#!/usr/bin/python3
# coding=utf-8

import falcon
import json
import client
from errors.session import NoSuchSession, AuthenticationFailed

MAX_REQUEST_LENGTH = 1024 * 1024  # 1 MB

api = application = falcon.API()


def get_json_payload(req, session_is_optional=False):
    content_type_parts = req.content_type.split(';')
    content_type = content_type_parts[0].strip()
    encoding = 'utf-8'
    if len(content_type_parts) > 1:
        for part in content_type_parts[1:]:
            subparts = part.strip().split('=')
            if (len(subparts) == 2) and subparts[0] == 'charset':
                encoding = subparts[1]
    if not ((content_type == 'application/json') or (content_type == 'text/json')):
        raise falcon.HTTPUnsupportedMediaType('Unsupported content-type: {0}'.format(req.content_type))
    length = req.get_header('Content-Length')
    if length is None:
        raise falcon.HTTPLengthRequired('Requests without content-length are not accepted')
    try:
        l = int(length)
    except:
        raise falcon.HTTPBadRequest('Invalid Content-Length', 'The given Content-Length is not a number: {0}'.format(length))
    if l > MAX_REQUEST_LENGTH:
        raise falcon.HTTPError(falcon.HTTP_413, 'Request Entity Too Large', 'Cannot accept the request of length {0}: maximum allowed content-length is {1}'.format(length, MAX_REQUEST_LENGTH))
    try:
        txt = req.stream.read()
    except Exception as e:
        raise falcon.HTTPBadRequest('Error reading request', 'Error while reading the request body: {0}'.format(e.message))
    try:
        js = json.loads(txt.decode(encoding=encoding, errors='replace'))
    except ValueError as e:
        raise falcon.HTTPBadRequest('Error parsing JSON payload', 'Error while parsing the request as JSON: {0}'.format(e.message))
    sid = js.get('sid')
    if sid is None:
        if session_is_optional:
            return js, None
        raise falcon.HTTPBadRequest('No Session', 'Request is missing a session-ID')
    del js['sid']
    try:
        session = client.get_session_by_id(sid)
    except NoSuchSession:
        if session_is_optional:
            return js, None
        raise falcon.HTTPBadRequest('Session Expired', 'This user session has expired. Please log-in again.')
    return js, session


class CodeqService(object):
    """Base class for all CodeQ services.
     It only support the POST method and JSON data.
     Handles JSON decoding and encoding, and session retrieval which can be optional.
    """
    session_is_optional = False

    def on_post(self, req, resp):
        js, session = get_json_payload(req, self.session_is_optional)
        resp.body = json.dumps(self.process(js, session))
        resp.cache_control = 'private, no-cache, no-store'
        resp.content_type = 'application/json'
        resp.status = falcon.HTTP_200

    def process(self, js, session):
        raise falcon.HTTPNotFound()

class ProblemList(CodeqService):
    session_is_optional = True

    def process(self, js, session):
        language = js.get('language')
        if language is None:
            return {'code': 1, 'message': 'Language was not provided'}
        else:
            return {'code': 0, 'message': 'ok', 'problems': client.list_problems_in_groups(language)}

class Login(CodeqService):
    session_is_optional = True

    def process(self, js, old_session):
        username = js.get('username')
        password = js.get('password')
        if username is None:
            return {'code': 1, 'message': 'Username was not provided'}
        elif password is None:
            return {'code': 2, 'message': 'Password was not provided'}
        else:
            try:
                session = client.authenticate_and_create_session(username, password)
            except AuthenticationFailed:
                return {'code': 3, 'message': 'Username or password do not match'}
            else:
                if old_session:
                    old_session.destroy()
                return {'code': 0, 'message': 'OK', 'sid':session.get_sid()}

class Activity(CodeqService):
    def process(self, js, session):
        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:
                return {'code': 1, 'message': 'Problem ID is missing'}
            else:
                session.update_solution(problem_id, trace, solution)

class Query(CodeqService):
    def process(self, js, session):
        step = js.get('step')
        if step is None:
            return {'code': 1, 'message': '"step" is not set'}
        else:
            problem_id = js.get('problem_id')
            if problem_id is None:
                return {'code': 4, 'message': 'Problem ID not given'}
            trace = js.get('trace')
            prolog = session.get_prolog()
            program = None
            if 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.end()
                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, program)
            return result

class Hint(CodeqService):
    def process(self, js, session):
        problem_id = js.get('problem_id')
        program = js.get('program')
        if problem_id is None:
            return {'code': 1, 'message': 'Problem ID not given'}
        if program is None:
            return {'code': 2, 'message': 'No program specified'}

        prolog = session.get_prolog()
        hints = prolog.hint(session.get_uid(), problem_id, program)
        return {'code': 0, 'message': 'ok', 'hints': hints}

class Test(CodeqService):
    def process(self, js, session):
        problem_id = js.get('problem_id')
        program = js.get('program')
        if problem_id is None:
            return {'code': 1, 'message': 'Problem ID not given'}
        if program is None:
            return {'code': 2, 'message': 'No program specified'}

        prolog = session.get_prolog()
        messages = prolog.test(session.get_uid(), problem_id, program)
        return {'code': 0, 'message': 'ok', 'hints': messages}

class GetProblem(CodeqService):
    def process(self, js, session):
        language = js.get('language')
        problem_group = js.get('problem_group')
        problem = js.get('problem')
        if language is None:
            return {'code': 1, 'message': 'Language identifier not given'}
        elif problem_group is None:
            return {'code': 2, 'message': 'Problem group identifier not given'}
        elif problem is None:
            return {'code': 3, 'message': 'Problem identifier not given'}
        else:
            return {'code': 0, 'message': 'ok', 'data': session.get_problem_data(language, problem_group, problem)}

problem_list = ProblemList()
api.add_route('/list_problems', problem_list)

login = Login()
api.add_route('/login', login)

activity = Activity()
api.add_route('/activity', activity)

query = Query()
api.add_route('/query', query)

hint = Hint()
api.add_route('/hint', hint)

test = Test()
api.add_route('/test', test)

get_problem = GetProblem()
api.add_route('/get_problem', get_problem)

if __name__ == '__main__':
    import logging
    from waitress import serve
    logger = logging.getLogger('waitress')
    logger.setLevel(logging.DEBUG)
    serve(application, host='0.0.0.0', port=8082)