itowns/lib/Layer/LayerUpdateState.js

A JS/WebGL framework for 3D geospatial data visualization

const UPDATE_STATE = {
  IDLE: 0,
  PENDING: 1,
  ERROR: 2,
  DEFINITIVE_ERROR: 3,
  FINISHED: 4
};
const PAUSE_BETWEEN_ERRORS = [1.0, 3.0, 7.0, 60.0];

/**
 * LayerUpdateState is the update state of a layer, for a given object (e.g tile).
 * It stores information to allow smart update decisions, and especially network
 * error handling.
 * @constructor
 */
class LayerUpdateState {
  constructor() {
    this.state = UPDATE_STATE.IDLE;
    this.lastErrorTimestamp = 0;
    this.errorCount = 0;
    // lowestLevelError is lowest level with error.
    //
    // if lowestLevelError is Infinity, so there has been no error.
    //
    // if lowestLevelError isn't Infinity, so the strategy is to find the
    // highest level between the current level and lowestLevelError.
    // the dichotomy method is used to find it.
    this.failureParams = {
      lowestLevelError: Infinity
    };
  }
  hasFinished() {
    return UPDATE_STATE.FINISHED == this.state;
  }
  canTryUpdate() {
    let timestamp = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : Date.now();
    switch (this.state) {
      case UPDATE_STATE.IDLE:
        {
          return true;
        }
      case UPDATE_STATE.DEFINITIVE_ERROR:
      case UPDATE_STATE.PENDING:
      case UPDATE_STATE.FINISHED:
        {
          return false;
        }
      case UPDATE_STATE.ERROR:
      default:
        {
          const errorDuration = this.secondsUntilNextTry() * 1000;
          return errorDuration <= timestamp - this.lastErrorTimestamp;
        }
    }
  }
  secondsUntilNextTry() {
    if (this.state !== UPDATE_STATE.ERROR) {
      return 0;
    }
    const idx = Math.max(0, Math.min(this.errorCount, PAUSE_BETWEEN_ERRORS.length) - 1);
    return PAUSE_BETWEEN_ERRORS[idx];
  }
  newTry() {
    this.state = UPDATE_STATE.PENDING;
  }
  success() {
    this.lastErrorTimestamp = 0;
    this.state = UPDATE_STATE.IDLE;
  }
  noMoreUpdatePossible() {
    this.state = UPDATE_STATE.FINISHED;
  }
  noData(failureParams) {
    this.state = UPDATE_STATE.IDLE;
    this.failureParams.lowestLevelError = Math.min(failureParams.targetLevel, this.failureParams.lowestLevelError);
  }
  failure(timestamp, definitive, failureParams) {
    if (failureParams && failureParams.targetLevel != undefined) {
      this.failureParams.lowestLevelError = Math.min(failureParams.targetLevel, this.failureParams.lowestLevelError);
    }
    this.lastErrorTimestamp = timestamp;
    this.state = definitive ? UPDATE_STATE.DEFINITIVE_ERROR : UPDATE_STATE.ERROR;
    this.errorCount++;
  }
  inError() {
    return this.state == UPDATE_STATE.DEFINITIVE_ERROR || this.state == UPDATE_STATE.ERROR;
  }
}
export default LayerUpdateState;