phase 0 complete

internal/httpserver/spa.go

@@ -0,0 +1,37 @@
+package httpserver
+
+import (
+	"io/fs"
+	"net/http"
+)
+
+// spaHandler serves the embedded Vue SPA out of distFS (already rooted at
+// web/dist, i.e. index.html is at its top level). Any request path that
+// doesn't match a real file falls back to index.html so client-side routes
+// (deep links) resolve correctly.
+func spaHandler(distFS fs.FS) http.HandlerFunc {
+	fileServer := http.FileServer(http.FS(distFS))
+
+	return func(w http.ResponseWriter, r *http.Request) {
+		upath := r.URL.Path
+		if upath == "" || upath == "/" {
+			upath = "index.html"
+		} else {
+			upath = upath[1:] // strip leading slash for fs.Stat
+		}
+
+		if _, err := fs.Stat(distFS, upath); err != nil {
+			r = cloneWithPath(r, "/")
+		}
+
+		fileServer.ServeHTTP(w, r)
+	}
+}
+
+// cloneWithPath returns a shallow copy of r with URL.Path replaced, so the
+// original request (and its URL) is left untouched.
+func cloneWithPath(r *http.Request, path string) *http.Request {
+	r2 := r.Clone(r.Context())
+	r2.URL.Path = path
+	return r2
+}