# CodeQ: an online programming tutor.
# Copyright (C) 2015 UL FRI
#
# This program is free software: you can redistribute it and/or modify it under
# the terms of the GNU Affero General Public License as published by the Free
# Software Foundation, either version 3 of the License, or (at your option) any
# later version.
#
# This program is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
# FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
# details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.

from concurrent.futures import ThreadPoolExecutor
import traceback
from errors.session import *
import server
import logging


class CodeqService(object):
    """Base class for all CodeQ services.
    """
    session_is_optional = False

    def process(self, request):
        pass


class CreateSession(CodeqService):
    """Creates a new anonymous session.
    To promote the session to the authenticated status, a subsequent
    login or signup must follow.
    """
    session_is_optional = True

    def process(self, request):
        request.reply({'code': 0, 'message': 'OK', 'sid': server.user_session.UserSession().get_sid()})


class DestroySession(CodeqService):
    def process(self, request):
        request.session.destroy()
        request.reply({'code': 0, 'message': 'OK'})


class Login(CodeqService):
    """Logs in a client, authenticating the session.
    """
    def process(self, request):
        js = request.data
        username = js.get('username')
        password = js.get('password')
        if username is None:
            request.reply({'code': 1, 'message': 'Username was not provided'})
        elif password is None:
            request.reply({'code': 2, 'message': 'Password was not provided'})
        else:
            session = request.session
            try:
                name, email, is_admin, date_joined, last_login = session.login(username, password)
            except AuthenticationFailed:
                request.reply({'code': 3, 'message': 'Username or password do not match'})
            else:
                settings = session.get_settings()
                request.reply({
                    'code': 0,
                    'message': 'OK',
                    'username': username,
                    'name': name,
                    'email': email,
                    'admin': is_admin,
                    'joined': date_joined.isoformat(),
                    'last-login': last_login.isoformat(),
                    'settings': settings
                })


class Logout(CodeqService):
    def process(self, request):
        request.session.logout()
        request.reply({'code': 0, 'message': 'OK'})


class Signup(CodeqService):
    def process(self, request):
        js = request.data
        username = js.get('username')
        name = js.get('name')
        email = js.get('email')
        password = js.get('password')
        lang = js.get('lang') or 'en'
        if username is None:
            request.reply({'code': 1, 'message': 'Username was not provided'})
        if email is None:
            request.reply({'code': 2, 'message': 'Email was not provided'})
        elif password is None:
            request.reply({'code': 3, 'message': 'Password was not provided'})
        else:
            try:
                request.session.signup(username, name, email, password, lang)
            except UserExists:
                request.reply({'code': 10, 'message': 'Username already exists'})
            except SignupFailed:
                request.reply({'code': 11, 'message': 'Sign-up failed'})
            else:
                request.reply({'code': 0, 'message': 'OK'})


class ChangePassword(CodeqService):
    def process(self, request):
        js = request.data
        password = js.get('password')
        if password is None:
            request.reply({'code': 1, 'message': 'Password was not provided'})
        else:
            try:
                request.session.change_password(password)
            except PasswordChangeFailed:
                request.reply({'code': 2, 'message': 'Password change failed'})
            else:
                request.reply({'code': 0, 'message': 'OK'})


class UpdateSettings(CodeqService):
    def process(self, request):
        js = request.data
        settings = js.get('settings')
        if settings is None:
            request.reply({'code': 1, 'message': 'New settings not provided'})
        else:
            try:
                request.session.update_settings(settings)
            except NoSuchSession:
                request.reply({'code': 2, 'message': 'No such session'})
            else:
                request.reply({'code': 0, 'message': 'OK'})


class Activity(CodeqService):
    def process(self, request):
        js = request.data
        trace = js.get('trace')
        solution = js.get('solution')
        problem_id = js.get('problem_id')
        if (trace is not None) or (solution is not None):
            # we have something to do
            if problem_id is None:
                request.reply({'code': 1, 'message': 'Problem ID is missing'})
            else:
                request.session.update_solution(problem_id, trace=trace, solution=solution)
                request.end()  # no feedback, just acknowledge the reception


class Query(CodeqService):
    def process(self, request):
        js = request.data
        step = js.get('step')
        if step is None:
            request.reply({'code': 1, 'message': '"step" is not set'})
        else:
            problem_id = js.get('problem_id')
            if problem_id is None:
                request.reply({'code': 4, 'message': 'Problem ID not given'})
            else:
                session = request.session
                trace = js.get('trace')
                program = None
                prolog = session.current_language_session()
                if prolog is None:
                    result = {'code': 6, 'message': 'No language session is active'}
                elif not isinstance(prolog, server.prolog_session.PrologSession):
                    result = {'code': 7, 'message': 'The currently active session is not Prolog'}
                elif step == 'run':
                    program = js.get('program')
                    query = js.get('query')
                    if program is None:
                        result = {'code': 2, 'message': 'No program specified'}
                    elif query is None:
                        result = {'code': 3, 'message': 'No query specified'}
                    else:
                        messages, status, have_more = prolog.run_for_user(session.get_uid(), problem_id, program, query)
                        result = {'code': 0, 'message': 'ok', 'terminal': {'messages': messages, 'status': status, 'have_more': have_more}}
                elif step == 'next':
                    messages, status, have_more = prolog.step()
                    result = {'code': 0, 'message': 'ok', 'terminal': {'messages': messages, 'status': status, 'have_more': have_more}}
                elif step == 'end':
                    messages, status, have_more = prolog.destroy()
                    result = {'code': 0, 'message': 'ok', 'terminal': {'messages': messages, 'status': status, 'have_more': have_more}}
                else:
                    result = {'code': 5, 'message': 'Unknown prolog step: {0}'.format(step)}
                if program or trace:
                    session.update_solution(problem_id, trace=trace, solution=program)
                request.reply(result)


# Push user program to the Python interpreter to be exec'd.
class PythonExec(CodeqService):
    def process(self, request):
        program = request.data.get('program')
        python = request.session.current_language_session()
        if program is None:
            request.reply({'code': 1, 'message': 'No program specified'})
        elif not isinstance(python, server.python_session.PythonSession):
            request.reply({'code': 2, 'message': 'The currently active session is not Python'})
        else:
            python.exec(program)
            request.reply({'code': 0, 'message': 'ok'})


# Send an interrupt to the Python interpreter.
class PythonStop(CodeqService):
    def process(self, request):
        python = request.session.current_language_session()
        if not isinstance(python, server.python_session.PythonSession):
            request.reply({'code': 2, 'message': 'The currently active session is not Python'})
        else:
            python.stop()
            request.reply({'code': 0, 'message': 'ok'})


# Push stdin to the Python interpreter.
class PythonPush(CodeqService):
    def process(self, request):
        text = request.data.get('text')
        python = request.session.current_language_session()
        if text is None:
            request.reply({'code': 1, 'message': 'No input specified'})
        elif not isinstance(python, server.python_session.PythonSession):
            request.reply({'code': 2, 'message': 'The currently active session is not Python'})
        else:
            python.push(text)
            request.reply({'code': 0, 'message': 'ok'})


class Hint(CodeqService):
    def process(self, request):
        js = request.data
        problem_id = js.get('problem_id')
        program = js.get('program')

        if problem_id is None:
            request.reply({'code': 1, 'message': 'No problem ID specified'})
        elif program is None:
            request.reply({'code': 2, 'message': 'No program specified'})
        else:
            session = request.session
            lang_session = session.current_language_session()
            if lang_session is None:
                request.reply({'code': 3, 'message': 'No active session exists'})
            else:
                hints = lang_session.hint(session.get_sid(), problem_id, program)
                request.reply({'code': 0, 'message': 'ok', 'hints': hints})


class Test(CodeqService):
    def process(self, request):
        js = request.data
        problem_id = js.get('problem_id')
        program = js.get('program')

        if problem_id is None:
            request.reply({'code': 1, 'message': 'No problem ID specified'})
        elif program is None:
            request.reply({'code': 2, 'message': 'No program specified'})
        else:
            session = request.session
            lang_session = session.current_language_session()
            if lang_session is None:
                request.reply({'code': 3, 'message': 'No active session exists'})
            else:
                try:
                    hints = lang_session.test(session.get_sid(), problem_id, program)
                    request.reply({'code': 0, 'message': 'ok', 'hints': hints})
                except Exception as ex:
                    request.reply({'code': 4, 'message': str(ex)})


class GetAttempts(CodeqService):
    def process(self, request):
        language = request.data.get('language')
        if language is None:
            request.reply({'code': 1, 'message': 'No language specified'})
        else:
            request.reply({'code': 0, 'data': request.session.get_attempts(language)})


class GetSolutions(CodeqService):
    def process(self, request):
        problem_ids = request.data.get('problem_ids')
        if problem_ids is None:
            request.reply({'code': 1, 'message': 'No problem IDs specified'})
        else:
            request.reply({'code': 0, 'data': request.session.get_solutions(problem_ids)})


class GetCurrentSolution(CodeqService):
    def process(self, request):
        js = request.data
        problem_id = js.get('problem_id')
        if problem_id is None:
            request.reply({'code': 1, 'message': 'Problem ID not specified'})
        else:
            request.reply({'code': 0, 'message': 'ok', 'data': request.session.current_solution(problem_id)})


class LoadProblem(CodeqService):
    def process(self, request):
        problem_id = request.data.get('problem_id')
        if problem_id is None:
            request.reply({'code': 1, 'message': 'There is no active session'})
        else:
            session = request.session.load_language_session(problem_id)
            if session is None:
                request.reply({'code': 2, 'message': 'The session failed to load'})
            else:
                request.reply({'code': 0, 'message': 'OK'})


class EndProblem(CodeqService):
    def process(self, request):
        request.session.end_language_session()
        request.end()


class GetUserStat(CodeqService):
    def process(self, request):
        stat = request.session.get_stat()
        request.reply({'code': 0, 'stat': stat})


class SamlLogin(CodeqService):
    def process(self, request):
        js = request.data
        saml_data = js.get('saml_data')
        gui_lang = js.get('gui_lang', 'en')
        upgrade_account = js.get('upgrade_account')
        upgrade_password = js.get('upgrade_password')
        if saml_data is None:
            request.reply({'code': 3, 'message': 'SAML user data not specified'})
        else:
            session = request.session
            try:
                name, email, date_joined, last_login = session.saml_login_or_signup(saml_data, gui_lang, upgrade_account, upgrade_password)
            except AccountMergeRequired as amr:
                request.reply({'code': 1, 'message': 'Retry with "upgrade_account" and "upgrade_password"', 'username': amr.username})
            except AuthenticationFailed as af:
                request.reply({'code': 4, 'message': 'Password is incorrect'})
#            except Exception as e:
#                request.reply({'code': 2, 'message': 'SAML login failed: ' + str(e)})
            else:
                request.reply({'code': 0, 'message': 'OK', 'name': name, 'email': email, 'joined': date_joined.isoformat(), 'last-login': last_login.isoformat(), 'settings': session.get_settings()})


# maps actions to their handlers
incoming_handlers = {
    'create_session': CreateSession(),
    'destroy_session': DestroySession(),
    'login': Login(),
    'signup': Signup(),
    'change_password': ChangePassword(),
    'get_attempts': GetAttempts(),
    'get_solutions': GetSolutions(),
    'get_current_solution': GetCurrentSolution(),
    'logout': Logout(),
    'activity': Activity(),
    'query': Query(),
    'python_exec': PythonExec(),
    'python_push': PythonPush(),
    'python_stop': PythonStop(),
    'hint': Hint(),
    'update_settings': UpdateSettings(),
    'test': Test(),
    'load_problem': LoadProblem(),
    'end_problem': EndProblem(),
    'user_stat': GetUserStat(),
    'saml_login': SamlLogin(),
    'saml_logout': Logout()
}


class Request(object):
    def __init__(self, tid, original_sid, session, data):
        """Creates a new request

        :param tid: communicator-level transaction ID (global relative to the specific communicator where it originated)
        :param original_sid: session ID, optional
        :param session: the actual session with the original_sid, if it exists; the processor may swap it for a new session
        :param data: the request data from the client
        :return: new instance
        """
        self._tid = tid
        self._original_sid = original_sid
        self.session = session
        self.data = data
        self.is_finished = False

    def reply(self, data):
        """Reply to this request.

        :param data: the dictionary representing the reply, that will be converted to JSON
        :return: None
        """
        if data is None:
            self.end()
            return
        if self._original_sid is not None:
            sid = data.get('sid')
            if sid is None:
                data['sid'] = self._original_sid
            elif sid != self._original_sid:
                data['sid'] = self._original_sid
                data['new_sid'] = sid
        # it is important to reply with the same tid and sid parameters as were in the request, so message accounting doesn't get confused
        send(self._tid, self._original_sid, data)
        self.is_finished = True

    def end(self):
        """Conclude the request, without sending a response.

        This is to acknowledge that the response has been received.
        :return: None
        """
        send(self._tid, self._original_sid, None)
        self.is_finished = True


########## low-level machinery, subject to change to support more than the single socket communicator ##########

_executor = ThreadPoolExecutor(max_workers=100)

def _invoke_handler(handler, request):
    try:
        logging.debug('Worker thread processing data={}'.format(str(request.data)))
        handler.process(request)
        if not request.is_finished:
            logging.error('ERROR: the request was not concluded!')
            request.reply({'code': -1, 'message': 'Request processing did not provide a reply'})
        logging.debug('Processing finished')
    except NotLoggedIn:
        if request.is_finished:
            logging.error('Caught the NotLoggedIn exception, but the request has already been replied to!')
        else:
            request.reply({'code': -1, 'message': 'Cannot execute the request: not logged in'})
    except Exception as e:
        logging.critical('ERROR: data processing failed: ' + str(e))
        logging.critical(traceback.format_exc())
        if request.is_finished:
            logging.critical('The request has already been replied to, the client will not be aware of the error!')
        else:
            request.reply({'code': -1, 'message': 'Internal error: ' + str(e)})

def serve_request(json_obj):
    if not isinstance(json_obj, dict):
        raise RequestProcessingError('Require a request represented as a dict, instead got: ' + str(type(json_obj)))
    tid = json_obj.get('tid')  # session ID and transaction ID uniquely identify a transaction
    sid = json_obj.get('sid')
    action = json_obj.get('action')
    if action is None:
        raise RequestProcessingError('Request does not contain an action')
    if not isinstance(action, str):
        raise RequestProcessingError('Requested action must be a string, got: ' + str(type(action)))
    handler = incoming_handlers.get(action)
    if handler is None:
        raise RequestProcessingError('No handler for ' + action)
    logging.debug("Attempting to serve action={}".format(action))
    session = None
    if sid is None:
        if not handler.session_is_optional:
            raise RequestProcessingError('Request is missing a session-ID')
    else:
        del json_obj['sid']
        try:
            session = server.user_session.get_session_by_id(sid)
        except NoSuchSession:
            if not handler.session_is_optional:
                raise RequestProcessingError('This user session has expired. Please log-in again.')
    _executor.submit(_invoke_handler, handler, Request(tid, sid, session, json_obj))

def send(tid, sid, json_obj):
    # just a proxy function for now
    logging.debug('Sending reply: {}'.format(str(json_obj)))
    server.socket.sendPacket(tid, sid, json_obj)

def stop():
    global _executor
    _executor.shutdown()
    _executor = None