messaging.py

from enum import Enum
from django.contrib import messages

from .models import Activity


class MESSAGES(Enum):
    UPDATE_LEAD = 'update_lead'
    NEW_SUBMISSION = 'new_submission'
    NEW_DETERMINATION = 'new_determination'
    DETERMINATION_OUTCOME = 'determination_outcome'
    INVITED_TO_PROPOSAL = 'invited_to_proposal'
    REVIEWERS_UPDATED = 'reviewers_updated'


class MessageAdapter:
    def process(self, request, payload):
        messages.add_message(request, messages.INFO, 'Hello world.')


class ActivityAdapter:
    messages = {
        MESSAGES.NEW_SUBMISSION: 'Submitted {submission.title} for {submission.page.title}',
        MESSAGES.UPDATE_LEAD: 'Lead changed from {old.lead} to {new.lead}',
        MESSAGES.NEW_DETERMINATION: 'Created a determination for {submission.title}',
        MESSAGES.DETERMINATION_OUTCOME: 'Sent a {submission.determination.get_outcome_display} determination for {submission.title}:\r\n{determination.clean_message}',
        MESSAGES.INVITED_TO_PROPOSAL: '{submission.title} has been invited to submit a proposal.',
        MESSAGES.REVIEWERS_UPDATED: 'reviewers_updated',
    }

    def message(self, message_type, **kwargs):
        message = self.messages[message_type]
        try:
            method = getattr(self, message)
        except AttributeError:
            return message.format(**kwargs)
        else:
            return method(**kwargs)

    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 process(self, message_type, **kwargs):
        try:
            message = self.message(message_type, **kwargs)
        except KeyError:
            return

        Activity.actions.create(
            user=kwargs['user'],
            submission=kwargs['submission'],
            message=message,
        )


class MessengerBackend:
    adapters = [ActivityAdapter()]

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

    def send(self, message_type, **kwargs):
        for adapter in self.adapters:
            adapter.process(message_type, **kwargs)


messenger = MessengerBackend()