Add share link UI after upload

internal/server/server_test.go

@@ -957,3 +957,69 @@ func TestDownloadCSPStaysInert(t *testing.T) {
 		}
 	}
 }
+
+// The result page is the only place a link to the info page is ever offered,
+// so losing it strands that page with no way to discover it.
+func TestResultPageOffersBothLinksAndAWayBack(t *testing.T) {
+	h := newHarness(t, nil)
+
+	var body bytes.Buffer
+	mw := multipart.NewWriter(&body)
+	fw, _ := mw.CreateFormFile("file", "thing.bin")
+	fw.Write([]byte("data"))
+	mw.Close()
+
+	req, _ := http.NewRequest("POST", h.ts.URL+"/api/upload", &body)
+	req.Header.Set("Content-Type", mw.FormDataContentType())
+	req.Header.Set("Accept", "text/html")
+	resp, err := h.ts.Client().Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer resp.Body.Close()
+	raw, _ := io.ReadAll(resp.Body)
+	page := string(raw)
+
+	id := h.store.List()[0].ID
+	for _, want := range []struct{ what, fragment string }{
+		{"the info page link", "/i/" + id},
+		{"the direct download link", "/d/" + id},
+		{"a way to upload another file", `href="/">Upload another file`},
+		{"the script that enables the copy buttons", "static/app.js"},
+	} {
+		if !strings.Contains(page, want.fragment) {
+			t.Errorf("the result page is missing %s (%q)", want.what, want.fragment)
+		}
+	}
+
+	// Copy buttons ship hidden, so a reader without JavaScript never sees a
+	// button that does nothing.
+	if strings.Count(page, `class="copy"`) != strings.Count(page, `hidden>Copy<`) {
+		t.Error("a copy button is not hidden by default")
+	}
+}
+
+// The JSON reply has to carry the same two links, since the script builds the
+// result card from it alone.
+func TestUploadJSONCarriesBothLinks(t *testing.T) {
+	h := newHarness(t, nil)
+	res := decode[uploadResult](t, h.upload(t, []byte("x"), nil))
+
+	if res.URL == "" || !strings.Contains(res.URL, "/d/"+res.ID) {
+		t.Errorf("url = %q, want the direct download", res.URL)
+	}
+	if res.InfoURL == "" || !strings.Contains(res.InfoURL, "/i/"+res.ID) {
+		t.Errorf("info_url = %q, want the info page", res.InfoURL)
+	}
+	// Both must actually resolve.
+	for _, u := range []string{res.URL, res.InfoURL} {
+		get, err := h.ts.Client().Get(u)
+		if err != nil {
+			t.Fatal(err)
+		}
+		get.Body.Close()
+		if get.StatusCode != http.StatusOK {
+			t.Errorf("GET %s => %s", u, get.Status)
+		}
+	}
+}