-- Copyright 2006-2023 Mitchell. See LICENSE.
-- 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, S = lpeg.P, 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', '&' * 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.styles.type)

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

-- Strings.
local sq_str = lexer.range("'")
local dq_str = lexer.range('"')
lex:add_rule('string', token(lexer.STRING, sq_str + dq_str))

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

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

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

-- 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')

lexer.property['scintillua.comment'] = '#'

return lex
