Move filter state to a global map

Background

This is a reboot of https://issues.adblockplus.org/ticket/7453

We have now stopped referring to the filter classes in the rest of eyeo/adblockplus/adblockpluscore> (#157 (closed), #159 (closed)) and the next step is to make the classes private (#19). Before we do this, we still need to address the issue that the state of a filter lives with the filter object itself. The last time we discussed this, we got caught up in discussions about what the API should look like exactly.

I'd like to propose a new filterState module with the following functions:

State: enabled

• isEnabled(filterText: string): boolean
• setEnabled(filterText: string, enabled: boolean)
• toggleEnabled(filterText: string)
• resetEnabled(filterText: string)

State: hitCount

• getHitCount(filterText: string): number
• setHitCount(filterText: string, hitCount: number)
• resetHitCount(filterText: string)

State: lastHit

• getLastHit(filterText: string): number
• setLastHit(filterText: string, lastHit: number)
• resetLastHit(filterText: string)

Hits

• registerHit(filterText: string)
• resetHits(filterText: string)

Reset

• reset(filterText: string)

Serialization

• *serialize(filterText: string)
• fromObject(filterText: string, object: object)

Additionally, in this proposal, the filter.disabled, filter.hitCount, and filter.lastHit events emitted by filterNotifier are now replaced with filterState.enabled (note: not disabled), filterState.hitCount, and filterState.lastHit and include the filter text rather than the filter object.

What to change

See !248 (closed).

Related issues

There is #115 (closed) for keeping a disabled state at the subscription level.

There is follow-up issue #199 (closed) for writing tests for lib/filterState.js.

/cc @ThomasGreiner @hfiguiere @snoack