Passive Core Watcher

Run conditional logic on a corestore's hypercores when they open. Useful for example when one hypercore being active implies other hypercores should be active too.

``
npm i passive-core-watcher
`

API

#### const watcher = new PassiveCoreWatcher(corestore, { watch, open })

Create a new passive core watcher, and start watching new cores. Existing cores are also processed (e.g. open will be called for all existing cores for which watch returns true).

corestore is a Corestore

watch is a (possibly async) function, returning a boolean for a given Hypercore.Core object indicating whether the Hypercore should be watched.

open is a (possibly async) function containing the intended side effects for Hypercores which should be watched. Its input is a Hypercore session. It is a weak session, closing when no other sessions exist.

The session emits a close event when it is closing. If teardown of the side effects is needed, a listener needs to be defined in the open function:

session.on('close', () => { / run teardown logic for side effects / } )

#### watcher.destroy()

Stops watching the corestore for new cores, and closes all weak sessions.

#### await watcher.ensureTracked(key)

key is a hypercore key (buffer, z32 or hex format).

If the hypercore is open in the corestore, it is added to the watcher lifecycle, and the open method is called (does nothing otherwise).

Useful when the watch condition might be false when the core first opens, but became true later.

#### watcher.on('oncoreopen-error', e)

Emitted when an error is thrown while a new core is being processed (for example during the passed-in watch or open functions). Useful for debugging and logging.

e` is an error object.