Add backend for merge conflicts reading

2 files changed, 150 insertions, 0 deletions

diff --git a/lib/gitlab/conflict/file.rb b/lib/gitlab/conflict/file.rb
new file mode 100644
index 00000000000..84d3e6f4e03
--- /dev/null
+++ b/lib/gitlab/conflict/file.rb
@@ -0,0 +1,91 @@
+module Gitlab
+  module Conflict
+    class File
+      CONTEXT_LINES = 3
+
+      attr_reader :merge_file, :their_path, :their_ref, :our_path, :our_ref, :repository
+
+      def initialize(merge_file, conflict, their_ref, our_ref, repository)
+        @merge_file = merge_file
+        @their_path = conflict[:theirs][:path]
+        @our_path = conflict[:ours][:path]
+        @their_ref = their_ref
+        @our_ref = our_ref
+        @repository = repository
+      end
+
+      # Array of Gitlab::Diff::Line objects
+      def lines
+        @lines ||= Gitlab::Conflict::Parser.new.parse(merge_file[:data], their_path, our_path)
+      end
+
+      def highlighted_lines
+        return @highlighted_lines if @highlighted_lines
+
+        their_highlight = Gitlab::Highlight.highlight_lines(repository, their_ref, their_path)
+        our_highlight = Gitlab::Highlight.highlight_lines(repository, our_ref, our_path)
+
+        @highlighted_lines = lines.map do |line|
+          line = line.dup
+          if line.type == 'old'
+            line.rich_text = their_highlight[line.old_line - 1].delete("\n")
+          else
+            line.rich_text = our_highlight[line.new_line - 1].delete("\n")
+          end
+          line
+        end
+      end
+
+      def sections
+        return @sections if @sections
+
+        chunked_lines = highlighted_lines.chunk { |line| line.type.nil? }
+        match_line = nil
+
+        @sections = chunked_lines.flat_map.with_index do |(no_conflict, lines), i|
+          section = nil
+
+          if no_conflict
+            conflict_before = i > 0
+            conflict_after = chunked_lines.peek
+
+            if conflict_before && conflict_after
+              if lines.length > CONTEXT_LINES * 2
+                tail_lines = lines.last(CONTEXT_LINES)
+                first_tail_line = tail_lines.first
+                match_line = Gitlab::Diff::Line.new('',
+                                                    'match',
+                                                    first_tail_line.index,
+                                                    first_tail_line.old_pos,
+                                                    first_tail_line.new_pos)
+
+                section = [
+                  { conflict: false, lines: lines.first(CONTEXT_LINES) },
+                  { conflict: false, lines: tail_lines.unshift(match_line) }
+                ]
+              end
+            elsif conflict_after
+              lines = lines.last(CONTEXT_LINES)
+            elsif conflict_before
+              lines = lines.first(CONTEXT_LINES)
+            end
+          end
+
+          if match_line && !section
+            match_line.text = "@@ -#{match_line.old_pos},#{lines.last.old_pos} +#{match_line.new_pos},#{lines.last.new_pos} @@"
+          end
+
+          section || { conflict: !no_conflict, lines: lines }
+        end
+      end
+
+      def as_json(opts = nil)
+        {
+          old_path: their_path,
+          new_path: our_path,
+          sections: sections
+        }
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/conflict/parser.rb b/lib/gitlab/conflict/parser.rb
new file mode 100644
index 00000000000..a233c268070
--- /dev/null
+++ b/lib/gitlab/conflict/parser.rb
@@ -0,0 +1,59 @@
+module Gitlab
+  module Conflict
+    class Parser
+      class UnexpectedDelimiter < StandardError
+      end
+
+      class MissingEndDelimiter < StandardError
+      end
+
+      def parse(text, their_path, our_path)
+        return [] if text.blank?
+
+        line_obj_index = 0
+        line_old = 1
+        line_new = 1
+        type = nil
+        lines = []
+        conflict_start = "<<<<<<< #{our_path}"
+        conflict_middle = '======='
+        conflict_end = ">>>>>>> #{their_path}"
+
+        text.each_line.map do |line|
+          full_line = line.delete("\n")
+
+          if full_line == conflict_start
+            raise UnexpectedDelimiter unless type.nil?
+
+            type = 'new'
+          elsif full_line == conflict_middle
+            raise UnexpectedDelimiter unless type == 'new'
+
+            type = 'old'
+          elsif full_line == conflict_end
+            raise UnexpectedDelimiter unless type == 'old'
+
+            type = nil
+          elsif line[0] == '\\'
+            type = 'nonewline'
+            lines << Gitlab::Diff::Line.new(full_line, type, line_obj_index, line_old, line_new)
+          else
+            lines << Gitlab::Diff::Line.new(full_line, type, line_obj_index, line_old, line_new)
+            line_old += 1 if type != 'new'
+            line_new += 1 if type != 'old'
+
+            line_obj_index += 1
+          end
+        end
+
+        raise MissingEndDelimiter unless type == nil
+
+        lines
+      end
+
+      def empty?
+        @lines.empty?
+      end
+    end
+  end
+end