"""
Badge Awarding backend for Badgr-Server.
"""


import hashlib
import logging
import mimetypes

import requests
from django.conf import settings
from django.core.exceptions import ImproperlyConfigured
from eventtracking import tracker
from lazy import lazy  # lint-amnesty, pylint: disable=no-name-in-module
from requests.packages.urllib3.exceptions import HTTPError  # lint-amnesty, pylint: disable=import-error

from lms.djangoapps.badges.backends.base import BadgeBackend
from lms.djangoapps.badges.models import BadgeAssertion

MAX_SLUG_LENGTH = 255
LOGGER = logging.getLogger(__name__)


class BadgrBackend(BadgeBackend):
    """
    Backend for Badgr-Server by Concentric Sky. http://info.badgr.io/
    """
    badges = []

    def __init__(self):
        super().__init__()
        if not settings.BADGR_API_TOKEN:
            raise ImproperlyConfigured("BADGR_API_TOKEN not set.")

    @lazy
    def _base_url(self):
        """
        Base URL for all API requests.
        """
        return f"{settings.BADGR_BASE_URL}/v1/issuer/issuers/{settings.BADGR_ISSUER_SLUG}"

    @lazy
    def _badge_create_url(self):
        """
        URL for generating a new Badge specification
        """
        return f"{self._base_url}/badges"

    def _badge_url(self, slug):
        """
        Get the URL for a course's badge in a given mode.
        """
        return f"{self._badge_create_url}/{slug}"

    def _assertion_url(self, slug):
        """
        URL for generating a new assertion.
        """
        return "{}/assertions".format(self._badge_url(slug))

    def _slugify(self, badge_class):
        """
        Get a compatible badge slug from the specification.
        """
        slug = badge_class.issuing_component + badge_class.slug
        if badge_class.issuing_component and badge_class.course_id:
            # Make this unique to the course, and down to 64 characters.
            # We don't do this to badges without issuing_component set for backwards compatibility.
            slug = hashlib.sha256((slug + str(badge_class.course_id)).encode('utf-8')).hexdigest()
        if len(slug) > MAX_SLUG_LENGTH:
            # Will be 64 characters.
            slug = hashlib.sha256(slug).hexdigest()
        return slug

    def _log_if_raised(self, response, data):
        """
        Log server response if there was an error.
        """
        try:
            response.raise_for_status()
        except HTTPError:
            LOGGER.error(
                "Encountered an error when contacting the Badgr-Server. Request sent to %r with headers %r.\n"
                "and data values %r\n"
                "Response status was %s.\n%s",
                response.request.url, response.request.headers,
                data,
                response.status_code, response.content
            )
            raise

    def _create_badge(self, badge_class):
        """
        Create the badge class on Badgr.
        """
        image = badge_class.image
        # We don't want to bother validating the file any further than making sure we can detect its MIME type,
        # for HTTP. The Badgr-Server should tell us if there's anything in particular wrong with it.
        content_type, __ = mimetypes.guess_type(image.name)
        if not content_type:
            raise ValueError(
                "Could not determine content-type of image! Make sure it is a properly named .png file. "
                "Filename was: {}".format(image.name)
            )
        files = {'image': (image.name, image, content_type)}
        data = {
            'name': badge_class.display_name,
            'criteria': badge_class.criteria,
            'slug': self._slugify(badge_class),
            'description': badge_class.description,
        }
        result = requests.post(
            self._badge_create_url, headers=self._get_headers(), data=data, files=files,
            timeout=settings.BADGR_TIMEOUT
        )
        self._log_if_raised(result, data)

    def _send_assertion_created_event(self, user, assertion):
        """
        Send an analytics event to record the creation of a badge assertion.
        """
        tracker.emit(
            'edx.badge.assertion.created', {
                'user_id': user.id,
                'badge_slug': assertion.badge_class.slug,
                'badge_name': assertion.badge_class.display_name,
                'issuing_component': assertion.badge_class.issuing_component,
                'course_id': str(assertion.badge_class.course_id),
                'enrollment_mode': assertion.badge_class.mode,
                'assertion_id': assertion.id,
                'assertion_image_url': assertion.image_url,
                'assertion_json_url': assertion.assertion_url,
                'issuer': assertion.data.get('issuer'),
            }
        )

    def _create_assertion(self, badge_class, user, evidence_url):
        """
        Register an assertion with the Badgr server for a particular user for a specific class.
        """
        data = {
            'email': user.email,
            'evidence': evidence_url,
        }
        response = requests.post(
            self._assertion_url(self._slugify(badge_class)), headers=self._get_headers(), data=data,
            timeout=settings.BADGR_TIMEOUT
        )
        self._log_if_raised(response, data)
        assertion, __ = BadgeAssertion.objects.get_or_create(user=user, badge_class=badge_class)
        assertion.data = response.json()
        assertion.backend = 'BadgrBackend'
        assertion.image_url = assertion.data['image']
        assertion.assertion_url = assertion.data['json']['id']
        assertion.save()
        self._send_assertion_created_event(user, assertion)
        return assertion

    @staticmethod
    def _get_headers():
        """
        Headers to send along with the request-- used for authentication.
        """
        return {'Authorization': f'Token {settings.BADGR_API_TOKEN}'}

    def _ensure_badge_created(self, badge_class):
        """
        Verify a badge has been created for this badge class, and create it if not.
        """
        slug = self._slugify(badge_class)
        if slug in BadgrBackend.badges:
            return
        response = requests.get(self._badge_url(slug), headers=self._get_headers(), timeout=settings.BADGR_TIMEOUT)
        if response.status_code != 200:
            self._create_badge(badge_class)
        BadgrBackend.badges.append(slug)

    def award(self, badge_class, user, evidence_url=None):
        """
        Make sure the badge class has been created on the backend, and then award the badge class to the user.
        """
        self._ensure_badge_created(badge_class)
        return self._create_assertion(badge_class, user, evidence_url)