Fixes #29385: Add /shrug and /tableflip commands

- Updated DSL to support substitution definitions
- Added substitution definition, inherits from command definition
- Added tabelflip and shrug substitutions to interpret service
- Added support for substitution definitions to the extractor for preview mode.
- Added substitution handling in the interpret service

Signed-off-by: Alex Ives <alex@ives.mn>

3 files changed, 70 insertions, 5 deletions

diff --git a/lib/gitlab/quick_actions/dsl.rb b/lib/gitlab/quick_actions/dsl.rb
index a4a97236ffc..536765305e1 100644
--- a/lib/gitlab/quick_actions/dsl.rb
+++ b/lib/gitlab/quick_actions/dsl.rb
@@ -105,9 +105,32 @@ module Gitlab
         #     # Awesome code block
         #   end
         def command(*command_names, &block)
+          define_command(CommandDefinition, *command_names, &block)
+        end
+
+        # Registers a new substitution which is recognizable from body of email or
+        # comment.
+        # It accepts aliases and takes a block with the formatted content.
+        #
+        # Example:
+        #
+        #   command :my_substitution, :alias_for_my_substitution do |text|
+        #     "#{text} MY AWESOME SUBSTITUTION"
+        #   end
+        def substitution(*substitution_names, &block)
+          define_command(SubstitutionDefinition, *substitution_names, &block)
+        end
+
+        def definition_by_name(name)
+          command_definitions_by_name[name.to_sym]
+        end
+
+        private
+
+        def define_command(klass, *command_names, &block)
           name, *aliases = command_names
 
-          definition = CommandDefinition.new(
+          definition = klass.new(
             name,
             aliases: aliases,
             description: @description,
@@ -130,10 +153,6 @@ module Gitlab
           @condition_block = nil
           @parse_params_block = nil
         end
-
-        def definition_by_name(name)
-          command_definitions_by_name[name.to_sym]
-        end
       end
     end
   end
diff --git a/lib/gitlab/quick_actions/extractor.rb b/lib/gitlab/quick_actions/extractor.rb
index 09576be7156..3ebfa3bd4b8 100644
--- a/lib/gitlab/quick_actions/extractor.rb
+++ b/lib/gitlab/quick_actions/extractor.rb
@@ -46,6 +46,8 @@ module Gitlab
           end
         end
 
+        content, commands = perform_substitutions(content, commands)
+
         [content.strip, commands]
       end
 
@@ -110,6 +112,26 @@ module Gitlab
         }mx
       end
 
+      def perform_substitutions(content, commands)
+        return unless content
+
+        substitution_definitions = self.command_definitions.select do |definition|
+          definition.is_a?(Gitlab::QuickActions::SubstitutionDefinition)
+        end
+
+        substitution_definitions.each do |substitution|
+          match_data = substitution.match(content)
+          if match_data
+            command = [substitution.name.to_s]
+            command << match_data[1] unless match_data[1].empty?
+            commands << command
+          end
+          content = substitution.perform_substitution(self, content)
+        end
+
+        [content, commands]
+      end
+
       def command_names(opts)
         command_definitions.flat_map do |command|
           next if command.noop?
diff --git a/lib/gitlab/quick_actions/substitution_definition.rb b/lib/gitlab/quick_actions/substitution_definition.rb
new file mode 100644
index 00000000000..032c49ed159
--- /dev/null
+++ b/lib/gitlab/quick_actions/substitution_definition.rb
@@ -0,0 +1,24 @@
+module Gitlab
+  module QuickActions
+    class SubstitutionDefinition < CommandDefinition
+      # noop?=>true means these won't get extracted or removed by Gitlab::QuickActions::Extractor#extract_commands
+      # QuickActions::InterpretService#perform_substitutions handles them separately
+      def noop?
+        true
+      end
+
+      def match(content)
+        content.match %r{^/#{all_names.join('|')} ?(.*)$}
+      end
+
+      def perform_substitution(context, content)
+        return unless content
+
+        all_names.each do |a_name|
+          content.gsub!(%r{/#{a_name} ?(.*)$}, execute_block(action_block, context, '\1'))
+        end
+        content
+      end
+    end
+  end
+end