# This file is part of the MapProxy project.
# Copyright (C) 2010-2017 Omniscale <http://omniscale.de>
#
# 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.

"""
Tile retrieval (WMS, TMS, etc.).
"""
import sys
import time

from mapproxy.version import version
from mapproxy.image import ImageSource
from mapproxy.util.py import reraise_exception
from mapproxy.client.log import log_request

from urllib import request as urllib2
from urllib.error import URLError, HTTPError
from urllib.request import HTTPCookieProcessor
from http import client as httplib
from http.cookiejar import CookieJar

import socket
import ssl


class HTTPClientError(Exception):
    def __init__(self, arg, response_code=None, full_msg=None):
        Exception.__init__(self, arg)
        self.response_code = response_code
        self.full_msg = full_msg


def build_https_handler(ssl_ca_certs, insecure):
    if insecure:
        ctx = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
        ctx.check_hostname = False
        ctx.verify_mode = ssl.CERT_NONE
    elif ssl_ca_certs:
        ctx = ssl.create_default_context(cafile=ssl_ca_certs)
    else:
        ctx = ssl.create_default_context()
    return urllib2.HTTPSHandler(context=ctx)


class VerifiedHTTPSConnection(httplib.HTTPSConnection):
    def __init__(self, *args, **kw):
        self._ca_certs = kw.pop('ca_certs', None)
        httplib.HTTPSConnection.__init__(self, *args, **kw)

    def connect(self):
        # overrides the version in httplib so that we do
        #    certificate verification

        if hasattr(socket, 'create_connection') and hasattr(self, 'source_address'):
            sock = socket.create_connection((self.host, self.port),
                                            self.timeout, self.source_address)
        else:
            sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
            sock.connect((self.host, self.port))

        if hasattr(self, '_tunnel_host') and self._tunnel_host:
            # for Python >= 2.6 with proxy support
            self.sock = sock
            self._tunnel()

        # wrap the socket using verification with the root
        #    certs in self.ca_certs_path
        self.sock = ssl.wrap_socket(sock,
                                    self.key_file,
                                    self.cert_file,
                                    cert_reqs=ssl.CERT_REQUIRED,
                                    ca_certs=self._ca_certs)


def verified_https_connection_with_ca_certs(ca_certs):
    """
    Creates VerifiedHTTPSConnection classes with given ca_certs file.
    """
    def wrapper(*args, **kw):
        kw['ca_certs'] = ca_certs
        return VerifiedHTTPSConnection(*args, **kw)
    return wrapper


class VerifiedHTTPSHandler(urllib2.HTTPSHandler):
    def __init__(self, connection_class=VerifiedHTTPSConnection):
        self.specialized_conn_class = connection_class
        urllib2.HTTPSHandler.__init__(self)

    def https_open(self, req):
        return self.do_open(self.specialized_conn_class, req)


class _URLOpenerCache(object):
    """
    Creates custom URLOpener with BasicAuth and HTTPS handler.

    Caches and reuses opener if possible (i.e. if they share the same
    ssl_ca_certs).
    """

    def __init__(self):
        self._opener = {}

    def __call__(self, ssl_ca_certs, url, username, password, insecure=False, manage_cookies=False):
        cache_key = (ssl_ca_certs, insecure, manage_cookies)
        if cache_key not in self._opener:
            handlers = []
            https_handler = build_https_handler(ssl_ca_certs, insecure)
            if https_handler:
                handlers.append(https_handler)
            passman = urllib2.HTTPPasswordMgrWithDefaultRealm()
            authhandler = urllib2.HTTPBasicAuthHandler(passman)
            handlers.append(authhandler)
            authhandler = urllib2.HTTPDigestAuthHandler(passman)
            handlers.append(authhandler)
            if manage_cookies:
                cj = CookieJar()
                handlers.append(HTTPCookieProcessor(cj))

            opener = urllib2.build_opener(*handlers)

            opener.addheaders = [('User-agent', 'MapProxy-%s' % (version,))]

            self._opener[cache_key] = (opener, passman)
        else:
            opener, passman = self._opener[cache_key]

        if url is not None and username is not None and password is not None:
            passman.add_password(None, url, username, password)

        return opener


create_url_opener = _URLOpenerCache()


class HTTPClient(object):
    def __init__(self, url=None, username=None, password=None, insecure=False,
                 ssl_ca_certs=None, timeout=None, headers=None, hide_error_details=False,
                 manage_cookies=False):
        self._timeout = timeout
        if url and url.startswith('https'):
            if insecure:
                ssl_ca_certs = None

        self.opener = create_url_opener(ssl_ca_certs, url, username, password,
                                        insecure=insecure, manage_cookies=manage_cookies)
        self.header_list = headers.items() if headers else []
        self.hide_error_details = hide_error_details

    def open(self, url, data=None, method=None):
        code = None
        result = None
        try:
            req = urllib2.Request(url, data=data)
        except ValueError as e:
            err = self.handle_url_exception(url, 'URL not correct', e.args[0])
            reraise_exception(err, sys.exc_info())
        for key, value in self.header_list:
            req.add_header(key, value)
        if method:
            req.method = method
        try:
            start_time = time.time()
            if self._timeout is not None:
                result = self.opener.open(req, timeout=self._timeout)
            else:
                result = self.opener.open(req)
        except HTTPError as e:
            code = e.code
            err = self.handle_url_exception(url, 'HTTP Error', str(code), response_code=code)
            reraise_exception(err, sys.exc_info())
        except URLError as e:
            if isinstance(e.reason, ssl.SSLError):
                err = self.handle_url_exception(url, 'Could not verify connection to URL', e.reason.args[1])
                reraise_exception(err, sys.exc_info())
            try:
                reason = e.reason.args[1]
            except (AttributeError, IndexError):
                reason = e.reason
            err = self.handle_url_exception(url, 'No response from URL', reason)
            reraise_exception(err, sys.exc_info())
        except ValueError as e:
            err = self.handle_url_exception(url, 'URL not correct', e.args[0])
            reraise_exception(err, sys.exc_info())
        except Exception as e:
            err = self.handle_url_exception(url, 'Internal HTTP error', repr(e))
            reraise_exception(err, sys.exc_info())
        else:
            code = getattr(result, 'code', 200)
            if code == 204:
                raise HTTPClientError('HTTP Error "204 No Content"', response_code=204)
            return result
        finally:
            log_request(url, code, result, duration=time.time()-start_time, method=req.get_method())

    def open_image(self, url, data=None):
        resp = self.open(url, data=data)
        if 'content-type' in resp.headers:
            if not resp.headers['content-type'].lower().startswith('image'):
                raise HTTPClientError('response is not an image: (%s)' % (resp.read()))
        return ImageSource(resp)

    def handle_url_exception(self, url, message, reason, response_code=None):
        full_msg = '%s "%s": %s' % (message, url, reason)
        if self.hide_error_details:
            return HTTPClientError(
                '{} (see logs for URL and reason).'.format(message),
                response_code=response_code,
                full_msg=full_msg,
            )
        else:
            return HTTPClientError(
                full_msg,
                response_code=response_code,
            )


def auth_data_from_url(url):
    """
    >>> auth_data_from_url('invalid_url')
    ('invalid_url', (None, None))
    >>> auth_data_from_url('http://localhost/bar')
    ('http://localhost/bar', (None, None))
    >>> auth_data_from_url('http://bar@localhost/bar')
    ('http://localhost/bar', ('bar', None))
    >>> auth_data_from_url('http://bar:baz@localhost/bar')
    ('http://localhost/bar', ('bar', 'baz'))
    >>> auth_data_from_url('http://bar:b:az@@localhost/bar')
    ('http://localhost/bar', ('bar', 'b:az@'))
    >>> auth_data_from_url('http://bar foo; foo@bar:b:az@@localhost/bar')
    ('http://localhost/bar', ('bar foo; foo@bar', 'b:az@'))
    >>> auth_data_from_url('https://bar:foo#;%$@localhost/bar')
    ('https://localhost/bar', ('bar', 'foo#;%$'))
    >>> auth_data_from_url('http://localhost/bar@2x')
    ('http://localhost/bar@2x', (None, None))
    >>> auth_data_from_url('http://bar@localhost/bar@2x')
    ('http://localhost/bar@2x', ('bar', None))
    >>> auth_data_from_url('http://bar:baz@localhost/bar@2x')
    ('http://localhost/bar@2x', ('bar', 'baz'))
    >>> auth_data_from_url('https://bar@localhost/bar/0/0/0@2x.png')
    ('https://localhost/bar/0/0/0@2x.png', ('bar', None))
    >>> auth_data_from_url('http://bar:baz@localhost/bar@2x.png')
    ('http://localhost/bar@2x.png', ('bar', 'baz'))
    """
    if not url or '://' not in url:
        # be silent for invalid URLs
        return url, (None, None)

    schema, url = url.split('://', 1)
    if '/' in url:
        host, request = url.split('/', 1)
    else:
        host, request = url, ''

    username = password = None
    if '@' in host:
        auth_data, host = host.rsplit('@', 1)
        if ':' in auth_data:
            username, password = auth_data.split(':', 1)
        else:
            username = auth_data
    url = schema + "://" + host + "/" + request
    return url, (username, password)


def open_url(url):
    url, (username, password) = auth_data_from_url(url)
    http_client = HTTPClient(url, username, password)
    return http_client.open(url)


def retrieve_image(url, client=None):
    """
    Retrive an image from `url`.

    :return: the image as a file object (with url .header and .info)
    :raise HTTPClientError: if response content-type doesn't start with image
    """
    resp = open_url(url)
    if not resp.headers['content-type'].startswith('image'):
        raise HTTPClientError('response is not an image: (%s)' % (resp.read()))
    return ImageSource(resp)
