1 files changed, 122 insertions, 0 deletions
diff --git a/lib/gitlab/slash_commands/extractor.rb b/lib/gitlab/slash_commands/extractor.rb
new file mode 100644
index 00000000000..a672e5e4855
--- /dev/null
+++ b/lib/gitlab/slash_commands/extractor.rb
@@ -0,0 +1,122 @@
+module Gitlab
+  module SlashCommands
+    # This class takes an array of commands that should be extracted from a
+    # given text.
+    #
+    # ```
+    # extractor = Gitlab::SlashCommands::Extractor.new([:open, :assign, :labels])
+    # ```
+    class Extractor
+      attr_reader :command_definitions
+
+      def initialize(command_definitions)
+        @command_definitions = command_definitions
+      end
+
+      # Extracts commands from content and return an array of commands.
+      # The array looks like the following:
+      # [
+      #   ['command1'],
+      #   ['command3', 'arg1 arg2'],
+      # ]
+      # The command and the arguments are stripped.
+      # The original command text is removed from the given `content`.
+      #
+      # Usage:
+      # ```
+      # extractor = Gitlab::SlashCommands::Extractor.new([:open, :assign, :labels])
+      # msg = %(hello\n/labels ~foo ~"bar baz"\nworld)
+      # commands = extractor.extract_commands(msg) #=> [['labels', '~foo ~"bar baz"']]
+      # msg #=> "hello\nworld"
+      # ```
+      def extract_commands(content, opts = {})
+        return [content, []] unless content
+
+        content = content.dup
+
+        commands = []
+
+        content.delete!("\r")
+        content.gsub!(commands_regex(opts)) do
+          if $~[:cmd]
+            commands << [$~[:cmd], $~[:arg]].reject(&:blank?)
+            ''
+          else
+            $~[0]
+          end
+        end
+
+        [content.strip, commands]
+      end
+
+      private
+
+      # Builds a regular expression to match known commands.
+      # First match group captures the command name and
+      # second match group captures its arguments.
+      #
+      # It looks something like:
+      #
+      #   /^\/(?<cmd>close|reopen|...)(?:( |$))(?<arg>[^\/\n]*)(?:\n|$)/
+      def commands_regex(opts)
+        names = command_names(opts).map(&:to_s)
+
+        @commands_regex ||= %r{
+            (?<code>
+              # Code blocks:
+              # ```
+              # Anything, including `/cmd arg` which are ignored by this filter
+              # ```
+
+              ^```
+              .+?
+              \n```$
+            )
+          |
+            (?<html>
+              # HTML block:
+              # <tag>
+              # Anything, including `/cmd arg` which are ignored by this filter
+              # </tag>
+
+              ^<[^>]+?>\n
+              .+?
+              \n<\/[^>]+?>$
+            )
+          |
+            (?<html>
+              # Quote block:
+              # >>>
+              # Anything, including `/cmd arg` which are ignored by this filter
+              # >>>
+
+              ^>>>
+              .+?
+              \n>>>$
+            )
+          |
+            (?:
+              # Command not in a blockquote, blockcode, or HTML tag:
+              # /close
+
+              ^\/
+              (?<cmd>#{Regexp.union(names)})
+              (?:
+                [ ]
+                (?<arg>[^\/\n]*)
+              )?
+              (?:\n|$)
+            )
+        }mx
+      end
+
+      def command_names(opts)
+        command_definitions.flat_map do |command|
+          next if command.noop?
+
+          command.all_names
+        end.compact
+      end
+    end
+  end
+end