Simplify ACL path algorithm.

Author: RubenVerborgh

lib/acl-checker.js

@@ -1,9 +1,7 @@
 'use strict'
 
-const path = require('path')
 const PermissionSet = require('solid-permissions').PermissionSet
 const rdf = require('rdflib')
-const url = require('url')
 const debug = require('./debug').ACL
 const HTTPError = require('./http-error')
 
@@ -73,28 +71,21 @@ class ACLChecker {
 
   // Gets all possible ACL paths that apply to the resource
   getPossibleACLs () {
-    let uri = this.resource
-    const suffix = this.suffix
-    const first = uri.endsWith(suffix) ? uri : uri + suffix
-    const urls = [first]
-    const parsedUri = url.parse(uri)
-    const baseUrl = (parsedUri.protocol ? parsedUri.protocol + '//' : '') +
-      (parsedUri.host || '')
-    if (baseUrl + '/' === uri) {
-      return urls
-    }
+    // Obtain the resource URI and the length of its base
+    let { resource: uri, suffix } = this
+    const [ { length: base } ] = uri.match(/^[^:]+:\/*[^/]+/)
 
-    let times = parsedUri.pathname.split('/').length
-    // TODO: improve temporary solution to stop recursive path walking above root
-    if (parsedUri.pathname.endsWith('/')) {
-      times--
+    // If the URI points to a file, append the file's ACL
+    const possibleAcls = []
+    if (!uri.endsWith('/')) {
+      possibleAcls.push(uri.endsWith(suffix) ? uri : uri + suffix)
     }
 
-    for (let i = 0; i < times - 1; i++) {
-      uri = path.dirname(uri)
-      urls.push(uri + (uri[uri.length - 1] === '/' ? suffix : '/' + suffix))
+    // Append the ACLs of all parent directories
+    for (let i = lastSlash(uri); i >= base; i = lastSlash(uri, i - 1)) {
+      possibleAcls.push(uri.substr(0, i + 1) + suffix)
     }
-    return urls
+    return possibleAcls
   }
 
   // Tests whether the permissions allow a given operation
@@ -144,5 +135,10 @@ class ACLChecker {
   }
 }
 
+// Returns the index of the last slash before the given position
+function lastSlash (string, pos = string.length) {
+  return string.lastIndexOf('/', pos)
+}
+
 module.exports = ACLChecker
 module.exports.DEFAULT_ACL_SUFFIX = DEFAULT_ACL_SUFFIX