-- Copyright © 2017-2019 Michael T. Richter <ttmrichter@gmail.com>. See License.txt.
-- Logtalk 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('logtalk', {inherit = lexer.load('prolog')})

-- add logtalk keywords to prolog ones
local directives = [[
  set_logtalk_flag object info built_in threaded uses alias use_module
  coinductive export reexport public metapredicate mode meta_non_terminal
  protected synchronized private module if elif else endif category protocol
  end_object end_category end_protocol meta_predicate
]]
lex:modify_rule('directive',
  (
    token(lexer.WHITESPACE, lexer.starts_line(S(' \t'))^0) *
    token(lexer.OPERATOR, P':-') *
    token(lexer.WHITESPACE, (S(' \t')^0)) *
    token(lexer.PREPROCESSOR, P(word_match(directives)))
  ) +
  lex:get_rule('directive')
)

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

local zero_arity_keywords = [[
  -- extracted from test document in logtalk distribution
  comment argnames arguments author version date parameters parnames copyright
  license remarks see_also as logtalk_make instantiation_error system_error
]]
local one_plus_arity_keywords = [[
  -- extracted from test document in logtalk distribution
  implements imports extends instantiates specializes number_chars number_code
  current_category current_object current_protocol create_category
  create_object create_protocol abolish_category abolish_object
  abolish_protocol category_property object_property protocol_property
  extends_category extends_object extends_protocol implements_protocol
  imports_category instantiates_class specializes_class complements_object
  conforms_to_protocol abolish_events current_event define_events threaded
  threaded_call  threaded_call threaded_once threaded_ignore threaded_exit
  threaded_peek  threaded_cancel threaded_wait threaded_notify threaded_engine
  threaded_engine_create threaded_engine_destroy threaded_engine_self
  threaded_engine_next threaded_engine_next_reified threaded_engine_yield
  threaded_engine_post threaded_engine_fetch logtalk_compile logtalk_load
  logtalk_library_path logtalk_load_context  logtalk_make_target_action
  current_logtalk_flag set_logtalk_flag create_logtalk_flag context parameter
  self sender this type_error domain_error existence_error permission_error
  representation_error evaluation_error resource_error syntax_error bagof
  findall forall setof before after forward phrase expand_term expand_goal
  term_expansion goal_expansion numbervars put_code put_byte current_op op
  ignore repeat number_codes current_prolog_flag set_prolog_flag keysort sort
]]
lex:modify_rule('keyword', token(lexer.KEYWORD,
  word_match(zero_arity_keywords) +
  (word_match(one_plus_arity_keywords) * #(P'('))) +
  lex:get_rule('keyword')
)

local operators = [[
  -- extracted from test document in logtalk distribution
  as
]]
lex:modify_rule('operator', token(lexer.OPERATOR, word_match(operators)) +
                            lex:get_rule('operator'))

return lex