Address PR feedback.

Author: ditman

packages/google_sign_in/google_sign_in/CHANGELOG.md

@@ -1,6 +1,6 @@
 ## 4.0.13
 
-* Fix GoogleUserCircleAvatar to handle new style profile image URLs.
+* Fix `GoogleUserCircleAvatar` to handle new style profile image URLs.
 
 ## 4.0.12
 

packages/google_sign_in/lib/src/fife.dart

@@ -1,39 +1,58 @@
+// Copyright 2019 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
 /// A regular expression that matches against the "size directive" path
 /// segment of Google profile image URLs.
 ///
 /// The format is is "`/sNN-c/`", where `NN` is the max width/height of the
 /// image, and "`c`" indicates we want the image cropped.
 final RegExp sizeDirective = RegExp(r'^s[0-9]{1,5}(-c)?$');
 
-/// Adds [size] directive to [photoUrl].
+/// Adds [size] (and crop) directive to [photoUrl].
+///
+/// There are two formats for photoUrls coming from the Sign In backend.
+///
+/// The two formats can be told apart by the number of path segments in the
+/// URL (path segments: parts of the URL separated by slashes "/"):
+///
+///  * If the URL has 2 or less path segments, it is a *new* style URL.
+///  * If the URL has more than 2 path segments, it is an old style URL.
+///
+/// Old style URLs encode the image transformation directives as the last
+/// path segment. Look at the [sizeDirective] Regular Expression for more
+/// information about these URLs.
 ///
-/// Depending on the format of photoUrl, this might:
-///  * Insert information as the last path segment (old style URLs), before
-///    the image filename. The format is described in [sizeDirective].
-///  * Insert information at the end of the URL, after an = sign. The format
-///    is described within this method.
+/// New style URLs carry the same directives at the end of the URL,
+/// after an = sign, like: "`=s120-c-fSoften=1,50,0`".
+///
+/// Directives may contain the "=" sign (`fSoften=1,50,0`), but it seems the
+/// base URL of the images don't. "Everything after the first = sign" is a
+/// good heuristic to split new style URLs.
+///
+/// Each directive is separated from others by dashes. Directives are the same
+/// as described in the [sizeDirective] RegExp.
+///
+/// Modified image URLs are recomposed by performing the parsing steps in reverse.
 String addSizeDirectiveToUrl(String photoUrl, double size) {
   final Uri profileUri = Uri.parse(photoUrl);
   final List<String> pathSegments = List<String>.from(profileUri.pathSegments);
   if (pathSegments.length <= 2) {
-    /// New URLs may have directives at the end of the URL, like "`=sNN-c`".
-    /// Each filter is separated by dashes. Filters may contain = signs:
-    /// "`=s120-c-fSoften=1,50,0`"
     final String imagePath = pathSegments.last;
-    // Locate the first =
+    // Does this have any existing transformation directives?
     final int directiveSeparator = imagePath.indexOf('=');
     if (directiveSeparator >= 0) {
-      // Split the image URL by the first =
-      final String image = imagePath.substring(0, directiveSeparator);
+      // Split the baseUrl from the sizing directive by the first "="
+      final String baseUrl = imagePath.substring(0, directiveSeparator);
       final String directive = imagePath.substring(directiveSeparator + 1);
-      // Split the second half by -
+      // Split the directive by "-"
       final Set<String> directives = Set<String>.from(directive.split('-'))
-        // Remove the size directive, if present, and empty values
+        // Remove the size directive, if present, and any empty values
         ..removeWhere((String s) => s.isEmpty || sizeDirective.hasMatch(s))
         // Add the size and crop directives
         ..addAll(<String>['c', 's${size.round()}']);
-
-      pathSegments.last = '$image=${directives.join("-")}';
+      // Recompose the URL by performing the reverse of the parsing
+      pathSegments.last = '$baseUrl=${directives.join("-")}';
     } else {
       pathSegments.last = '${pathSegments.last}=c-s${size.round()}';
     }