79 @@
+namespace AltGen.API.Generate.Providers.Gemini;
+
+class GeminiService(HttpClient httpClient) : IGeminiService
+{
+  const string BaseUri = "https://generativelanguage.googleapis.com/v1beta/models";
+  const string Method = "generateContent";
+  const string ModelId = "gemini-1.5-flash";
+  const string ApiKeyQueryKey = "key";
+
+  // TODO: Use Lazy<T> to load the prompt resource
+  string _prompt = "";
+  string Prompt
+  {
+    get
+    {
+      if (string.IsNullOrWhiteSpace(_prompt))
+      {
+        var resource = Assembly.GetExecutingAssembly()
+          .GetManifestResourceStream("AltGen.API.Resources.prompt.txt") ?? throw new AltGenException("Failed to load the prompt resource.");
+        using var reader = new StreamReader(resource);
+        _prompt = reader.ReadToEnd();
+      }
+
+      return _prompt;
+    }
+  }
+
+  static readonly JsonSerializerOptions Options = new()
+  {
+    PropertyNameCaseInsensitive = true,
+    PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
+    Converters = { new PartConverter() }
+  };
+  readonly HttpClient _httpClient = httpClient;
+
+  public async Task<string> GenerateContentAsync(string providerKey, string mimeType, MemoryStream image)
+  {
+    var requestUri = GetRequestUri(providerKey);
+    var imageBase64 = ConvertToBase64(image);
+
+    var request = new GeminiRequest(
+      new Content([new TextPart(Prompt)], GeminiRole.System),
+      [new Content(
+        [
+          new TextPart(""),
+          new InlineDataPart(new InlineData(mimeType, imageBase64))
+        ],
+        GeminiRole.User
+      )]
+    );
+
+    var response = await _httpClient.PostAsJsonAsync(requestUri, request, Options);
+    var content = await response.Content.ReadAsStringAsync();
+
+    if (response.IsSuccessStatusCode is false)
+    {
+      throw new AltGenException("Failed to generate alt text.");
+    }
+
+    var geminiResponse = JsonSerializer.Deserialize<GeminiResponse>(content, Options) ?? throw new AltGenException("Failed to deserialize the Gemini response.");
+    var firstCandidate = geminiResponse.Candidates.FirstOrDefault() ?? throw new AltGenException("No candidates found in the Gemini response.");
+    var altText = firstCandidate.Content.Parts
+      .OfType<TextPart>()
+      .Aggregate(new StringBuilder(), static (sb, part) => sb.Append(part.Text))
+      .ToString();
+
+    return altText;
+  }
+
+  static string GetRequestUri(string providerKey)
+  {
+    return $"{BaseUri}/{ModelId}:{Method}/?{ApiKeyQueryKey}={providerKey}";
+  }
+
+  static string ConvertToBase64(MemoryStream image)
+  {
+    return Convert.ToBase64String(image.ToArray());
+  }
+}