read-trips: use for-await, minor changes

examples/read-trips.js

@@ -0,0 +1,19 @@
+'use strict'
+
+const readCsv = require('../read-csv')
+const readTrips = require('../read-trips')
+
+const readFile = (file) => {
+	return readCsv(require.resolve('sample-gtfs-feed/gtfs/' + file + '.txt'))
+}
+
+;(async () => {
+	const trips = await readTrips(readFile)
+	for await (const trip of trips.values()) {
+		console.log(trip)
+	}
+})()
+.catch((err) => {
+	console.error(err)
+	process.exit(1)
+})

lib/expect-sorting.js

@@ -0,0 +1,22 @@
+'use strict'
+
+const expectSorting = (filename, compareFn) => {
+	let prevRow = null
+	let rowNr = 0
+
+	const checkRow = (row) => {
+		rowNr++
+
+		if (prevRow !== null && compareFn(prevRow, row) > 0) {
+			const err = new Error(filename + ' is not sorted as needed')
+			err.previousRow = prevRow
+			err.row = row
+			err.rowNr = rowNr
+			throw err
+		}
+		prevRow = row
+	}
+	return checkRow
+}
+
+module.exports = expectSorting

package.json

@@ -18,6 +18,7 @@
 		"compute-service-breaks.js",
 		"route-types.js",
 		"read-stops.js",
+		"read-trips.js",
 		"lib",
 		"examples",
 		"test"

read-trips.js

@@ -1,24 +1,40 @@
 'use strict'
 
 const inMemoryStore = require('./lib/in-memory-store')
-const processFile = require('./lib/process-file')
+const expectSorting = require('./lib/expect-sorting')
 
-const noFilter = () => true
+const readTrips = async (readFile, filters = {}, opt = {}) => {
+	if (typeof readFile !== 'function') {
+		throw new TypeError('readFile must be a function')
+	}
+	const {
+		trip: tripFilter,
+	} = {
+		trip: () => true,
+		...filters,
+	}
+	if (typeof tripFilter !== 'function') {
+		throw new TypeError('filters.trip must be a function')
+	}
 
-const readTrips = async (readFile, filter = noFilter, opt = {}) => {
 	const {
 		createStore,
 	} = {
 		createStore: inMemoryStore,
 		...opt,
 	}
 
-	const trips = createStore()
-	const processTrip = async (t) => {
-		if (!filter(t)) return;
+	const checkSorting = expectSorting('trips', (a, b) => {
+		if (a.trip_id === b.trip_id) return 0
+		return a.trip_id < b.trip_id ? -1 : 1
+	})
+
+	const trips = createStore() // by ID
+	for await (const t of readFile('trips')) {
+		if (!tripFilter(t)) continue
+		checkSorting(t)
 		await trips.set(t.trip_id, t)
 	}
-	await processFile('trips', readFile('trips'), processTrip)
 
 	return trips
 }

readme.md

@@ -114,6 +114,36 @@ readTrips(readFile, filter)
 
 Will read `trips.txt` and reduce it into a map `tripId => trip`. Returns a [Promise](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/promise).
 
+### `readTrips(readFile, filters = {})`
+
+```js
+const readCsv = require('gtfs-utils/read-csv')
+const readTrips = require('gtfs-utils/read-trips')
+
+const readFile = name => readCsv('path/to/gtfs/' + name + '.txt')
+
+const trips = readTrips(readFile, {
+	trip: s => s.trip_id === '1234',
+})
+for await (const trip of trips) console.log(trip)
+```
+
+```js
+{
+	route_id: 'A',
+	service_id: 'all-day',
+	trip_id: 'a-downtown-all-day',
+	trip_headsign: '',
+	trip_short_name: '',
+	direction_id: '',
+	wheelchair_accessible: '',
+	bikes_allowed: '',
+}
+
+```
+
+`readTrips` is an [async generator function](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for-await...of).
+
 ### `parseDate(dateStr, timezone)`
 
 ```js