todos-contra-el-fuego-mobile/lib/redux/fetchDataMiddleware.dart

import 'dart:async';

import 'package:fires_flutter/models/fireNotification.dart';
import 'package:fires_flutter/models/yourLocation.dart';
import 'package:get_it/get_it.dart';
import 'package:objectid/objectid.dart';
import 'package:redux/redux.dart';

import '../models/appState.dart';
import '../models/fireNotificationsPersist.dart';
import '../models/firesApi.dart';
import '../models/yourLocationPersist.dart';
import '../objectIdUtils.dart';
import 'actions.dart';

// A middleware takes in 3 parameters: your Store, which you can use to
// read state or dispatch new actions, the action that was dispatched,
// and a `next` function. The first two you know about, and the `next`
// function is responsible for sending the action to your Reducer, or
// the next Middleware if you provide more than one.
//
// Middleware do not return any values themselves. They simply forward
// actions on to the Reducer or swallow actions in some special cases.

FiresApi api = GetIt.instance<FiresApi>();

// Simple debounce mechanism
Timer? _locationUpdateDebounceTimer;

void debounceLocationUpdate(Duration duration, Function() callback) {
  _locationUpdateDebounceTimer?.cancel();
  _locationUpdateDebounceTimer = Timer(duration, callback);
}

void fetchDataMiddleware(Store<AppState> store, action, NextDispatcher next) {
  // If our Middleware encounters a `FetchYourLocationAction`

  if (action is OnUserLangAction) {
    // I can create the user with the lang and the token
    createUser(store, action.lang, store.state.user.token);
  }

  if (action is OnUserTokenAction) {
    // I can create the user with the lang and the token
    createUser(store, store.state.user.lang, action.token);
  }

  if (action is EditConfirmYourLocationAction) {
    if (action.loc.subscribed) {
      // FXIME save lat/lon
    } else {
      // No subscribed (only local)
    }
  }

  if (action is AddYourLocationAction) {
    if (action.loc.subscribed) {
      subscribeViaApi(store, action.loc, (sub) {
        store.dispatch(new AddedYourLocationAction(sub));
        persistYourLocations(store.state.yourLocations);
      });
    } else {
      // No subscribed (only local)
      store.dispatch(new AddedYourLocationAction(action.loc));
      persistYourLocations(store.state.yourLocations);
    }
    getFiresStatsInLocation(store, action.loc);
  }

  if (action is DeleteYourLocationAction) {
    store.dispatch(new DeletedYourLocationAction(action.loc.id));
    if (action.loc.subscribed) {
      unsubsViaApi(store, action.loc.id, () {
        persistYourLocations(store.state.yourLocations);
      });
    } else {
      persistYourLocations(store.state.yourLocations);
    }
  }

  if (action is DeleteFireNotificationAction) {
    store.dispatch(new DeletedFireNotificationAction(action.notif));
    persistFireNotifications(store.state.fireNotifications);
  }

  if (action is DeleteAllFireNotificationAction) {
    store.dispatch(new DeletedAllFireNotificationAction());
    persistFireNotifications(store.state.fireNotifications);
  }

  if (action is AddFireNotificationAction) {
    store.dispatch(new AddedFireNotificationAction(action.notif));
    persistFireNotifications(store.state.fireNotifications);
  }

  if (action is ShowYourLocationMapAction) {
    getFiresStatsInLocation(store, action.loc);
  }

  if (action is ShowFireNotificationMapAction) {
    getFiresStatsInFire(store, action.notif);
  }

  if (action is UpdateYourLocationAction) {
    if (action.loc.subscribed)
      debounceLocationUpdate(
          Duration(seconds: 2),
          () => api
              .getFiresInLocation(
                  state: store.state,
                  lat: action.loc.lat,
                  lon: action.loc.lon,
                  distance: action.loc.distance)
              .then((result) => store.dispatch(result)));
    store.dispatch(new UpdatedYourLocationAction(action.loc));
    persistYourLocations(store.state.yourLocations);
  }

  if (action is SubscribeConfirmAction) {
    subscribeViaApi(store, action.loc, (sub) {
      store.dispatch(new UpdateYourLocationAction(action.loc));
      persistYourLocations(store.state.yourLocations);
    });
  }

  if (action is UnSubscribeAction) {
    unsubsViaApi(store, action.loc.id, () {
      store.dispatch(new UpdateYourLocationAction(action.loc));
      persistYourLocations(store.state.yourLocations);
    });
  }

  if (action is ToggleSubscriptionAction) {
    if (action.loc.subscribed) {
      subscribeViaApi(store, action.loc,
          (sub) => store.dispatch(new ToggledSubscriptionAction(sub)));
    } else {
      unsubsViaApi(store, action.loc.id,
          () => store.dispatch(new ToggledSubscriptionAction(action.loc)));
    }
  }

  if (action is ReadFireNotificationAction) {
    store.dispatch(new ReadedFireNotificationAction(action.notif));
    persistFireNotifications(store.state.fireNotifications);
  }

  if (action is FetchYourLocationsAction) {
    // Use the api to fetch the YourLocations
    loadYourLocations().then((localLocations) {
      api
          .fetchYourLocations(store.state)
          .then((List<YourLocation> subscribedLocations) {
        // If it succeeds, dispatch a success action with the YourLocations.
        // Our reducer will then update the State using these YourLocations.
        print('Subscribed to: ${subscribedLocations.length}');
        // unsubscribe all locally to sync the subs state
        localLocations.forEach((location) => location.subscribed = false);
        print('Local persisted: ${localLocations.length}');
        subscribedLocations.forEach((subsLoc) {
          var locSubs = localLocations.firstWhere(
              (localLocation) => localLocation.id == subsLoc.id, orElse: () {
            localLocations.add(subsLoc);
            return subsLoc;
          });
          locSubs.subscribed = true;
        });

        store.dispatch(new FetchYourLocationsSucceededAction(localLocations));
        persistYourLocations(localLocations);

        localLocations.forEach((yl) {
          api
              .getFiresInLocation(
                  state: store.state,
                  lat: yl.lat,
                  lon: yl.lon,
                  distance: yl.distance)
              .then((value) {
            yl.currentNumFires = value.numFires;
            store.dispatch(new UpdateYourLocationAction(yl));
          });
        });

        final Completer<Null>? completer = action.refreshCallback;
        completer?.complete(null);
      });
    }).catchError((Exception onError) {
      // If it fails, dispatch a failure action. The reducer will
      // update the state with the error.
      store.dispatch(new FetchYourLocationsFailedAction(onError));
    });
  }

  if (action is FetchFireNotificationsAction) {
    loadFireNotifications().then((fireNotifications) {
      int unread = 0;
      for (FireNotification notif in fireNotifications) {
        if (!notif.read) {
          unread++;
        }
      }
      store.dispatch(
          new FetchFireNotificationsSucceededAction(fireNotifications, unread));
      persistFireNotifications(fireNotifications);
    });
  }

  if (action is FetchMonitoredAreasAction) {
    api.getMonitoredAreas(state: store.state).then((result) {
      // store.dispatch()
      store.dispatch(new FetchMonitoredAreasSucceededAction(result));
    });
  }

  if (action is MarkFireAsFalsePositiveAction) {
    api
        .markFalsePositive(store.state, store.state.user.token,
            action.notif.sealed, action.type)
        .then((result) {
      if (result) {
        // Not necessary
        getFiresStatsInFire(store, action.notif);
        store.dispatch(new UpdatedFireNotificationAction(action.notif));
      }
    });
  }

  // Make sure our actions continue on to the reducer.
  next(action);
}

void getFiresStatsInLocation(Store<AppState> store, YourLocation loc) {
  api
      .getFiresInLocation(
          state: store.state,
          lat: loc.lat,
          lon: loc.lon,
          distance: loc.distance)
      .then((result) {
    store.dispatch(result);
    loc.currentNumFires = result.numFires;
    store.dispatch(new UpdateYourLocationAction(loc));
  });
}

void getFiresStatsInFire(Store<AppState> store, FireNotification notif) {
  api
      .getFiresInLocation(
          state: store.state,
          lat: notif.lat,
          lon: notif.lon,
          distance: 1) // FalsePositive/server/publications.js
      .then((result) => store.dispatch(result));
}

void unsubsViaApi(Store<AppState> store, ObjectId id, onUnsubs) {
  api.unsubscribe(store.state, id.hexString).then((res) {
    onUnsubs();
    persistYourLocations(store.state.yourLocations);
  });
}

void subscribeViaApi(
    Store<AppState> store, YourLocation loc, Function(YourLocation) onSubs) {
  api.subscribe(store.state, loc).then((subsId) {
    YourLocation sub = loc;
    // if (loc.id != subsId) {
    sub.id = objectIdFromJson(subsId);
    // }
    onSubs(sub);
    persistYourLocations(store.state.yourLocations);
  });
}

void createUser(Store<AppState> store, String lang, String token) {
  assert(token != null, "User lang is null");
  assert(token != null, "User mobile token is null");
  api.createUser(store.state, token, lang).then((userId) {
    store.dispatch(new OnUserCreatedAction(userId));
    store.dispatch(new FetchYourLocationsAction());
    store.dispatch(new FetchFireNotificationsAction());
    store.dispatch(new FetchMonitoredAreasAction());
  });
}