Overhaul Link parsing

We were mixing up header links with wiki links and the alt text. It was
a bit messy. We currently do not support linking to a particular part of
a note. Nor do we support wiki links as link references.

Fixes APP-A0

lib/core/link.dart

@@ -2,10 +2,22 @@ import 'package:markdown/markdown.dart' as md;
 import 'package:meta/meta.dart';
 
 class Link {
-  String term;
-  String filePath;
+  String publicTerm = "";
+  String filePath = "";
+  String headingID = "";
+  String alt = "";
 
-  Link({@required this.term, @required this.filePath});
+  String wikiTerm = "";
+
+  Link({
+    @required this.publicTerm,
+    @required this.filePath,
+    this.headingID = "",
+    this.alt = "",
+  });
+  Link.wiki(this.wikiTerm);
+
+  bool get isWikiLink => wikiTerm.isNotEmpty;
 
   @override
   int get hashCode => filePath.hashCode;
@@ -15,17 +27,26 @@ class Link {
       identical(this, other) ||
       other is Link &&
           runtimeType == other.runtimeType &&
-          filePath == other.filePath;
+          filePath == other.filePath &&
+          publicTerm == other.publicTerm &&
+          wikiTerm == other.wikiTerm &&
+          headingID == other.headingID &&
+          alt == other.alt;
 
   @override
   String toString() {
-    return 'Link{term: $term, filePath: $filePath}';
+    return wikiTerm.isNotEmpty
+        ? 'WikiLink($wikiTerm)'
+        : 'Link{publicTerm: $publicTerm, filePath: $filePath, headingID: $headingID}';
   }
 }
 
 class LinkExtractor implements md.NodeVisitor {
+  final String filePath;
   List<Link> links = [];
 
+  LinkExtractor(this.filePath);
+
   @override
   bool visitElementBefore(md.Element element) {
     return true;
@@ -42,33 +63,69 @@ class LinkExtractor implements md.NodeVisitor {
       var type = el.attributes['type'] ?? "";
       if (type == "wiki") {
         var term = el.attributes['term'];
-        var link = Link(term: term, filePath: null);
+        var link = Link.wiki(term);
+
+        assert(link.filePath.isEmpty);
+        assert(link.publicTerm.isEmpty);
+        assert(link.alt.isEmpty);
+        assert(link.headingID.isEmpty);
+
         links.add(link);
         return;
       }
 
-      var title = el.attributes['title'] ?? "";
-      if (title.isEmpty) {
-        for (var child in el.children) {
-          if (child is md.Text) {
-            title += child.text;
-          }
-        }
-      }
+      var alt = el.attributes['title'] ?? "";
+      var title = _getText(el.children);
 
       var url = el.attributes['href'];
-      var link = Link(term: title, filePath: url);
+      if (isExternalLink(url)) {
+        return;
+      }
+
+      if (url.startsWith('#')) {
+        var link = Link(
+          publicTerm: title,
+          filePath: filePath,
+          alt: alt,
+          headingID: url,
+        );
+        links.add(link);
+        return;
+      }
+
+      var link = Link(publicTerm: title, filePath: url, alt: alt);
       links.add(link);
       return;
     }
   }
 
+  static bool isExternalLink(String url) {
+    return url.startsWith(RegExp(r'[A-Za-z]{2,5}:\/\/'));
+  }
+
   List<Link> visit(List<md.Node> nodes) {
     for (final node in nodes) {
       node.accept(this);
     }
     return links;
   }
+
+  String _getText(List<md.Node> nodes) {
+    if (nodes == null) {
+      return "";
+    }
+
+    var text = "";
+    for (final node in nodes) {
+      if (node is md.Text) {
+        text += node.text;
+      } else if (node is md.Element) {
+        text += _getText(node.children);
+      }
+    }
+
+    return text;
+  }
 }
 
 /// Parse [[term]]

lib/core/links_loader.dart

@@ -1,6 +1,7 @@
 import 'dart:io';
 import 'dart:isolate';
 
+import 'package:flutter/material.dart';
 import 'package:markdown/markdown.dart' as md;
 import 'package:path/path.dart' as p;
 import 'package:synchronized/synchronized.dart';
@@ -31,11 +32,11 @@ class LinksLoader {
     });
   }
 
-  Future<List<Link>> parseLinks(String body, String parentFolderPath) async {
+  Future<List<Link>> parseLinks({String body, String filePath}) async {
     await _initIsolate();
 
     var rec = ReceivePort();
-    _sendPort.send(_LoadingMessage(body, parentFolderPath, rec.sendPort));
+    _sendPort.send(_LoadingMessage(body, filePath, rec.sendPort));
 
     var data = await rec.first;
     assert(data is List<Link>);
@@ -46,10 +47,10 @@ class LinksLoader {
 
 class _LoadingMessage {
   String body;
-  String parentFolderPath;
+  String filePath;
   SendPort sendPort;
 
-  _LoadingMessage(this.body, this.parentFolderPath, this.sendPort);
+  _LoadingMessage(this.body, this.filePath, this.sendPort);
 }
 
 void _isolateMain(SendPort toMainSender) {
@@ -60,12 +61,15 @@ void _isolateMain(SendPort toMainSender) {
     assert(data is _LoadingMessage);
     var msg = data as _LoadingMessage;
 
-    var links = _parseLinks(msg.body, msg.parentFolderPath);
+    var links = parseLinks(msg.body, msg.filePath);
     msg.sendPort.send(links);
   });
 }
 
-List<Link> _parseLinks(String body, String parentFolderPath) {
+@visibleForTesting
+List<Link> parseLinks(String body, String filePath) {
+  var parentFolderPath = p.dirname(filePath);
+
   final doc = md.Document(
     encodeHtml: false,
     extensionSet: md.ExtensionSet.gitHubFlavored,
@@ -74,29 +78,34 @@ List<Link> _parseLinks(String body, String parentFolderPath) {
 
   var lines = body.replaceAll('\r\n', '\n').split('\n');
   var nodes = doc.parseLines(lines);
-  var possibleLinks = LinkExtractor().visit(nodes);
+  var possibleLinks = LinkExtractor(filePath).visit(nodes);
 
   var links = <Link>[];
   for (var l in possibleLinks) {
-    var path = l.filePath;
-    if (path == null) {
+    if (l.isWikiLink) {
       links.add(l);
       continue;
     }
 
-    var isLocal = !path.contains('://');
-    if (isLocal) {
-      l.filePath = p.join(parentFolderPath, p.normalize(l.filePath));
-      links.add(l);
-    }
+    l.filePath = p.join(parentFolderPath, p.normalize(l.filePath));
+    links.add(l);
   }
 
   doc.linkReferences.forEach((key, value) {
     var path = value.destination;
-    var isLocal = !path.contains('://');
-    if (isLocal) {
-      links.add(Link(term: key, filePath: path));
+    if (LinkExtractor.isExternalLink(path)) {
+      return;
     }
+
+    var l = Link(publicTerm: value.label, filePath: "", alt: value.title);
+
+    if (path.startsWith('#') || path.startsWith('//')) {
+      l.headingID = path;
+      l.filePath = filePath;
+    } else {
+      l.filePath = p.join(parentFolderPath, p.normalize(path));
+    }
+    links.add(l);
   });
 
   return links;

lib/core/note.dart

@@ -512,7 +512,7 @@ class Note with NotesNotifier {
       return _links;
     }
 
-    _links = await _linksLoader.parseLinks(_body, parent.folderPath);
+    _links = await _linksLoader.parseLinks(body: _body, filePath: _filePath);
     return _links;
   }
 

lib/utils/link_resolver.dart

@@ -10,11 +10,12 @@ class LinkResolver {
   LinkResolver(this.inputNote);
 
   Note resolveLink(Link l) {
-    if (l.filePath == null) {
-      return resolveWikiLink(l.term);
+    if (l.isWikiLink) {
+      return resolveWikiLink(l.publicTerm);
     }
 
     var rootFolder = inputNote.parent.rootFolder;
+    assert(l.filePath.startsWith(rootFolder.folderPath));
     var spec = l.filePath.substring(rootFolder.folderPath.length + 1);
 
     return rootFolder.getNoteWithSpec(spec);

lib/widgets/notes_backlinks.dart

@@ -173,7 +173,11 @@ class NoteSnippet extends StatelessWidget {
 
     var body = note.body.split('\n');
     var paragraph = body.firstWhere(
-      (line) => line.contains('[${link.term}]'),
+      (String line) {
+        return link.isWikiLink
+            ? line.contains('[[${link.wikiTerm}}]]')
+            : line.contains('[${link.publicTerm}]');
+      },
       orElse: () => "",
     );
 

test/link_resolver_test.dart

@@ -158,7 +158,7 @@ void main() {
     var note = rootFolder.notes[0];
     var linkResolver = LinkResolver(note);
 
-    var link = Link(filePath: note.filePath, term: 'foo');
+    var link = Link(filePath: note.filePath, publicTerm: 'foo');
 
     var resolvedNote = linkResolver.resolveLink(link);
     expect(resolvedNote.filePath, note.filePath);

test/links_loader_test.dart

@@ -8,7 +8,7 @@ void main() {
 
 [GitJournal](./gitjournal.md)
 [GitJournal](gitjournal.md)
-[GitJournal](gitjournal)
+[GitJournal](gitjournal "alt-text")
 
 [Google](https://google.com)
 
@@ -19,21 +19,81 @@ void main() {
 
     test('Should load links', () async {
       var loader = LinksLoader();
-      var links = await loader.parseLinks(contents, "/tmp/foo");
+      var links = await loader.parseLinks(
+        body: contents,
+        filePath: "/tmp/foo/file.md",
+      );
 
-      expect(links[0].filePath, null);
-      expect(links[0].term, "GitJournal");
+      expect(links[0].filePath.isEmpty, true);
+      expect(links[0].headingID.isEmpty, true);
+      expect(links[0].alt.isEmpty, true);
+      expect(links[0].publicTerm.isEmpty, true);
+      expect(links[0].wikiTerm, "GitJournal");
+      expect(links[0].isWikiLink, true);
 
       expect(links[1].filePath, "/tmp/foo/gitjournal.md");
-      expect(links[1].term, "GitJournal");
+      expect(links[1].publicTerm, "GitJournal");
+      expect(links[1].alt.isEmpty, true);
+      expect(links[1].wikiTerm.isEmpty, true);
 
       expect(links[2].filePath, "/tmp/foo/gitjournal.md");
-      expect(links[2].term, "GitJournal");
+      expect(links[2].publicTerm, "GitJournal");
+      expect(links[2].alt.isEmpty, true);
+      expect(links[2].wikiTerm.isEmpty, true);
 
       expect(links[3].filePath, "/tmp/foo/gitjournal");
-      expect(links[3].term, "GitJournal");
+      expect(links[3].publicTerm, "GitJournal");
+      expect(links[3].alt, "alt-text");
+      expect(links[3].wikiTerm.isEmpty, true);
 
       expect(links.length, 4);
     });
+
+    test('Foam Documentation', () async {
+      var contents = """
+[![All Contributors](https://img.shields.io/badge/all_contributors-38-orange.svg?style=flat-square)](#contributors-)
+
+3. Use Foam's shortcuts and autocompletions to link your thoughts together with `[[wiki-links]]`, and navigate between them to explore your knowledge graph.
+4. the [[Graph Visualisation](https://foambubble.github.io/foam/graph-visualisation)], of [[Backlinking](https://foambubble.github.io/foam/backlinking)].
+
+![Foam kitchen sink, showing a few of the key features](docs/assets/images/foam-features-dark-mode-demo.png)
+
+Foam is licensed under the [MIT license](license).
+
+[//begin]: # "Autogenerated link references for markdown compatibility"
+[wiki-links]: wiki-links "Wiki Links"
+[//end]: # "Autogenerated link references"
+""";
+
+      var links = parseLinks(contents, "/tmp/foo.md");
+      expect(links.length, 5);
+
+      expect(links[0].filePath, "/tmp/foo.md");
+      expect(links[0].alt.isEmpty, true);
+      expect(links[0].headingID, "#contributors-");
+      expect(links[0].publicTerm.isEmpty, true);
+
+      expect(links[1].filePath, "/tmp/license");
+      expect(links[1].alt.isEmpty, true);
+      expect(links[1].headingID.isEmpty, true);
+      expect(links[1].publicTerm, "MIT license");
+
+      expect(links[2].filePath, "/tmp/foo.md");
+      expect(links[2].publicTerm, '//begin');
+      expect(links[2].headingID, "#");
+      expect(links[2].alt,
+          "Autogenerated link references for markdown compatibility");
+
+      // FIXME: link-references for wiki Links
+      // expect(links[3].filePath.isEmpty, true);
+      // expect(links[3].isWikiLink, true);
+      expect(links[3].headingID.isEmpty, true);
+      expect(links[3].alt, "Wiki Links");
+
+      expect(links[4].filePath, "/tmp/foo.md");
+      expect(links[4].publicTerm, '//end');
+      expect(links[4].headingID, "#");
+      expect(links[4].alt, "Autogenerated link references");
+    });
   });
 }

test/note_test.dart

@@ -133,10 +133,10 @@ bar: Foo
 
       var links = await note.fetchLinks();
       expect(links[0].filePath, p.join(tempDir.path, "foo.md"));
-      expect(links[0].term, "Hi");
+      expect(links[0].publicTerm, "Hi");
 
       expect(links[1].filePath, p.join(tempDir.path, "food.md"));
-      expect(links[1].term, "Hi2");
+      expect(links[1].publicTerm, "Hi2");
 
       expect(links.length, 2);
     });
@@ -152,11 +152,11 @@ bar: Foo
       await note.load();
 
       var links = await note.fetchLinks();
-      expect(links[0].filePath, null);
-      expect(links[0].term, "GitJournal");
+      expect(links[0].isWikiLink, true);
+      expect(links[0].wikiTerm, "GitJournal");
 
-      expect(links[1].filePath, null);
-      expect(links[1].term, "Wild Fire");
+      expect(links[1].isWikiLink, true);
+      expect(links[1].wikiTerm, "Wild Fire");
 
       expect(links.length, 2);
     });