Add media proxy feature for resource downloading

- Introduced a new API endpoint `GET /api/v1/video/proxy` to facilitate media resource downloads, allowing users to bypass domain restrictions imposed by WeChat.
- Updated configuration to include proxy settings such as `SHORT_VIDEO_PROXY_ENABLED`, `SHORT_VIDEO_PROXY_ALLOWED_DOMAINS`, `SHORT_VIDEO_PROXY_MAX_SIZE_MB`, and `SHORT_VIDEO_PROXY_TIMEOUT_SECONDS`.
- Enhanced the `ShortVideoConfig` struct to accommodate new proxy-related fields.
- Improved error handling for proxy requests, including checks for allowed domains and file size limits.
- Updated documentation to reflect the new proxy functionality and its configuration options, ensuring clarity for users and developers.

internal/remove_watermark/handler/video_handler.go

@@ -2,8 +2,10 @@ package handler
 
 import (
 	"errors"
+	"io"
 	"net/http"
 	"net/url"
+	"strconv"
 	"strings"
 	"time"
 
@@ -36,6 +38,10 @@ type reportDownloadFailureRequest struct {
 	UserAgent    string `json:"userAgent"`
 }
 
+type proxyMediaRequest struct {
+	URL string `form:"url" binding:"required"`
+}
+
 func (h *VideoHandler) RemoveWatermark(c *gin.Context) {
 	var req removeWatermarkRequest
 	if err := c.ShouldBindJSON(&req); err != nil {
@@ -136,3 +142,65 @@ func (h *VideoHandler) ReportDownloadFailure(c *gin.Context) {
 		"reported": true,
 	}))
 }
+
+// ProxyMedia 代理媒体资源下载
+// 该接口用于中转视频/图片等媒体资源，使小程序可以通过当前域名下载，避免微信域名限制
+func (h *VideoHandler) ProxyMedia(c *gin.Context) {
+	var req proxyMediaRequest
+	if err := c.ShouldBindQuery(&req); err != nil {
+		c.JSON(http.StatusBadRequest, model.Error(http.StatusBadRequest, "请求参数错误，缺少 url 参数"))
+		return
+	}
+
+	targetURL := strings.TrimSpace(req.URL)
+	if targetURL == "" {
+		c.JSON(http.StatusBadRequest, model.Error(http.StatusBadRequest, "url 参数不能为空"))
+		return
+	}
+
+	// 调用 service 层进行代理
+	result, err := h.videoService.ProxyMedia(c.Request.Context(), targetURL)
+	if err != nil {
+		switch {
+		case errors.Is(err, service.ErrProxyDisabled):
+			c.JSON(http.StatusServiceUnavailable, model.Error(http.StatusServiceUnavailable, "代理服务未启用"))
+			return
+		case errors.Is(err, service.ErrProxyInvalidURL):
+			c.JSON(http.StatusBadRequest, model.Error(http.StatusBadRequest, "无效的代理地址"))
+			return
+		case errors.Is(err, service.ErrProxyDomainBlocked):
+			c.JSON(http.StatusForbidden, model.Error(http.StatusForbidden, "该域名不在允许列表中"))
+			return
+		case errors.Is(err, service.ErrProxyFileTooLarge):
+			c.JSON(http.StatusRequestEntityTooLarge, model.Error(http.StatusRequestEntityTooLarge, "文件过大，超出限制"))
+			return
+		default:
+			var thirdPartyErr *service.ThirdPartyError
+			if errors.As(err, &thirdPartyErr) {
+				c.JSON(http.StatusBadGateway, model.Error(http.StatusBadGateway, "上游服务返回错误"))
+				return
+			}
+			c.JSON(http.StatusInternalServerError, model.Error(http.StatusInternalServerError, "代理请求失败"))
+			return
+		}
+	}
+
+	// 确保关闭响应体
+	defer result.Body.Close()
+
+	// 设置响应头
+	c.Header("Content-Type", result.ContentType)
+	if result.ContentLength > 0 {
+		c.Header("Content-Length", strconv.FormatInt(result.ContentLength, 10))
+	}
+	// 允许跨域（如果需要）
+	c.Header("Access-Control-Allow-Origin", "*")
+	// 设置缓存头，减少重复请求
+	c.Header("Cache-Control", "public, max-age=86400")
+
+	// 流式输出响应体
+	c.Status(result.StatusCode)
+
+	// 使用 io.Copy 进行流式传输，避免一次性加载到内存
+	_, _ = io.Copy(c.Writer, result.Body)
+}