1 files changed, 102 insertions, 0 deletions
diff --git a/lib/gitlab/changelog/release.rb b/lib/gitlab/changelog/release.rb
new file mode 100644
index 00000000000..f2a01c2b0dc
--- /dev/null
+++ b/lib/gitlab/changelog/release.rb
@@ -0,0 +1,102 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Changelog
+    # A release to add to a changelog.
+    class Release
+      attr_reader :version
+
+      def initialize(version:, date:, config:)
+        @version = version
+        @date = date
+        @config = config
+        @entries = Hash.new { |h, k| h[k] = [] }
+
+        # This ensures that entries are presented in the same order as the
+        # categories Hash in the user's configuration.
+        @config.categories.values.each do |category|
+          @entries[category] = []
+        end
+      end
+
+      def add_entry(
+        title:,
+        commit:,
+        category:,
+        author: nil,
+        merge_request: nil
+      )
+        # When changing these fields, keep in mind that this needs to be
+        # backwards compatible. For example, you can't just remove a field as
+        # this will break the changelog generation process for existing users.
+        entry = {
+          'title' => title,
+          'commit' => {
+            'reference' => commit.to_reference(full: true),
+            'trailers' => commit.trailers
+          }
+        }
+
+        if author
+          entry['author'] = {
+            'reference' => author.to_reference(full: true),
+            'contributor' => @config.contributor?(author)
+          }
+        end
+
+        if merge_request
+          entry['merge_request'] = {
+            'reference' => merge_request.to_reference(full: true)
+          }
+        end
+
+        @entries[@config.category(category)] << entry
+      end
+
+      def to_markdown
+        state = EvalState.new
+        data = { 'categories' => entries_for_template }
+
+        # While not critical, we would like release sections to be separated by
+        # an empty line in the changelog; ensuring it's readable even in its
+        # raw form.
+        #
+        # Since it can be a bit tricky to get this right in a template, we
+        # enforce an empty line separator ourselves.
+        markdown = @config.template.evaluate(state, data).strip
+
+        # The release header can't be changed using the Liquid template, as we
+        # need this to be in a known format. Without this restriction, we won't
+        # know where to insert a new release section in an existing changelog.
+        "## #{@version} (#{release_date})\n\n#{markdown}\n\n"
+      end
+
+      def header_start_pattern
+        /^##\s*#{Regexp.escape(@version)}/
+      end
+
+      private
+
+      def release_date
+        @config.format_date(@date)
+      end
+
+      def entries_for_template
+        rows = []
+
+        @entries.each do |category, entries|
+          next if entries.empty?
+
+          rows << {
+            'title' => category,
+            'count' => entries.length,
+            'single_change' => entries.length == 1,
+            'entries' => entries
+          }
+        end
+
+        rows
+      end
+    end
+  end
+end