require_relative '../code_objects'

module Puppetx::Strings::YARD::Handlers
  # Handles `dispatch` calls within a future parser function declaration. For
  # now, it just treats any docstring as an `@overlaod` tag and attaches the
  # overload to the parent function.
  class FutureParserDispatchHandler < YARD::Handlers::Ruby::Base
    include Puppetx::Strings::YARD::CodeObjects

    handles method_call(:dispatch)

    process do
      return unless owner.is_a?(MethodObject) && owner['future_parser_function']
      return unless statement.docstring

      docstring = ::YARD::Docstring.new(statement.docstring, nil)

      # FIXME: This does a wholesale copy of all possible tags. But, we're only
      # interested in the @overload tag.
      owner.add_tag *docstring.tags
    end
  end

  class FutureParserFunctionHandler < YARD::Handlers::Ruby::Base
    include Puppetx::Strings::YARD::CodeObjects

    handles method_call(:create_function)

    process do
      name = process_parameters

      obj = MethodObject.new(function_namespace, name)
      obj['future_parser_function'] = true

      register obj

      obj.add_tag YARD::Tags::Tag.new(:api, 'public')

      blk = statement.block.children.first
      parse_block(blk, :owner => obj)
    end

    private

    # Returns a {PuppetNamespaceObject} for holding functions. Creates this
    # object if necessary.
    #
    # @return [PuppetNamespaceObject]
    def function_namespace
      # NOTE: This tricky. If there is ever a Ruby class or module with the
      # name ::ParserFunctions, then there will be a clash. Hopefully the name
      # is sufficiently uncommon.
      obj = P(:root, 'FutureParserFunctions')
      if obj.is_a? Proxy
        namespace_obj = PuppetNamespaceObject.new(:root, 'FutureParserFunctions')

        register namespace_obj
        # FIXME: The docstring has to be cleared. Otherwise, the namespace
        # object will be registered using the docstring of the
        # `create_function` call that is currently being processed.
        #
        # Figure out how to properly register the namespace without using the
        # function handler object.
        register_docstring(namespace_obj, '', nil)
        namespace_obj.add_tag YARD::Tags::Tag.new(:api, 'public')
      end

      obj
    end

    # NOTE: The following methods duplicate functionality from
    # Puppet::Util::Reference and Puppet::Parser::Functions.functiondocs
    #
    # However, implementing this natively in YARD is a good test for the
    # feasibility of extracting custom Ruby documentation. In the end, the
    # existing approach taken by Puppet::Util::Reference may be the best due to
    # the heavy use of metaprogramming in Types and Providers.

    # Extracts the Puppet function name and options hash from the parsed
    # definition.
    #
    # @return [(String, Hash{String => String})]
    def process_parameters
      # Passing `false` to prameters excludes the block param from the returned
      # list.
      name, _ = statement.parameters(false).compact

      name = process_element(name)

      name
    end

    # Sometimes the YARD parser returns Heredoc strings that start with `<-`
    # instead of `<<-`.
    HEREDOC_START = /^<?<-/

    # Turns an entry in the method parameter list into a string.
    #
    # @param ele [YARD::Parser::Ruby::AstNode]
    # @return [String]
    def process_element(ele)
      ele = ele.jump(:ident, :string_content)

      case ele.type
      when :ident
        ele.source
      when :string_content
        source = ele.source
        if HEREDOC_START.match(source)
          process_heredoc(source)
        else
          source
        end
      end
    end

    # Cleans up and formats Heredoc contents parsed by YARD.
    #
    # @param source [String]
    # @return [String]
    def process_heredoc(source)
      source = source.lines.to_a

      # YARD adds a line of source context on either side of the Heredoc
      # contents.
      source.shift
      source.pop

      # This utility method normalizes indentation and trims whitespace.
      Puppet::Util::Docs.scrub(source.join)
    end
  end
end