Frontend: Add a first page and previous page buttons for channel navigation (#4123)

7 files changed, 139 insertions, 5 deletions

diff --git a/assets/js/pagination.js b/assets/js/pagination.js
new file mode 100644
index 00000000..2e560a34
--- /dev/null
+++ b/assets/js/pagination.js
@@ -0,0 +1,93 @@
+'use strict';
+
+const CURRENT_CONTINUATION = (new URL(document.location)).searchParams.get("continuation");
+const CONT_CACHE_KEY = `continuation_cache_${encodeURIComponent(window.location.pathname)}`;
+
+function get_data(){
+    return JSON.parse(sessionStorage.getItem(CONT_CACHE_KEY)) || [];
+}
+
+function save_data(){
+    const prev_data = get_data();
+    prev_data.push(CURRENT_CONTINUATION);
+
+    sessionStorage.setItem(CONT_CACHE_KEY, JSON.stringify(prev_data));
+}
+
+function button_press(){
+    let prev_data = get_data();
+    if (!prev_data.length) return null;
+
+    // Sanity check. Nowhere should the current continuation token exist in the cache 
+    // but it can happen when using the browser's back feature. As such we'd need to travel
+    // back to the point where the current continuation token first appears in order to 
+    // account for the rewind.
+    const conflict_at = prev_data.indexOf(CURRENT_CONTINUATION);
+    if (conflict_at != -1) {
+        prev_data.length = conflict_at;
+    }
+
+    const prev_ctoken = prev_data.pop();
+
+    // On the first page, the stored continuation token is null.
+    if (prev_ctoken === null) {
+        sessionStorage.removeItem(CONT_CACHE_KEY);
+        let url = set_continuation();
+        window.location.href = url;
+
+        return;
+    }
+
+    sessionStorage.setItem(CONT_CACHE_KEY, JSON.stringify(prev_data));
+    let url = set_continuation(prev_ctoken);
+
+    window.location.href = url;
+};
+
+// Method to set the current page's continuation token
+// Removes the continuation parameter when a continuation token is not given
+function set_continuation(prev_ctoken = null){
+    let url = window.location.href.split('?')[0];
+    let params = window.location.href.split('?')[1];
+    let url_params = new URLSearchParams(params);
+
+    if (prev_ctoken) {
+        url_params.set("continuation", prev_ctoken);
+    } else {
+        url_params.delete('continuation');
+    };
+
+    if(Array.from(url_params).length > 0){
+        return `${url}?${url_params.toString()}`;
+    } else {
+        return url;
+    }
+}
+
+addEventListener('DOMContentLoaded', function(){
+    const pagination_data = JSON.parse(document.getElementById('pagination-data').textContent);
+    const next_page_containers = document.getElementsByClassName("page-next-container");
+
+    for (let container of next_page_containers){
+        const next_page_button = container.getElementsByClassName("pure-button")
+
+        // exists?
+        if (next_page_button.length > 0){
+            next_page_button[0].addEventListener("click", save_data);
+        }
+    }
+
+    // Only add previous page buttons when not on the first page
+    if (CURRENT_CONTINUATION) {
+        const prev_page_containers = document.getElementsByClassName("page-prev-container")
+
+        for (let container of prev_page_containers) {
+            if (pagination_data.is_rtl) {
+                container.innerHTML = `<button class="pure-button pure-button-secondary">${pagination_data.prev_page}&nbsp;&nbsp;<i class="icon ion-ios-arrow-forward"></i></button>`
+            } else {
+                container.innerHTML = `<button class="pure-button pure-button-secondary"><i class="icon ion-ios-arrow-back"></i>&nbsp;&nbsp;${pagination_data.prev_page}</button>`
+            }
+            container.getElementsByClassName("pure-button")[0].addEventListener("click", button_press);
+        }
+    }
+});
diff --git a/locales/de.json b/locales/de.json
index 151f2abe..a9a62619 100644
--- a/locales/de.json
+++ b/locales/de.json
@@ -11,6 +11,7 @@
     "last": "neueste",
     "Next page": "Nächste Seite",
     "Previous page": "Vorherige Seite",
+    "First page": "Erste Seite",
     "Clear watch history?": "Verlauf löschen?",
     "New password": "Neues Passwort",
     "New passwords must match": "Neue Passwörter müssen übereinstimmen",
diff --git a/locales/en-US.json b/locales/en-US.json
index c23f6bc3..381bcab5 100644
--- a/locales/en-US.json
+++ b/locales/en-US.json
@@ -33,6 +33,7 @@
     "last": "last",
     "Next page": "Next page",
     "Previous page": "Previous page",
+    "First page": "First page",
     "Clear watch history?": "Clear watch history?",
     "New password": "New password",
     "New passwords must match": "New passwords must match",
diff --git a/locales/ru.json b/locales/ru.json
index 80c98de8..31ef1a33 100644
--- a/locales/ru.json
+++ b/locales/ru.json
@@ -11,6 +11,7 @@
     "last": "последние",
     "Next page": "Следующая страница",
     "Previous page": "Предыдущая страница",
+    "First page": "Первая страница",
     "Clear watch history?": "Очистить историю просмотров?",
     "New password": "Новый пароль",
     "New passwords must match": "Новые пароли не совпадают",
diff --git a/src/invidious/frontend/pagination.cr b/src/invidious/frontend/pagination.cr
index 3f931f4e..a29f5936 100644
--- a/src/invidious/frontend/pagination.cr
+++ b/src/invidious/frontend/pagination.cr
@@ -3,6 +3,24 @@ require "uri"
 module Invidious::Frontend::Pagination
   extend self
 
+  private def first_page(str : String::Builder, locale : String?, url : String)
+    str << %(<a href=") << url << %(" class="pure-button pure-button-secondary">)
+
+    if locale_is_rtl?(locale)
+      # Inverted arrow ("first" points to the right)
+      str << translate(locale, "First page")
+      str << "&nbsp;&nbsp;"
+      str << %(<i class="icon ion-ios-arrow-forward"></i>)
+    else
+      # Regular arrow ("first" points to the left)
+      str << %(<i class="icon ion-ios-arrow-back"></i>)
+      str << "&nbsp;&nbsp;"
+      str << translate(locale, "First page")
+    end
+
+    str << "</a>"
+  end
+
   private def previous_page(str : String::Builder, locale : String?, url : String)
     # Link
     str << %(<a href=") << url << %(" class="pure-button pure-button-secondary">)
@@ -72,18 +90,24 @@ module Invidious::Frontend::Pagination
     end
   end
 
-  def nav_ctoken(locale : String?, *, base_url : String | URI, ctoken : String?)
+  def nav_ctoken(locale : String?, *, base_url : String | URI, ctoken : String?, first_page : Bool, params : URI::Params)
     return String.build do |str|
       str << %(<div class="h-box">\n)
       str << %(<div class="page-nav-container flexible">\n)
 
-      str << %(<div class="page-prev-container flex-left"></div>\n)
+      str << %(<div class="page-prev-container flex-left">)
+
+      if !first_page
+        self.first_page(str, locale, base_url.to_s)
+      end
+
+      str << %(</div>\n)
 
       str << %(<div class="page-next-container flex-right">)
 
       if !ctoken.nil?
-        params_next = URI::Params{"continuation" => ctoken}
-        url_next = HttpServer::Utils.add_params_to_url(base_url, params_next)
+        params["continuation"] = ctoken
+        url_next = HttpServer::Utils.add_params_to_url(base_url, params)
 
         self.next_page(str, locale, url_next.to_s)
       end
diff --git a/src/invidious/views/channel.ecr b/src/invidious/views/channel.ecr
index a84e44bc..1fe8ab7e 100644
--- a/src/invidious/views/channel.ecr
+++ b/src/invidious/views/channel.ecr
@@ -20,7 +20,9 @@
 
   page_nav_html = IV::Frontend::Pagination.nav_ctoken(locale,
     base_url: relative_url,
-    ctoken: next_continuation
+    ctoken: next_continuation,
+    first_page: continuation.nil?,
+    params: env.params.query,
   )
 %>
 
@@ -40,6 +42,8 @@
 <link rel="alternate" type="application/rss+xml" title="RSS" href="/feed/channel/<%= ucid %>" />
 <%- end -%>
 
+<script src="/js/pagination.js?v=<%= ASSET_COMMIT %>"></script>
+
 <link rel="alternate" href="<%= youtube_url %>">
 <title><%= author %> - Invidious</title>
 <% end %>
diff --git a/src/invidious/views/components/items_paginated.ecr b/src/invidious/views/components/items_paginated.ecr
index 4534a0a3..f69df3fe 100644
--- a/src/invidious/views/components/items_paginated.ecr
+++ b/src/invidious/views/components/items_paginated.ecr
@@ -8,4 +8,14 @@
 
 <%= page_nav_html %>
 
+<script id="pagination-data" type="application/json">
+<%=
+{
+   "next_page" => translate(locale, "Next page"),
+   "prev_page" => translate(locale, "Previous page"),
+   "is_rtl"    => locale_is_rtl?(locale)
+}.to_pretty_json
+%>
+</script>
+
 <script src="/js/watched_indicator.js"></script>