Fix URL of mirror being mangled on failure (#15443)

replaceUrlPrefixWithRandomMirror() is not meant to be called twice on
the same elements and this leads to the URL of the mirror being mangled.

This commit introduces another class (.use-mirror-pool-on-retry) on
which replaceUrlPrefixWithRandomMirror() is called when the verification
fails. The download button with .use-mirror-pool gets hidden and
replaced by one with .use-mirror-pool-on-retry.

This not very elegant but probably the simplest solution.

wiki/src/install/inc/js/download.js

@@ -216,7 +216,10 @@ document.addEventListener("DOMContentLoaded", function() {
     }
     else if (result === "failed") {
       show(document.getElementById("verification-failed"));
-      replaceUrlPrefixWithRandomMirror(document.querySelectorAll(".use-mirror-pool")); // Try again with different mirrors
+      // Try again with different mirrors
+      toggleDisplay(document.getElementsByClassName("use-mirror-pool"), "hide");
+      toggleDisplay(document.getElementsByClassName("use-mirror-pool-on-retry"), "show");
+      replaceUrlPrefixWithRandomMirror(document.querySelectorAll(".use-mirror-pool-on-retry"));
     }
     else if (result === "failed-again") {
       show(document.getElementById("verification-failed-again"));

wiki/src/install/inc/steps/download.inline.html

@@ -12,6 +12,7 @@
       <div id="step-download-iso">
         <h3><span class="step-number"><span class="debian windows linux mac-usb mac-dvd upgrade-tails">1.</span>1</span>Download Tails</h3>
         <a href="[[!inline pages="inc/stable_amd64_iso_url" raw="yes" sort="age"]]" id="download-iso" class="use-mirror-pool btn btn-primary inline-block indent">Download Tails [[!inline pages="inc/stable_amd64_version" raw="yes" sort="age"]] ISO image (<span class="remove-extra-space">[[!inline pages="inc/stable_amd64_iso_size" raw="yes" sort="age"]]</span>)</a>
+        <a href="[[!inline pages="inc/stable_amd64_iso_url" raw="yes" sort="age"]]" id="download-iso" class="use-mirror-pool-on-retry btn btn-primary inline-block indent">Download Tails [[!inline pages="inc/stable_amd64_version" raw="yes" sort="age"]] ISO image (<span class="remove-extra-space">[[!inline pages="inc/stable_amd64_iso_size" raw="yes" sort="age"]]</span>)</a>
         <p id="already-downloaded" class="indent"><a>I already downloaded Tails <span class="remove-extra-space">&nbsp;[[!inline pages="inc/stable_amd64_version" raw="yes" sort="age"]]</span>.</a></p>
       </div>
 
@@ -86,7 +87,7 @@
             <p>[[How does the extension work?|contribute/design/verification_extension]]</p>
             """]]
             </div>
-            <p><a href="[[!inline pages="inc/stable_amd64_iso_url" raw="yes" sort="age"]]" id="download-iso-again" class="use-mirror-pool">Please try to download again&hellip;</a></p>
+            <p><a href="[[!inline pages="inc/stable_amd64_iso_url" raw="yes" sort="age"]]" id="download-iso-again" class="use-mirror-pool-on-retry">Please try to download again&hellip;</a></p>
           </div>
           <div id="verification-failed-again" class="block">
             <p><b>Verification failed again!</b></p>

wiki/src/install/inc/stylesheets/download.css

@@ -23,7 +23,8 @@ h1 {
 #verification-failed-again,
 #skip-download-direct,
 #skip-download-bittorrent,
-#extension-version {
+#extension-version,
+.use-mirror-pool-on-retry {
   display: none;
 }