Add file part support to chat message structure

Introduces ChatMessagePartFile struct and ChatMessagePartTypeFile constant to support file attachments in chat messages. Updates ChatMessagePart to include file parts and adds comprehensive tests for serialization, deserialization, and constant definitions.

Author: alejandrojnm

chat.go

@@ -81,17 +81,26 @@ type ChatMessageImageURL struct {
 	Detail ImageURLDetail `json:"detail,omitempty"`
 }
 
+// ChatMessagePartFile is a placeholder for file parts in chat messages.
+type ChatMessagePartFile struct {
+	FileID   string `json:"file_id,omitempty"`
+	FileName string `json:"filename,omitempty"`
+	FileData string `json:"file_data,omitempty"` // Base64 encoded file data
+}
+
 type ChatMessagePartType string
 
 const (
 	ChatMessagePartTypeText     ChatMessagePartType = "text"
 	ChatMessagePartTypeImageURL ChatMessagePartType = "image_url"
+	ChatMessagePartTypeFile     ChatMessagePartType = "file"
 )
 
 type ChatMessagePart struct {
 	Type     ChatMessagePartType  `json:"type,omitempty"`
 	Text     string               `json:"text,omitempty"`
 	ImageURL *ChatMessageImageURL `json:"image_url,omitempty"`
+	File	 *ChatMessagePartFile `json:"file,omitempty"`
 }
 
 type ChatCompletionMessage struct {

chat_test.go

@@ -677,6 +677,14 @@ func TestMultipartChatCompletions(t *testing.T) {
 							Detail: openai.ImageURLDetailLow,
 						},
 					},
+					{
+						Type: openai.ChatMessagePartTypeFile,
+						File: &openai.ChatMessagePartFile{
+							FileID:   "file-123",
+							FileName: "test.txt",
+							FileData: "dGVzdCBmaWxlIGNvbnRlbnQ=", // base64 encoded "test file content"
+						},
+					},
 				},
 			},
 		},
@@ -687,7 +695,8 @@ func TestMultipartChatCompletions(t *testing.T) {
 func TestMultipartChatMessageSerialization(t *testing.T) {
 	jsonText := `[{"role":"system","content":"system-message"},` +
 		`{"role":"user","content":[{"type":"text","text":"nice-text"},` +
-		`{"type":"image_url","image_url":{"url":"URL","detail":"high"}}]}]`
+		`{"type":"image_url","image_url":{"url":"URL","detail":"high"}},` +
+		`{"type":"file","file":{"file_id":"file-123","filename":"test.txt","file_data":"dGVzdA=="}}]}]`
 
 	var msgs []openai.ChatCompletionMessage
 	err := json.Unmarshal([]byte(jsonText), &msgs)
@@ -700,7 +709,7 @@ func TestMultipartChatMessageSerialization(t *testing.T) {
 	if msgs[0].Role != "system" || msgs[0].Content != "system-message" || msgs[0].MultiContent != nil {
 		t.Errorf("invalid user message: %v", msgs[0])
 	}
-	if msgs[1].Role != "user" || msgs[1].Content != "" || len(msgs[1].MultiContent) != 2 {
+	if msgs[1].Role != "user" || msgs[1].Content != "" || len(msgs[1].MultiContent) != 3 {
 		t.Errorf("invalid user message")
 	}
 	parts := msgs[1].MultiContent
@@ -710,6 +719,9 @@ func TestMultipartChatMessageSerialization(t *testing.T) {
 	if parts[1].Type != "image_url" || parts[1].ImageURL.URL != "URL" || parts[1].ImageURL.Detail != "high" {
 		t.Errorf("invalid image_url part")
 	}
+	if parts[2].Type != "file" || parts[2].File.FileID != "file-123" || parts[2].File.FileName != "test.txt" || parts[2].File.FileData != "dGVzdA==" {
+		t.Errorf("invalid file part: %v", parts[2])
+	}
 
 	s, err := json.Marshal(msgs)
 	if err != nil {
@@ -756,6 +768,103 @@ func TestMultipartChatMessageSerialization(t *testing.T) {
 	}
 }
 
+func TestChatMessagePartFile(t *testing.T) {
+	// Test file part with FileID
+	filePart := openai.ChatMessagePart{
+		Type: openai.ChatMessagePartTypeFile,
+		File: &openai.ChatMessagePartFile{
+			FileID: "file-abc123",
+		},
+	}
+
+	// Test serialization
+	data, err := json.Marshal(filePart)
+	if err != nil {
+		t.Fatalf("Expected no error: %s", err)
+	}
+
+	expected := `{"type":"file","file":{"file_id":"file-abc123"}}`
+	result := strings.ReplaceAll(string(data), " ", "")
+	if result != expected {
+		t.Errorf("Expected %s, got %s", expected, result)
+	}
+
+	// Test deserialization
+	var parsedPart openai.ChatMessagePart
+	err = json.Unmarshal(data, &parsedPart)
+	if err != nil {
+		t.Fatalf("Expected no error: %s", err)
+	}
+
+	if parsedPart.Type != openai.ChatMessagePartTypeFile {
+		t.Errorf("Expected type %s, got %s", openai.ChatMessagePartTypeFile, parsedPart.Type)
+	}
+	if parsedPart.File == nil {
+		t.Fatal("Expected File to be non-nil")
+	}
+	if parsedPart.File.FileID != "file-abc123" {
+		t.Errorf("Expected FileID %s, got %s", "file-abc123", parsedPart.File.FileID)
+	}
+
+	// Test file part with all fields
+	filePartComplete := openai.ChatMessagePart{
+		Type: openai.ChatMessagePartTypeFile,
+		File: &openai.ChatMessagePartFile{
+			FileID:   "file-xyz789",
+			FileName: "document.pdf",
+			FileData: "JVBERi0xLjQK", // base64 for "%PDF-1.4\n"
+		},
+	}
+
+	data, err = json.Marshal(filePartComplete)
+	if err != nil {
+		t.Fatalf("Expected no error: %s", err)
+	}
+
+	expected = `{"type":"file","file":{"file_id":"file-xyz789","filename":"document.pdf","file_data":"JVBERi0xLjQK"}}`
+	result = strings.ReplaceAll(string(data), " ", "")
+	if result != expected {
+		t.Errorf("Expected %s, got %s", expected, result)
+	}
+
+	// Test deserialization of complete file part
+	var parsedCompleteFile openai.ChatMessagePart
+	err = json.Unmarshal(data, &parsedCompleteFile)
+	if err != nil {
+		t.Fatalf("Expected no error: %s", err)
+	}
+
+	if parsedCompleteFile.File.FileID != "file-xyz789" {
+		t.Errorf("Expected FileID %s, got %s", "file-xyz789", parsedCompleteFile.File.FileID)
+	}
+	if parsedCompleteFile.File.FileName != "document.pdf" {
+		t.Errorf("Expected FileName %s, got %s", "document.pdf", parsedCompleteFile.File.FileName)
+	}
+	if parsedCompleteFile.File.FileData != "JVBERi0xLjQK" {
+		t.Errorf("Expected FileData %s, got %s", "JVBERi0xLjQK", parsedCompleteFile.File.FileData)
+	}
+}
+
+func TestChatMessagePartTypeConstants(t *testing.T) {
+	// Test that the new file constant is properly defined
+	if openai.ChatMessagePartTypeFile != "file" {
+		t.Errorf("Expected ChatMessagePartTypeFile to be 'file', got %s", openai.ChatMessagePartTypeFile)
+	}
+
+	// Test all part type constants
+	expectedTypes := map[openai.ChatMessagePartType]string{
+		openai.ChatMessagePartTypeText:     "text",
+		openai.ChatMessagePartTypeImageURL: "image_url",
+		openai.ChatMessagePartTypeFile:     "file",
+	}
+
+	for constant, expected := range expectedTypes {
+		if string(constant) != expected {
+			t.Errorf("Expected %s to be %s, got %s", constant, expected, string(constant))
+		}
+	}
+}
+
 // handleChatCompletionEndpoint Handles the ChatGPT completion endpoint by the test server.
 func handleChatCompletionEndpoint(w http.ResponseWriter, r *http.Request) {
 	var err error