Replace FeedItem.priority with signals (#39)

* feat: replace FeedItem.priority with signals

Remove priority field from FeedItem and engine-level sorting.
Add FeedItemSignals with urgency and timeRelevance fields.
Update all source packages to emit signals instead of priority.

Ranking is now the post-processing layer's responsibility.
Urgency values are unchanged from the old priority values.

Co-authored-by: Ona <no-reply@ona.com>

* fix: use TimeRelevance enum in all tests

Co-authored-by: Ona <no-reply@ona.com>

---------

Co-authored-by: Ona <no-reply@ona.com>

packages/aris-source-tfl/src/tfl-source.test.ts

@@ -184,7 +184,8 @@ describe("TflSource", () => {
 				expect(typeof item.id).toBe("string")
 				expect(item.id).toMatch(/^tfl-alert-/)
 				expect(item.type).toBe("tfl-alert")
-				expect(typeof item.priority).toBe("number")
+				expect(item.signals).toBeDefined()
+				expect(typeof item.signals!.urgency).toBe("number")
 				expect(item.timestamp).toBeInstanceOf(Date)
 			}
 		})
@@ -220,29 +221,29 @@ describe("TflSource", () => {
 			expect(uniqueIds.size).toBe(ids.length)
 		})
 
-		test("feed items are sorted by priority descending", async () => {
+		test("feed items are sorted by urgency descending", async () => {
 			const source = new TflSource({ client: api })
 			const items = await source.fetchItems(createContext())
 
 			for (let i = 1; i < items.length; i++) {
 				const prev = items[i - 1]!
 				const curr = items[i]!
-				expect(prev.priority).toBeGreaterThanOrEqual(curr.priority)
+				expect(prev.signals!.urgency).toBeGreaterThanOrEqual(curr.signals!.urgency!)
 			}
 		})
 
-		test("priority values match severity levels", async () => {
+		test("urgency values match severity levels", async () => {
 			const source = new TflSource({ client: api })
 			const items = await source.fetchItems(createContext())
 
-			const severityPriority: Record<string, number> = {
+			const severityUrgency: Record<string, number> = {
 				closure: 1.0,
 				"major-delays": 0.8,
 				"minor-delays": 0.6,
 			}
 
 			for (const item of items) {
-				expect(item.priority).toBe(severityPriority[item.data.severity]!)
+				expect(item.signals!.urgency).toBe(severityUrgency[item.data.severity]!)
 			}
 		})
 
@@ -316,9 +317,7 @@ describe("TflSource", () => {
 		test("executeAction throws on invalid input", async () => {
 			const source = new TflSource({ client: api })
 
-			await expect(
-				source.executeAction("set-lines-of-interest", "not-an-array"),
-			).rejects.toThrow()
+			await expect(source.executeAction("set-lines-of-interest", "not-an-array")).rejects.toThrow()
 		})
 
 		test("executeAction throws for unknown action", async () => {

packages/aris-source-tfl/src/tfl-source.ts

@@ -1,6 +1,6 @@
-import type { ActionDefinition, Context, FeedSource } from "@aris/core"
+import type { ActionDefinition, Context, FeedItemSignals, FeedSource } from "@aris/core"
 
-import { UnknownActionError, contextValue } from "@aris/core"
+import { TimeRelevance, UnknownActionError, contextValue } from "@aris/core"
 import { LocationKey } from "@aris/source-location"
 import { type } from "arktype"
 
@@ -18,12 +18,18 @@ import { TflApi, lineId } from "./tfl-api.ts"
 
 const setLinesInput = lineId.array()
 
-const SEVERITY_PRIORITY: Record<TflAlertSeverity, number> = {
+const SEVERITY_URGENCY: Record<TflAlertSeverity, number> = {
 	closure: 1.0,
 	"major-delays": 0.8,
 	"minor-delays": 0.6,
 }
 
+const SEVERITY_TIME_RELEVANCE: Record<TflAlertSeverity, TimeRelevance> = {
+	closure: TimeRelevance.Imminent,
+	"major-delays": TimeRelevance.Imminent,
+	"minor-delays": TimeRelevance.Upcoming,
+}
+
 /**
  * A FeedSource that provides TfL (Transport for London) service alerts.
  *
@@ -137,19 +143,26 @@ export class TflSource implements FeedSource<TflAlertFeedItem> {
 				closestStationDistance,
 			}
 
+			const signals: FeedItemSignals = {
+				urgency: SEVERITY_URGENCY[status.severity],
+				timeRelevance: SEVERITY_TIME_RELEVANCE[status.severity],
+			}
+
 			return {
 				id: `tfl-alert-${status.lineId}-${status.severity}`,
 				type: "tfl-alert",
-				priority: SEVERITY_PRIORITY[status.severity],
 				timestamp: context.time,
 				data,
+				signals,
 			}
 		})
 
-		// Sort by severity (desc), then by proximity (asc) if location available
+		// Sort by urgency (desc), then by proximity (asc) if location available
 		items.sort((a, b) => {
-			if (b.priority !== a.priority) {
-				return b.priority - a.priority
+			const aUrgency = a.signals?.urgency ?? 0
+			const bUrgency = b.signals?.urgency ?? 0
+			if (bUrgency !== aUrgency) {
+				return bUrgency - aUrgency
 			}
 			if (a.data.closestStationDistance !== null && b.data.closestStationDistance !== null) {
 				return a.data.closestStationDistance - b.data.closestStationDistance