-- Copyright 2006-2022 Mitchell. See LICENSE.
-- Io 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('io_lang')

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

-- Keywords.
lex:add_rule('keyword', token(lexer.KEYWORD, word_match{
  'block', 'method', 'while', 'foreach', 'if', 'else', 'do', 'super', 'self', 'clone', 'proto',
  'setSlot', 'hasSlot', 'type', 'write', 'print', 'forward'
}))

-- Types.
lex:add_rule('type', token(lexer.TYPE, word_match{
  'Block', 'Buffer', 'CFunction', 'Date', 'Duration', 'File', 'Future', 'LinkedList', 'List', 'Map',
  'Message', 'Nil', 'Nop', 'Number', 'Object', 'String', 'WeakLink'
}))

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

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

-- Comments.
local line_comment = lexer.to_eol(P('#') + '//')
local block_comment = lexer.range('/*', '*/')
lex:add_rule('comment', token(lexer.COMMENT, line_comment + block_comment))

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

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

-- Fold points.
lex:add_fold_point(lexer.OPERATOR, '(', ')')
lex:add_fold_point(lexer.COMMENT, '/*', '*/')
lex:add_fold_point(lexer.COMMENT, lexer.fold_consecutive_lines('//'))

return lex