feat: ship Barkstack UI plugin

internal/adminui/handler.go

@@ -0,0 +1,118 @@
+// Package adminui serves PawSQL's Barkstack UI plugin and small read-only status API.
+package adminui
+
+import (
+	"embed"
+	"encoding/json"
+	"io/fs"
+	"mime"
+	"net/http"
+	"path"
+	"strings"
+)
+
+//go:embed dist
+var embeddedUI embed.FS
+
+const entryPath = "/barkstack/ui/assets/entry.js"
+
+type manifest struct {
+	APIVersion  string           `json:"apiVersion"`
+	ID          string           `json:"id"`
+	Name        string           `json:"name"`
+	Description string           `json:"description"`
+	Icon        string           `json:"icon"`
+	Mount       string           `json:"mount"`
+	Entry       string           `json:"entry"`
+	Element     string           `json:"element"`
+	Navigation  []navigationItem `json:"navigation"`
+}
+
+type navigationItem struct {
+	Label string `json:"label"`
+	Path  string `json:"path"`
+	Icon  string `json:"icon"`
+}
+
+type RouteSummary struct {
+	Name     string `json:"name"`
+	Hostname string `json:"hostname,omitempty"`
+	Managed  bool   `json:"managed"`
+}
+
+type statusResponse struct {
+	Status   string         `json:"status"`
+	Routes   []RouteSummary `json:"routes"`
+	Endpoint string         `json:"endpoint"`
+}
+
+type handler struct {
+	assets fs.FS
+	routes []RouteSummary
+}
+
+func Handler(routes []RouteSummary) http.Handler {
+	assets, err := fs.Sub(embeddedUI, "dist")
+	if err != nil {
+		panic(err)
+	}
+	copyRoutes := append([]RouteSummary(nil), routes...)
+	return &handler{assets: assets, routes: copyRoutes}
+}
+
+func (h *handler) ServeHTTP(response http.ResponseWriter, request *http.Request) {
+	if request.Method != http.MethodGet && request.Method != http.MethodHead {
+		response.Header().Set("Allow", "GET, HEAD")
+		http.Error(response, "method not allowed", http.StatusMethodNotAllowed)
+		return
+	}
+	switch request.URL.Path {
+	case "/barkstack/ui/manifest.json":
+		h.serveJSON(response, request, manifest{
+			APIVersion: "barkstack.dev/ui/v1", ID: "pawsql", Name: "PawSQL",
+			Description: "PostgreSQL routing for Barkstack", Icon: "database", Mount: "/pawsql",
+			Entry: entryPath, Element: "barkstack-pawsql",
+			Navigation: []navigationItem{{Label: "PawSQL", Path: "/pawsql", Icon: "database"}},
+		})
+	case "/barkstack/ui/status.json":
+		h.serveJSON(response, request, statusResponse{Status: "running", Routes: h.routes, Endpoint: "*.pawsql.barkstack.dev:5432"})
+	default:
+		h.serveAsset(response, request)
+	}
+}
+
+func (h *handler) serveJSON(response http.ResponseWriter, request *http.Request, value any) {
+	response.Header().Set("Content-Type", "application/json")
+	response.Header().Set("Cache-Control", "no-store")
+	if request.Method == http.MethodHead {
+		return
+	}
+	_ = json.NewEncoder(response).Encode(value)
+}
+
+func (h *handler) serveAsset(response http.ResponseWriter, request *http.Request) {
+	const prefix = "/barkstack/ui/assets/"
+	if !strings.HasPrefix(request.URL.Path, prefix) {
+		http.NotFound(response, request)
+		return
+	}
+	assetName := strings.TrimPrefix(request.URL.Path, "/barkstack/ui/")
+	if assetName == "" || !fs.ValidPath(assetName) || path.Clean(assetName) != assetName || strings.Contains(assetName, "\\") {
+		http.NotFound(response, request)
+		return
+	}
+	contents, err := fs.ReadFile(h.assets, assetName)
+	if err != nil {
+		http.NotFound(response, request)
+		return
+	}
+	if contentType := mime.TypeByExtension(path.Ext(assetName)); contentType != "" {
+		response.Header().Set("Content-Type", contentType)
+	}
+	response.Header().Set("Cache-Control", "public, max-age=31536000, immutable")
+	response.Header().Set("X-Content-Type-Options", "nosniff")
+	if request.Method == http.MethodHead {
+		return
+	}
+	_, _ = response.Write(contents)
+}