const config = require("../config.json");

const GRAPH_UPDATE_TIME_GAP = 60 * 1000; // 60 seconds

class TimeTracker {
  constructor(app) {
    this._app = app;
    this._serverGraphPoints = [];
    this._graphPoints = [];
  }

  newPointTimestamp() {
    const timestamp = TimeTracker.getEpochMillis();

    TimeTracker.pushAndShift(
      this._serverGraphPoints,
      timestamp,
      TimeTracker.getMaxServerGraphDataLength()
    );

    // Flag each group as history graph additions each minute
    // This is sent to the frontend for graph updates
    const updateHistoryGraph =
      config.logToDatabase &&
      (!this._lastHistoryGraphUpdate ||
        timestamp - this._lastHistoryGraphUpdate >= GRAPH_UPDATE_TIME_GAP);

    if (updateHistoryGraph) {
      this._lastHistoryGraphUpdate = timestamp;

      // Push into timestamps array to update backend state
      TimeTracker.pushAndShift(
        this._graphPoints,
        timestamp,
        TimeTracker.getMaxGraphDataLength()
      );
    }

    return {
      timestamp,
      updateHistoryGraph,
    };
  }

  loadGraphPoints(startTime, timestamps) {
    // This is a copy of ServerRegistration#loadGraphPoints
    // timestamps contains original timestamp data and needs to be filtered into minutes
    this._graphPoints = TimeTracker.everyN(
      timestamps,
      startTime,
      GRAPH_UPDATE_TIME_GAP,
      (i) => timestamps[i]
    );
  }

  getGraphPointAt(i) {
    return TimeTracker.toSeconds(this._graphPoints[i]);
  }

  getServerGraphPoints() {
    return this._serverGraphPoints.map(TimeTracker.toSeconds);
  }

  getGraphPoints() {
    return this._graphPoints.map(TimeTracker.toSeconds);
  }

  static toSeconds = (timestamp) => {
    return Math.floor(timestamp / 1000);
  };

  static getEpochMillis() {
    return new Date().getTime();
  }

  static getMaxServerGraphDataLength() {
    return Math.ceil(config.serverGraphDuration / config.rates.pingAll);
  }

  static getMaxGraphDataLength() {
    return Math.ceil(config.graphDuration / GRAPH_UPDATE_TIME_GAP);
  }

  static everyN(array, start, diff, adapter) {
    const selected = [];
    let lastPoint = start;

    for (let i = 0; i < array.length; i++) {
      const point = array[i];

      if (point - lastPoint >= diff) {
        lastPoint = point;
        selected.push(adapter(i));
      }
    }

    return selected;
  }

  static pushAndShift(array, value, maxLength) {
    array.push(value);

    if (array.length > maxLength) {
      array.splice(0, array.length - maxLength);
    }
  }
}

module.exports = {
  GRAPH_UPDATE_TIME_GAP,
  TimeTracker,
};