'''
Url Request
===========

.. versionadded:: 1.0.8

You can use the :class:`UrlRequest` to make asynchronous request on the web, and
get the result when the request is completed. The spirit is the same as XHR
object in Javascript.

The content is also decoded, aka for now, if the Content-Type is
application/json, the result will be automatically passed through json.loads.


The syntax to create a request::

    from kivy.network.urlrequest import UrlRequest
    req = UrlRequest(url, callback_success, callback_error, body, headers)


Only the first argument is mandatory, all the rest is optional.
By default, a "GET" request will be done. If :data:`UrlRequest.req_body` is not
None, a "POST" request will be done. It's up to you to adjust
:data:`UrlRequest.req_headers` if necessary.


Example of fetching twitter trends::

    def got_twitter_trends(req, result):
        trends = result[0]['trends']
        print 'Last %d twitter trends:' % len(trends),
        for trend in trends:
            print trend['name'],
        print '!'

    req = UrlRequest('https://api.twitter.com/1/trends/1.json',
            got_twitter_trends)

Example of Posting data (adapted from httplib example)::

    import urllib

    def bug_posted(req, result):
        print 'Our bug is posted !'
        print result

    params = urllib.urlencode({'@number': 12524, '@type': 'issue',
        '@action': 'show'})
    headers = {'Content-type': 'application/x-www-form-urlencoded',
              'Accept': 'text/plain'}
    req = UrlRequest('bugs.python.org', on_success=bug_posted, req_body=params,
            req_headers=headers)


'''

from collections import deque
from threading import Thread
from json import loads
from httplib import HTTPConnection
from time import sleep

HTTPSConnection = None
try:
    from httplib import HTTPSConnection
except ImportError:
    # on android platform, this is not available yet.
    pass

from urlparse import urlparse
from kivy.clock import Clock
from kivy.weakmethod import WeakMethod


# list to save UrlRequest and prevent GC on un-referenced objects
g_requests = []


class UrlRequest(Thread):
    '''Url request. See module documentation for usage.

    .. versionchanged:: 1.0.10
        Add `method` parameters

    :Parameters:
        `url`: str
            Complete url string to call.
        `on_success`: callback(request, result)
            Callback function to call when the result have been fetched
        `on_error`: callback(request, error)
            Callback function to call when an error happen
        `on_progress`: callback(request, current_size, total_size)
            Callback function that will be called to report progression of the
            download. `total_size` might be -1 if no Content-Length have been
            reported in the http response.
            This callback will be called after each `chunk_size` read.
        `req_body`: str, default to None
            Data to sent in the request. If it's not None, a POST will be done
            instead of a GET
        `req_headers`: dict, default to None
            Custom headers to add for the request
        `chunk_size`: int, default to 8192
            Size of each chunk to read, used only when `on_progress` callback
            have been set. If you decrease it too much, a lot of on_progress
            will be fired, and will slow down your download. If you want to have
            the maximum download speed, increase chunk_size, or don't use
            on_progress.
        `timeout`: int, default to None
            If set, blocking operations will timeout after that many seconds.
        `method'`: str, default to 'GET' (or 'POST' if body)
            HTTP method to use
    '''

    def __init__(self, url, on_success=None, on_error=None, on_progress=None,
            req_body=None, req_headers=None, chunk_size=8192, timeout=None,
            method=None):
        super(UrlRequest, self).__init__()
        self._queue = deque()
        self._trigger_result = Clock.create_trigger(self._dispatch_result, 0)
        self.daemon = True
        self.on_success = WeakMethod(on_success) if on_success else None
        self.on_error = WeakMethod(on_error) if on_error else None
        self.on_progress = WeakMethod(on_progress) if on_progress else None
        self._result = None
        self._error = None
        self._is_finished = False
        self._resp_status = None
        self._resp_headers = None
        self._resp_length = -1
        self._chunk_size = chunk_size
        self._timeout = timeout
        self._method = method

        #: Url of the request
        self.url = url

        #: Request body passed in __init__
        self.req_body = req_body

        #: Request headers passed in __init__
        self.req_headers = req_headers

        # save our request to prevent GC
        g_requests.append(self)

        self.start()

    def run(self):
        q = self._queue.appendleft
        url = self.url
        req_body = self.req_body
        req_headers = self.req_headers
        resp = result = e = None

        try:
            result, resp = self._fetch_url(url, req_body, req_headers, q)
            result = self.decode_result(result, resp)
        except Exception, e:
            pass

        if e is not None:
            q(('error', resp, e))
        else:
            q(('success', resp, result))

        # using trigger can result in a missed on_success event
        self._trigger_result()

        # clean ourself when the queue is empty
        while len(self._queue):
            sleep(.1)
            self._trigger_result()

        # ok, authorize the GC to clean us.
        if self in g_requests:
            g_requests.remove(self)

    def _fetch_url(self, url, body, headers, q):
        # Parse and fetch the current url
        trigger = self._trigger_result
        chunk_size = self._chunk_size
        report_progress = self.on_progress is not None
        timeout = self._timeout

        # parse url
        parse = urlparse(url)

        # translate scheme to connection class
        cls = self.get_connection_for_scheme(parse.scheme)

        # correctly determine host/port
        port = None
        host = parse.netloc.split(':')
        if len(host) > 1:
            port = int(host[1])
        host = host[0]

        # create connection instance
        args = {}
        if timeout is not None:
            args['timeout'] = timeout
        req = cls(host, port, **args)

        # reconstruct path to pass on the request
        path = parse.path
        if parse.query:
            path += '?' + parse.query
        if parse.fragment:
            path += '#' + parse.fragment

        # send request
        method = self._method
        if method is None:
            method = 'GET' if body is None else 'POST'
        req.request(method, path, body, headers or {})

        # read header
        resp = req.getresponse()

        # read content
        if report_progress:
            bytes_so_far = 0
            result = ''
            try:
                total_size = int(resp.getheader('content-length'))
            except:
                total_size = -1
            # before starting the download, send a fake progress to permit the
            # user to initialize his ui
            q(('progress', resp, (bytes_so_far, total_size)))
            while 1:
                chunk = resp.read(chunk_size)
                if not chunk:
                    break
                bytes_so_far += len(chunk)
                result += chunk
                # report progress to user
                q(('progress', resp, (bytes_so_far, total_size)))
                trigger()
            # ensure that restults are dispatch for the last chunk,
            # avaoid trigger
            q(('progress', resp, (bytes_so_far, total_size)))
            trigger()
        else:
            result = resp.read()
        req.close()

        # return everything
        return result, resp

    def get_connection_for_scheme(self, scheme):
        '''Return the Connection class from a particular scheme.
        This is an internal that can be expanded to support custom scheme.

        Actual supported schemes: http, https.
        '''
        if scheme == 'http':
            return HTTPConnection
        elif scheme == 'https' and HTTPSConnection is not None:
            return HTTPSConnection
        else:
            raise Exception('No class for scheme %s' % scheme)

    def decode_result(self, result, resp):
        '''Decode the result fetched from url according to his Content-Type.
        Actually, only decode application/json.
        '''
        # Entry to decode url from the content type.
        # For example, if the content type is a json, it will be automatically
        # decoded.
        ct = resp.getheader('Content-Type', None).split(';')[0]
        if ct == 'application/json':
            try:
                return loads(result)
            except:
                return result
        return result

    def _dispatch_result(self, dt):
        while True:
            # Read the result pushed on the queue, and dispatch to the client
            try:
                result, resp, data = self._queue.pop()
            except IndexError:
                return
            if resp:
                # XXX usage of dict can be dangerous if multiple headers are set
                # even if it's invalid. But it look like it's ok ?
                # http://stackoverflow.com/questions/2454494/..
                # ..urllib2-multiple-set-cookie-headers-in-response
                self._resp_headers = dict(resp.getheaders())
                self._resp_status = resp.status
            if result == 'success':
                self._is_finished = True
                self._result = data
                if self.on_success:
                    func = self.on_success()
                    if func:
                        func(self, data)
            elif result == 'error':
                self._is_finished = True
                self._error = data
                if self.on_error:
                    func = self.on_error()
                    if func:
                        func(self, data)
            elif result == 'progress':
                if self.on_progress:
                    func = self.on_progress()
                    if func:
                        func(self, data[0], data[1])
            else:
                assert(0)

    @property
    def is_finished(self):
        '''Return True if the request have finished, whatever is if it's a
        success or a failure.
        '''
        return self._is_finished

    @property
    def result(self):
        '''Return the result of the request.
        This value is not undeterminate until the request is finished.
        '''
        return self._result

    @property
    def resp_headers(self):
        '''If the request have been done, return a dictionnary containing the
        headers of the response. Otherwise, it will return None
        '''
        return self._resp_headers

    @property
    def resp_status(self):
        '''Return the status code of the response if the request have been done,
        otherwise, return None
        '''
        return self._resp_status

    @property
    def error(self):
        '''Return the error of the request.
        This value is not undeterminate until the request is finished.
        '''
        return self._error

    @property
    def chunk_size(self):
        '''Return the size of a chunk, used only in "progress" mode (when
        on_progress callback is set.)
        '''
        return self._chunk_size

    def wait(self, delay=0.5):
        '''If you want a sync request, you can call the wait() method. It will
        wait for the request to be finished (until :data:`resp_status` is not
        None)

        .. note::
            This method is intended to be used in the main thread, and the
            callback will be dispatched from the same thread as the thread
            you're calling it.

        .. versionadded:: 1.1.0
        '''
        while self.resp_status is None:
            self._dispatch_result(delay)
            sleep(delay)


if __name__ == '__main__':

    from pprint import pprint

    def on_success(req, result):
        pprint('Got the result:')
        pprint(result)

    def on_error(req, error):
        pprint('Got an error:')
        pprint(error)

    req = UrlRequest('http://api.twitter.com/1/trends.json',
            on_success, on_error)
    while not req.is_finished:
        sleep(1)
        Clock.tick()

    print 'result =', req.result
    print 'error =', req.error

