fix: integrate Gemini v2 modalities support and refactor response handling

relay/adaptor/gemini/main.go

@@ -8,19 +8,18 @@ import (
 	"net/http"
 	"strings"
 
-	"github.com/songquanpeng/one-api/common/render"
-
+	"github.com/gin-gonic/gin"
 	"github.com/songquanpeng/one-api/common"
 	"github.com/songquanpeng/one-api/common/config"
 	"github.com/songquanpeng/one-api/common/helper"
 	"github.com/songquanpeng/one-api/common/image"
 	"github.com/songquanpeng/one-api/common/logger"
 	"github.com/songquanpeng/one-api/common/random"
+	"github.com/songquanpeng/one-api/common/render"
+	"github.com/songquanpeng/one-api/relay/adaptor/geminiv2"
 	"github.com/songquanpeng/one-api/relay/adaptor/openai"
 	"github.com/songquanpeng/one-api/relay/constant"
 	"github.com/songquanpeng/one-api/relay/model"
-
-	"github.com/gin-gonic/gin"
 )
 
 // https://ai.google.dev/docs/gemini_api_overview?hl=zh-cn
@@ -61,12 +60,10 @@ func ConvertRequest(textRequest model.GeneralOpenAIRequest) *ChatRequest {
 			},
 		},
 		GenerationConfig: ChatGenerationConfig{
-			Temperature:     textRequest.Temperature,
-			TopP:            textRequest.TopP,
-			MaxOutputTokens: textRequest.MaxTokens,
-			ResponseModalities: []string{
-				"TEXT", "IMAGE",
-			},
+			Temperature:        textRequest.Temperature,
+			TopP:               textRequest.TopP,
+			MaxOutputTokens:    textRequest.MaxTokens,
+			ResponseModalities: geminiv2.GetModelModalities(textRequest.Model),
 		},
 	}
 	if textRequest.ResponseFormat != nil {

relay/adaptor/geminiv2/constants.go

@@ -1,5 +1,7 @@
 package geminiv2
 
+import "strings"
+
 // https://ai.google.dev/models/gemini
 
 var ModelList = []string{
@@ -14,3 +16,17 @@ var ModelList = []string{
 	"gemini-2.0-pro-exp-02-05",
 	"gemini-2.0-flash-exp-image-generation",
 }
+
+const (
+	ModalityText  = "TEXT"
+	ModalityImage = "IMAGE"
+)
+
+// GetModelModalities returns the modalities of the model.
+func GetModelModalities(model string) []string {
+	if strings.Contains(model, "-image-generation") {
+		return []string{ModalityText, ModalityImage}
+	}
+
+	return []string{ModalityText}
+}