Simple term parser

parser1.rb

require 'parslet'
require 'pp'

class AdvParser < Parslet::Parser
  rule(:space)  { match['\\s\\t'].repeat(1) } # at least one space/tab
  rule(:space?) { space.maybe } # zero or 1 things that match the 'space' rule
  
  rule(:startexpr) { str('(') >> space? } # '(' followed by optional space
  rule(:endexpr)   { space? >> str(')') }
  
  # A phrase is anything (but a double-quote) between double-quotes
  rule(:phrase)    { str('"') >> match['^"'].repeat(1).as(:phrase) >> str('"') }
  rule(:opand) { str('AND') }
  rule(:opor)  { str('OR')  }
  rule(:opnot) { str('NOT') }
  rule(:op)    { opand | opor | opnot }
  
  rule(:fname) { str('TI') | str('AU') | str('KY') }
  rule(:field) { fname.as(:field) >> str(':') } 

  rule(:word)     { match['^\\s\\t"()'].repeat(1) }
  rule(:searchword)  { field.absent? >> op.absent? >> word }
  rule(:searchwords) { (space? >> searchword).repeat(1) }
  
  rule(:term)     { phrase | searchwords.as(:words) }
  rule(:terms)    { (space? >> term).repeat(1) }
  
  rule(:fsearch) { field >> space? >> terms.as(:search) }
  
  root(:fsearch)
end

pp AdvParser.new.parse('TI: hello there "Bill Dueber" how are you?')
# puts AdvParser.new.parse('TI: bill AND dueber')