feat: Manifest 接口支持 ETag 条件请求

- ETag = SHA256(所有 siteId + configHash 拼接)
- 客户端传 If-None-Match 命中返回 304 无数据
- 替代新增 /latest 接口，同一端点高效轮询

par-api/src/main/java/com/par/api/controller/ManifestController.java

@@ -1,12 +1,16 @@
 package com.par.api.controller;
 
+import com.par.common.util.HmacUtil;
 import com.par.core.dto.ApiResponse;
 import com.par.core.entity.Site;
 import com.par.core.entity.SiteConfig;
 import com.par.core.mapper.SiteConfigMapper;
 import com.par.core.mapper.SiteMapper;
 import lombok.RequiredArgsConstructor;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
 import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestHeader;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RestController;
 
@@ -17,7 +21,7 @@ import java.util.stream.Collectors;
 
 /**
  * Manifest 控制器
- * 返回所有站点最新配置的索引
+ * 返回所有站点最新配置的索引，支持 ETag 条件请求
  */
 @RestController
 @RequestMapping("/api/v1/manifest")
@@ -28,15 +32,20 @@ public class ManifestController {
     private final SiteConfigMapper siteConfigMapper;
 
     /**
-     * 获取全局 Manifest
+     * 获取全局 Manifest（支持 ETag）
+     * 客户端传 If-None-Match 避免重复传输
      */
     @GetMapping
-    public ApiResponse<Map<String, Object>> getManifest() {
+    public ResponseEntity<ApiResponse<Map<String, Object>>> getManifest(
+            @RequestHeader(value = "If-None-Match", required = false) String ifNoneMatch) {
+
         List<Site> sites = siteMapper.selectList(
                 new com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper<Site>()
                         .eq(Site::getDeleted, 0)
         );
 
+        // 构建 entries 并计算 ETag
+        StringBuilder etagBuilder = new StringBuilder();
         List<Map<String, Object>> entries = sites.stream().map(site -> {
             Map<String, Object> entry = new HashMap<>();
             entry.put("siteId", site.getSiteId());
@@ -45,21 +54,31 @@ public class ManifestController {
             entry.put("schemaVersion", site.getSchemaVersion());
             entry.put("status", site.getStatus() != null ? site.getStatus().getValue() : null);
 
-            // 获取最新已批准配置
             SiteConfig latest = siteConfigMapper.selectLatestBySiteId(site.getSiteId());
             if (latest != null) {
                 entry.put("latestVersion", latest.getVersion());
                 entry.put("configHash", latest.getConfigHash());
                 entry.put("updatedAt", latest.getCreatedAt());
             }
+            // 参与 ETag 计算
+            etagBuilder.append(site.getSiteId())
+                    .append(latest != null ? latest.getConfigHash() : "none")
+                    .append(";");
 
             return entry;
         }).collect(Collectors.toList());
 
+        String etag = HmacUtil.sha256(etagBuilder.toString());
+
+        // ETag 匹配 → 304
+        if (ifNoneMatch != null && ifNoneMatch.equals(etag)) {
+            return ResponseEntity.status(HttpStatus.NOT_MODIFIED).eTag(etag).build();
+        }
+
         Map<String, Object> manifest = new HashMap<>();
         manifest.put("version", "1.0");
         manifest.put("sites", entries);
 
-        return ApiResponse.success(manifest);
+        return ResponseEntity.ok().eTag(etag).body(ApiResponse.success(manifest));
     }
 }