event-bus-examples.oak

#!/usr/bin/env oak

// Async Event Bus Examples
// Demonstrates publish/subscribe event-driven messaging

{
	println: println
	string: string
	each: each
} := import('std')
EventBus := import('async-event-bus')

fn main() {
	println('=== Async Event Bus Examples ===')
	println('')

	// 1. Create event bus and subscribe
	println('1. Basic emit/on:')
	bus := EventBus.create()

	bus.on(:greet, fn(payload) {
		println('  [greet] Hello, ' + string(payload.name) + '!')
	})
	bus.emit(:greet, { name: 'Alice' })
	bus.emit(:greet, { name: 'Bob' })
	println('')

	// 2. Multiple listeners
	println('2. Multiple listeners on same event:')
	bus2 := EventBus.create()
	bus2.on(:log, fn(msg) println('  [Logger A] ' + string(msg)))
	bus2.on(:log, fn(msg) println('  [Logger B] ' + string(msg)))
	bus2.emit(:log, 'Something happened')
	println('')

	// 3. Once (one-shot listener)
	println('3. Once (fires only on first emit):')
	bus3 := EventBus.create()
	bus3.once(:init, fn(payload) {
		println('  [init] Initialized with: ' + string(payload))
	})
	bus3.emit(:init, 'first call')
	bus3.emit(:init, 'second call (should not print)')
	println('')

	// 4. Unsubscribe with off
	println('4. Unsubscribe (off):')
	bus4 := EventBus.create()
	token := bus4.on(:tick, fn(n) println('  [tick] ' + string(n)))
	bus4.emit(:tick, 1)
	bus4.emit(:tick, 2)
	bus4.off(:tick, token)
	bus4.emit(:tick, 3) // should not print
	println('  (tick 3 should not appear)')
	println('')

	// 5. Listener count
	println('5. Listener count:')
	bus5 := EventBus.create()
	bus5.on(:data, fn {})
	bus5.on(:data, fn {})
	bus5.on(:other, fn {})
	println('  Listeners for :data = ' + string(bus5.listenerCount(:data)))
	println('  Listeners for :other = ' + string(bus5.listenerCount(:other)))
	println('')

	// 6. Clear listeners
	println('6. Clear all listeners for event:')
	bus6 := EventBus.create()
	bus6.on(:temp, fn { println('  should not fire') })
	bus6.on(:temp, fn { println('  should not fire') })
	bus6.clear(:temp)
	bus6.emit(:temp, ?)
	println('  Listeners after clear: ' + string(bus6.listenerCount(:temp)))
	println('')

	// 7. Practical: simple state machine
	println('7. Practical: order state machine:')
	sm := EventBus.create()
	state := { current: 'pending' }

	sm.on(:transition, fn(evt) {
		println('  ' + state.current + ' -> ' + evt.to)
		state.current <- evt.to
	})

	sm.emit(:transition, { to: 'processing' })
	sm.emit(:transition, { to: 'shipped' })
	sm.emit(:transition, { to: 'delivered' })
	println('  Final state: ' + state.current)
}

main()