feat(ai-proxy): add context cleanup command support (#3409)

plugins/wasm-go/extensions/ai-proxy/provider/request_helper.go

@@ -73,6 +73,73 @@ func insertContextMessage(request *chatCompletionRequest, content string) {
 	}
 }
 
+// cleanupContextMessages 根据配置的清理命令清理上下文消息
+// 查找最后一个完全匹配任意 cleanupCommands 的 user 消息，将该消息及之前所有非 system 消息清理掉，只保留 system 消息
+func cleanupContextMessages(body []byte, cleanupCommands []string) ([]byte, error) {
+	if len(cleanupCommands) == 0 {
+		return body, nil
+	}
+
+	request := &chatCompletionRequest{}
+	if err := json.Unmarshal(body, request); err != nil {
+		return body, fmt.Errorf("unable to unmarshal request for context cleanup: %v", err)
+	}
+
+	if len(request.Messages) == 0 {
+		return body, nil
+	}
+
+	// 从后往前查找最后一个匹配任意清理命令的 user 消息
+	cleanupIndex := -1
+	for i := len(request.Messages) - 1; i >= 0; i-- {
+		msg := request.Messages[i]
+		if msg.Role == roleUser {
+			content := msg.StringContent()
+			for _, cmd := range cleanupCommands {
+				if content == cmd {
+					cleanupIndex = i
+					break
+				}
+			}
+			if cleanupIndex != -1 {
+				break
+			}
+		}
+	}
+
+	// 没有找到匹配的清理命令
+	if cleanupIndex == -1 {
+		return body, nil
+	}
+
+	log.Debugf("[contextCleanup] found cleanup command at index %d, cleaning up messages", cleanupIndex)
+
+	// 构建新的消息列表：
+	// 1. 保留 cleanupIndex 之前的 system 消息（只保留 system，其他都清理）
+	// 2. 删除 cleanupIndex 位置的清理命令消息
+	// 3. 保留 cleanupIndex 之后的所有消息
+	var newMessages []chatMessage
+
+	// 处理 cleanupIndex 之前的消息，只保留 system
+	for i := 0; i < cleanupIndex; i++ {
+		msg := request.Messages[i]
+		if msg.Role == roleSystem {
+			newMessages = append(newMessages, msg)
+		}
+	}
+
+	// 跳过 cleanupIndex 位置的消息（清理命令本身）
+	// 保留 cleanupIndex 之后的所有消息
+	for i := cleanupIndex + 1; i < len(request.Messages); i++ {
+		newMessages = append(newMessages, request.Messages[i])
+	}
+
+	request.Messages = newMessages
+	log.Debugf("[contextCleanup] messages after cleanup: %d", len(newMessages))
+
+	return json.Marshal(request)
+}
+
 func ReplaceResponseBody(body []byte) error {
 	log.Debugf("response body: %s", string(body))
 	err := proxywasm.ReplaceHttpResponseBody(body)