feat: 添加基础通道实现和请求处理逻辑

internal/channel/base_channel.go

@@ -0,0 +1,122 @@
+package channel
+
+import (
+	"bytes"
+	"compress/gzip"
+	"fmt"
+	"gpt-load/internal/models"
+	"gpt-load/internal/response"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+
+	"github.com/gin-gonic/gin"
+	"github.com/sirupsen/logrus"
+)
+
+// RequestModifier defines a function that can modify the upstream request,
+// for example, by adding authentication headers.
+type RequestModifier func(req *http.Request, apiKey *models.APIKey)
+
+// BaseChannel provides a foundation for specific channel implementations.
+type BaseChannel struct {
+	Name       string
+	BaseURL    *url.URL
+	HTTPClient *http.Client
+}
+
+// ProcessRequest handles the generic logic of creating, sending, and handling an upstream request.
+func (ch *BaseChannel) ProcessRequest(c *gin.Context, apiKey *models.APIKey, modifier RequestModifier) error {
+	// 1. Create the upstream request
+	req, err := ch.createUpstreamRequest(c, apiKey, modifier)
+	if err != nil {
+		response.Error(c, http.StatusInternalServerError, "Failed to create upstream request")
+		return fmt.Errorf("create upstream request failed: %w", err)
+	}
+
+	// 2. Send the request
+	resp, err := ch.HTTPClient.Do(req)
+	if err != nil {
+		response.Error(c, http.StatusServiceUnavailable, "Upstream service unavailable")
+		return fmt.Errorf("upstream request failed: %w", err)
+	}
+	defer resp.Body.Close()
+
+	// 3. Handle non-200 status codes
+	if resp.StatusCode != http.StatusOK {
+		errorMsg := ch.getErrorMessage(resp)
+		response.Error(c, resp.StatusCode, errorMsg)
+		return fmt.Errorf("upstream returned status %d: %s", resp.StatusCode, errorMsg)
+	}
+
+	// 4. Stream the successful response back to the client
+	for key, values := range resp.Header {
+		for _, value := range values {
+			c.Header(key, value)
+		}
+	}
+	c.Status(http.StatusOK)
+	_, err = io.Copy(c.Writer, resp.Body)
+	if err != nil {
+		logrus.Errorf("Failed to copy response body to client: %v", err)
+		return fmt.Errorf("copy response body failed: %w", err)
+	}
+
+	return nil
+}
+
+func (ch *BaseChannel) createUpstreamRequest(c *gin.Context, apiKey *models.APIKey, modifier RequestModifier) (*http.Request, error) {
+	targetURL := *ch.BaseURL
+	targetURL.Path = c.Param("path")
+
+	body, err := io.ReadAll(c.Request.Body)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read request body: %w", err)
+	}
+	c.Request.Body = io.NopCloser(bytes.NewBuffer(body))
+
+	req, err := http.NewRequestWithContext(c.Request.Context(), c.Request.Method, targetURL.String(), bytes.NewBuffer(body))
+	if err != nil {
+		return nil, fmt.Errorf("failed to create new request: %w", err)
+	}
+
+	req.Header = c.Request.Header.Clone()
+	req.Host = ch.BaseURL.Host
+
+	// Apply the channel-specific modifications
+	if modifier != nil {
+		modifier(req, apiKey)
+	}
+
+	return req, nil
+}
+
+func (ch *BaseChannel) getErrorMessage(resp *http.Response) string {
+	bodyBytes, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return fmt.Sprintf("HTTP %d (failed to read error body: %v)", resp.StatusCode, err)
+	}
+
+	var errorMessage string
+	if resp.Header.Get("Content-Encoding") == "gzip" {
+		reader, gErr := gzip.NewReader(bytes.NewReader(bodyBytes))
+		if gErr != nil {
+			return string(bodyBytes)
+		}
+		defer reader.Close()
+		uncompressedBytes, rErr := io.ReadAll(reader)
+		if rErr != nil {
+			return fmt.Sprintf("gzip read error: %v", rErr)
+		}
+		errorMessage = string(uncompressedBytes)
+	} else {
+		errorMessage = string(bodyBytes)
+	}
+
+	if strings.TrimSpace(errorMessage) == "" {
+		return fmt.Sprintf("HTTP %d: %s", resp.StatusCode, http.StatusText(resp.StatusCode))
+	}
+
+	return errorMessage
+}