feat(knowledge): 图片上传接口（S3 存储，限 5MB jpg/png/webp）

server-go/internal/handler/knowledge_image.go

@@ -0,0 +1,101 @@
+package handler
+
+import (
+	"crypto/rand"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"net/http"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"silk-server-go/internal/middleware"
+	"silk-server-go/internal/service"
+
+	"github.com/gin-gonic/gin"
+	"gorm.io/gorm"
+)
+
+// maxImageSize 知识库图片大小上限（5MB）
+const maxImageSize = 5 << 20
+
+// imageContentType 根据扩展名返回图片 Content-Type
+func imageContentType(ext string) (string, bool) {
+	switch strings.ToLower(ext) {
+	case ".jpg", ".jpeg":
+		return "image/jpeg", true
+	case ".png":
+		return "image/png", true
+	case ".webp":
+		return "image/webp", true
+	}
+	return "", false
+}
+
+// validateImageFile 校验图片文件名扩展名与大小
+func validateImageFile(filename string, size int64) error {
+	if size <= 0 || size > maxImageSize {
+		return errors.New("图片大小需在 1B~5MB 之间")
+	}
+	ext := strings.ToLower(filepath.Ext(filename))
+	if _, ok := imageContentType(ext); !ok {
+		return errors.New("仅支持 jpg/jpeg/png/webp 图片")
+	}
+	return nil
+}
+
+// buildImageKey 生成 knowledge/<日期>/<随机>.ext 的对象键
+func buildImageKey(filename string) (string, string, error) {
+	ext := strings.ToLower(filepath.Ext(filename))
+	if _, ok := imageContentType(ext); !ok {
+		return "", "", errors.New("仅支持 jpg/jpeg/png/webp 图片")
+	}
+	buf := make([]byte, 8)
+	if _, err := rand.Read(buf); err != nil {
+		return "", "", err
+	}
+	date := time.Now().Format("20060102")
+	key := fmt.Sprintf("knowledge/%s/%s%s", date, hex.EncodeToString(buf), ext)
+	return key, ext, nil
+}
+
+// uploadKnowledgeImage 上传知识库图片（multipart 字段名 file）
+func uploadKnowledgeImage(s3 *service.S3Service, bucket string) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		file, header, err := c.Request.FormFile("file")
+		if err != nil {
+			c.JSON(http.StatusBadRequest, gin.H{"error": "请选择图片文件（字段名 file）"})
+			return
+		}
+		defer file.Close()
+
+		if err := validateImageFile(header.Filename, header.Size); err != nil {
+			c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+			return
+		}
+		key, ext, err := buildImageKey(header.Filename)
+		if err != nil {
+			c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+			return
+		}
+		contentType, _ := imageContentType(ext)
+
+		if err := s3.EnsureBucket(bucket); err != nil {
+			c.JSON(http.StatusInternalServerError, gin.H{"error": "图片存储不可用: " + err.Error()})
+			return
+		}
+		if err := s3.UploadImage(bucket, key, file, contentType); err != nil {
+			c.JSON(http.StatusInternalServerError, gin.H{"error": "图片上传失败: " + err.Error()})
+			return
+		}
+
+		url := fmt.Sprintf("%s/%s/%s", s3.Endpoint(), bucket, key)
+		c.JSON(http.StatusOK, gin.H{"url": url, "name": header.Filename, "size": header.Size})
+	}
+}
+
+// uploadImageRoute 在知识库路由组中注册图片上传（由 RegisterKnowledgeRoutes 调用）
+func registerKnowledgeImageRoute(rg *gin.RouterGroup, db *gorm.DB, s3 *service.S3Service, bucket string) {
+	rg.POST("/knowledge/images", middleware.RequirePermission(db, "knowledge:write"), uploadKnowledgeImage(s3, bucket))
+}