self-ml/selfml

require 'parslet'

module SelfML

  # Helper methods
  class Parslet::Parser

    rule(:space)  { match('\s').repeat(1) }
    rule(:space?) { space.maybe }

    rule(:word)   { match('\w').repeat }
    rule(:word?)  { word.maybe }
  end # monkey patching in a couple of helpers

  # Class responsible for parsing all the things.
  #
  class Parser < Parslet::Parser
    root(:top)
    rule(:top)  do
      (space? >> node >> space?).repeat.as(:document)
    end

    rule(:node) { comment.as(:comment) | list.as(:list) | string.as(:string) }

    # String
    rule(:string)    { backtick.as(:backticks) | bracketed.as(:brackets) | verbatim.as(:verbatim) }
    rule(:backtick) do
      str('`') >> (
        # str('``').as(:ticks) | match('``|[^`]').as(:text)
        str('``').as(:ticks) | (str("`").absent? >> any).as(:text)
      ).repeat >> str('`')
    end
    rule(:bracketed) do
      str('[') >> (
        # bracketed.as(:nested) | match('[^\]]').as(:text)
        bracketed.as(:nested) | (str("]").absent? >> any).as(:text)
      ).repeat >> str(']')
    end
    rule(:verbatim)  { str("#").absnt? >> match['^\[\](){}\s'].repeat(1) }

    # List
    rule(:tail) do
      (node >> space?).repeat
    end
    rule(:list) do
      str('(') >> space? >>
      comment.as(:comment).maybe >> space? >>
      string.as(:head)           >> space? >>
      tail.as(:tail)             >> space? >>
      space?   >> str(')')
    end

    # Comment
    rule(:comment) { line.as(:line) | block.as(:block) }
    rule(:line)    { str('#') >> match['^\\n'].repeat.as(:text) >> (str("\n") | any.absent?) }
    rule(:block) do
      str('{#') >> (
        block.as(:block) |  match['^#}'].as(:text)
      ).repeat >> str('#}')
    end

  end
end