parse.rb

require "rsec"

module Parsing
  extend Rsec::Helpers

  # build the parser
  def self.query_lang
    # Predicate should be constructed with loop over keywords
    predicate = /.*?(?=STATUS IS|TYPE IS|AND|OR|\(|\)|$)/.r.map { |s| s.strip }

    # write a helper method to add new statement types
    status_statement = (symbol('STATUS IS') >> predicate).map { |s| {status: s} }
    type_statement = (symbol('TYPE IS') >> predicate).map { |s| {type: s} }

    # statement should loop over all statement types
    statement = status_statement | type_statement

    # Once this part is settled, it shouldn't need to change. Hardest
    # part: building a query for TASK THING OR (TASK THING AND TASK
    # THING)
    parenthetical = ('('.r >> lazy { expr } << ')')
    unit = statement | parenthetical
    and_ = symbol('AND').map { {} } # cheating, won't work forever
    anded = unit.join(and_).map { |s| s.reduce(&:merge) }
    expr = anded.join(symbol('OR'))
    expr.eof
  end

  def self.parse str
    query_lang.parse! str
  end
end

p Parsing::parse 'STATUS IS hi'
p Parsing::parse 'STATUS IS hi AND TYPE IS good bye'
p Parsing::parse 'STATUS IS sweet OR (TYPE IS sweet AND STATUS IS super sweet)'
p Parsing::parse 'STATUS IS sweet OR ((STATUS IS super sweet AND TYPE IS rockin) OR TYPE IS sweet)'