Add Gemini-compatible API and improve error handling

- Introduced a new Gemini-compatible API with routes under `/v1beta`.
- Added `GeminiHandler` to manage `generateContent` and `streamGenerateContent` actions.
- Enhanced `AuthMiddleware` to support `X-Goog-Api-Key` header.
- Improved client metadata handling and added conditional project ID updates in API calls.
- Updated logging to debug raw API request payloads for better traceability.

internal/api/gemini-handlers.go

@@ -0,0 +1,215 @@
+package api
+
+import (
+	"context"
+	"fmt"
+	"github.com/gin-gonic/gin"
+	"github.com/luispater/CLIProxyAPI/internal/client"
+	log "github.com/sirupsen/logrus"
+	"github.com/tidwall/gjson"
+	"github.com/tidwall/sjson"
+	"net/http"
+	"strings"
+	"time"
+)
+
+func (h *APIHandlers) GeminiHandler(c *gin.Context) {
+	var person struct {
+		Action string `uri:"action" binding:"required"`
+	}
+	if err := c.ShouldBindUri(&person); err != nil {
+		c.JSON(http.StatusBadRequest, ErrorResponse{
+			Error: ErrorDetail{
+				Message: fmt.Sprintf("Invalid request: %v", err),
+				Type:    "invalid_request_error",
+			},
+		})
+		return
+	}
+	action := strings.Split(person.Action, ":")
+	if len(action) != 2 {
+		c.JSON(http.StatusNotFound, ErrorResponse{
+			Error: ErrorDetail{
+				Message: fmt.Sprintf("%s not found.", c.Request.URL.Path),
+				Type:    "invalid_request_error",
+			},
+		})
+		return
+	}
+
+	modelName := action[0]
+	method := action[1]
+	rawJson, _ := c.GetRawData()
+	rawJson, _ = sjson.SetBytes(rawJson, "model", []byte(modelName))
+
+	if method == "generateContent" {
+		h.geminiGenerateContent(c, rawJson)
+	} else if method == "streamGenerateContent" {
+		h.geminiStreamGenerateContent(c, rawJson)
+	}
+}
+
+func (h *APIHandlers) geminiStreamGenerateContent(c *gin.Context, rawJson []byte) {
+	// Get the http.Flusher interface to manually flush the response.
+	flusher, ok := c.Writer.(http.Flusher)
+	if !ok {
+		c.JSON(http.StatusInternalServerError, ErrorResponse{
+			Error: ErrorDetail{
+				Message: "Streaming not supported",
+				Type:    "server_error",
+			},
+		})
+		return
+	}
+
+	modelResult := gjson.GetBytes(rawJson, "model")
+	modelName := modelResult.String()
+
+	cliCtx, cliCancel := context.WithCancel(context.Background())
+	var cliClient *client.Client
+	defer func() {
+		// Ensure the client's mutex is unlocked on function exit.
+		if cliClient != nil {
+			cliClient.RequestMutex.Unlock()
+		}
+	}()
+
+outLoop:
+	for {
+		var errorResponse *client.ErrorMessage
+		cliClient, errorResponse = h.getClient(modelName)
+		if errorResponse != nil {
+			c.Status(errorResponse.StatusCode)
+			_, _ = fmt.Fprint(c.Writer, errorResponse.Error)
+			flusher.Flush()
+			cliCancel()
+			return
+		}
+
+		template := `{"project":"","request":{},"model":""}`
+		template, _ = sjson.SetRaw(template, "request", string(rawJson))
+		template, _ = sjson.Set(template, "model", gjson.Get(template, "request.model").String())
+		template, _ = sjson.Delete(template, "request.model")
+		systemInstructionResult := gjson.Get(template, "request.system_instruction")
+		if systemInstructionResult.Exists() {
+			template, _ = sjson.SetRaw(template, "request.systemInstruction", systemInstructionResult.Raw)
+			template, _ = sjson.Delete(template, "request.system_instruction")
+		}
+		rawJson = []byte(template)
+
+		if glAPIKey := cliClient.GetGenerativeLanguageAPIKey(); glAPIKey != "" {
+			log.Debugf("Request use generative language API Key: %s", glAPIKey)
+		} else {
+			log.Debugf("Request use account: %s, project id: %s", cliClient.GetEmail(), cliClient.GetProjectID())
+		}
+
+		// Send the message and receive response chunks and errors via channels.
+		respChan, errChan := cliClient.SendRawMessageStream(cliCtx, rawJson)
+		for {
+			select {
+			// Handle client disconnection.
+			case <-c.Request.Context().Done():
+				if c.Request.Context().Err().Error() == "context canceled" {
+					log.Debugf("Client disconnected: %v", c.Request.Context().Err())
+					cliCancel() // Cancel the backend request.
+					return
+				}
+			// Process incoming response chunks.
+			case chunk, okStream := <-respChan:
+				if !okStream {
+					cliCancel()
+					return
+				} else {
+					if cliClient.GetGenerativeLanguageAPIKey() == "" {
+						responseResult := gjson.GetBytes(chunk, "response")
+						if responseResult.Exists() {
+							chunk = []byte(responseResult.Raw)
+						}
+					}
+					_, _ = c.Writer.Write([]byte("data: "))
+					_, _ = c.Writer.Write(chunk)
+					_, _ = c.Writer.Write([]byte("\n\n"))
+					flusher.Flush()
+				}
+			// Handle errors from the backend.
+			case err, okError := <-errChan:
+				if okError {
+					if err.StatusCode == 429 && h.cfg.QuotaExceeded.SwitchProject {
+						continue outLoop
+					} else {
+						c.Status(err.StatusCode)
+						_, _ = fmt.Fprint(c.Writer, err.Error.Error())
+						flusher.Flush()
+						cliCancel()
+					}
+					return
+				}
+			// Send a keep-alive signal to the client.
+			case <-time.After(500 * time.Millisecond):
+			}
+		}
+	}
+}
+
+func (h *APIHandlers) geminiGenerateContent(c *gin.Context, rawJson []byte) {
+	c.Header("Content-Type", "application/json")
+
+	modelResult := gjson.GetBytes(rawJson, "model")
+	modelName := modelResult.String()
+	cliCtx, cliCancel := context.WithCancel(context.Background())
+	var cliClient *client.Client
+	defer func() {
+		if cliClient != nil {
+			cliClient.RequestMutex.Unlock()
+		}
+	}()
+
+	for {
+		var errorResponse *client.ErrorMessage
+		cliClient, errorResponse = h.getClient(modelName)
+		if errorResponse != nil {
+			c.Status(errorResponse.StatusCode)
+			_, _ = fmt.Fprint(c.Writer, errorResponse.Error)
+			cliCancel()
+			return
+		}
+
+		template := `{"project":"","request":{},"model":""}`
+		template, _ = sjson.SetRaw(template, "request", string(rawJson))
+		template, _ = sjson.Set(template, "model", gjson.Get(template, "request.model").String())
+		template, _ = sjson.Delete(template, "request.model")
+		systemInstructionResult := gjson.Get(template, "request.system_instruction")
+		if systemInstructionResult.Exists() {
+			template, _ = sjson.SetRaw(template, "request.systemInstruction", systemInstructionResult.Raw)
+			template, _ = sjson.Delete(template, "request.system_instruction")
+		}
+		rawJson = []byte(template)
+
+		if glAPIKey := cliClient.GetGenerativeLanguageAPIKey(); glAPIKey != "" {
+			log.Debugf("Request use generative language API Key: %s", glAPIKey)
+		} else {
+			log.Debugf("Request use account: %s, project id: %s", cliClient.GetEmail(), cliClient.GetProjectID())
+		}
+		resp, err := cliClient.SendRawMessage(cliCtx, rawJson)
+		if err != nil {
+			if err.StatusCode == 429 && h.cfg.QuotaExceeded.SwitchProject {
+				continue
+			} else {
+				c.Status(err.StatusCode)
+				_, _ = c.Writer.Write([]byte(err.Error.Error()))
+				cliCancel()
+			}
+			break
+		} else {
+			if cliClient.GetGenerativeLanguageAPIKey() == "" {
+				responseResult := gjson.GetBytes(resp, "response")
+				if responseResult.Exists() {
+					resp = []byte(responseResult.Raw)
+				}
+			}
+			_, _ = c.Writer.Write(resp)
+			cliCancel()
+			break
+		}
+	}
+}

internal/api/server.go

@@ -70,6 +70,14 @@ func (s *Server) setupRoutes() {
 		v1.POST("/chat/completions", s.handlers.ChatCompletions)
 	}
 
+	// Gemini compatible API routes
+	v1beta := s.engine.Group("/v1beta")
+	v1beta.Use(AuthMiddleware(s.cfg))
+	{
+		v1beta.GET("/models", s.handlers.Models)
+		v1beta.POST("/models/:action", s.handlers.GeminiHandler)
+	}
+
 	// Root endpoint
 	s.engine.GET("/", func(c *gin.Context) {
 		c.JSON(http.StatusOK, gin.H{
@@ -140,7 +148,8 @@ func AuthMiddleware(cfg *config.Config) gin.HandlerFunc {
 
 		// Get the Authorization header
 		authHeader := c.GetHeader("Authorization")
-		if authHeader == "" {
+		authHeaderGoogle := c.GetHeader("X-Goog-Api-Key")
+		if authHeader == "" && authHeaderGoogle == "" {
 			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{
 				"error": "Missing API key",
 			})
@@ -159,7 +168,7 @@ func AuthMiddleware(cfg *config.Config) gin.HandlerFunc {
 		// Find the API key in the in-memory list
 		var foundKey string
 		for i := range cfg.ApiKeys {
-			if cfg.ApiKeys[i] == apiKey {
+			if cfg.ApiKeys[i] == apiKey || cfg.ApiKeys[i] == authHeaderGoogle {
 				foundKey = cfg.ApiKeys[i]
 				break
 			}

internal/client/client.go

@@ -311,6 +311,7 @@ func (c *Client) APIRequest(ctx context.Context, endpoint string, body interface
 			}
 		}()
 		bodyBytes, _ := io.ReadAll(resp.Body)
+		// log.Debug(string(jsonBody))
 		return nil, &ErrorMessage{resp.StatusCode, fmt.Errorf(string(bodyBytes))}
 	}
 
@@ -534,7 +535,9 @@ func (c *Client) SendMessageStream(ctx context.Context, rawJson []byte, model st
 
 // SendRawMessage handles a single conversational turn, including tool calls.
 func (c *Client) SendRawMessage(ctx context.Context, rawJson []byte) ([]byte, *ErrorMessage) {
+	if c.glAPIKey == "" {
 		rawJson, _ = sjson.SetBytes(rawJson, "project", c.GetProjectID())
+	}
 
 	modelResult := gjson.GetBytes(rawJson, "model")
 	model := modelResult.String()
@@ -584,7 +587,9 @@ func (c *Client) SendRawMessageStream(ctx context.Context, rawJson []byte) (<-ch
 		defer close(errChan)
 		defer close(dataChan)
 
+		if c.glAPIKey == "" {
 			rawJson, _ = sjson.SetBytes(rawJson, "project", c.GetProjectID())
+		}
 
 		modelResult := gjson.GetBytes(rawJson, "model")
 		model := modelResult.String()