1 files changed, 91 insertions, 0 deletions
diff --git a/lib/gitlab/git/conflict/parser.rb b/lib/gitlab/git/conflict/parser.rb
new file mode 100644
index 00000000000..3effa9d2d31
--- /dev/null
+++ b/lib/gitlab/git/conflict/parser.rb
@@ -0,0 +1,91 @@
+module Gitlab
+  module Git
+    module Conflict
+      class Parser
+        UnresolvableError = Class.new(StandardError)
+        UnmergeableFile = Class.new(UnresolvableError)
+        UnsupportedEncoding = Class.new(UnresolvableError)
+
+        # Recoverable errors - the conflict can be resolved in an editor, but not with
+        # sections.
+        ParserError = Class.new(StandardError)
+        UnexpectedDelimiter = Class.new(ParserError)
+        MissingEndDelimiter = Class.new(ParserError)
+
+        class << self
+          def parse(text, our_path:, their_path:, parent_file: nil)
+            validate_text!(text)
+
+            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
+                validate_delimiter!(type.nil?)
+
+                type = 'new'
+              elsif full_line == conflict_middle
+                validate_delimiter!(type == 'new')
+
+                type = 'old'
+              elsif full_line == conflict_end
+                validate_delimiter!(type == 'old')
+
+                type = nil
+              elsif line[0] == '\\'
+                type = 'nonewline'
+                lines << {
+                  full_line: full_line,
+                  type: type,
+                  line_obj_index: line_obj_index,
+                  line_old: line_old,
+                  line_new: line_new
+                }
+              else
+                lines << {
+                  full_line: full_line,
+                  type: type,
+                  line_obj_index: line_obj_index,
+                  line_old: line_old,
+                  line_new: 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
+
+          private
+
+          def validate_text!(text)
+            raise UnmergeableFile if text.blank? # Typically a binary file
+            raise UnmergeableFile if text.length > 200.kilobytes
+
+            text.force_encoding('UTF-8')
+
+            raise UnsupportedEncoding unless text.valid_encoding?
+          end
+
+          def validate_delimiter!(condition)
+            raise UnexpectedDelimiter unless condition
+          end
+        end
+      end
+    end
+  end
+end