import { put } from 'redux-saga/effects'

import Immutable from 'immutable';

export const SyncMixin = Base => class extends Base {

  constructor(syncEntries, client) {

    super();

    this.syncEntries = syncEntries;

    this.client = client;

    this.localDiffs = null;

  }

  // abstract methods

  // local diffs (immutable)

  // getLocalDiffs()

  // remote urls

  // getRemoteLoadUrl()

  // getRemoteDeleteUrl(localObjInst);

  // getRemoteCreateUrl(localObjInst)

  // getRemoteUpdateUrl(localObjInst)

  // build remote json message

  // getRemoteData(localObjInst)

  // getLocalRecord(remoteObj)

  // actions

  // doDeleteLocalObj(localObjId);

  // resetLocalObj(localObjInst)

  // loadObj(objRecord)

  * loadFromRemote() {

    const objIds = this.syncEntries

      .filter((syncEntry) => syncEntry.action !== 2)

      .map((syncEntry) => syncEntry.ext_id);

    if(objIds.length === 0) {

      return ;

    }

    //TODO: manage pagination

    const remoteObjs = yield this.client.get(this.getRemoteLoadUrl(), { ext_id__in: objIds.join(',') })

    for (var remoteObj of remoteObjs.results) {

      if(this.localDiffs.get('deleted').has(remoteObj.ext_id)) {

        // The session has been deleted locally, we will delete it later

        continue;

      }

      if(this.localDiffs.get('created').has(remoteObj.ext_id)) {

        // The session has been modified both locally and remotely

        // the server wins, it will be loaded locally, we must remove it from the list of locally changed sessions

        const newCreatedMap = this.localDiffs.get('created').delete(remoteObj.ext_id);

        this.localDiffs = this.localDiffs.set('created', newCreatedMap);

      }

      if(this.localDiffs.get('updated').has(remoteObj.ext_id)) {

        // The session has been modified both locally and remotely

        // the server wins, it will be loaded locally, we must remove it from the list of locally changed sessions

        const newModifiedMap = this.localDiffs.get('updated').delete(remoteObj.ext_id);

        this.localDiffs = this.localDiffs.set('updated', newModifiedMap);

      }

      let objRecord = this.getLocalRecord(remoteObj);

      yield put(this.loadObj(objRecord));

    }

  }

  * deleteFromRemote() {

    const objToDelete = this.syncEntries

      .filter((syncObj) => syncObj.action === 2)

      .map((syncObj) => syncObj.ext_id);

    let deleteObjs = this.localDiffs.get('deleted');

    let updatedObjs = this.localDiffs.get('updated');

    let createdObjs = this.localDiffs.get('created');

    for (var objId of objToDelete) {

      if(deleteObjs.has(objId)) {

        // we remove it from the list of sessions to delete

        deleteObjs = deleteObjs.delete(objId);

      }

      if(updatedObjs.has(objId)) {

        updatedObjs = updatedObjs.delete(objId);

      }

      if(createdObjs.has(objId)) {

        createdObjs = createdObjs.delete(objId);

      }

      yield put(this.doDeleteLocalObj(objId));

    }

    this.localDiffs = Immutable.Map({created: createdObjs, updated: updatedObjs, deleted: deleteObjs});

  }

  * syncObjects() {

    this.localDiffs = yield this.getLocalDiffs();

    yield this.loadFromRemote();

    yield this.deleteFromRemote();

    let localObjInst;

    // delete remote obj

    for(localObjInst of this.localDiffs.get('deleted').values()) {

      try {

        yield this.client.delete(this.getRemoteDeleteUrl(localObjInst));

      } catch(err) {

        if(err.status !== 404) {

          //TODO: better error handling ???

          console.log("error whe deleting object", err);

        }

        // otherwise, this is ok

      }

      yield put(this.doDeleteLocalObj(localObjInst.get('_id')));

    }

    for(localObjInst of this.localDiffs.get('created').values()) {

      const remoteData = this.getRemoteData(localObjInst);

      //TODO: SET VERSION !!!!

      yield this.client.post(this.getRemoteCreateUrl(localObjInst), remoteData);

      yield put(this.resetLocalObj(localObjInst));

    }

    for(localObjInst of this.localDiffs.get('updated').values()) {

      const remoteData = this.getRemoteData(localObjInst);

      //TODO: SET VERSION !!!!

      yield this.client.put(this.getRemoteUpdateUrl(localObjInst), remoteData);

      yield put(this.resetLocalObj(localObjInst));

    }

  }

}

export default SyncMixin;