-- Copyright 2006-2023 Mitchell. See LICENSE.
-- Fennel LPeg lexer.
-- Contributed by Momohime Honda.
local lexer = require('lexer')
local token, word_match = lexer.token, lexer.word_match
local P, S = lpeg.P, lpeg.S

local lex = lexer.new('fennel', {inherit = lexer.load('lua')})

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

-- Keywords.
lex:modify_rule('keyword', token(lexer.KEYWORD, word_match {
    '#', '%', '*', '+', '-', '->>', '->', '-?>>', '-?>', '..', '.', '//', '/',
    ':', '<=', '<', '=', '>=', '>', '?.', '^', '~=', 'λ', 'accumulate', 'and',
    'band', 'bnot', 'bor', 'bxor', 'collect', 'comment', 'do', 'doto', 'each',
    'eval-compiler', 'fn', 'for', 'global', 'hashfn', 'icollect', 'if',
    'import-macros', 'include', 'lambda', 'length', 'let', 'local', 'lshift',
    'lua', 'macro', 'macrodebug', 'macros', 'match', 'not', 'not=', 'or',
    'partial', 'pick-args', 'pick-values', 'quote', 'require-macros', 'rshift',
    'set', 'set-forcibly!', 'tset', 'values', 'var', 'when', 'while',
    'with-open'
}))

-- Identifiers.
local initial = lexer.alpha + S('|$%&#*+-/<=>?~^_λ!')
local subsequent = initial + lexer.digit
lex:modify_rule('identifier',
                token(lexer.IDENTIFIER, initial * subsequent ^ 0 * P('#') ^ -1))

-- Strings.
local dq_str = lexer.range('"')
local kw_str = lpeg.B(1 - subsequent) * ':' * subsequent ^ 1
lex:modify_rule('string', token(lexer.STRING, dq_str + kw_str))

-- Comments.
lex:modify_rule('comment', token(lexer.COMMENT, lexer.to_eol(';')))

-- Ignore these rules.
-- lex:modify_rule('longstring', P(false))
lex:modify_rule('label', P(false))
lex:modify_rule('operator', P(false))

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

return lex
