import { createPushSubsription, updatePushSubscription } from 'soapbox/actions/push_subscriptions';
import { pushNotificationsSetting } from 'soapbox/settings';
import { getVapidKey } from 'soapbox/utils/auth';
import { decode as decodeBase64 } from 'soapbox/utils/base64';

import { setBrowserSupport, setSubscription, clearSubscription } from './setter';

// Taken from https://www.npmjs.com/package/web-push
const urlBase64ToUint8Array = (base64String) => {
  const padding = '='.repeat((4 - base64String.length % 4) % 4);
  const base64 = (base64String + padding)
    .replace(/\-/g, '+')
    .replace(/_/g, '/');

  return decodeBase64(base64);
};

const getRegistration = () => navigator.serviceWorker.ready;

const getPushSubscription = (registration) =>
  registration.pushManager.getSubscription()
    .then(subscription => ({ registration, subscription }));

const subscribe = (registration, getState) =>
  registration.pushManager.subscribe({
    userVisibleOnly: true,
    applicationServerKey: urlBase64ToUint8Array(getVapidKey(getState())),
  });

const unsubscribe = ({ registration, subscription }) =>
  subscription ? subscription.unsubscribe().then(() => registration) : registration;

const sendSubscriptionToBackend = (subscription, me) => {
  return (dispatch, getState) => {
    const alerts = getState().getIn(['push_notifications', 'alerts']).toJS();
    const params = { subscription, data: { alerts } };

    if (me) {
      const data = pushNotificationsSetting.get(me);
      if (data) {
        params.data = data;
      }
    }

    return dispatch(createPushSubsription(params));
  };
};

// Last one checks for payload support: https://web-push-book.gauntface.com/chapter-06/01-non-standards-browsers/#no-payload
const supportsPushNotifications = ('serviceWorker' in navigator && 'PushManager' in window && 'getKey' in PushSubscription.prototype);

export function register() {
  return (dispatch, getState) => {
    const me = getState().get('me');
    const vapidKey = getVapidKey(getState());

    dispatch(setBrowserSupport(supportsPushNotifications));

    if (!supportsPushNotifications) {
      console.warn('Your browser does not support Web Push Notifications.');
      return;
    }

    if (!vapidKey) {
      console.error('The VAPID public key is not set. You will not be able to receive Web Push Notifications.');
      return;
    }

    getRegistration()
      .then(getPushSubscription)
      .then(({ registration, subscription }) => {
        if (subscription !== null) {
          // We have a subscription, check if it is still valid
          const currentServerKey = (new Uint8Array(subscription.options.applicationServerKey)).toString();
          const subscriptionServerKey = urlBase64ToUint8Array(vapidKey).toString();
          const serverEndpoint = getState().getIn(['push_notifications', 'subscription', 'endpoint']);

          // If the VAPID public key did not change and the endpoint corresponds
          // to the endpoint saved in the backend, the subscription is valid
          if (subscriptionServerKey === currentServerKey && subscription.endpoint === serverEndpoint) {
            return subscription;
          } else {
            // Something went wrong, try to subscribe again
            return unsubscribe({ registration, subscription }).then(registration => {
              return subscribe(registration, getState);
            }).then(
              subscription => dispatch(sendSubscriptionToBackend(subscription, me)));
          }
        }

        // No subscription, try to subscribe
        return subscribe(registration, getState)
          .then(subscription => dispatch(sendSubscriptionToBackend(subscription, me)));
      })
      .then(subscription => {
        // If we got a PushSubscription (and not a subscription object from the backend)
        // it means that the backend subscription is valid (and was set during hydration)
        if (!(subscription instanceof PushSubscription)) {
          dispatch(setSubscription(subscription));
          if (me) {
            pushNotificationsSetting.set(me, { alerts: subscription.alerts });
          }
        }
      })
      .catch(error => {
        console.error(error);
        if (error.code === 20 && error.name === 'AbortError') {
          console.warn('Your browser supports Web Push Notifications, but does not seem to implement the VAPID protocol.');
        } else if (error.code === 5 && error.name === 'InvalidCharacterError') {
          console.error('The VAPID public key seems to be invalid:', vapidKey);
        }

        // Clear alerts and hide UI settings
        dispatch(clearSubscription());

        if (me) {
          pushNotificationsSetting.remove(me);
        }

        return getRegistration()
          .then(getPushSubscription)
          .then(unsubscribe);
      })
      .catch(console.warn);
  };
}

export function saveSettings() {
  return (dispatch, getState) => {
    const state = getState().get('push_notifications');
    const alerts = state.get('alerts');
    const data = { alerts };
    const me = getState().get('me');

    return dispatch(updatePushSubscription({ data })).then(() => {
      if (me) {
        pushNotificationsSetting.set(me, data);
      }
    }).catch(console.warn);
  };
}
