Split the development into daemon and wsgi_server.

Implemented basic infrastructure for daemon (Prolog), and partial support for services in wsgi_server.

4 files changed, 345 insertions, 0 deletions

diff --git a/server/__init__.py b/server/__init__.py
new file mode 100644
index 0000000..f2c73b7
--- /dev/null
+++ b/server/__init__.py
@@ -0,0 +1,23 @@
+# coding=utf-8
+
+import multiprocessing.managers
+from . import user_session
+from . import prolog_session
+
+__all__ = ['user_session']
+
+class CodeqManager(multiprocessing.managers.BaseManager):
+    pass
+
+class UserSessionProxy(multiprocessing.managers.BaseProxy):
+    _method_to_typeid_ = {'get_prolog':'PrologSession'}
+
+CodeqManager.register('PrologSession')
+CodeqManager.register('UserSession', proxytype=UserSessionProxy)
+CodeqManager.register('get_session_by_id', callable=user_session.get_session_by_id, proxytype=UserSessionProxy)
+CodeqManager.register('get_or_create_session', callable=user_session.get_or_create_session, proxytype=UserSessionProxy)
+CodeqManager.register('authenticate_and_create_session', callable=user_session.authenticate_and_create_session, proxytype=UserSessionProxy)
+
+def start():
+    m = CodeqManager(address=('localhost', 16231), authkey=b'c0d3q3y')
+    m.get_server().serve_forever()
diff --git a/server/problems.py b/server/problems.py
new file mode 100644
index 0000000..7fb2606
--- /dev/null
+++ b/server/problems.py
@@ -0,0 +1,83 @@
+# coding=utf-8
+
+import sys
+import importlib.machinery
+import threading
+
+#sys.path.append('/home/aless/job/codeq/source/codeq-problems/')
+_path_prefix = '/home/aless/job/codeq/source/codeq-problems/'
+_module_loading_lock = threading.RLock()  # TODO: make a more fine-grained locking import machinery
+
+def load_module(fullname):
+#   return importlib.import_module(fullname)
+    with _module_loading_lock:
+        mod = sys.modules.get(fullname, None)
+        if mod is None:
+            parts = fullname.split('.')
+            d = _path_prefix + '/'.join(parts[0:-1])
+            ff = importlib.machinery.FileFinder(d, (importlib.machinery.SourceFileLoader, ['.py']))
+            spec = ff.find_spec(fullname)
+            mod = type(sys)(fullname)
+            mod.__loader__ = spec.loader
+            mod.__package__ = spec.parent
+            mod.__spec__ = spec
+            if spec.has_location:
+                mod.__file__ = spec.origin
+                mod.__cached__ = spec.cached
+            sys.modules[fullname] = mod
+            try:
+                spec.loader.exec_module(mod)
+            except:
+                try:
+                    del sys.modules[fullname]
+                except KeyError:
+                    pass
+                raise
+        return mod
+
+def load_problem(language, problem_group, problem, tail_module):
+    return load_module('{0}.problems.{1}.{2}.{3}'.format(language, problem_group, problem, tail_module))
+
+def load_facts(language, fact_module):
+    return load_module('{0}.facts.{1}'.format(language, fact_module))
+
+def load_problems(language, tuples, tail_module):
+    modules = []
+    for problem_group, problem in tuples:
+        mod = '{0}.problems.{1}.{2}.{3}'.format(language, problem_group, problem, tail_module)
+        print('importing {}'.format(mod))
+        modules.append(load_module(mod))
+    return modules
+
+def get_facts(language, problem_module):
+    try:
+        facts = problem_module.facts
+    except AttributeError as e:
+        return None
+    if facts is None:
+        return None
+    module = load_facts(language, facts)
+    if module:
+        try:
+            return module.facts
+        except AttributeError as e:
+            return None
+    return None
+
+def solutions_for_problems(language, tuples):
+    if not tuples:
+        return ''
+    modules = load_problems(language, tuples, 'common')
+    solutions = set()
+    facts = set()
+    for module in modules:
+        try:
+            solution = module.solution
+        except AttributeError as me:
+            pass
+        else:
+            solutions.add(solution)
+            f = get_facts(language, module)
+            if f:
+                facts.add(f)
+    return '\n'.join(facts) + '\n' + '\n'.join(solutions)
diff --git a/server/prolog_session.py b/server/prolog_session.py
new file mode 100644
index 0000000..e00afd8
--- /dev/null
+++ b/server/prolog_session.py
@@ -0,0 +1,117 @@
+# 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):
+        self._access_lock = threading.Lock()
+        self._engine_id = None
+
+    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
+            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, language, problem_group, problem, 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, p.id 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 l.identifier = %s and g.identifier = %s and p.identifier = %s', (language, problem_group, problem))
+                row = cur.fetchone()
+                language_id = row[0]
+                problem_id = row[1]
+                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)
+        return messages, status, have_more
diff --git a/server/user_session.py b/server/user_session.py
new file mode 100644
index 0000000..e418f8d
--- /dev/null
+++ b/server/user_session.py
@@ -0,0 +1,122 @@
+# coding=utf-8
+
+import uuid
+import threading  # multiprocessing.managers.BaseManager uses threading to serve incoming requests
+import hashlib
+import base64
+import random
+from . import prolog_session
+import db
+from errors.session import NoSuchSession, AuthenticationFailed
+
+__all__ = ['get_session_by_id', 'get_or_create_session', 'UserSession']
+
+sessions = {}  # maps session IDs to session objects
+
+module_access_lock = threading.Lock()  # use this lock to access the sessions dictionary
+
+class UserSession(object):
+    """Abstracts a user 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, uid, username):
+        self._access_lock = threading.Lock()
+        self.sid = uuid.uuid4().hex
+        self.uid = uid
+        self.username = username
+        self.prolog_session = None
+
+    def destroy(self):
+        """Destroys the session."""
+        with self._access_lock:
+            with module_access_lock:
+                del sessions[self.sid]
+            if self.prolog_session is not None:
+                self.prolog_session.end()
+                self.prolog_session = None
+            # TODO: add any cleanups as features are added!
+
+    def get_sid(self):
+        return self.sid
+
+    def get_uid(self):
+        return self.uid
+
+    def get_prolog(self):
+        with self._access_lock:
+            if self.prolog_session is None:
+                self.prolog_session = prolog_session.PrologSession()  # lazy init
+            return self.prolog_session
+
+    def __del__(self):
+        #  no locking needed if GC is removing us, as there cannot be any concurrent access by definition
+        if hasattr(self, 'prolog_session') and (self.prolog_session is not None):
+            self.prolog_session.end()
+            self.prolog_session = None
+        # TODO: add any cleanups as features are added!
+
+def get_session_by_id(sid):
+    with module_access_lock:
+        s = sessions.get(sid, None)
+        if s is None:
+            raise NoSuchSession('There is no session with SID {}'.format(sid))
+        return s
+
+def get_or_create_session(uid, username, sid=None):
+    with module_access_lock:
+        if sid is not None:
+            s = sessions.get(sid)
+            if s is not None:
+                return s
+        s = UserSession(uid, username)
+        sessions[s.sid] = s
+        return s
+
+def authenticate_and_create_session(username, password):
+    conn = db.get_connection()
+    try:
+        cur = conn.cursor()
+        try:
+            cur.execute('select id, password from codeq_user where username = %s', (username,))
+            row = cur.fetchone()
+            if row is None:
+                raise AuthenticationFailed('No such user: {}'.format(username))
+            if verify_password(password, row[1]):
+                return get_or_create_session(row[0], username)
+            raise AuthenticationFailed('Password mismatch')
+        finally:
+            cur.close()
+    finally:
+        conn.commit()
+        db.return_connection(conn)
+
+def verify_password(plain_password, encrypted_password):
+    elts = encrypted_password.split('$')
+    if len(elts) != 4:
+        return False
+    if elts[0] != 'pkbdf2_sha256':
+        return False
+    try:
+        rounds = int(elts[1])
+    except:
+        return False
+    enc = hashlib.pbkdf2_hmac('sha256', plain_password.encode('utf-8'), elts[2].encode('utf-8'), rounds)
+    return base64.b64encode(enc).decode('utf-8') == elts[3]
+
+_salt_chars = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'
+_salt_chars_len = len(_salt_chars)
+def encrypt_password(plain_password):
+    rounds = 20000
+    chosen_chars = []
+    for i in range(0, 12):
+        chosen_chars.append(_salt_chars[random.randrange(0, _salt_chars_len)])
+    salt = ''.join(chosen_chars)
+    enc = hashlib.pbkdf2_hmac('sha256', plain_password.encode('utf-8'), salt.encode('utf-8'), rounds)
+    return '{0}${1}${2}${3}'.format('pkbdf2_sha256', rounds, salt, base64.b64encode(enc).decode('utf-8'))
+
+random.seed()
+
+# TODO: add a session timeout timer