-- Copyright 2006-2020 Mitchell. See LICENSE.
-- Postscript LPeg lexer.

local lexer = require('lexer')
local token, word_match = lexer.token, lexer.word_match
local P, S = lpeg.P, lpeg.S

local lex = lexer.new('ps')

-- Whitespace.
lex:add_rule('whitespace', token(lexer.WHITESPACE, lexer.space^1))

-- Keywords.
lex:add_rule('keyword', token(lexer.KEYWORD, word_match[[
  pop exch dup copy roll clear count mark cleartomark counttomark exec if ifelse
  for repeat loop exit stop stopped countexecstack execstack quit start
  true false NULL
]]))

-- Functions.
lex:add_rule('function', token(lexer.FUNCTION, word_match[[
  add div idiv mod mul sub abs ned ceiling floor round truncate sqrt atan cos
  sin exp ln log rand srand rrand
]]))

-- Identifiers.
local word = (lexer.alpha + '-') * (lexer.alnum + '-')^0
lex:add_rule('identifier', token(lexer.IDENTIFIER, word))

-- Strings.
local arrow_string = lexer.range('<', '>')
local nested_string = lexer.range('(', ')', false, false, true)
lex:add_rule('string', token(lexer.STRING, arrow_string + nested_string))

-- Comments.
lex:add_rule('comment', token(lexer.COMMENT, lexer.to_eol('%')))

-- Numbers.
lex:add_rule('number', token(lexer.NUMBER, lexer.number))

-- Labels.
lex:add_rule('label', token(lexer.LABEL, '/' * word))

-- Operators.
lex:add_rule('operator', token(lexer.OPERATOR, S('[]{}')))

return lex
