All zone types

This walkthrough covers 02-multi-zone.ts — both zone types registered on a single engine, with one entity moving through each.

1. Register zone types

import { GeoEngine, type GeoEvent } from '@jamesholcombe/geo-stream'

const engine = new GeoEngine()

// Polygon zone: rectangular area from (0,0) to (2,2)
engine.registerZone('warehouse', {
  type: 'Polygon',
  coordinates: [[[0, 0], [2, 0], [2, 2], [0, 2], [0, 0]]],
})

// Circle: centred at (7, 7), radius 1.5 units
engine.registerCircle('depot-beacon', 7, 7, 1.5)

Both types coexist on the same engine instance. ingest() evaluates every registered zone for every update.

2. Waypoint sequence

truck-1 moves through four positions, each triggering different events:

Time	Position	Location	Events
t+0s	(1.0, 1.0)	inside warehouse	enter warehouse
t+30s	(4.0, 0.25)	open road	exit warehouse
t+60s	(7.0, 7.0)	inside depot-beacon	approach depot-beacon
t+90s	(20.0, 20.0)	open space (no zones)	recede depot-beacon

const t0 = 1_700_000_000_000

const waypoints = [
  { x: 1.0,  y: 1.0,  label: 'inside warehouse'      },
  { x: 4.0,  y: 0.25, label: 'open road'             },
  { x: 7.0,  y: 7.0,  label: 'inside depot-beacon'   },
  { x: 20.0, y: 20.0, label: 'open space (no zones)' },
]

for (let i = 0; i < waypoints.length; i++) {
  const { x, y, label } = waypoints[i]
  const tMs = t0 + i * 30_000

  const events = engine.ingest([{ id: 'truck-1', x, y, tMs }])

  console.log(`\n[t+${i * 30}s]  pos=(${x}, ${y})  — ${label}`)
  for (const ev of events) {
    console.log(' ', formatEvent(ev))
  }
}

3. The event handler switch

function formatEvent(ev: GeoEvent): string {
  switch (ev.kind) {
    case 'enter':
      return `ENTER zone "${ev.zone}"`
    case 'exit':
      return `EXIT  zone "${ev.zone}"`
    case 'approach':
      return `APPROACH circle "${ev.circle}"`
    case 'recede':
      return `RECEDE   circle "${ev.circle}"`
    default:
      return JSON.stringify(ev)
  }
}

This switch pattern is recommended over if/else chains for clarity.

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Next: Dwell debounce