import { AnalyticsTask, AnalyticsTaskType } from '../models/analytics_task_model';
import * as AnalyticUnit from '../models/analytic_unit_model';
import * as AnalyticUnitCache from '../models/analytic_unit_cache_model';
import { AnalyticsService } from './analytics_service';
import { HASTIC_API_KEY } from '../config';

import { queryByMetric } from 'grafana-datasource-kit';

import * as _ from 'lodash';


type MetricDataChunk = { values: [number, number][], columns: string[] };

const PULL_PERIOD_MS = 5000;

export class DataPuller {

  private _unitTimes: { [analyticUnitId: string]: number } = {};

  constructor(private analyticsService: AnalyticsService) {};

  public addUnit(analyticUnit: AnalyticUnit.AnalyticUnit) {
    this._runAnalyticUnitPuller(analyticUnit);
  }

  public deleteUnit(analyticUnitId: AnalyticUnit.AnalyticUnitId) {
    if(_.has(this._unitTimes, analyticUnitId)) {
      delete this._unitTimes[analyticUnitId];
    }
  }

  private async pullData(unit: AnalyticUnit.AnalyticUnit, from: number, to: number): Promise<MetricDataChunk> {
    if(unit === undefined) {
      throw Error(`puller: can't pull undefined unit`);
    }

    return queryByMetric(unit.metric, unit.panelUrl, from, to, HASTIC_API_KEY);
  }

  private pushData(unit: AnalyticUnit.AnalyticUnit, data: any) {
    if(unit === undefined || data === undefined) {
      throw Error(`can't push unit: ${unit} data: ${data}`);
    }
    let task = new AnalyticsTask(unit.id, AnalyticsTaskType.PUSH, data);
    this.analyticsService.sendTask(task);
  }

  //TODO: group analyticUnits by panelID and send same dataset for group
  public async runPuller() {
    const analyticUnits = await AnalyticUnit.findMany({ alert: true });

    _.each(analyticUnits, analyticUnit => {
      this._runAnalyticUnitPuller(analyticUnit);
    });

    console.log('Data puller started');
  }

  public stopPuller() {
    this._unitTimes = {};
  }

  private async _runAnalyticUnitPuller(analyticUnit: AnalyticUnit.AnalyticUnit) {
    // TODO: lastDetectionTime can be in ns
    const time = analyticUnit.lastDetectionTime + 1 || Date.now();
    this._unitTimes[analyticUnit.id] = time;

    const dataGenerator = this.getDataGenerator(
      analyticUnit, PULL_PERIOD_MS
    );

    for await (const data of dataGenerator) {
      if(!_.has(this._unitTimes, analyticUnit.id)) {
        break;
      }

      if(data.values.length === 0) {
        continue;
      }

      const now = Date.now();
      let payloadValues = data.values;
      let cache = await AnalyticUnitCache.findById(analyticUnit.id);
      if(cache !== null) {
        cache = cache.data
      }
      let payload = {
        data: payloadValues,
        from: time,
        to: now,
        pattern: analyticUnit.type,
        cache
      };
      this._unitTimes[analyticUnit.id] = now;
      this.pushData(analyticUnit, payload);
    }
  }

  async * getDataGenerator(analyticUnit: AnalyticUnit.AnalyticUnit, duration: number):
    AsyncIterableIterator<MetricDataChunk> {

    const getData = async () => {
      try {
        const time = this._unitTimes[analyticUnit.id]
        const now = Date.now();
        return await this.pullData(analyticUnit, time, now);
      } catch(err) {
        throw new Error(`Error while pulling data: ${err.message}`);
      }
    }

    const timeout = async () => new Promise(
      resolve => setTimeout(resolve, duration)
    );

    while(true) {
      yield await getData();
      await timeout();
    }
  }

}