feat: add tool choice configuration and update steam handling in Gemini

relay/adaptor/gemini/main.go

@@ -34,6 +34,12 @@
 	"text":        "text/plain",
 }
 
+var toolChoiceTypeMap = map[string]string{
+	"none":     "NONE",
+	"auto":     "AUTO",
+	"required": "ANY",
+}
+
 // Setting safety to the lowest possible values since Gemini is already powerless enough
 func ConvertRequest(textRequest model.GeneralOpenAIRequest) *ChatRequest {
 	geminiRequest := ChatRequest{
@@ -92,7 +98,24 @@
 			},
 		}
 	}
-	shouldAddDummyModelMessage := false
+	if textRequest.ToolChoice != nil {
+		geminiRequest.ToolConfig = &ToolConfig{
+			FunctionCallingConfig: FunctionCallingConfig{
+				Mode: "auto",
+			},
+		}
+		switch mode := textRequest.ToolChoice.(type) {
+		case string:
+			geminiRequest.ToolConfig.FunctionCallingConfig.Mode = toolChoiceTypeMap[mode]
+		case map[string]interface{}:
+			geminiRequest.ToolConfig.FunctionCallingConfig.Mode = "ANY"
+			if fn, ok := mode["function"].(map[string]interface{}); ok {
+				if name, ok := fn["name"].(string); ok {
+					geminiRequest.ToolConfig.FunctionCallingConfig.AllowedFunctionNames = []string{name}
+				}
+			}
+		}
+	}
 	for _, message := range textRequest.Messages {
 		content := ChatContent{
 			Role: message.Role,
@@ -130,25 +153,12 @@
 		if content.Role == "assistant" {
 			content.Role = "model"
 		}
-		// Converting system prompt to prompt from user for the same reason
+		// Converting system prompt to SystemInstructions
 		if content.Role == "system" {
-			content.Role = "user"
-			shouldAddDummyModelMessage = true
+			geminiRequest.SystemInstruction = &content
+			continue
 		}
 		geminiRequest.Contents = append(geminiRequest.Contents, content)
-
-		// If a system message is the last message, we need to add a dummy model message to make gemini happy
-		if shouldAddDummyModelMessage {
-			geminiRequest.Contents = append(geminiRequest.Contents, ChatContent{
-				Role: "model",
-				Parts: []Part{
-					{
-						Text: "Okay",
-					},
-				},
-			})
-			shouldAddDummyModelMessage = false
-		}
 	}
 
 	return &geminiRequest
@@ -186,10 +196,16 @@
 	if g == nil {
 		return ""
 	}
-	if len(g.Candidates) > 0 && len(g.Candidates[0].Content.Parts) > 0 {
-		return g.Candidates[0].Content.Parts[0].Text
+	var builder strings.Builder
+	for _, candidate := range g.Candidates {
+		for idx, part := range candidate.Content.Parts {
+			if idx > 0 {
+				builder.WriteString("\n")
+			}
+			builder.WriteString(part.Text)
+		}
 	}
-	return ""
+	return builder.String()
 }
 
 type ChatCandidate struct {
@@ -252,8 +268,8 @@
 				choice.Message.ToolCalls = getToolCalls(&candidate)
 			} else {
 				var builder strings.Builder
-				for _, part := range candidate.Content.Parts {
-					if i > 0 {
+				for idx, part := range candidate.Content.Parts {
+					if idx > 0 {
 						builder.WriteString("\n")
 					}
 					builder.WriteString(part.Text)

relay/adaptor/gemini/model.go

@@ -1,10 +1,12 @@
 package gemini
 
 type ChatRequest struct {
-	Contents         []ChatContent        `json:"contents"`
-	SafetySettings   []ChatSafetySettings `json:"safety_settings,omitempty"`
-	GenerationConfig ChatGenerationConfig `json:"generation_config,omitempty"`
-	Tools            []ChatTools          `json:"tools,omitempty"`
+	Contents          []ChatContent        `json:"contents"`
+	SystemInstruction *ChatContent         `json:"system_instruction,omitempty"`
+	SafetySettings    []ChatSafetySettings `json:"safety_settings,omitempty"`
+	GenerationConfig  ChatGenerationConfig `json:"generation_config,omitempty"`
+	Tools             []ChatTools          `json:"tools,omitempty"`
+	ToolConfig        *ToolConfig          `json:"tool_config,omitempty"`
 }
 
 type EmbeddingRequest struct {
@@ -74,3 +76,12 @@ type ChatGenerationConfig struct {
 	CandidateCount   int      `json:"candidateCount,omitempty"`
 	StopSequences    []string `json:"stopSequences,omitempty"`
 }
+
+type FunctionCallingConfig struct {
+	Mode                 string   `json:"mode,omitempty"`
+	AllowedFunctionNames []string `json:"allowed_function_names,omitempty"`
+}
+
+type ToolConfig struct {
+	FunctionCallingConfig FunctionCallingConfig `json:"function_calling_config"`
+}