-- Copyright 2006-2018 Mitchell mitchell.att.foicica.com. See License.txt.
-- Prolog 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('prolog')

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

-- Keywords.
lex:add_rule('keyword', token(lexer.KEYWORD, word_match[[
  -- Directives by manual scanning of SWI-Prolog source code
  abolish arithmetic_function at_halt create_prolog_flag discontiguous dynamic
  elif else endif format_predicate if initialization lazy_list_iterator listing
  load_extensions meta_predicate mode module module_transparent multifile op
  persistent pop_operators pred predicate_options prolog_load_context public
  push_operators record redefine_system_predicate reexport set_prolog_flag
  setting thread_local type use_foreign_library use_module volatile
  -- Built-in predicates generated in SWI-Prolog via current_predictate/1.
  abolish abort absolute_file_name access_file acyclic_term add_import_module
  append apply arg assert asserta assertz at_end_of_stream at_halt atom
  atom_chars atom_codes atom_concat atomic atomic_concat atomic_list_concat
  atomics_to_string atom_length atom_number atom_prefix atom_string atom_to_term
  attach_packs attvar autoload_path bagof between b_getval blob break b_set_dict
  b_setval byte_count call callable call_cleanup call_continuation call_dcg
  call_residue_vars call_shared_object_function call_with_depth_limit
  call_with_inference_limit cancel_halt catch character_count char_code
  char_conversion char_type clause clause_property close close_shared_object
  code_type collation_key compare compile_aux_clauses compile_predicates
  compiling compound compound_name_arguments compound_name_arity consult
  context_module copy_predicate_clauses copy_stream_data copy_term copy_term_nat
  create_prolog_flag current_arithmetic_function current_atom current_blob
  current_char_conversion current_engine current_flag current_format_predicate
  current_functor current_input current_key current_locale current_module
  current_op current_output current_predicate current_prolog_flag
  current_resource current_signal current_trie cwd cyclic_term date_time_stamp
  dcg_translate_rule debugging default_module del_attr del_attrs del_dict
  delete_directory delete_file delete_import_module deterministic dict_create
  dict_pairs directory_files divmod downcase_atom duplicate_term dwim_match
  dwim_predicate engine_create engine_destroy engine_fetch engine_next
  engine_next_reified engine_post engine_self engine_yield ensure_loaded erase
  exception exists_directory exists_file expand_answer expand_file_name
  expand_file_search_path expand_goal expand_query expand_term export
  extern_indirect fail false fast_read fast_term_serialized fast_write
  file_base_name file_directory_name file_name_extension file_search_path
  fill_buffer findall findnsols flag float flush_output forall format
  format_predicate format_time freeze frozen functor garbage_collect
  garbage_collect_atoms garbage_collect_clauses gc_file_search_cache get0 get
  get_attr get_attrs get_byte get_char get_code get_dict getenv get_flag
  get_single_char get_string_code get_time goal_expansion ground halt ignore
  import import_module instance integer intern_indirect is_absolute_file_name
  is_dict is_engine is_list is_stream is_thread keysort known_licenses leash
  length library_directory license line_count line_position load_files
  locale_create locale_destroy locale_property make_directory make_library_index
  memberchk message_hook message_property message_queue_create
  message_queue_destroy message_queue_property message_to_string module
  module_property msort mutex_create mutex_destroy mutex_lock mutex_property
  mutex_statistics mutex_trylock mutex_unlock mutex_unlock_all name nb_current
  nb_delete nb_getval nb_linkarg nb_link_dict nb_linkval nb_setarg nb_set_dict
  nb_setval nl nonvar noprofile noprotocol normalize_space nospy nospyall not
  notrace nth_clause nth_integer_root_and_remainder number number_chars
  number_codes number_string numbervars once on_signal op open open_null_stream
  open_resource open_shared_object open_string open_xterm peek_byte peek_char
  peek_code peek_string phrase plus portray predicate_option_mode
  predicate_option_type predicate_property print print_message
  print_message_lines print_toplevel_variables profiler prolog
  prolog_choice_attribute prolog_current_choice prolog_current_frame
  prolog_cut_to prolog_debug prolog_event_hook prolog_file_type
  prolog_frame_attribute prolog_list_goal prolog_load_context prolog_load_file
  prolog_nodebug prolog_skip_frame prolog_skip_level prolog_stack_property
  prolog_to_os_filename prompt1 prompt protocol protocola protocolling put
  put_attr put_attrs put_byte put_char put_code put_dict pwd qcompile
  random_property rational read read_clause read_history read_link
  read_pending_chars read_pending_codes read_string read_term
  read_term_from_atom recorda recorded recordz redefine_system_predicate
  reexport reload_library_index rename_file repeat require reset reset_profiler
  residual_goals resource retract retractall same_file same_term see seeing seek
  seen select_dict setarg set_end_of_stream setenv set_flag set_input set_locale
  setlocale set_module setof set_output set_prolog_flag set_prolog_IO
  set_prolog_stack set_random set_stream set_stream_position
  setup_call_catcher_cleanup setup_call_cleanup shell shift size_file skip sleep
  sort source_file source_file_property source_location split_string spy
  stamp_date_time statistics stream_pair stream_position_data stream_property
  string string_chars string_code string_codes string_concat string_length
  string_lower string_upper strip_module style_check sub_atom sub_atom_icasechk
  sub_string subsumes_term succ swiplrc tab tell telling term_attvars
  term_expansion term_hash term_string term_to_atom term_variables
  text_to_string thread_at_exit thread_create thread_detach thread_exit
  thread_get_message thread_join thread_message_hook thread_peek_message
  thread_property thread_self thread_send_message thread_setconcurrency
  thread_signal thread_statistics throw time_file tmp_file tmp_file_stream told
  trace tracing trie_destroy trie_gen trie_insert trie_insert_new trie_lookup
  trie_new trie_property trie_term trim_stacks true ttyflush tty_get_capability
  tty_goto tty_put tty_size unifiable unify_with_occurs_check unload_file
  unsetenv upcase_atom use_module var variant_hash variant_sha1 var_number
  var_property verbose_expansion version visible wait_for_input wildcard_match
  with_mutex with_output_to working_directory write write_canonical write_length
  writeln writeq write_term
  -- Built-in functions generated in SWI-Prolog via current_arithmetic_function/1.
  xor rem rdiv mod div abs acos acosh asin asinh atan2 atan atanh ceil ceiling
  copysign cos cosh cputime e epsilon erf erfc eval exp float
  float_fractional_part float_integer_part floor gcd getbit inf integer lgamma
  log10 log lsb max min msb nan pi popcount powm random random_float rational
  rationalize round sign sin sinh sqrt tan tanh truncate
]]))

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

-- Strings.
lex:add_rule('string', token(lexer.STRING, lexer.delimited_range("'", true) +
                                           lexer.delimited_range('"', true)))

-- 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.digit^1 *
                                           ('.' * lexer.digit^1)^-1))

-- Operators.
lex:add_rule('operator', token(lexer.OPERATOR, S('-!+\\|=:;&<>()[]{}')))

return lex