1 files changed, 155 insertions, 0 deletions
diff --git a/lib/gitlab/diff/position.rb b/lib/gitlab/diff/position.rb
new file mode 100644
index 00000000000..989fff8918e
--- /dev/null
+++ b/lib/gitlab/diff/position.rb
@@ -0,0 +1,155 @@
+# Defines a specific location, identified by paths and line numbers,
+# within a specific diff, identified by start, head and base commit ids.
+module Gitlab
+  module Diff
+    class Position
+      attr_reader :old_path
+      attr_reader :new_path
+      attr_reader :old_line
+      attr_reader :new_line
+      attr_reader :base_sha
+      attr_reader :start_sha
+      attr_reader :head_sha
+
+      def initialize(attrs = {})
+        @old_path = attrs[:old_path]
+        @new_path = attrs[:new_path]
+        @old_line = attrs[:old_line]
+        @new_line = attrs[:new_line]
+
+        if attrs[:diff_refs]
+          @base_sha  = attrs[:diff_refs].base_sha
+          @start_sha = attrs[:diff_refs].start_sha
+          @head_sha  = attrs[:diff_refs].head_sha
+        else
+          @base_sha  = attrs[:base_sha]
+          @start_sha = attrs[:start_sha]
+          @head_sha  = attrs[:head_sha]
+        end
+      end
+
+      # `Gitlab::Diff::Position` objects are stored as serialized attributes in
+      # `DiffNote`, which use YAML to encode and decode objects.
+      # `#init_with` and `#encode_with` can be used to customize the en/decoding
+      # behavior. In this case, we override these to prevent memoized instance
+      # variables like `@diff_file` and `@diff_line` from being serialized.
+      def init_with(coder)
+        initialize(coder['attributes'])
+
+        self
+      end
+
+      def encode_with(coder)
+        coder['attributes'] = self.to_h
+      end
+
+      def key
+        @key ||= [base_sha, start_sha, head_sha, Digest::SHA1.hexdigest(old_path || ""), Digest::SHA1.hexdigest(new_path || ""), old_line, new_line]
+      end
+
+      def ==(other)
+        other.is_a?(self.class) && key == other.key
+      end
+
+      def to_h
+        {
+          old_path: old_path,
+          new_path: new_path,
+          old_line: old_line,
+          new_line: new_line,
+          base_sha:  base_sha,
+          start_sha: start_sha,
+          head_sha:  head_sha
+        }
+      end
+
+      def inspect
+        %(#<#{self.class}:#{object_id} #{to_h}>)
+      end
+
+      def complete?
+        file_path.present? &&
+          (old_line || new_line) &&
+          diff_refs.complete?
+      end
+
+      def to_json
+        JSON.generate(self.to_h)
+      end
+
+      def type
+        if old_line && new_line
+          nil
+        elsif new_line
+          'new'
+        else
+          'old'
+        end
+      end
+
+      def unchanged?
+        type.nil?
+      end
+
+      def added?
+        type == 'new'
+      end
+
+      def removed?
+        type == 'old'
+      end
+
+      def paths
+        [old_path, new_path].compact.uniq
+      end
+
+      def file_path
+        new_path.presence || old_path
+      end
+
+      def diff_refs
+        @diff_refs ||= DiffRefs.new(base_sha: base_sha, start_sha: start_sha, head_sha: head_sha)
+      end
+
+      def diff_file(repository)
+        @diff_file ||= begin
+          if RequestStore.active?
+            key = {
+              project_id: repository.project.id,
+              start_sha: start_sha,
+              head_sha: head_sha,
+              path: file_path
+            }
+
+            RequestStore.fetch(key) { find_diff_file(repository) }
+          else
+            find_diff_file(repository)
+          end
+        end
+      end
+
+      def diff_line(repository)
+        @diff_line ||= diff_file(repository).line_for_position(self)
+      end
+
+      def line_code(repository)
+        @line_code ||= diff_file(repository).line_code_for_position(self)
+      end
+
+      private
+
+      def find_diff_file(repository)
+        diffs = Gitlab::Git::Compare.new(
+          repository.raw_repository,
+          start_sha,
+          head_sha
+        ).diffs(paths: paths)
+
+        diff = diffs.first
+        return unless diff
+
+        Gitlab::Diff::File.new(diff, repository: repository, diff_refs: diff_refs)
+      end
+    end
+  end
+end