-- Copyright 2006-2019 Mitchell mitchell.att.foicica.com. See License.txt.
-- LPeg lexer for the Icon programming language.
-- http://www.cs.arizona.edu/icon
-- Contributed by Carl Sturtivant.

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

local lex = lexer.new('icon')

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

-- Keywords.
lex:add_rule('keyword', token(lexer.KEYWORD, word_match[[
  break by case create default do else end every fail global if initial
  invocable link local next not of procedure record repeat return static suspend
  then to until while
]]))

-- Icon Keywords: unique to Icon.
lex:add_rule('special_keyword', token('special_keyword', P('&') * word_match[[
  allocated ascii clock collections cset current date dateline digits dump e
  error errornumber errortext errorvalue errout fail features file host input
  lcase letters level line main null output phi pi pos progname random regions
  source storage subject time trace ucase version
]]))
lex:add_style('special_keyword', lexer.STYLE_TYPE)

-- Identifiers.
lex:add_rule('identifier', token(lexer.IDENTIFIER, lexer.word))

-- Strings.
lex:add_rule('string', token(lexer.STRING, lexer.delimited_range("'") +
                                           lexer.delimited_range('"')))

-- Comments.
lex:add_rule('comment', token(lexer.COMMENT, '#' * lexer.nonnewline_esc^0))

-- Numbers.
local radix_literal = P('-')^-1 * lexer.dec_num * S('rR') * lexer.alnum^1
lex:add_rule('number', token(lexer.NUMBER, radix_literal + lexer.float +
                                           lexer.integer))

-- Preprocessor.
local preproc_word = word_match[[
  define else endif error ifdef ifndef include line undef
]]
lex:add_rule('preproc', token(lexer.PREPROCESSOR, P('$') * preproc_word))

-- Operators.
lex:add_rule('operator', token(lexer.OPERATOR, S('+-/*%<>~!=^&|?~@:;,.()[]{}')))

-- Fold points.
lex:add_fold_point(lexer.PREPROCESSOR, 'ifdef', 'endif')
lex:add_fold_point(lexer.PREPROCESSOR, 'ifndef', 'endif')
lex:add_fold_point(lexer.KEYWORD, 'procedure', 'end')
lex:add_fold_point(lexer.COMMENT, '#', lexer.fold_line_comments('#'))

return lex