common web, refactor route finding/handling

* less duplication between alertmanager api and rest of the web handlers
* no need to replicate the context key

pkg/web/alerts.go

@@ -5,6 +5,7 @@ import (
 	"path/filepath"
 	"strings"
 
+	"github.com/synyx/tuwat/pkg/web/common"
 	"github.com/uptrace/opentelemetry-go-extra/otelzap"
 	"go.opentelemetry.io/otel/trace"
 	"go.uber.org/zap"
@@ -87,7 +88,7 @@ func (h *webHandler) ssealerts(w http.ResponseWriter, req *http.Request) {
 		}
 	}()
 
-	dashboardName := getField(req, 0)
+	dashboardName := common.GetField(req, 0)
 
 	renderer, cancel := h.sseRenderer(w, req, "alerts.gohtml")
 	defer cancel()

pkg/web/api/alertmanager/web.go

@@ -4,7 +4,6 @@ import (
 	"encoding/json"
 	"net/http"
 	"slices"
-	"strings"
 	"time"
 
 	"github.com/synyx/tuwat/pkg/aggregation"
@@ -48,29 +47,12 @@ func (h *alertmanagerHandler) ServeHTTP(w http.ResponseWriter, r *http.Request)
 			}
 
 			http.Error(w, "500 Internal Server Error", http.StatusInternalServerError)
-
 		}
 	}()
 
-	var allow []string
-	for _, route := range h.routes {
-		matches := route.Regex.FindStringSubmatch(r.URL.Path)
-		if len(matches) > 0 {
-			if r.Method != route.Method {
-				allow = append(allow, route.Method)
-				continue
-			}
-			route.Handler(w, r.WithContext(r.Context()))
-			return
-		}
-	}
-	if len(allow) > 0 {
-		w.Header().Set("Allow", strings.Join(allow, ", "))
-		http.Error(w, "405 method not allowed", http.StatusMethodNotAllowed)
-		return
+	if ok := common.HandleRoute(h.routes, w, r); !ok {
+		http.Error(w, "404 not found", http.StatusNotFound)
 	}
-
-	http.Error(w, "404 not found", http.StatusNotFound)
 }
 
 func (h *alertmanagerHandler) status(w http.ResponseWriter, _ *http.Request) {

pkg/web/common/routing.go

@@ -1,8 +1,10 @@
 package common
 
 import (
+	"context"
 	"net/http"
 	"regexp"
+	"strings"
 )
 
 func NewRoute(method, pattern string, handler http.HandlerFunc) Route {
@@ -14,3 +16,34 @@ type Route struct {
 	Regex   *regexp.Regexp
 	Handler http.HandlerFunc
 }
+
+func HandleRoute(routes []Route, w http.ResponseWriter, r *http.Request) bool {
+
+	var allow []string
+	for _, route := range routes {
+		matches := route.Regex.FindStringSubmatch(r.URL.Path)
+		if len(matches) > 0 {
+			if r.Method != route.Method {
+				allow = append(allow, route.Method)
+				continue
+			}
+			ctx := context.WithValue(r.Context(), ctxKey{}, matches[1:])
+			route.Handler(w, r.WithContext(ctx))
+			return true
+		}
+	}
+	if len(allow) > 0 {
+		w.Header().Set("Allow", strings.Join(allow, ", "))
+		http.Error(w, "405 method not allowed", http.StatusMethodNotAllowed)
+		return true
+	}
+
+	return false
+}
+
+type ctxKey struct{}
+
+func GetField(r *http.Request, index int) string {
+	fields := r.Context().Value(ctxKey{}).([]string)
+	return fields[index]
+}

pkg/web/silence.go

@@ -1,6 +1,10 @@
 package web
 
-import "net/http"
+import (
+	"net/http"
+
+	"github.com/synyx/tuwat/pkg/web/common"
+)
 
 func (h *webHandler) silence(w http.ResponseWriter, req *http.Request) {
 
@@ -9,12 +13,12 @@ func (h *webHandler) silence(w http.ResponseWriter, req *http.Request) {
 		user = hdr
 	}
 
-	alertId := getField(req, 0)
+	alertId := common.GetField(req, 0)
 
 	h.aggregator.Silence(req.Context(), alertId, user)
 
 	if req.Header.Get("Accept") == "text/vnd.turbo-stream.html" {
-		dashboardName := getField(req, 0)
+		dashboardName := common.GetField(req, 0)
 		renderer := h.partialRenderer(req, "alerts.gohtml")
 		aggregate := h.aggregator.Alerts(dashboardName)
 		renderer(w, 200, webContent{Content: aggregate})

pkg/web/web.go

@@ -7,19 +7,18 @@ import (
 	"embed"
 	"encoding/json"
 	"fmt"
-	"github.com/synyx/tuwat/pkg/web/common"
 	html "html/template"
 	"io/fs"
 	"net/http"
 	"os"
 	"path"
 	"runtime"
-	"strings"
 	"time"
 
 	"github.com/synyx/tuwat/pkg/aggregation"
 	"github.com/synyx/tuwat/pkg/config"
 	"github.com/synyx/tuwat/pkg/version"
+	"github.com/synyx/tuwat/pkg/web/common"
 	"github.com/uptrace/opentelemetry-go-extra/otelzap"
 	"go.opentelemetry.io/otel/trace"
 	"go.uber.org/zap"
@@ -89,30 +88,12 @@ func (h *webHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 			}
 
 			http.Error(w, "500 Internal Server Error", http.StatusInternalServerError)
-
 		}
 	}()
 
-	var allow []string
-	for _, route := range h.routes {
-		matches := route.Regex.FindStringSubmatch(r.URL.Path)
-		if len(matches) > 0 {
-			if r.Method != route.Method {
-				allow = append(allow, route.Method)
-				continue
-			}
-			ctx := context.WithValue(r.Context(), ctxKey{}, matches[1:])
-			route.Handler(w, r.WithContext(ctx))
-			return
-		}
+	if ok := common.HandleRoute(h.routes, w, r); !ok {
+		h.notFound(w, r)
 	}
-	if len(allow) > 0 {
-		w.Header().Set("Allow", strings.Join(allow, ", "))
-		http.Error(w, "405 method not allowed", http.StatusMethodNotAllowed)
-		return
-	}
-
-	h.notFound(w, r)
 }
 
 type renderFunc func(w http.ResponseWriter, statusCode int, data webContent)
@@ -312,13 +293,6 @@ func (h *webHandler) wsRenderer(s *websocket.Conn, patterns ...string) wsRenderF
 	}
 }
 
-type ctxKey struct{}
-
-func getField(r *http.Request, index int) string {
-	fields := r.Context().Value(ctxKey{}).([]string)
-	return fields[index]
-}
-
 func niceDuration(d time.Duration) string {
 	if d > 2*time.Hour*24 {
 		return fmt.Sprintf("%.0fd", d.Hours()/24)