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# coding=utf-8
import operator
import threading
import prolog.engine
import server
import server.user_session
from db.models import CodeqUser, Problem
from . import problems
__all__ = ['PrologSession']
def format_prolog_output(reply, output):
messages = [text for text in map(operator.itemgetter(1), output)]
# When an engine is destroyed, a nested data object has the actual query result.
event = reply['event']
if event == 'destroy':
reply = reply['data']
event = reply['event']
if event == 'success':
messages.append(prolog.engine.pretty_vars(reply['data'][0]))
return messages, 'ok', True and reply['more']
if event == 'failure':
messages.append('false')
return messages, 'ok', False
if event == 'error':
# Remove potential module name (engine ID) from the error message.
messages.append('error: ' + reply['data'].replace("'{}':".format(reply['id']), ''))
return messages, 'error', False
return messages, 'ok', False # TODO: is it possible to reach this return statement?
class PrologSession(server.LanguageSession):
"""Abstracts a Prolog session.
Only public methods are available to the outside world due to the use of multiprocessing managers.
Therefore prefix any private methods with an underscore (_).
No properties are accessible; use getters and setters instead.
Values are passed by value instead of by reference (deep copy!).
"""
def __init__(self):
self._access_lock = threading.Lock()
self._engine_id = None
self._problem_id = -1
self._sent_hints = []
def run(self, code):
with self._access_lock:
if self._engine_id is not None:
prolog.engine.stop(self._engine_id)
self._engine_id = None
engine_id, output = prolog.engine.create(code=code)
if not engine_id:
raise Exception('System error: could not create a prolog engine')
self._engine_id = engine_id
messages = [text for text in map(operator.itemgetter(1), output)]
status = 'error' if 'error' in map(operator.itemgetter(0), output) else 'ok'
return messages, status, False
def query(self, query):
with self._access_lock:
if self._engine_id is None:
return ['Prolog is not running'], 'error', False
try:
return format_prolog_output(*prolog.engine.ask(self._engine_id, query))
except Exception as e:
return [str(e)], 'error', False
def step(self):
with self._access_lock:
if self._engine_id is None:
return ['Prolog is not running'], 'error', False
try:
return format_prolog_output(*prolog.engine.next(self._engine_id))
except Exception as e:
return [str(e)], 'error', False
def destroy(self): # this method was previously named: end()
"""Stops the Prolog engine."""
with self._access_lock:
if self._engine_id is not None:
prolog.engine.destroy(self._engine_id)
self._engine_id = None
self._problem_id = -1
return [], 'ok', False
def __del__(self):
# no locking needed if GC is removing us, as there cannot be any concurrent access by definition
if hasattr(self, '_engine_id') and (self._engine_id is not None):
prolog.engine.destroy(self._engine_id)
self._engine_id = None
def hint(self, sid, problem_id, program):
session = server.user_session.get_session_by_id(sid)
language, problem_group, problem = Problem.get_identifier(problem_id)
language_module = problems.load_language(language, 'common')
problem_module = problems.load_problem(language, problem_group, problem, 'common')
solved_problems = [p for p in CodeqUser.solved_problems(session.get_uid(), language)
if p != (problem_group, problem)]
hints = []
# check if the program is already correct
passed, _ = problem_module.test(program, solved_problems)
if passed:
hints = [{'id': 'program_already_correct'}]
if not hints and hasattr(language_module, 'hint'):
hints = language_module.hint(program, solved_problems)
if not hints and hasattr(problem_module, 'hint'):
hints = problem_module.hint(program, solved_problems)
if not hints:
hints = [{'id': 'no_hint'}]
self._instantiate_and_save_hints(language_module, problem_module, hints)
return hints
def test(self, sid, problem_id, program):
session = server.user_session.get_session_by_id(sid)
language, problem_group, problem = Problem.get_identifier(problem_id)
language_module = problems.load_language(language, 'common')
problem_module = problems.load_problem(language, problem_group, problem, 'common')
solved_problems = [p for p in CodeqUser.solved_problems(session.get_uid(), language)
if p != (problem_group, problem)]
try:
passed, hints = problem_module.test(program, solved_problems)
except AttributeError as ex:
hints = [{'id': 'system_error', 'args': {'message': 'test function does not exist'}}]
self._instantiate_and_save_hints(language_module, problem_module, hints)
return hints
# Add hint parameters (such as message index) based on hint class. Append
# the finalized hints to the list of sent hints.
def _instantiate_and_save_hints(self, language_mod, problem_mod, hints):
with self._access_lock:
for hint in hints:
for mod in [language_mod, problem_mod]:
if hasattr(mod, 'hint_type') and hint['id'] in mod.hint_type:
hint_type = mod.hint_type[hint['id']]
hint_type.instantiate(hint, self._sent_hints)
self._sent_hints.extend(hints)
def run_for_user(self, user_id, problem_id, program, query):
"""A "shorthand" method to start a Prolog session, load correct solutions of all user's solved
problems and the given program, and ask a query.
"""
language, problem_group, problem = Problem.get_identifier(problem_id)
problem_module = problems.load_problem(language, problem_group, problem, 'common')
solved_problems = [p for p in CodeqUser.solved_problems(user_id, language)
if p != (problem_group, problem)]
other_solutions = problems.solutions_for_problems(language, solved_problems)
problem_facts = problems.get_facts(language, problem_module) or ''
code = program + '\n' + other_solutions + '\n' + problem_facts
messages, status, have_more = self.run(code)
if status == 'ok':
more_messages, status, have_more = self.query(query)
messages.extend(more_messages)
self._problem_id = problem_id
return messages, status, have_more
def get_problem_id(self):
return self._problem_id
server.language_session_handlers['prolog'] = lambda user_session, problem_id, language_identifier, group_identifier, problem_identifier: PrologSession()
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