Implement UI to prune to last N replies. #767

src/General/Config.coffee

@@ -1012,3 +1012,7 @@ Config =
 
   customCooldown: 0
   customCooldownEnabled: true
+
+  pruneReplies:
+    'Prune Replies': false
+    'Max Replies': 1000

src/General/Main.coffee

@@ -446,6 +446,7 @@ Main =
     ['Keybinds',                  Keybinds]
     ['Banner',                    Banner]
     ['Flash Features',            Flash]
+    ['Prune Replies',             PruneReplies]
     <% if (tests_enabled) { %>
     ['Build Test',                BuildTest]
     <% } %>

src/Monitoring/PruneReplies.coffee

@@ -0,0 +1,72 @@
+PruneReplies =
+  init: ->
+    return unless g.VIEW is 'thread' and not Conf['Quote Threading']
+
+    label = UI.checkbox 'Prune Replies', 'Show Last'
+    el = $.el 'span',
+      title: 'Maximum number of replies to show.'
+    ,
+      <%= html(' <input type="number" name="Max Replies" min="0" step="1" value="${Conf["Max Replies"]}" class="field">') %>
+    $.prepend el, label
+
+    @inputs =
+      enabled: label.firstElementChild
+      replies: el.lastElementChild
+
+    $.on @inputs.enabled, 'change', $.cb.checked
+    $.on @inputs.replies, 'change', $.cb.value
+
+    Header.menu.addEntry
+      el:    el
+      order: 190
+
+    Thread.callbacks.push
+      name: 'Prune Replies'
+      cb:   @node
+
+  position: 0
+  hidden: 0
+  total: 0
+
+  node: ->
+    PruneReplies.thread = @
+    PruneReplies.total = @posts.keys.length - 1
+    $.on PruneReplies.inputs.enabled, 'change', PruneReplies.setEnabled
+    $.on PruneReplies.inputs.enabled, 'change', PruneReplies.update
+    if Conf['Prune Replies']
+      PruneReplies.setEnabled()
+      PruneReplies.update()
+
+  setEnabled: ->
+    PruneReplies.container or= $.frag()
+    onOff = if Conf['Prune Replies'] then $.on else $.off
+    onOff PruneReplies.inputs.replies, 'change',       PruneReplies.update
+    onOff d,                           'ThreadUpdate', PruneReplies.update
+
+  update: (e) ->
+    if e and e.type is 'ThreadUpdate' and not e.detail[404]
+      PruneReplies.total += e.detail.newPosts.length
+
+    hidden2 = if Conf['Prune Replies']
+      Math.max(PruneReplies.total - +Conf["Max Replies"], 0)
+    else
+      0
+
+    {posts, OP} = PruneReplies.thread
+
+    if PruneReplies.hidden < hidden2
+      while PruneReplies.hidden < hidden2 and PruneReplies.position < posts.keys.length
+        post = posts[posts.keys[PruneReplies.position++]]
+        if post.isReply and not post.isFetchedQuote
+          $.add PruneReplies.container, post.nodes.root
+          PruneReplies.hidden++
+
+    else if PruneReplies.hidden > hidden2
+      frag = $.frag()
+      while PruneReplies.hidden > hidden2 and PruneReplies.position > 0
+        post = posts[posts.keys[--PruneReplies.position]]
+        if post.isReply and not post.isFetchedQuote
+          $.prepend frag, post.nodes.root
+          PruneReplies.hidden--
+      $.after OP.nodes.root, frag
+      $.event 'PostsInserted'

src/css/style.css

@@ -1759,6 +1759,9 @@ a:only-of-type > .remove {
   position: relative;
   top: 2px;
 }
+.entry input[type="number"] {
+  width: 4em;
+}
 .entry.has-shortcut-text {
   display: flex;
   justify-content: space-between;
@@ -2077,9 +2080,6 @@ grunt.file.expand('src/Linkification/icons/*.png').map(function(file) {
 :root.gal-hide-thumbnails:.gal-fit-height:not(.gal-pdf) .gal-count {
   right: 28px !important;
 }
-.field[name="Slide Delay"] {
-  width: 4em;
-}
 :root.gallery-open.fixed #header-bar:not(.autohide),
 :root.gallery-open.fixed #header-bar:not(.autohide) #shortcuts .fa::before {
   visibility: hidden;