-- Copyright 2006-2015 Mitchell mitchell.att.foicica.com. See LICENSE.
-- Plain TeX LPeg lexer.
-- Modified by Robert Gieseke.

local l = require('lexer')
local token, word_match = l.token, l.word_match
local P, R, S = lpeg.P, lpeg.R, lpeg.S

local M = {_NAME = 'tex'}

-- Whitespace.
local ws = token(l.WHITESPACE, l.space^1)

-- Comments.
local comment = token(l.COMMENT, '%' * l.nonnewline^0)

-- TeX environments.
local environment = token('environment', '\\' * (P('begin') + 'end') * l.word)

-- Commands.
local command = token(l.KEYWORD, '\\' * (l.alpha^1 + S('#$&~_^%{}')))

-- Operators.
local operator = token(l.OPERATOR, S('$&#{}[]'))

M._rules = {
  {'whitespace', ws},
  {'comment', comment},
  {'environment', environment},
  {'keyword', command},
  {'operator', operator},
}

M._tokenstyles = {
  environment = l.STYLE_KEYWORD
}

M._foldsymbols = {
  _patterns = {'\\begin', '\\end', '[{}]', '%%'},
  [l.COMMENT] = {['%'] = l.fold_line_comments('%')},
  ['environment'] = {['\\begin'] = 1, ['\\end'] = -1},
  [l.OPERATOR] = {['{'] = 1, ['}'] = -1}
}

return M