-- Copyright 2006-2019 Mitchell mitchell.att.foicica.com. See License.txt.
-- Go LPeg lexer.

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('go')

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

-- Keywords.
lex:add_rule('keyword', token(lexer.KEYWORD, word_match[[
  break case chan const continue default defer else fallthrough for func go goto
  if import interface map package range return select struct switch type var
]]))

-- Constants.
lex:add_rule('constant', token(lexer.CONSTANT, word_match[[
  true false iota nil
]]))

-- Types.
lex:add_rule('type', token(lexer.TYPE, word_match[[
  bool byte complex64 complex128 error float32 float64 int int8 int16 int32
  int64 rune string uint uint8 uint16 uint32 uint64 uintptr
]]))

-- Functions.
lex:add_rule('function', token(lexer.FUNCTION, word_match[[
  append cap close complex copy delete imag len make new panic print println
  real recover
]]))

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

-- Strings.
local sq_str = lexer.delimited_range("'", true)
local dq_str = lexer.delimited_range('"', true)
local raw_str = lexer.delimited_range('`', false, true)
lex:add_rule('string', token(lexer.STRING, sq_str + dq_str + raw_str))

-- Comments.
local line_comment = '//' * lexer.nonnewline^0
local block_comment = '/*' * (lexer.any - '*/')^0 * P('*/')^-1
lex:add_rule('comment', token(lexer.COMMENT, line_comment + block_comment))

-- Numbers.
lex:add_rule('number', token(lexer.NUMBER, (lexer.float + lexer.integer) *
                                           P('i')^-1))

-- 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_line_comments('//'))

return lex