1 files changed, 75 insertions, 0 deletions
diff --git a/app/presenters/blobs/unfold_presenter.rb b/app/presenters/blobs/unfold_presenter.rb
new file mode 100644
index 00000000000..7b13db3bb74
--- /dev/null
+++ b/app/presenters/blobs/unfold_presenter.rb
@@ -0,0 +1,75 @@
+# frozen_string_literal: true
+
+require 'gt_one_coercion'
+
+module Blobs
+  class UnfoldPresenter < BlobPresenter
+    include Virtus.model
+    include Gitlab::Utils::StrongMemoize
+
+    attribute :full, Boolean, default: false
+    attribute :since, GtOneCoercion
+    attribute :to, GtOneCoercion
+    attribute :bottom, Boolean
+    attribute :unfold, Boolean, default: true
+    attribute :offset, Integer
+    attribute :indent, Integer, default: 0
+
+    def initialize(blob, params)
+      @subject = blob
+      @all_lines = highlight.lines
+      super(params)
+
+      if full?
+        self.attributes = { since: 1, to: @all_lines.size, bottom: false, unfold: false, offset: 0, indent: 0 }
+      end
+    end
+
+    # Converts a String array to Gitlab::Diff::Line array, with match line added
+    def diff_lines
+      diff_lines = lines.map do |line|
+        Gitlab::Diff::Line.new(line, nil, nil, nil, nil, rich_text: line)
+      end
+
+      add_match_line(diff_lines)
+
+      diff_lines
+    end
+
+    def lines
+      strong_memoize(:lines) do
+        lines = @all_lines
+        lines = lines[since - 1..to - 1] unless full?
+        lines.map(&:html_safe)
+      end
+    end
+
+    def match_line_text
+      return '' if bottom?
+
+      lines_length = lines.length - 1
+      line = [since, lines_length].join(',')
+      "@@ -#{line}+#{line} @@"
+    end
+
+    private
+
+    def add_match_line(diff_lines)
+      return unless unfold?
+
+      if bottom? && to < @all_lines.size
+        old_pos = to - offset
+        new_pos = to
+      elsif since != 1
+        old_pos = new_pos = since
+      end
+
+      # Match line is not needed when it reaches the top limit or bottom limit of the file.
+      return unless new_pos
+
+      match_line = Gitlab::Diff::Line.new(match_line_text, 'match', nil, old_pos, new_pos)
+
+      bottom? ? diff_lines.push(match_line) : diff_lines.unshift(match_line)
+    end
+  end
+end