QS: logs pipelines preview http handler (#3701)

* feat: add logsparsingpipeline controller api for pipeline previews

* feat: add http handler and route for generating pipeline previews

* feat: use a response model for pipeline previews response

pkg/query-service/app/http_handler.go

@@ -2320,6 +2320,7 @@ func (aH *APIHandler) RegisterLogsRoutes(router *mux.Router, am *AuthMiddleware)
 	subRouter.HandleFunc("/aggregate", am.ViewAccess(aH.logAggregate)).Methods(http.MethodGet)
 
 	// log pipelines
+	subRouter.HandleFunc("/pipelines/preview", am.ViewAccess(aH.PreviewLogsPipelinesHandler)).Methods(http.MethodPost)
 	subRouter.HandleFunc("/pipelines/{version}", am.ViewAccess(aH.ListLogsPipelinesHandler)).Methods(http.MethodGet)
 	subRouter.HandleFunc("/pipelines", am.EditAccess(aH.CreateLogsPipeline)).Methods(http.MethodPost)
 }
@@ -2455,6 +2456,26 @@ func parseAgentConfigVersion(r *http.Request) (int, *model.ApiError) {
 	return int(version64), nil
 }
 
+func (ah *APIHandler) PreviewLogsPipelinesHandler(w http.ResponseWriter, r *http.Request) {
+	req := logparsingpipeline.PipelinesPreviewRequest{}
+
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		RespondError(w, model.BadRequest(err), nil)
+		return
+	}
+
+	resultLogs, apiErr := ah.LogsParsingPipelineController.PreviewLogsPipelines(
+		r.Context(), &req,
+	)
+
+	if apiErr != nil {
+		RespondError(w, apiErr, nil)
+		return
+	}
+
+	ah.Respond(w, resultLogs)
+}
+
 func (ah *APIHandler) ListLogsPipelinesHandler(w http.ResponseWriter, r *http.Request) {
 
 	version, err := parseAgentConfigVersion(r)

pkg/query-service/app/logparsingpipeline/controller.go

@@ -140,3 +140,29 @@ func (ic *LogParsingPipelineController) GetPipelinesByVersion(
 		Pipelines:     pipelines,
 	}, nil
 }
+
+type PipelinesPreviewRequest struct {
+	Pipelines []Pipeline        `json:"pipelines"`
+	Logs      []model.SignozLog `json:"logs"`
+}
+
+type PipelinesPreviewResponse struct {
+	OutputLogs []model.SignozLog `json:"logs"`
+}
+
+func (ic *LogParsingPipelineController) PreviewLogsPipelines(
+	ctx context.Context,
+	request *PipelinesPreviewRequest,
+) (*PipelinesPreviewResponse, *model.ApiError) {
+	result, err := SimulatePipelinesProcessing(
+		ctx, request.Pipelines, request.Logs,
+	)
+
+	if err != nil {
+		return nil, err
+	}
+
+	return &PipelinesPreviewResponse{
+		OutputLogs: result,
+	}, nil
+}