initial commit

internal/web/web.go

@@ -0,0 +1,99 @@
+// Package web serves the embedded admin console as a single-page app.
+//
+// The assets are compiled into the binary, so a deployment is one file plus a
+// config; there is no node process in production and no CDN dependency. When
+// the assets are absent (a `go build` without `npm run build`) the server says
+// so plainly instead of returning a confusing 404.
+package web
+
+import (
+	"embed"
+	"fmt"
+	"io/fs"
+	"net/http"
+	"strconv"
+	"strings"
+)
+
+//go:embed all:dist
+var dist embed.FS
+
+// Available reports whether compiled assets are present in this binary.
+func Available() bool {
+	_, err := dist.Open("dist/index.html")
+	return err == nil
+}
+
+// Handler serves the console, falling back to index.html for client-side
+// routes so a deep link like /logs works on a hard refresh.
+func Handler(basePath string) (http.Handler, error) {
+	sub, err := fs.Sub(dist, "dist")
+	if err != nil {
+		return nil, fmt.Errorf("web: open assets: %w", err)
+	}
+	if _, err := fs.Stat(sub, "index.html"); err != nil {
+		return http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+			w.Header().Set("Content-Type", "text/html; charset=utf-8")
+			w.WriteHeader(http.StatusServiceUnavailable)
+			_, _ = w.Write([]byte(missingAssets))
+		}), nil
+	}
+	files := http.FileServer(http.FS(sub))
+	prefix := "/"
+	if basePath != "" && basePath != "/" {
+		prefix = "/" + strings.Trim(basePath, "/") + "/"
+	}
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		// Hashed asset filenames are immutable, so they can be cached hard.
+		if strings.HasPrefix(r.URL.Path, prefix+"assets/") {
+			w.Header().Set("Cache-Control", "public, max-age=31536000, immutable")
+		} else {
+			w.Header().Set("Cache-Control", "no-cache")
+		}
+		clean := strings.TrimPrefix(r.URL.Path, strings.TrimSuffix(prefix, "/"))
+		clean = strings.TrimPrefix(clean, "/")
+		if clean == "" {
+			clean = "index.html"
+		}
+		if _, err := fs.Stat(sub, clean); err != nil {
+			// Unknown path: hand it to the SPA router.
+			b, rerr := fs.ReadFile(sub, "index.html")
+			if rerr != nil {
+				http.NotFound(w, r)
+				return
+			}
+			w.Header().Set("Content-Type", "text/html; charset=utf-8")
+			w.Header().Set("Cache-Control", "no-cache")
+			w.WriteHeader(http.StatusOK)
+			_, _ = w.Write(b)
+			return
+		}
+		files.ServeHTTP(w, r)
+	}), nil
+}
+
+const missingAssets = `<!doctype html>
+<html><head><meta charset="utf-8"><title>fancy-dns</title>
+<style>body{font:16px/1.6 system-ui,sans-serif;max-width:40rem;margin:4rem auto;padding:0 1rem;color:#0f172a;background:#f8fafc}
+code{background:#e2e8f0;padding:.15em .4em;border-radius:.25rem}</style></head>
+<body><h1>fancy-dns</h1>
+<p>The admin API is running, but the web console was not built into this binary.</p>
+<p>Build it with <code>make web</code> (or <code>cd web &amp;&amp; npm ci &amp;&amp; npm run build</code>), then rebuild the binary.</p>
+<p>The JSON API is available under <code>/api</code>.</p></body></html>`
+
+// Version is the asset build stamp, exposed in the UI footer.
+func Version() string {
+	b, err := dist.ReadFile("dist/.build-version")
+	if err != nil {
+		return ""
+	}
+	return strings.TrimSpace(string(b))
+}
+
+// CacheControlMaxAge is the immutable-asset max age in seconds.
+const CacheControlMaxAge = 31536000
+
+// maxAgeHeader builds the Cache-Control value for a hashed asset.
+func maxAgeHeader(seconds int) string {
+	return "public, max-age=" + strconv.Itoa(seconds) + ", immutable"
+}