This file documents the persistence mechanism used by JSMaze.

Persistence is all done via billstclair/elm-localstorage. On the server, this also requires the node-localstorage NPM package.

JSMaze.EncodeDecode contains all the functions that convert between Value and different data structures.

JSMaze.Persistence actually does all the persisting.

Philosophy

Everything is persisted all the time. On the client, this means that the part of the Model that cannot be computed is saved on every update. On the server, it means that every change to a board or player is persisted before it is sent out to the clients.

Keys

A Board is persisted separately from its Players. This is so that not much needs to be written when a player moves.

Board.id is world global. It is created by appending the date and time with an optional index, to make it unique.

"2018-03-27T23:29:03"
"2018-03-27T23:29:03-2"

A persisted board key is "B:" prepended to the board id:

"B:2018-03-27T23:29:03"
"B:2018-03-27T23:29:03-2"

Player.id is unique to a board. It is the player name followed by an optional index, to make it unique:

"Bill"
"Bill-12"

A persisted player key is "P:", followed by the board-id, followed by a "/" and the player id:

"P:2018-03-27T23:29:03/Bill"
"P:2018-03-27T23:29:03/Bill-12"

Values

The Values are EncodeDecode.encodeBoard for boards and EncodeDecode.decodePlayer for players.

Accounts (server only)

TBD

Images

TBD