import requests

from django.db import models
from django.conf import settings
from django.contrib import messages
from django.template.loader import render_to_string

from .options import MESSAGES
from .tasks import send_mail


def link_to(target, request):
    return request.scheme + '://' + request.get_host() + target.get_absolute_url()


neat_related = {
    MESSAGES.DETERMINATION_OUTCOME: 'determination',
    MESSAGES.UPDATE_LEAD: 'old',
    MESSAGES.NEW_REVIEW: 'review',
    MESSAGES.TRANSITION: 'old_phase',
}


class AdapterBase:
    messages = {}
    always_send = False

    def message(self, message_type, **kwargs):
        try:
            message = self.messages[message_type]
        except KeyError:
            # We don't know how to handle that message type
            return

        try:
            # see if its a method on the adapter
            method = getattr(self, message)
        except AttributeError:
            return self.render_message(message, **kwargs)
        else:
            # Delegate all responsibility to the custom method
            return method(**kwargs)

    def render_message(self, message, **kwargs):
        return message.format(**kwargs)

    def extra_kwargs(self, message_type, **kwargs):
        return {}

    def get_neat_related(self, message_type, related):
        # We translate the related kwarg into something we can understand
        try:
            neat_name = neat_related[message_type]
        except KeyError:
            # Message type doesn't expect a related object
            if related:
                raise ValueError(f"Unexpected 'related' kwarg provided for {message_type}") from None

        if not related:
            raise ValueError(f"{message_type} expects a 'related' kwarg")
        return {neat_name: related}

    def recipients(self, message_type, **kwargs):
        raise NotImplementedError()

    def process(self, message_type, event, request, user, submission, related=None):
        kwargs = {
            'request': request,
            'user': user,
            'submission': submission,
            'related': related,
        }
        kwargs.update(self.get_neat_related(message_type, related))
        kwargs.update(self.extra_kwargs(message_type, **kwargs))

        message = self.message(message_type, **kwargs)
        if not message:
            return

        for recipient in self.recipients(message_type, **kwargs):
            message_log = self.create_log(message, recipient, event)
            if settings.SEND_MESSAGES or self.always_send:
                status = self.send_message(message, recipient=recipient, message_log=message_log, **kwargs)
            else:
                status = 'Message not sent as SEND_MESSAGES==FALSE'

            message_log.update_status(status)

            if not settings.SEND_MESSAGES:
                if recipient:
                    message = '{} [to: {}]: {}'.format(self.adapter_type, recipient, message)
                else:
                    message = '{}: {}'.format(self.adapter_type, message)
                messages.add_message(request, messages.INFO, message)

    def create_log(self, message, recipient, event):
        from .models import Message
        return Message.objects.create(
            type=self.adapter_type,
            content=message,
            recipient=recipient or '',
            event=event,
        )

    def send_message(self, message, **kwargs):
        # Process the message, should return the result of the send
        # Returning None will not record this action
        raise NotImplementedError()


class ActivityAdapter(AdapterBase):
    adapter_type = "Activity Feed"
    always_send = True
    messages = {
        MESSAGES.TRANSITION: 'Progressed from {old_phase.display_name} to {submission.phase}',
        MESSAGES.NEW_SUBMISSION: 'Submitted {submission.title} for {submission.page.title}',
        MESSAGES.EDIT: 'Edited',
        MESSAGES.APPLICANT_EDIT: 'Edited',
        MESSAGES.UPDATE_LEAD: 'Lead changed from {old.lead} to {submission.lead}',
        MESSAGES.DETERMINATION_OUTCOME: 'Sent a determination. Outcome: {determination.clean_outcome}',
        MESSAGES.INVITED_TO_PROPOSAL: 'Invited to submit a proposal',
        MESSAGES.REVIEWERS_UPDATED: 'reviewers_updated',
        MESSAGES.NEW_REVIEW: MESSAGES.NEW_REVIEW.name,
        MESSAGES.OPENED_SEALED: 'Opened the submission while still sealed',
    }

    def recipients(self, message_type, **kwargs):
        return [None]

    def extra_kwargs(self, message_type, **kwargs):
        if message_type in [MESSAGES.OPENED_SEALED, MESSAGES.REVIEWERS_UPDATED]:
            from .models import INTERNAL
            return {'visibility': INTERNAL}
        return {}

    def reviewers_updated(self, added, removed, **kwargs):
        message = ['Reviewers updated.']
        if added:
            message.append('Added:')
            message.append(', '.join([str(user) for user in added]) + '.')

        if removed:
            message.append('Removed:')
            message.append(', '.join([str(user) for user in removed]) + '.')

        return ' '.join(message)

    def send_message(self, message, user, submission, **kwargs):
        from .models import Activity, PUBLIC
        visibility = kwargs.get('visibility', PUBLIC)

        related =kwargs['related']
        if isinstance(related, models.Model):
            related_object = related
        else:
            related_object = None

        Activity.actions.create(
            user=user,
            submission=submission,
            message=message,
            visibility=visibility,
            related_object=related_object,
        )


class SlackAdapter(AdapterBase):
    adapter_type = "Slack"
    always_send = True
    messages = {
        MESSAGES.NEW_SUBMISSION: 'A new submission has been submitted for {submission.page.title}: <{link}|{submission.title}>',
        MESSAGES.UPDATE_LEAD: 'The lead of <{link}|{submission.title}> has been updated from {old.lead} to {submission.lead} by {user}',
        MESSAGES.COMMENT: 'A new comment has been posted on <{link}|{submission.title}>',
        MESSAGES.EDIT: '{user} has edited <{link}|{submission.title}>',
        MESSAGES.APPLICANT_EDIT: '{user} has edited <{link}|{submission.title}>',
        MESSAGES.REVIEWERS_UPDATED: '{user} has updated the reviewers on <{link}|{submission.title}>',
        MESSAGES.TRANSITION: '{user} has updated the status of <{link}|{submission.title}>: {old_phase.display_name} → {submission.phase}',
        MESSAGES.DETERMINATION_OUTCOME: 'A determination for <{link}|{submission.title}> was sent by email. Outcome: {determination.clean_outcome}',
        MESSAGES.PROPOSAL_SUBMITTED: 'A proposal has been submitted for review: <{link}|{submission.title}>',
        MESSAGES.INVITED_TO_PROPOSAL: '<{link}|{submission.title}> by {submission.user} has been invited to submit a proposal',
        MESSAGES.NEW_REVIEW: '{user} has submitted a review for <{link}|{submission.title}>. Outcome: {review.outcome},  Score: {review.score}',
        MESSAGES.READY_FOR_REVIEW: 'notify_reviewers',
        MESSAGES.OPENED_SEALED: '{user} has opened the sealed submission: <{link}|{submission.title}>'
    }

    def __init__(self):
        super().__init__()
        self.destination = settings.SLACK_DESTINATION_URL
        self.target_room = settings.SLACK_DESTINATION_ROOM

    def extra_kwargs(self, message_type, **kwargs):
        submission = kwargs['submission']
        request = kwargs['request']
        link = link_to(submission, request)
        return {'link': link}

    def recipients(self, message_type, submission, **kwargs):
        return [self.slack_id(submission.lead)]

    def notify_reviewers(self, submission, **kwargs):
        reviewers_to_notify = []
        for reviewer in submission.reviewers.all():
            if submission.phase.permissions.can_review(reviewer):
                reviewers_to_notify.append(reviewer)

        reviewers = ', '.join(
            self.slack_id(reviewer) or str(reviewer) for reviewer in reviewers_to_notify
        )

        return (
            '<{link}|{submission.title}> is ready for review. The following are assigned as reviewers: {reviewers}'.format(
                reviewers=reviewers,
                submission=submission,
                **kwargs
            )
        )

    def slack_id(self, user):
        if user.slack:
            return f'<{user.slack}>'
        return ''

    def send_message(self, message, recipient, **kwargs):
        if not self.destination or not self.target_room:
            errors = list()
            if not self.destination:
                errors.append('Destination URL')
            if not self.target_room:
                errors.append('Room ID')
            return 'Missing configuration: {}'.format(', '.join(errors))

        message = ' '.join([recipient, message]).strip()

        data = {
            "room": self.target_room,
            "message": message,
        }
        response = requests.post(self.destination, json=data)

        return str(response.status_code) + ': ' + response.content.decode()


class EmailAdapter(AdapterBase):
    adapter_type = 'Email'
    messages = {
        MESSAGES.NEW_SUBMISSION: 'funds/email/confirmation.html',
        MESSAGES.COMMENT: 'notify_comment',
        MESSAGES.EDIT: 'messages/email/edit.html',
        MESSAGES.TRANSITION: 'messages/email/transition.html',
        MESSAGES.DETERMINATION_OUTCOME: 'messages/email/determination.html',
        MESSAGES.INVITED_TO_PROPOSAL: 'messages/email/invited_to_proposal.html',
        MESSAGES.READY_FOR_REVIEW: 'messages/email/ready_to_review.html',
    }

    def extra_kwargs(self, message_type, submission, **kwargs):
        if message_type == MESSAGES.READY_FOR_REVIEW:
            subject = 'Application ready to review: {submission.title}'.format(submission=submission)
        else:
            subject = submission.page.specific.subject or 'Your application to Open Technology Fund: {submission.title}'.format(submission=submission)
        return {
            'subject': subject,
        }

    def notify_comment(self, **kwargs):
        comment = kwargs['comment']
        submission = kwargs['submission']
        if not comment.priviledged and not comment.user == submission.user:
            return self.render_message('messages/email/comment.html', **kwargs)

    def recipients(self, message_type, submission, **kwargs):
        if message_type == MESSAGES.READY_FOR_REVIEW:
            return self.reviewers(submission)
        return [submission.user.email]

    def reviewers(self, submission):
        return [
            reviewer.email
            for reviewer in submission.missing_reviewers.all()
            if submission.phase.permissions.can_review(reviewer)
        ]

    def render_message(self, template, **kwargs):
        return render_to_string(template, kwargs)

    def send_message(self, message, submission, subject, recipient, **kwargs):
        try:
            send_mail(
                subject,
                message,
                submission.page.specific.from_address,
                [recipient],
                log=kwargs['message_log']
            )
        except Exception as e:
            return 'Error: ' + str(e)


class MessengerBackend:
    def __init__(self, *adpaters):
        self.adapters = adpaters

    def __call__(self, message_type, request, user, submission, **kwargs):
        return self.send(message_type, request=request, user=user, submission=submission, **kwargs)

    def send(self, message_type, request, user, submission, related):
        from .models import Event
        event = Event.objects.create(type=message_type.name, by=user, submission=submission)
        for adapter in self.adapters:
            adapter.process(message_type, event, request=request, user=user, submission=submission, related=related)


adapters = [
    ActivityAdapter(),
    SlackAdapter(),
    EmailAdapter(),
]


messenger = MessengerBackend(*adapters)