# -*- coding: utf-8 -*-
#
# Copyright 2012-2015 Spotify AB
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
"""
Implementation of the REST interface between the workers and the server.
rpc.py implements the client side of it, server.py implements the server side.
"""

import json
import logging
import time
try:
    from urllib import urlencode
    from urllib2 import urlopen, HTTPError, URLError, Request
except ImportError:
    from urllib.parse import urlencode
    from urllib.request import Request, urlopen
    from urllib.error import HTTPError, URLError

from luigi import configuration
from luigi.scheduler import PENDING, Scheduler

logger = logging.getLogger('luigi-interface')  # TODO: 'interface'?


class RPCError(Exception):

    def __init__(self, message, sub_exception=None):
        super(RPCError, self).__init__(message)
        self.sub_exception = sub_exception


class RemoteScheduler(Scheduler):
    """
    Scheduler proxy object. Talks to a RemoteSchedulerResponder.
    """

    def __init__(self, host='localhost', port=8082, connect_timeout=None):
        self._host = host
        self._port = port

        config = configuration.get_config()

        if connect_timeout is None:
            connect_timeout = config.getfloat('core', 'rpc-connect-timeout', 10.0)
        self._connect_timeout = connect_timeout

    def _wait(self):
        time.sleep(30)

    def _get(self, url, data):
        url = 'http://%s:%d%s?%s' % \
              (self._host, self._port, url, urlencode(data))
        return Request(url)

    def _post(self, url, data):
        url = 'http://%s:%d%s' % (self._host, self._port, url)
        return Request(url, urlencode(data).encode('utf8'))

    def _request(self, url, data, log_exceptions=True, attempts=3):
        data = {'data': json.dumps(data)}

        req = self._post(url, data)
        last_exception = None
        attempt = 0
        while attempt < attempts:
            attempt += 1
            if last_exception:
                logger.info("Retrying...")
                self._wait()  # wait for a bit and retry
            try:
                response = urlopen(req, None, self._connect_timeout)
                break
            except URLError as e:
                last_exception = e
                if isinstance(last_exception, HTTPError) and last_exception.code == 405:
                    # TODO(f355): 2014-08-29 Remove this fallback after several weeks
                    logger.warning("POST requests are unsupported. Please upgrade scheduler ASAP. Falling back to GET for now.")
                    req = self._get(url, data)
                    last_exception = None
                    attempt -= 1
                elif log_exceptions:
                    logger.exception("Failed connecting to remote scheduler %r", self._host)
                continue
        else:
            raise RPCError(
                "Errors (%d attempts) when connecting to remote scheduler %r" %
                (attempts, self._host),
                last_exception
            )
        page = response.read().decode('utf8')
        result = json.loads(page)
        return result["response"]

    def ping(self, worker):
        # just one attemtps, keep-alive thread will keep trying anyway
        self._request('/api/ping', {'worker': worker}, attempts=1)

    def add_task(self, worker, task_id, status=PENDING, runnable=False,
                 deps=None, new_deps=None, expl=None, resources={}, priority=0,
                 family='', params={}):
        self._request('/api/add_task', {
            'task_id': task_id,
            'worker': worker,
            'status': status,
            'runnable': runnable,
            'deps': deps,
            'new_deps': new_deps,
            'expl': expl,
            'resources': resources,
            'priority': priority,
            'family': family,
            'params': params,
        })

    def get_work(self, worker, host=None):
        return self._request(
            '/api/get_work',
            {'worker': worker, 'host': host},
            log_exceptions=False,
            attempts=1)

    def graph(self):
        return self._request('/api/graph', {})

    def dep_graph(self, task_id):
        return self._request('/api/dep_graph', {'task_id': task_id})

    def inverse_dep_graph(self, task_id):
        return self._request('/api/inverse_dep_graph', {'task_id': task_id})

    def task_list(self, status, upstream_status):
        return self._request('/api/task_list', {'status': status, 'upstream_status': upstream_status})

    def worker_list(self):
        return self._request('/api/worker_list', {})

    def task_search(self, task_str):
        return self._request('/api/task_search', {'task_str': task_str})

    def fetch_error(self, task_id):
        return self._request('/api/fetch_error', {'task_id': task_id})

    def add_worker(self, worker, info):
        return self._request('/api/add_worker', {'worker': worker, 'info': info})
