Make applyBlocks return a list of incrementally-updated wallet states.

[jonathanknowles]

Issue Number

#639

Overview

This PR is a refactoring: it adjusts the applyBlocks function so that it returns a list of incrementally-updated wallet states.

The list returned is non-empty, where:

• the initial element is the original wallet state;
• each successive element is the result of applying the next available unprocessed block from the original list to the previous element;
• the final element is the state obtained by applying all blocks from the specified list, in order, to the original wallet state.

Callers of applyBlocks now obtain the final state by applying Data.NonEmpty.last to the returned list.

Comments

A future PR will adjust restoreBlocks so that it calls DB.putCheckpoint once per checkpoint.

[rvl]

Sweet 👍