from __future__ import unicode_literals

import hashlib
import hmac
import logging

from django.contrib.sites.models import Site
from django.http.request import HttpRequest
from django.utils.six.moves.urllib.parse import urlencode
from django.utils.six.moves.urllib.request import Request, urlopen
from django.template import Context, Template
from django.template.base import Lexer, Parser
from djblets.siteconfig.models import SiteConfiguration
from djblets.webapi.encoders import (JSONEncoderAdapter, ResourceAPIEncoder,
                                     XMLEncoderAdapter)

from reviewboard import get_package_version
from reviewboard.notifications.models import WebHookTarget
from reviewboard.reviews.models import Review, ReviewRequest
from reviewboard.reviews.signals import (review_request_closed,
                                         review_request_published,
                                         review_request_reopened,
                                         review_published,
                                         reply_published)
from reviewboard.webapi.resources import resources


class FakeHTTPRequest(HttpRequest):
    """A fake HttpRequest implementation.

    The WebAPI serialization methods use HttpRequest.build_absolute_uri to
    generate all the links, but none of the various signals that generate
    webhook events have the request plumbed through. Since we don't actually
    need a valid request, this impersonates it enough to get valid results from
    build_absolute_uri.
    """
    _is_secure = None
    _host = None

    def __init__(self, user, local_site_name=None):
        """Initialize a FakeHTTPRequest.

        Args:
            user (django.contrib.auth.models.User):
                The user who initiated the request.

            local_site_name (unicode, optional):
                The local site name (if the request was carried out against a
                local site).
        """
        super(FakeHTTPRequest, self).__init__()

        self.user = user
        self._local_site_name = local_site_name

        if self._is_secure is None:
            siteconfig = SiteConfiguration.objects.get_current()
            self._is_secure = siteconfig.get('site_domain_method') == 'https'
            self._host = Site.objects.get_current().domain

    def is_secure(self):
        return self._is_secure

    def get_host(self):
        return self._host


class CustomPayloadParser(Parser):
    """A custom template parser that blocks certain tags.

    This extends Django's Parser class for template parsing, and removes
    some built-in tags, in order to prevent mailicious use.
    """
    BLACKLISTED_TAGS = ('block', 'debug', 'extends', 'include', 'load', 'ssi')

    def __init__(self, *args, **kwargs):
        super(CustomPayloadParser, self).__init__(*args, **kwargs)

        # Remove some built-in tags that we don't want to expose.
        # There are no built-in filters we have to worry about.
        for tag_name in self.BLACKLISTED_TAGS:
            try:
                del self.tags[tag_name]
            except KeyError:
                pass


def render_custom_content(body, context_data={}):
    """Renders custom content for the payload using Django templating.

    This will take the custom payload content template provided by
    the user and render it using a stripped down version of Django's
    templating system.

    In order to keep the payload safe, we use a limited Context along with a
    custom Parser that blocks certain template tags. This gives us
    tags like {% for %} and {% if %}, but blacklists tags like {% load %}
    and {% include %}.
    """
    lexer = Lexer(body, origin=None)
    parser = CustomPayloadParser(lexer.tokenize())
    template = Template('')
    template.nodelist = parser.parse()

    return template.render(Context(context_data))


def dispatch_webhook_event(request, webhook_targets, event, payload):
    """Dispatch the given event and payload to the given WebHook targets."""
    encoder = ResourceAPIEncoder()
    bodies = {}

    for webhook_target in webhook_targets:
        if webhook_target.use_custom_content:
            try:
                body = render_custom_content(webhook_target.custom_content,
                                             payload)

                body = body.encode('utf-8')
            except Exception as e:
                logging.exception('Could not render WebHook payload: %s', e)
                continue

        else:
            encoding = webhook_target.encoding

            if encoding not in bodies:
                try:
                    if encoding == webhook_target.ENCODING_JSON:
                        adapter = JSONEncoderAdapter(encoder)
                        body = adapter.encode(payload, request=request)
                        body = body.encode('utf-8')
                    elif encoding == webhook_target.ENCODING_XML:
                        adapter = XMLEncoderAdapter(encoder)
                        body = adapter.encode(payload, request=request)
                    elif encoding == webhook_target.ENCODING_FORM_DATA:
                        adapter = JSONEncoderAdapter(encoder)
                        body = urlencode({
                            'payload': adapter.encode(payload,
                                                      request=request),
                        })
                        body = body.encode('utf-8')
                    else:
                        logging.error('Unexpected WebHookTarget encoding "%s" '
                                      'for ID %s',
                                      encoding, webhook_target.pk)
                        continue
                except Exception as e:
                    logging.exception('Could not encode WebHook payload: %s',
                                      e)
                    continue

                bodies[encoding] = body
            else:
                body = bodies[encoding]

        headers = {
            b'X-ReviewBoard-Event': event.encode('utf-8'),
            b'Content-Type': webhook_target.encoding.encode('utf-8'),
            b'Content-Length': len(body),
            b'User-Agent':
                ('ReviewBoard-WebHook/%s' % get_package_version())
                .encode('utf-8'),
        }

        if webhook_target.secret:
            signer = hmac.new(webhook_target.secret.encode('utf-8'), body,
                              hashlib.sha1)
            headers[b'X-Hub-Signature'] = \
                ('sha1=%s' % signer.hexdigest()).encode('utf-8')

        logging.info('Dispatching webhook for event %s to %s',
                     event, webhook_target.url)
        try:
            url = webhook_target.url.encode('utf-8')
            urlopen(Request(url, body, headers))
        except Exception as e:
            logging.exception('Could not dispatch WebHook to %s: %s',
                              webhook_target.url, e)


def _serialize_review(review, request):
    return {
        'review_request': resources.review_request.serialize_object(
            review.review_request, request=request),
        'review': resources.review.serialize_object(
            review, request=request),
        'diff_comments': [
            resources.filediff_comment.serialize_object(
                comment, request=request)
            for comment in review.comments.all()
        ],
        'file_attachment_comments': [
            resources.file_attachment_comment.serialize_object(
                comment, request=request)
            for comment in review.file_attachment_comments.all()
        ],
        'screenshot_comments': [
            resources.screenshot_comment.serialize_object(
                comment, request=request)
            for comment in review.screenshot_comments.all()
        ],
        'general_comments': [
            resources.review_general_comment.serialize_object(
                comment, request=request)
            for comment in review.general_comments.all()
        ],
    }


def _serialize_reply(reply, request):
    return {
        'review_request': resources.review_request.serialize_object(
            reply.review_request, request=request),
        'reply': resources.review_reply.serialize_object(
            reply, request=request),
        'diff_comments': [
            resources.review_reply_diff_comment.serialize_object(
                comment, request=request)
            for comment in reply.comments.all()
        ],
        'file_attachment_comments': [
            resources.review_reply_file_attachment_comment.serialize_object(
                comment, request=request)
            for comment in reply.file_attachment_comments.all()
        ],
        'screenshot_comments': [
            resources.review_reply_screenshot_comment.serialize_object(
                comment, request=request)
            for comment in reply.screenshot_comments.all()
        ],
        'general_comments': [
            resources.review_reply_general_comment.serialize_object(
                comment, request=request)
            for comment in reply.general_comments.all()
        ],
    }


def review_request_closed_cb(user, review_request, type, **kwargs):
    event = 'review_request_closed'
    webhook_targets = WebHookTarget.objects.for_event(
        event, review_request.local_site_id, review_request.repository_id)

    if review_request.local_site_id:
        local_site_name = review_request.local_site.name
    else:
        local_site_name = None

    if webhook_targets:
        if type == review_request.SUBMITTED:
            close_type = 'submitted'
        elif type == review_request.DISCARDED:
            close_type = 'discarded'
        else:
            logging.error('Unexpected close type %s for review request %s '
                          'when dispatching webhook.',
                          type, review_request.pk)
            return

        if not user:
            user = review_request.submitter

        request = FakeHTTPRequest(user, local_site_name=local_site_name)
        payload = {
            'event': event,
            'closed_by': resources.user.serialize_object(
                user, request=request),
            'close_type': close_type,
            'review_request': resources.review_request.serialize_object(
                review_request, request=request),
        }

        dispatch_webhook_event(request, webhook_targets, event, payload)


def review_request_published_cb(user, review_request, changedesc,
                                **kwargs):
    event = 'review_request_published'
    webhook_targets = WebHookTarget.objects.for_event(
        event, review_request.local_site_id, review_request.repository_id)

    if review_request.local_site_id:
        local_site_name = review_request.local_site.name
    else:
        local_site_name = None

    if webhook_targets:
        request = FakeHTTPRequest(user, local_site_name=local_site_name)
        payload = {
            'event': event,
            'is_new': changedesc is None,
            'review_request': resources.review_request.serialize_object(
                review_request, request=request),
        }

        if changedesc:
            payload['change'] = resources.change.serialize_object(
                changedesc, request=request),

        dispatch_webhook_event(request, webhook_targets, event, payload)


def review_request_reopened_cb(user, review_request, **kwargs):
    event = 'review_request_reopened'
    webhook_targets = WebHookTarget.objects.for_event(
        event, review_request.local_site_id, review_request.repository_id)

    if review_request.local_site_id:
        local_site_name = review_request.local_site.name
    else:
        local_site_name = None

    if webhook_targets:
        if not user:
            user = review_request.submitter

        request = FakeHTTPRequest(user, local_site_name=local_site_name)
        payload = {
            'event': event,
            'reopened_by': resources.user.serialize_object(
                user, request=request),
            'review_request': resources.review_request.serialize_object(
                review_request, request=request),
        }

        dispatch_webhook_event(request, webhook_targets, event, payload)


def review_published_cb(user, review, **kwargs):
    event = 'review_published'
    review_request = review.review_request
    webhook_targets = WebHookTarget.objects.for_event(
        event, review_request.local_site_id, review_request.repository_id)

    if review_request.local_site_id:
        local_site_name = review_request.local_site.name
    else:
        local_site_name = None

    if webhook_targets:
        request = FakeHTTPRequest(user, local_site_name=local_site_name)
        payload = _serialize_review(review, request)
        payload['event'] = event
        dispatch_webhook_event(request, webhook_targets, event, payload)


def reply_published_cb(user, reply, **kwargs):
    event = 'reply_published'
    review_request = reply.review_request
    webhook_targets = WebHookTarget.objects.for_event(
        event, review_request.local_site_id, review_request.repository_id)

    if review_request.local_site_id:
        local_site_name = review_request.local_site.name
    else:
        local_site_name = None

    if webhook_targets:
        request = FakeHTTPRequest(user, local_site_name=local_site_name)
        payload = _serialize_reply(reply, request)
        payload['event'] = event
        dispatch_webhook_event(request, webhook_targets, event, payload)


def connect_signals():
    review_request_closed.connect(review_request_closed_cb,
                                  sender=ReviewRequest)
    review_request_published.connect(review_request_published_cb,
                                     sender=ReviewRequest)
    review_request_reopened.connect(review_request_reopened_cb,
                                    sender=ReviewRequest)

    review_published.connect(review_published_cb, sender=Review)
    reply_published.connect(reply_published_cb, sender=Review)
