add ability to specify a specific file to write results to too

src/brave/crawl.ts

@@ -1,5 +1,6 @@
 'use strict'
 
+import fsLib from 'node:fs/promises'
 import * as osLib from 'os'
 
 import fsExtraLib from 'fs-extra'
@@ -8,6 +9,7 @@ import Xvbf from 'xvfb'
 
 import { getLogger } from './debug.js'
 import { puppeteerConfigForArgs, launchWithRetry } from './puppeteer.js'
+import { isDir } from './validate.js'
 
 const xvfbPlatforms = new Set(['linux', 'openbsd'])
 
@@ -55,11 +57,11 @@ function createFilename (url: Url) : FilePath {
   return `page_graph_${url?.replace(/[^\w]/g, '_')}_${Math.floor(Date.now() / 1000)}.graphml`
 }
 
-function writeToFile (args: CrawlArgs, url: Url, response: any, logger: Logger) {
-  const outputFilename = pathLib.join(
-    args.outputPath,
-    createFilename(url)
-  )
+async function writeToFile (args: CrawlArgs, url: Url, response: any, logger: Logger) {
+  const outputFilename = isDir(args.outputPath)
+    ? pathLib.join(args.outputPath, createFilename(url))
+    : args.outputPath
+
   fsExtraLib.writeFile(outputFilename, response.data).catch((err: Error) => {
     logger.debug('ERROR saving Page.generatePageGraph output:', err)
   })

src/brave/validate.ts

@@ -17,11 +17,11 @@ const isUrl = (possibleUrl: string): boolean => {
   }
 }
 
-const isFile = (path: string): boolean => {
+export const isFile = (path: string): boolean => {
   return fsLib.existsSync(path) && fsLib.lstatSync(path).isFile()
 }
 
-const isDir = (path: string): boolean => {
+export const isDir = (path: string): boolean => {
   if (!fsLib.existsSync(path)) {
     return false
   }
@@ -83,8 +83,13 @@ export const validate = (rawArgs: any): ValidationResult => {
     executablePath = rawArgs.binary
   }
 
+  // The output path either needs to be a directory, or a filename in
+  // an existing directory.
   if (!isDir(rawArgs.output)) {
-    return [false, `Invalid path to write results to: ${rawArgs.output}`]
+    const outputPathParts = pathLib.parse(rawArgs.output)
+    if (!isDir(outputPathParts.dir)) {
+      return [false, `Invalid path to write results to: ${rawArgs.output}`]
+    }
   }
   const outputPath: FilePath = rawArgs.output
 

src/run.ts

@@ -23,7 +23,9 @@ parser.addArgument(['-r', '--recursive-depth'], {
   help: 'If provided, choose a link at random on page and do another crawl to this depth. Default: 1 (no recursion).'
 })
 parser.addArgument(['-o', '--output'], {
-  help: 'Path (directory) to write graphs to.',
+  help: 'Path to write to. If a directory is provided, then results are ' +
+        'written to a file in that directory. If a full path is given, ' +
+        'then results are written to that path.',
   required: true
 })
 parser.addArgument(['-u', '--url'], {