-- Copyright 2006-2021 Mitchell. See LICENSE.
-- Go 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('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.range("'", true)
local dq_str = lexer.range('"', true)
local raw_str = lexer.range('`', false, false)
lex:add_rule('string', token(lexer.STRING, sq_str + dq_str + raw_str))

-- Comments.
local line_comment = lexer.to_eol('//')
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 * 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_consecutive_lines('//'))

return lex
