#!/usr/bin/env python
#
# A library that provides a Python interface to the Telegram Bot API
# Copyright (C) 2015-2016
# Leandro Toledo de Souza <devs@python-telegram-bot.org>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser 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 Lesser Public License for more details.
#
# You should have received a copy of the GNU Lesser Public License
# along with this program.  If not, see [http://www.gnu.org/licenses/].
"""This module contains methods to make POST and GET requests"""

import json

import certifi
import urllib3

from telegram import (InputFile, TelegramError)
from telegram.error import Unauthorized, NetworkError, TimedOut, BadRequest

_CON_POOL = None
CON_POOL_SIZE = 1


def _get_con_pool():
    if _CON_POOL is not None:
        return _CON_POOL

    global _CON_POOL
    _CON_POOL = urllib3.HTTPSConnectionPool(host='api.telegram.org',
                                            maxsize=CON_POOL_SIZE,
                                            cert_reqs='CERT_REQUIRED',
                                            ca_certs=certifi.where())
    return _CON_POOL


def _parse(json_data):
    """Try and parse the JSON returned from Telegram.

    Returns:
        dict: A JSON parsed as Python dict with results - on error this dict will be empty.

    """
    decoded_s = json_data.decode('utf-8')
    try:
        data = json.loads(decoded_s)
    except ValueError:
        raise TelegramError('Invalid server response')

    if not data.get('ok') and data.get('description'):
        return data['description']

    return data['result']


def _request_wrapper(*args, **kwargs):
    """Wraps urllib3 request for handling known exceptions.

    Args:
        args: unnamed arguments, passed to urllib3 request.
        kwargs: keyword arguments, passed tp urllib3 request.

    Returns:
        str: A non-parsed JSON text.

    Raises:
        TelegramError

    """

    try:
        resp = _get_con_pool().request(*args, **kwargs)
    except urllib3.exceptions.TimeoutError as error:
        raise TimedOut()
    except urllib3.exceptions.HTTPError as error:
        # HTTPError must come last as its the base urllib3 exception class
        # TODO: do something smart here; for now just raise NetowrkError
        raise NetworkError('urllib3 HTTPError {0}'.format(error))

    if 200 <= resp.status <= 299:
        # 200-299 range are HTTP success statuses
        return resp.data

    try:
        message = _parse(resp.data)
    except ValueError:
        raise NetworkError('Unknown HTTPError {0}'.format(resp.status))

    if resp.status in (401, 403):
        raise Unauthorized()
    elif resp.status == 400:
        raise BadRequest(repr(message))
    elif resp.status == 502:
        raise NetworkError('Bad Gateway')
    else:
        raise NetworkError('{0} ({1})'.format(message, resp.status))


def get(url):
    """Request an URL.
    Args:
      url:
        The web location we want to retrieve.

    Returns:
      A JSON object.

    """
    result = _request_wrapper('GET', url)

    return _parse(result)


def post(url, data, timeout=None):
    """Request an URL.
    Args:
      url:
        The web location we want to retrieve.
      data:
        A dict of (str, unicode) key/value pairs.
      timeout:
        float. If this value is specified, use it as the definitive timeout (in
        seconds) for urlopen() operations. [Optional]

    Notes:
      If neither `timeout` nor `data['timeout']` is specified. The underlying
      defaults are used.

    Returns:
      A JSON object.

    """
    urlopen_kwargs = {}

    if timeout is not None:
        urlopen_kwargs['timeout'] = timeout

    if InputFile.is_inputfile(data):
        data = InputFile(data)
        result = _request_wrapper('POST', url, body=data.to_form(), headers=data.headers)
    else:
        data = json.dumps(data)
        result = _request_wrapper('POST',
                                  url,
                                  body=data.encode(),
                                  headers={'Content-Type': 'application/json'})

    return _parse(result)


def download(url, filename):
    """Download a file by its URL.
    Args:
      url:
        The web location we want to retrieve.

      filename:
        The filename within the path to download the file.

    """
    buf = _request_wrapper('GET', url)
    with open(filename, 'wb') as fobj:
        fobj.write(buf)