refactor: migrate aris-data-source-tfl to aris-source-tfl

Migrates TFL package from old DataSource interface to new FeedSource
interface for use with FeedEngine.

Changes:
- Rename package from @aris/data-source-tfl to @aris/source-tfl
- Replace TflDataSource class with TflSource implementing FeedSource
- Add dependency on @aris/source-location for LocationKey
- Use normalized priority values (0-1) instead of arbitrary numbers
- Update tests for FeedSource interface
- Update README.md with new package name

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

README.md

@@ -8,14 +8,14 @@ bun install
 
 ## Packages
 
-### @aris/data-source-tfl
+### @aris/source-tfl
 
-TfL (Transport for London) data source for tube, overground, and Elizabeth line alerts.
+TfL (Transport for London) feed source for tube, overground, and Elizabeth line alerts.
 
 #### Testing
 
 ```bash
-cd packages/aris-data-source-tfl
+cd packages/aris-source-tfl
 bun run test
 ```
 

bun.lock

@@ -17,14 +17,6 @@
       "name": "@aris/core",
       "version": "0.0.0",
     },
-    "packages/aris-data-source-tfl": {
-      "name": "@aris/data-source-tfl",
-      "version": "0.0.0",
-      "dependencies": {
-        "@aris/core": "workspace:*",
-        "arktype": "^2.1.0",
-      },
-    },
     "packages/aris-data-source-weatherkit": {
       "name": "@aris/data-source-weatherkit",
       "version": "0.0.0",
@@ -40,6 +32,15 @@
         "@aris/core": "workspace:*",
       },
     },
+    "packages/aris-source-tfl": {
+      "name": "@aris/source-tfl",
+      "version": "0.0.0",
+      "dependencies": {
+        "@aris/core": "workspace:*",
+        "@aris/source-location": "workspace:*",
+        "arktype": "^2.1.0",
+      },
+    },
     "packages/aris-source-weatherkit": {
       "name": "@aris/source-weatherkit",
       "version": "0.0.0",
@@ -53,12 +54,12 @@
   "packages": {
     "@aris/core": ["@aris/core@workspace:packages/aris-core"],
 
-    "@aris/data-source-tfl": ["@aris/data-source-tfl@workspace:packages/aris-data-source-tfl"],
-
     "@aris/data-source-weatherkit": ["@aris/data-source-weatherkit@workspace:packages/aris-data-source-weatherkit"],
 
     "@aris/source-location": ["@aris/source-location@workspace:packages/aris-source-location"],
 
+    "@aris/source-tfl": ["@aris/source-tfl@workspace:packages/aris-source-tfl"],
+
     "@aris/source-weatherkit": ["@aris/source-weatherkit@workspace:packages/aris-source-weatherkit"],
 
     "@ark/schema": ["@ark/schema@0.56.0", "", { "dependencies": { "@ark/util": "0.56.0" } }, "sha512-ECg3hox/6Z/nLajxXqNhgPtNdHWC9zNsDyskwO28WinoFEnWow4IsERNz9AnXRhTZJnYIlAJ4uGn3nlLk65vZA=="],

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

@@ -1,11 +0,0 @@
-export { TflDataSource } from "./data-source.ts"
-export { TflApi, type ITflApi, type TflLineStatus } from "./tfl-api.ts"
-export type {
-	TflAlertData,
-	TflAlertFeedItem,
-	TflAlertSeverity,
-	TflDataSourceConfig,
-	TflDataSourceOptions,
-	TflLineId,
-	StationLocation,
-} from "./types.ts"

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

@@ -1,208 +0,0 @@
-import type { Context } from "@aris/core"
-
-import { describe, expect, test } from "bun:test"
-
-import type { ITflApi, TflLineStatus } from "./tfl-api.ts"
-import type { StationLocation, TflLineId } from "./types.ts"
-
-import fixtures from "../fixtures/tfl-responses.json"
-import { TflDataSource } from "./data-source.ts"
-
-// Mock API that returns fixture data
-class FixtureTflApi implements ITflApi {
-	async fetchLineStatuses(_lines?: TflLineId[]): Promise<TflLineStatus[]> {
-		const statuses: TflLineStatus[] = []
-
-		for (const line of fixtures.lineStatuses as Record<string, unknown>[]) {
-			for (const status of line.lineStatuses as Record<string, unknown>[]) {
-				const severityCode = status.statusSeverity as number
-				const severity = this.mapSeverity(severityCode)
-				if (severity) {
-					statuses.push({
-						lineId: line.id as TflLineId,
-						lineName: line.name as string,
-						severity,
-						description: (status.reason as string) ?? (status.statusSeverityDescription as string),
-					})
-				}
-			}
-		}
-
-		return statuses
-	}
-
-	async fetchStations(): Promise<StationLocation[]> {
-		const stationMap = new Map<string, StationLocation>()
-
-		for (const [lineId, stops] of Object.entries(fixtures.stopPoints)) {
-			for (const stop of stops as Record<string, unknown>[]) {
-				const id = stop.naptanId as string
-				const existing = stationMap.get(id)
-				if (existing) {
-					if (!existing.lines.includes(lineId as TflLineId)) {
-						existing.lines.push(lineId as TflLineId)
-					}
-				} else {
-					stationMap.set(id, {
-						id,
-						name: stop.commonName as string,
-						lat: stop.lat as number,
-						lng: stop.lon as number,
-						lines: [lineId as TflLineId],
-					})
-				}
-			}
-		}
-
-		return Array.from(stationMap.values())
-	}
-
-	private mapSeverity(code: number): "minor-delays" | "major-delays" | "closure" | null {
-		const map: Record<number, "minor-delays" | "major-delays" | "closure" | null> = {
-			1: "closure",
-			2: "closure",
-			3: "closure",
-			4: "closure",
-			5: "closure",
-			6: "major-delays",
-			7: "major-delays",
-			8: "major-delays",
-			9: "minor-delays",
-			10: null,
-		}
-		return map[code] ?? null
-	}
-}
-
-const createContext = (location?: { lat: number; lng: number }): Context => ({
-	time: new Date("2026-01-15T12:00:00Z"),
-	location: location ? { ...location, accuracy: 10 } : undefined,
-})
-
-describe("TfL Feed Items (using fixture data)", () => {
-	const api = new FixtureTflApi()
-
-	test("query returns feed items array", async () => {
-		const dataSource = new TflDataSource(api)
-		const items = await dataSource.query(createContext(), {})
-		expect(Array.isArray(items)).toBe(true)
-	})
-
-	test("feed items have correct base structure", async () => {
-		const dataSource = new TflDataSource(api)
-		const items = await dataSource.query(createContext({ lat: 51.5074, lng: -0.1278 }), {})
-
-		for (const item of items) {
-			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.timestamp).toBeInstanceOf(Date)
-		}
-	})
-
-	test("feed items have correct data structure", async () => {
-		const dataSource = new TflDataSource(api)
-		const items = await dataSource.query(createContext({ lat: 51.5074, lng: -0.1278 }), {})
-
-		for (const item of items) {
-			expect(typeof item.data.line).toBe("string")
-			expect(typeof item.data.lineName).toBe("string")
-			expect(["minor-delays", "major-delays", "closure"]).toContain(item.data.severity)
-			expect(typeof item.data.description).toBe("string")
-			expect(
-				item.data.closestStationDistance === null ||
-					typeof item.data.closestStationDistance === "number",
-			).toBe(true)
-		}
-	})
-
-	test("feed item ids are unique", async () => {
-		const dataSource = new TflDataSource(api)
-		const items = await dataSource.query(createContext(), {})
-
-		const ids = items.map((item) => item.id)
-		const uniqueIds = new Set(ids)
-		expect(uniqueIds.size).toBe(ids.length)
-	})
-
-	test("feed items are sorted by priority descending", async () => {
-		const dataSource = new TflDataSource(api)
-		const items = await dataSource.query(createContext(), {})
-
-		for (let i = 1; i < items.length; i++) {
-			const prev = items[i - 1]!
-			const curr = items[i]!
-			expect(prev.priority).toBeGreaterThanOrEqual(curr.priority)
-		}
-	})
-
-	test("priority values match severity levels", async () => {
-		const dataSource = new TflDataSource(api)
-		const items = await dataSource.query(createContext(), {})
-
-		const severityPriority: Record<string, number> = {
-			closure: 100,
-			"major-delays": 80,
-			"minor-delays": 60,
-		}
-
-		for (const item of items) {
-			expect(item.priority).toBe(severityPriority[item.data.severity]!)
-		}
-	})
-
-	test("closestStationDistance is number when location provided", async () => {
-		const dataSource = new TflDataSource(api)
-		const items = await dataSource.query(createContext({ lat: 51.5074, lng: -0.1278 }), {})
-
-		for (const item of items) {
-			expect(typeof item.data.closestStationDistance).toBe("number")
-			expect(item.data.closestStationDistance!).toBeGreaterThan(0)
-		}
-	})
-
-	test("closestStationDistance is null when no location provided", async () => {
-		const dataSource = new TflDataSource(api)
-		const items = await dataSource.query(createContext(), {})
-
-		for (const item of items) {
-			expect(item.data.closestStationDistance).toBeNull()
-		}
-	})
-})
-
-describe("TfL Fixture Data Shape", () => {
-	test("fixtures have expected structure", () => {
-		expect(typeof fixtures.fetchedAt).toBe("string")
-		expect(Array.isArray(fixtures.lineStatuses)).toBe(true)
-		expect(typeof fixtures.stopPoints).toBe("object")
-	})
-
-	test("line statuses have required fields", () => {
-		for (const line of fixtures.lineStatuses as Record<string, unknown>[]) {
-			expect(typeof line.id).toBe("string")
-			expect(typeof line.name).toBe("string")
-			expect(Array.isArray(line.lineStatuses)).toBe(true)
-
-			for (const status of line.lineStatuses as Record<string, unknown>[]) {
-				expect(typeof status.statusSeverity).toBe("number")
-				expect(typeof status.statusSeverityDescription).toBe("string")
-			}
-		}
-	})
-
-	test("stop points have required fields", () => {
-		for (const [lineId, stops] of Object.entries(fixtures.stopPoints)) {
-			expect(typeof lineId).toBe("string")
-			expect(Array.isArray(stops)).toBe(true)
-
-			for (const stop of stops as Record<string, unknown>[]) {
-				expect(typeof stop.naptanId).toBe("string")
-				expect(typeof stop.commonName).toBe("string")
-				expect(typeof stop.lat).toBe("number")
-				expect(typeof stop.lon).toBe("number")
-			}
-		}
-	})
-})

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

@@ -1,33 +0,0 @@
-import type { FeedItem } from "@aris/core"
-
-import type { TflLineId } from "./tfl-api.ts"
-
-export type { TflLineId } from "./tfl-api.ts"
-
-export type TflAlertSeverity = "minor-delays" | "major-delays" | "closure"
-
-export interface TflAlertData extends Record<string, unknown> {
-	line: TflLineId
-	lineName: string
-	severity: TflAlertSeverity
-	description: string
-	closestStationDistance: number | null
-}
-
-export type TflAlertFeedItem = FeedItem<"tfl-alert", TflAlertData>
-
-export interface TflDataSourceConfig {
-	lines?: TflLineId[]
-}
-
-export interface TflDataSourceOptions {
-	apiKey: string
-}
-
-export interface StationLocation {
-	id: string
-	name: string
-	lat: number
-	lng: number
-	lines: TflLineId[]
-}

packages/aris-source-tfl/package.json

@@ -1,5 +1,5 @@
 {
-	"name": "@aris/data-source-tfl",
+	"name": "@aris/source-tfl",
 	"version": "0.0.0",
 	"type": "module",
 	"main": "src/index.ts",
@@ -10,6 +10,7 @@
 	},
 	"dependencies": {
 		"@aris/core": "workspace:*",
+		"@aris/source-location": "workspace:*",
 		"arktype": "^2.1.0"
 	}
 }

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

@@ -0,0 +1,11 @@
+export { TflSource } from "./tfl-source.ts"
+export { TflApi } from "./tfl-api.ts"
+export type { TflLineId } from "./tfl-api.ts"
+export type {
+	StationLocation,
+	TflAlertData,
+	TflAlertFeedItem,
+	TflAlertSeverity,
+	TflLineStatus,
+	TflSourceOptions,
+} from "./types.ts"

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

@@ -1,6 +1,6 @@
 import { type } from "arktype"
 
-import type { StationLocation, TflAlertSeverity } from "./types.ts"
+import type { StationLocation, TflAlertSeverity, TflLineStatus } from "./types.ts"
 
 const TFL_API_BASE = "https://api.tfl.gov.uk"
 
@@ -50,19 +50,7 @@ const SEVERITY_MAP: Record<number, TflAlertSeverity | null> = {
 	20: null, // Service Closed
 }
 
-export interface TflLineStatus {
+export class TflApi {
-	lineId: TflLineId
-	lineName: string
-	severity: TflAlertSeverity
-	description: string
-}
-
-export interface ITflApi {
-	fetchLineStatuses(lines?: TflLineId[]): Promise<TflLineStatus[]>
-	fetchStations(): Promise<StationLocation[]>
-}
-
-export class TflApi implements ITflApi {
 	private apiKey: string
 	private stationsCache: StationLocation[] | null = null
 

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

@@ -0,0 +1,243 @@
+import type { Context } from "@aris/core"
+
+import { LocationKey, type Location } from "@aris/source-location"
+import { describe, expect, test } from "bun:test"
+
+import type {
+	ITflApi,
+	StationLocation,
+	TflAlertSeverity,
+	TflLineId,
+	TflLineStatus,
+} from "./types.ts"
+
+import fixtures from "../fixtures/tfl-responses.json"
+import { TflSource } from "./tfl-source.ts"
+
+// Mock API that returns fixture data
+class FixtureTflApi implements ITflApi {
+	async fetchLineStatuses(_lines?: TflLineId[]): Promise<TflLineStatus[]> {
+		const statuses: TflLineStatus[] = []
+
+		for (const line of fixtures.lineStatuses as Record<string, unknown>[]) {
+			for (const status of line.lineStatuses as Record<string, unknown>[]) {
+				const severityCode = status.statusSeverity as number
+				const severity = this.mapSeverity(severityCode)
+				if (severity) {
+					statuses.push({
+						lineId: line.id as TflLineId,
+						lineName: line.name as string,
+						severity,
+						description: (status.reason as string) ?? (status.statusSeverityDescription as string),
+					})
+				}
+			}
+		}
+
+		return statuses
+	}
+
+	async fetchStations(): Promise<StationLocation[]> {
+		const stationMap = new Map<string, StationLocation>()
+
+		for (const [lineId, stops] of Object.entries(fixtures.stopPoints)) {
+			for (const stop of stops as Record<string, unknown>[]) {
+				const id = stop.naptanId as string
+				const existing = stationMap.get(id)
+				if (existing) {
+					if (!existing.lines.includes(lineId as TflLineId)) {
+						existing.lines.push(lineId as TflLineId)
+					}
+				} else {
+					stationMap.set(id, {
+						id,
+						name: stop.commonName as string,
+						lat: stop.lat as number,
+						lng: stop.lon as number,
+						lines: [lineId as TflLineId],
+					})
+				}
+			}
+		}
+
+		return Array.from(stationMap.values())
+	}
+
+	private mapSeverity(code: number): TflAlertSeverity | null {
+		const map: Record<number, TflAlertSeverity | null> = {
+			1: "closure",
+			2: "closure",
+			3: "closure",
+			4: "closure",
+			5: "closure",
+			6: "major-delays",
+			7: "major-delays",
+			8: "major-delays",
+			9: "minor-delays",
+			10: null,
+		}
+		return map[code] ?? null
+	}
+}
+
+function createContext(location?: Location): Context {
+	const ctx: Context = { time: new Date("2026-01-15T12:00:00Z") }
+	if (location) {
+		ctx[LocationKey] = location
+	}
+	return ctx
+}
+
+describe("TflSource", () => {
+	const api = new FixtureTflApi()
+
+	describe("interface", () => {
+		test("has correct id", () => {
+			const source = new TflSource({ client: api })
+			expect(source.id).toBe("tfl")
+		})
+
+		test("depends on location", () => {
+			const source = new TflSource({ client: api })
+			expect(source.dependencies).toEqual(["location"])
+		})
+
+		test("implements fetchItems", () => {
+			const source = new TflSource({ client: api })
+			expect(source.fetchItems).toBeDefined()
+		})
+
+		test("throws if neither client nor apiKey provided", () => {
+			expect(() => new TflSource({})).toThrow("Either client or apiKey must be provided")
+		})
+	})
+
+	describe("fetchItems", () => {
+		test("returns feed items array", async () => {
+			const source = new TflSource({ client: api })
+			const items = await source.fetchItems(createContext())
+			expect(Array.isArray(items)).toBe(true)
+		})
+
+		test("feed items have correct base structure", async () => {
+			const source = new TflSource({ client: api })
+			const location: Location = { lat: 51.5074, lng: -0.1278, accuracy: 10, timestamp: new Date() }
+			const items = await source.fetchItems(createContext(location))
+
+			for (const item of items) {
+				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.timestamp).toBeInstanceOf(Date)
+			}
+		})
+
+		test("feed items have correct data structure", async () => {
+			const source = new TflSource({ client: api })
+			const location: Location = { lat: 51.5074, lng: -0.1278, accuracy: 10, timestamp: new Date() }
+			const items = await source.fetchItems(createContext(location))
+
+			for (const item of items) {
+				expect(typeof item.data.line).toBe("string")
+				expect(typeof item.data.lineName).toBe("string")
+				expect(["minor-delays", "major-delays", "closure"]).toContain(item.data.severity)
+				expect(typeof item.data.description).toBe("string")
+				expect(
+					item.data.closestStationDistance === null ||
+						typeof item.data.closestStationDistance === "number",
+				).toBe(true)
+			}
+		})
+
+		test("feed item ids are unique", async () => {
+			const source = new TflSource({ client: api })
+			const items = await source.fetchItems(createContext())
+
+			const ids = items.map((item) => item.id)
+			const uniqueIds = new Set(ids)
+			expect(uniqueIds.size).toBe(ids.length)
+		})
+
+		test("feed items are sorted by priority 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)
+			}
+		})
+
+		test("priority values match severity levels", async () => {
+			const source = new TflSource({ client: api })
+			const items = await source.fetchItems(createContext())
+
+			const severityPriority: 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]!)
+			}
+		})
+
+		test("closestStationDistance is number when location provided", async () => {
+			const source = new TflSource({ client: api })
+			const location: Location = { lat: 51.5074, lng: -0.1278, accuracy: 10, timestamp: new Date() }
+			const items = await source.fetchItems(createContext(location))
+
+			for (const item of items) {
+				expect(typeof item.data.closestStationDistance).toBe("number")
+				expect(item.data.closestStationDistance!).toBeGreaterThan(0)
+			}
+		})
+
+		test("closestStationDistance is null when no location provided", async () => {
+			const source = new TflSource({ client: api })
+			const items = await source.fetchItems(createContext())
+
+			for (const item of items) {
+				expect(item.data.closestStationDistance).toBeNull()
+			}
+		})
+	})
+})
+
+describe("TfL Fixture Data Shape", () => {
+	test("fixtures have expected structure", () => {
+		expect(typeof fixtures.fetchedAt).toBe("string")
+		expect(Array.isArray(fixtures.lineStatuses)).toBe(true)
+		expect(typeof fixtures.stopPoints).toBe("object")
+	})
+
+	test("line statuses have required fields", () => {
+		for (const line of fixtures.lineStatuses as Record<string, unknown>[]) {
+			expect(typeof line.id).toBe("string")
+			expect(typeof line.name).toBe("string")
+			expect(Array.isArray(line.lineStatuses)).toBe(true)
+
+			for (const status of line.lineStatuses as Record<string, unknown>[]) {
+				expect(typeof status.statusSeverity).toBe("number")
+				expect(typeof status.statusSeverityDescription).toBe("string")
+			}
+		}
+	})
+
+	test("stop points have required fields", () => {
+		for (const [lineId, stops] of Object.entries(fixtures.stopPoints)) {
+			expect(typeof lineId).toBe("string")
+			expect(Array.isArray(stops)).toBe(true)
+
+			for (const stop of stops as Record<string, unknown>[]) {
+				expect(typeof stop.naptanId).toBe("string")
+				expect(typeof stop.commonName).toBe("string")
+				expect(typeof stop.lat).toBe("number")
+				expect(typeof stop.lon).toBe("number")
+			}
+		}
+	})
+})

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

@@ -1,21 +1,104 @@
-import type { Context, DataSource } from "@aris/core"
+import type { Context, FeedSource } from "@aris/core"
+
+import { contextValue } from "@aris/core"
+import { LocationKey } from "@aris/source-location"
 
 import type {
+	ITflApi,
 	StationLocation,
 	TflAlertData,
 	TflAlertFeedItem,
 	TflAlertSeverity,
-	TflDataSourceConfig,
-	TflDataSourceOptions,
 	TflLineId,
+	TflSourceOptions,
 } from "./types.ts"
 
-import { TflApi, type ITflApi } from "./tfl-api.ts"
+import { TflApi } from "./tfl-api.ts"
 
 const SEVERITY_PRIORITY: Record<TflAlertSeverity, number> = {
-	closure: 100,
+	closure: 1.0,
-	"major-delays": 80,
+	"major-delays": 0.8,
-	"minor-delays": 60,
+	"minor-delays": 0.6,
+}
+
+/**
+ * A FeedSource that provides TfL (Transport for London) service alerts.
+ *
+ * Depends on location source for proximity-based sorting. Produces feed items
+ * for tube, overground, and Elizabeth line disruptions.
+ *
+ * @example
+ * ```ts
+ * const tflSource = new TflSource({
+ *   apiKey: process.env.TFL_API_KEY!,
+ *   lines: ["northern", "victoria", "jubilee"],
+ * })
+ *
+ * const engine = new FeedEngine()
+ *   .register(locationSource)
+ *   .register(tflSource)
+ *
+ * const { items } = await engine.refresh()
+ * ```
+ */
+export class TflSource implements FeedSource<TflAlertFeedItem> {
+	readonly id = "tfl"
+	readonly dependencies = ["location"]
+
+	private readonly client: ITflApi
+	private readonly lines?: TflLineId[]
+
+	constructor(options: TflSourceOptions) {
+		if (!options.client && !options.apiKey) {
+			throw new Error("Either client or apiKey must be provided")
+		}
+		this.client = options.client ?? new TflApi(options.apiKey!)
+		this.lines = options.lines
+	}
+
+	async fetchItems(context: Context): Promise<TflAlertFeedItem[]> {
+		const [statuses, stations] = await Promise.all([
+			this.client.fetchLineStatuses(this.lines),
+			this.client.fetchStations(),
+		])
+
+		const location = contextValue(context, LocationKey)
+
+		const items: TflAlertFeedItem[] = statuses.map((status) => {
+			const closestStationDistance = location
+				? findClosestStationDistance(status.lineId, stations, location.lat, location.lng)
+				: null
+
+			const data: TflAlertData = {
+				line: status.lineId,
+				lineName: status.lineName,
+				severity: status.severity,
+				description: status.description,
+				closestStationDistance,
+			}
+
+			return {
+				id: `tfl-alert-${status.lineId}-${status.severity}`,
+				type: "tfl-alert",
+				priority: SEVERITY_PRIORITY[status.severity],
+				timestamp: context.time,
+				data,
+			}
+		})
+
+		// Sort by severity (desc), then by proximity (asc) if location available
+		items.sort((a, b) => {
+			if (b.priority !== a.priority) {
+				return b.priority - a.priority
+			}
+			if (a.data.closestStationDistance !== null && b.data.closestStationDistance !== null) {
+				return a.data.closestStationDistance - b.data.closestStationDistance
+			}
+			return 0
+		})
+
+		return items
+	}
 }
 
 function haversineDistance(lat1: number, lng1: number, lat2: number, lng2: number): number {
@@ -51,65 +134,3 @@ function findClosestStationDistance(
 
 	return minDistance
 }
-
-export class TflDataSource implements DataSource<TflAlertFeedItem, TflDataSourceConfig> {
-	readonly type = "tfl-alert"
-	private api: ITflApi
-
-	constructor(options: TflDataSourceOptions)
-	constructor(api: ITflApi)
-	constructor(optionsOrApi: TflDataSourceOptions | ITflApi) {
-		if ("fetchLineStatuses" in optionsOrApi) {
-			this.api = optionsOrApi
-		} else {
-			this.api = new TflApi(optionsOrApi.apiKey)
-		}
-	}
-
-	async query(context: Context, config: TflDataSourceConfig): Promise<TflAlertFeedItem[]> {
-		const [statuses, stations] = await Promise.all([
-			this.api.fetchLineStatuses(config.lines),
-			this.api.fetchStations(),
-		])
-
-		const items: TflAlertFeedItem[] = statuses.map((status) => {
-			const closestStationDistance = context.location
-				? findClosestStationDistance(
-						status.lineId,
-						stations,
-						context.location.lat,
-						context.location.lng,
-					)
-				: null
-
-			const data: TflAlertData = {
-				line: status.lineId,
-				lineName: status.lineName,
-				severity: status.severity,
-				description: status.description,
-				closestStationDistance,
-			}
-
-			return {
-				id: `tfl-alert-${status.lineId}-${status.severity}`,
-				type: this.type,
-				priority: SEVERITY_PRIORITY[status.severity],
-				timestamp: context.time,
-				data,
-			}
-		})
-
-		// Sort by severity (desc), then by proximity (asc) if location available
-		items.sort((a, b) => {
-			if (b.priority !== a.priority) {
-				return b.priority - a.priority
-			}
-			if (a.data.closestStationDistance !== null && b.data.closestStationDistance !== null) {
-				return a.data.closestStationDistance - b.data.closestStationDistance
-			}
-			return 0
-		})
-
-		return items
-	}
-}

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

@@ -0,0 +1,50 @@
+import type { FeedItem } from "@aris/core"
+
+import type { TflLineId } from "./tfl-api.ts"
+
+export type { TflLineId } from "./tfl-api.ts"
+
+export const TflAlertSeverity = {
+	MinorDelays: "minor-delays",
+	MajorDelays: "major-delays",
+	Closure: "closure",
+} as const
+
+export type TflAlertSeverity = (typeof TflAlertSeverity)[keyof typeof TflAlertSeverity]
+
+export interface TflAlertData extends Record<string, unknown> {
+	line: TflLineId
+	lineName: string
+	severity: TflAlertSeverity
+	description: string
+	closestStationDistance: number | null
+}
+
+export type TflAlertFeedItem = FeedItem<"tfl-alert", TflAlertData>
+
+export interface TflSourceOptions {
+	apiKey?: string
+	client?: ITflApi
+	/** Lines to monitor. Defaults to all lines. */
+	lines?: TflLineId[]
+}
+
+export interface StationLocation {
+	id: string
+	name: string
+	lat: number
+	lng: number
+	lines: TflLineId[]
+}
+
+export interface ITflApi {
+	fetchLineStatuses(lines?: TflLineId[]): Promise<TflLineStatus[]>
+	fetchStations(): Promise<StationLocation[]>
+}
+
+export interface TflLineStatus {
+	lineId: TflLineId
+	lineName: string
+	severity: TflAlertSeverity
+	description: string
+}