1 files changed, 46 insertions, 0 deletions
diff --git a/app/assets/javascripts/diff.js.coffee b/app/assets/javascripts/diff.js.coffee
new file mode 100644
index 00000000000..dbe00c487dc
--- /dev/null
+++ b/app/assets/javascripts/diff.js.coffee
@@ -0,0 +1,46 @@
+class Diff
+  UNFOLD_COUNT = 20
+  constructor: ->
+    $(document).on('click', '.js-unfold', (event) =>
+      target = $(event.target)
+      unfoldBottom = target.hasClass('js-unfold-bottom')
+      unfold = true
+
+      [old_line, line_number] = @lineNumbers(target.parent())
+      offset = line_number - old_line
+
+      if unfoldBottom
+        line_number += 1
+        since = line_number
+        to = line_number + UNFOLD_COUNT
+      else
+        [prev_old_line, prev_new_line] = @lineNumbers(target.parent().prev())
+        line_number -= 1
+        to = line_number
+        if line_number - UNFOLD_COUNT > prev_new_line + 1
+          since = line_number - UNFOLD_COUNT
+        else
+          since = prev_new_line + 1
+          unfold = false
+
+      link = target.parents('.diff-file').attr('data-blob-diff-path')
+      params =
+        since: since
+        to: to
+        bottom: unfoldBottom
+        offset: offset
+        unfold: unfold
+
+      $.get(link, params, (response) =>
+        target.parent().replaceWith(response)
+      )
+    )
+
+  lineNumbers: (line) ->
+    return ([0, 0]) unless line.children().length
+    lines = line.children().slice(0, 2)
+    line_numbers = ($(l).attr('data-linenumber') for l in lines)
+    (parseInt(line_number) for line_number in line_numbers)
+
+
+@Diff = Diff