feat: add caching to FeedEngine

Add lastFeed() method that returns cached FeedResult within
a configurable TTL (default 5 min). refresh() always fetches
fresh data and updates the cache. Periodic auto-refresh via
recursive setTimeout when engine is started. Reactive updates
reset the timer to avoid redundant fetches.

Co-authored-by: Ona <no-reply@ona.com>
This commit is contained in:
2026-02-24 01:13:41 +00:00
parent 2fc20759dd
commit 08dd437952
3 changed files with 370 additions and 9 deletions

View File

@@ -638,4 +638,290 @@ describe("FeedEngine", () => {
)
})
})
describe("lastFeed", () => {
test("returns null before any refresh", () => {
const engine = new FeedEngine()
expect(engine.lastFeed()).toBeNull()
})
test("returns cached result after refresh", async () => {
const location = createLocationSource()
location.simulateUpdate({ lat: 51.5, lng: -0.1 })
const weather = createWeatherSource()
const engine = new FeedEngine().register(location).register(weather)
const refreshResult = await engine.refresh()
const cached = engine.lastFeed()
expect(cached).not.toBeNull()
expect(cached!.items).toEqual(refreshResult.items)
expect(cached!.context).toEqual(refreshResult.context)
})
test("returns null after TTL expires", async () => {
const engine = new FeedEngine({ cacheTtlMs: 50 })
const location = createLocationSource()
location.simulateUpdate({ lat: 51.5, lng: -0.1 })
engine.register(location)
await engine.refresh()
expect(engine.lastFeed()).not.toBeNull()
await new Promise((resolve) => setTimeout(resolve, 60))
expect(engine.lastFeed()).toBeNull()
})
test("defaults to 5 minute TTL", async () => {
const engine = new FeedEngine()
const location = createLocationSource()
location.simulateUpdate({ lat: 51.5, lng: -0.1 })
engine.register(location)
await engine.refresh()
// Should still be cached immediately
expect(engine.lastFeed()).not.toBeNull()
})
test("refresh always fetches from sources", async () => {
let fetchCount = 0
const source: FeedSource = {
id: "counter",
...noActions,
async fetchContext() {
fetchCount++
return null
},
}
const engine = new FeedEngine().register(source)
await engine.refresh()
await engine.refresh()
await engine.refresh()
expect(fetchCount).toBe(3)
})
test("reactive context update refreshes cache", async () => {
const location = createLocationSource()
const weather = createWeatherSource()
const engine = new FeedEngine({ cacheTtlMs: 5000 }).register(location).register(weather)
engine.start()
// Simulate location update which triggers reactive refresh
location.simulateUpdate({ lat: 51.5, lng: -0.1 })
// Wait for async reactive refresh to complete
await new Promise((resolve) => setTimeout(resolve, 50))
const cached = engine.lastFeed()
expect(cached).not.toBeNull()
expect(cached!.items.length).toBeGreaterThan(0)
engine.stop()
})
test("reactive item update refreshes cache", async () => {
let itemUpdateCallback: (() => void) | null = null
const source: FeedSource = {
id: "reactive-items",
...noActions,
async fetchContext() {
return null
},
async fetchItems() {
return [
{
id: "item-1",
type: "test",
priority: 0.5,
timestamp: new Date(),
data: {},
},
]
},
onItemsUpdate(callback) {
itemUpdateCallback = callback
return () => {
itemUpdateCallback = null
}
},
}
const engine = new FeedEngine().register(source)
engine.start()
// Trigger item update
itemUpdateCallback!()
// Wait for async refresh
await new Promise((resolve) => setTimeout(resolve, 50))
const cached = engine.lastFeed()
expect(cached).not.toBeNull()
expect(cached!.items).toHaveLength(1)
engine.stop()
})
test("TTL resets after reactive update", async () => {
const location = createLocationSource()
const weather = createWeatherSource()
const engine = new FeedEngine({ cacheTtlMs: 100 }).register(location).register(weather)
engine.start()
// Initial reactive update
location.simulateUpdate({ lat: 51.5, lng: -0.1 })
await new Promise((resolve) => setTimeout(resolve, 50))
expect(engine.lastFeed()).not.toBeNull()
// Wait 70ms (total 120ms from first update, past original TTL)
// but trigger another update at 50ms to reset TTL
location.simulateUpdate({ lat: 52.0, lng: -0.2 })
await new Promise((resolve) => setTimeout(resolve, 50))
// Should still be cached because TTL was reset by second update
expect(engine.lastFeed()).not.toBeNull()
engine.stop()
})
test("cacheTtlMs is configurable", async () => {
const engine = new FeedEngine({ cacheTtlMs: 30 })
const location = createLocationSource()
location.simulateUpdate({ lat: 51.5, lng: -0.1 })
engine.register(location)
await engine.refresh()
expect(engine.lastFeed()).not.toBeNull()
await new Promise((resolve) => setTimeout(resolve, 40))
expect(engine.lastFeed()).toBeNull()
})
test("auto-refreshes on TTL interval after start", async () => {
let fetchCount = 0
const source: FeedSource = {
id: "counter",
...noActions,
async fetchContext() {
fetchCount++
return null
},
async fetchItems() {
return [
{
id: `item-${fetchCount}`,
type: "test",
priority: 0.5,
timestamp: new Date(),
data: {},
},
]
},
}
const engine = new FeedEngine({ cacheTtlMs: 50 }).register(source)
engine.start()
// Wait for two TTL intervals to elapse
await new Promise((resolve) => setTimeout(resolve, 120))
// Should have auto-refreshed at least twice
expect(fetchCount).toBeGreaterThanOrEqual(2)
expect(engine.lastFeed()).not.toBeNull()
engine.stop()
})
test("stop cancels periodic refresh", async () => {
let fetchCount = 0
const source: FeedSource = {
id: "counter",
...noActions,
async fetchContext() {
fetchCount++
return null
},
}
const engine = new FeedEngine({ cacheTtlMs: 50 }).register(source)
engine.start()
engine.stop()
const countAfterStop = fetchCount
// Wait past TTL
await new Promise((resolve) => setTimeout(resolve, 80))
// No additional fetches after stop
expect(fetchCount).toBe(countAfterStop)
})
test("reactive update resets periodic refresh timer", async () => {
let fetchCount = 0
const location = createLocationSource()
const countingWeather: FeedSource<WeatherFeedItem> = {
id: "weather",
dependencies: ["location"],
...noActions,
async fetchContext(ctx) {
fetchCount++
const loc = contextValue(ctx, LocationKey)
if (!loc) return null
return { [WeatherKey]: { temperature: 20, condition: "sunny" } }
},
async fetchItems(ctx) {
const weather = contextValue(ctx, WeatherKey)
if (!weather) return []
return [
{
id: `weather-${Date.now()}`,
type: "weather",
priority: 0.5,
timestamp: new Date(),
data: { temperature: weather.temperature, condition: weather.condition },
},
]
},
}
const engine = new FeedEngine({ cacheTtlMs: 100 })
.register(location)
.register(countingWeather)
engine.start()
// At 40ms, push a reactive update — this resets the timer
await new Promise((resolve) => setTimeout(resolve, 40))
const countBeforeUpdate = fetchCount
location.simulateUpdate({ lat: 51.5, lng: -0.1 })
await new Promise((resolve) => setTimeout(resolve, 20))
// Reactive update triggered a fetch
expect(fetchCount).toBeGreaterThan(countBeforeUpdate)
const countAfterUpdate = fetchCount
// At 100ms from start (60ms after reactive update), the original
// timer would have fired, but it was reset. No extra fetch yet.
await new Promise((resolve) => setTimeout(resolve, 40))
expect(fetchCount).toBe(countAfterUpdate)
engine.stop()
})
})
})