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# coding=utf-8
import operator
import threading
import prolog.engine
import db
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(object):
"""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, user_session):
self._user_session = user_session # the owning session
self._access_lock = threading.Lock()
self._engine_id = None
self._problem_id = -1
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
reply, output = prolog.engine.create(code=code)
if reply.get('event') != 'create':
raise Exception('System error: could not create a prolog engine')
self._engine_id = reply['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 end(self):
"""Stops the Prolog engine."""
with self._access_lock:
if self._engine_id is not None:
prolog.engine.stop(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.stop(self._engine_id)
self._engine_id = None
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.
"""
conn = db.get_connection()
try:
cur = conn.cursor()
try:
cur.execute('select l.id, l.identifier, g.identifier, p.identifier from problem p inner join problem_group g on g.id = p.problem_group_id inner join language l on l.id = p.language_id where p.id = %s', (problem_id,))
row = cur.fetchone()
language_id = row[0]
language = row[1]
problem_group = row[2]
problem = row[3]
cur.execute('select g.identifier, p.identifier from solution s inner join problem p on p.id = s.problem_id inner join problem_group g on g.id = p.problem_group_id where s.codeq_user_id = %s and s.done = True and s.problem_id != %s and p.language_id = %s', (user_id, problem_id, language_id))
solved_problems = cur.fetchall()
finally:
cur.close()
finally:
conn.commit()
db.return_connection(conn)
other_solutions = problems.solutions_for_problems(language, solved_problems)
problem_module = problems.load_problem(language, problem_group, problem, 'common')
problem_facts = problems.get_facts(language, problem_module) or ''
code = other_solutions + problem_facts + program
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
# self._user_session.update_solution(problem_id, [], program) # TODO
return messages, status, have_more
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