Tardis

Temporal property implementation for reading historized data.

Installation

npm install @georges-tech/tardis

Usage

You create a Tardis service through createHistoryService by providing an array of documents that must contain the following properties :

  /**
   * Date at which the configuration starts to be valid
   */
  effective_date: Date;

  /**
   * Date at which the new configuration has been created
   */
  known_at: Date;

  /**
   * Optional end date for limited time configurations 
   */
  end_date?: Date;

You can add as much properties as you like, depending on your use case, that will be returned by services.

Documents may contain a computed end_date, being the next effective document date if it exists. Otherwise, it is undefined.

While creating the service, you can provide a date to work on the related timeline.

Example

import tardis from '@georges-tech/tardis';

const documents = [{
  effective_date: new Date('2020-01-01'),
  known_at: new Date('2020-05-01'),
  data: {
    value: 'old',
  }
}, {
  effective_date: new Date('2020-03-01'),
  known_at: new Date('2020-10-01'),
  data: {
    value: 'new',
  }
}]
const historyService = tardis.createHistoryService({ documents });

const januaryConfiguration = historyService.getConfigurationAtDate({ date: new Date('2020-01-03') });
// januaryConfiguration.data.value = 'old'
// januaryConfiguration.end_date = new Date('2020-03-01')

const mayConfiguration = historyService.getConfigurationAtDate({ date: new Date('2020-05-03') });
// mayConfiguration.data.value = 'new'
// mayConfiguration.end_date = undefined

With given date

import tardis from '@georges-tech/tardis';

const documents = [{
  effective_date: new Date('2020-01-01'),
  known_at: new Date('2020-05-01'),
  data: {
    value: 'old',
  }
}, {
  effective_date: new Date('2020-03-01'),
  known_at: new Date('2020-10-01'),
  data: {
    value: 'new',
  },
  {
  effective_date: new Date('2020-04-01'),
  known_at: new Date('2020-12-01'),
  data: {
    value: 'new 2',
  }
}]
const historyService = tardis.createHistoryService({ documents, date: new Date('2020-11-01') });

const januaryConfiguration = historyService.getConfigurationAtDate({ date: new Date('2020-01-03') });
// januaryConfiguration.data.value = 'old'
// januaryConfiguration.end_date = new Date('2020-03-01')

const mayConfiguration = historyService.getConfigurationAtDate({ date: new Date('2020-05-03') });
// mayConfiguration.data.value = 'new'
// mayConfiguration.end_date = undefined
// Here we keep the configuration known on 01/10 because on the given date we did not yet know the "new2" configuration