from django.core import mail

from .base import AnymailBaseBackend, BasePayload
from ..exceptions import AnymailAPIError
from ..message import AnymailRecipientStatus


class EmailBackend(AnymailBaseBackend):
    """
    Anymail backend that simulates sending messages, useful for testing.

    Sent messages are collected in django.core.mail.outbox (as with Django's locmem backend).

    In addition:
    * Anymail send params parsed from the message will be attached to the outbox message
      as a dict in the attr `anymail_test_params`
    * If the caller supplies an `anymail_test_response` attr on the message, that will be
      used instead of the default "sent" response. It can be either an AnymailRecipientStatus
      or an instance of AnymailAPIError (or a subclass) to raise an exception.
    """

    esp_name = "Test"

    def __init__(self, *args, **kwargs):
        # Allow replacing the payload, for testing.
        # (Real backends would generally not implement this option.)
        self._payload_class = kwargs.pop('payload_class', TestPayload)
        super(EmailBackend, self).__init__(*args, **kwargs)
        if not hasattr(mail, 'outbox'):
            mail.outbox = []  # see django.core.mail.backends.locmem

    def get_esp_message_id(self, message):
        # Get a unique ID for the message.  The message must have been added to
        # the outbox first.
        return mail.outbox.index(message)

    def build_message_payload(self, message, defaults):
        return self._payload_class(backend=self, message=message, defaults=defaults)

    def post_to_esp(self, payload, message):
        # Keep track of the sent messages and params (for test cases)
        message.anymail_test_params = payload.params
        mail.outbox.append(message)
        try:
            # Tests can supply their own message.test_response:
            response = message.anymail_test_response
            if isinstance(response, AnymailAPIError):
                raise response
        except AttributeError:
            # Default is to return 'sent' for each recipient
            status = AnymailRecipientStatus(
                message_id=self.get_esp_message_id(message),
                status='sent'
            )
            response = {
                'recipient_status': {email: status for email in payload.recipient_emails}
            }
        return response

    def parse_recipient_status(self, response, payload, message):
        try:
            return response['recipient_status']
        except KeyError:
            raise AnymailAPIError('Unparsable test response')


class TestPayload(BasePayload):
    # For test purposes, just keep a dict of the params we've received.
    # (This approach is also useful for native API backends -- think of
    # payload.params as collecting kwargs for esp_native_api.send().)

    def init_payload(self):
        self.params = {}
        self.recipient_emails = []

    def set_from_email(self, email):
        self.params['from'] = email

    def set_envelope_sender(self, email):
        self.params['envelope_sender'] = email.addr_spec

    def set_to(self, emails):
        self.params['to'] = emails
        self.recipient_emails += [email.addr_spec for email in emails]

    def set_cc(self, emails):
        self.params['cc'] = emails
        self.recipient_emails += [email.addr_spec for email in emails]

    def set_bcc(self, emails):
        self.params['bcc'] = emails
        self.recipient_emails += [email.addr_spec for email in emails]

    def set_subject(self, subject):
        self.params['subject'] = subject

    def set_reply_to(self, emails):
        self.params['reply_to'] = emails

    def set_extra_headers(self, headers):
        self.params['extra_headers'] = headers

    def set_text_body(self, body):
        self.params['text_body'] = body

    def set_html_body(self, body):
        self.params['html_body'] = body

    def add_alternative(self, content, mimetype):
        self.unsupported_feature("alternative part with type '%s'" % mimetype)

    def add_attachment(self, attachment):
        self.params.setdefault('attachments', []).append(attachment)

    def set_metadata(self, metadata):
        self.params['metadata'] = metadata

    def set_send_at(self, send_at):
        self.params['send_at'] = send_at

    def set_tags(self, tags):
        self.params['tags'] = tags

    def set_track_clicks(self, track_clicks):
        self.params['track_clicks'] = track_clicks

    def set_track_opens(self, track_opens):
        self.params['track_opens'] = track_opens

    def set_template_id(self, template_id):
        self.params['template_id'] = template_id

    def set_merge_data(self, merge_data):
        self.params['merge_data'] = merge_data

    def set_merge_metadata(self, merge_metadata):
        self.params['merge_metadata'] = merge_metadata

    def set_merge_global_data(self, merge_global_data):
        self.params['merge_global_data'] = merge_global_data

    def set_esp_extra(self, extra):
        # Merge extra into params
        self.params.update(extra)