Refactor API handlers and proxy logic

- Centralized `getClient` logic into a dedicated function to reduce redundancy.
- Moved proxy initialization to a new utility function `SetProxy` in `internal/util/proxy.go`.
- Replaced `Internal` handler with `CLIHandler` in `server.go` for improved clarity and consistency.
- Removed unused functions and redundant HTTP client setup across the codebase for better maintainability.

internal/api/cli-handlers.go

@@ -0,0 +1,228 @@
+package api
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"github.com/gin-gonic/gin"
+	"github.com/luispater/CLIProxyAPI/internal/client"
+	"github.com/luispater/CLIProxyAPI/internal/util"
+	log "github.com/sirupsen/logrus"
+	"github.com/tidwall/gjson"
+	"github.com/tidwall/sjson"
+	"io"
+	"net/http"
+	"time"
+)
+
+func (h *APIHandlers) CLIHandler(c *gin.Context) {
+	rawJson, _ := c.GetRawData()
+	requestRawURI := c.Request.URL.Path
+	if requestRawURI == "/v1internal:generateContent" {
+		h.internalGenerateContent(c, rawJson)
+	} else if requestRawURI == "/v1internal:streamGenerateContent" {
+		h.internalStreamGenerateContent(c, rawJson)
+	} else {
+		reqBody := bytes.NewBuffer(rawJson)
+		req, err := http.NewRequest("POST", fmt.Sprintf("https://cloudcode-pa.googleapis.com%s", c.Request.URL.RequestURI()), reqBody)
+		if err != nil {
+			c.JSON(http.StatusBadRequest, ErrorResponse{
+				Error: ErrorDetail{
+					Message: fmt.Sprintf("Invalid request: %v", err),
+					Type:    "invalid_request_error",
+				},
+			})
+			return
+		}
+		for key, value := range c.Request.Header {
+			req.Header[key] = value
+		}
+
+		httpClient, err := util.SetProxy(h.cfg, &http.Client{})
+		if err != nil {
+			log.Fatalf("set proxy failed: %v", err)
+		}
+
+		resp, err := httpClient.Do(req)
+		if err != nil {
+			c.JSON(http.StatusBadRequest, ErrorResponse{
+				Error: ErrorDetail{
+					Message: fmt.Sprintf("Invalid request: %v", err),
+					Type:    "invalid_request_error",
+				},
+			})
+			return
+		}
+
+		if resp.StatusCode < 200 || resp.StatusCode >= 300 {
+			defer func() {
+				if err = resp.Body.Close(); err != nil {
+					log.Printf("warn: failed to close response body: %v", err)
+				}
+			}()
+			bodyBytes, _ := io.ReadAll(resp.Body)
+
+			c.JSON(http.StatusBadRequest, ErrorResponse{
+				Error: ErrorDetail{
+					Message: string(bodyBytes),
+					Type:    "invalid_request_error",
+				},
+			})
+			return
+		}
+
+		defer func() {
+			_ = resp.Body.Close()
+		}()
+
+		for key, value := range resp.Header {
+			c.Header(key, value[0])
+		}
+		output, err := io.ReadAll(resp.Body)
+		if err != nil {
+			log.Errorf("Failed to read response body: %v", err)
+			return
+		}
+		_, _ = c.Writer.Write(output)
+	}
+}
+
+func (h *APIHandlers) internalStreamGenerateContent(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
+		}
+
+		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)
+		hasFirstResponse := false
+		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 {
+					hasFirstResponse = true
+					if cliClient.GetGenerativeLanguageAPIKey() != "" {
+						chunk, _ = sjson.SetRawBytes(chunk, "response", chunk)
+					}
+					_, _ = 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):
+				if hasFirstResponse {
+					_, _ = c.Writer.Write([]byte("\n"))
+					flusher.Flush()
+				}
+			}
+		}
+	}
+}
+
+func (h *APIHandlers) internalGenerateContent(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
+		}
+
+		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 {
+			_, _ = c.Writer.Write(resp)
+			cliCancel()
+			break
+		}
+	}
+}