[Diary] local-storage lifecycle

[sashafirsov]

Data Source Transformation pipeline is applicable for all DS including local-storage which is selected as simplest demo case. There is no intermediate states and data available immediately.

initialization

Data Source would become a Data Request ( DR ) once template materialized as a part of DOM.

On the constructor execution time it is serving as a DS in the template DOM, hence there is no context to populate the own data slice. The actual data would be needed once the DS become DR in the context of template rendering DOM. From DR prospective it is a load event emitted by transformation owner.

Among HTMLElementEventMap events the Window/load_event looks most promising for DCE to fire down to its children to ignite the data load cycle.

slice propagation.

The complete transformation step should work against immutable data set. Since the DataRequest and DataTransformer(DT - link TBD) are multi-stage processes and deliver a slice per state change, it is a transformation owner responsibility to keep the slice available for the next transformation cycle and not to change the data during transformation.

DR/DT notifies its context by emitting loadend with own reference and slice content which would be used in following transformation cycle.

Runtime slice change

For DR asynchronous process the event could be fired at any time including when transformation is completed. The context would update the slice content and re-trigger the transformation.

[sashafirsov]

notification of final DR state

There are Data Sources which would go over multiple state changes before the full data set is available.

XHR has given a sample of events matching HTTP request life cycle:

• loadstart when connection established and response headers available
• progress with intermediate data
• loadend with final data set
• error

Those events would be used when deciding to replace or discard the slice data and mark the transformation process as completed.