Move links parsing from the markdown string to another thread

This can be very expensive and the UI hands for a large number of notes,
otherwise.

lib/core/links_loader.dart

@@ -0,0 +1,100 @@
+import 'dart:io';
+import 'dart:isolate';
+
+import 'package:gitjournal/core/link.dart';
+import 'package:synchronized/synchronized.dart';
+import 'package:path/path.dart' as p;
+
+import 'package:markdown/markdown.dart' as md;
+
+class LinksLoader {
+  Isolate _isolate;
+  ReceivePort _receivePort = ReceivePort();
+  SendPort _sendPort;
+
+  var _loadingLock = Lock();
+
+  Future<void> _initIsolate() async {
+    if (_isolate != null && _sendPort != null) return;
+
+    return await _loadingLock.synchronized(() async {
+      if (_isolate != null && _sendPort != null) return;
+      if (_isolate != null) {
+        _isolate.kill(priority: Isolate.immediate);
+        _isolate = null;
+      }
+      _isolate = await Isolate.spawn(_isolateMain, _receivePort.sendPort);
+
+      var data = await _receivePort.first;
+      assert(data is SendPort);
+      _sendPort = data as SendPort;
+    });
+  }
+
+  Future<List<Link>> parseLinks(String body, String parentFolderPath) async {
+    await _initIsolate();
+
+    var rec = ReceivePort();
+    _sendPort.send(_LoadingMessage(body, parentFolderPath, rec.sendPort));
+
+    var data = await rec.first;
+    assert(data is List<Link>);
+
+    return data;
+  }
+}
+
+class _LoadingMessage {
+  String body;
+  String parentFolderPath;
+  SendPort sendPort;
+
+  _LoadingMessage(this.body, this.parentFolderPath, this.sendPort);
+}
+
+void _isolateMain(SendPort toMainSender) {
+  ReceivePort fromMainRec = ReceivePort();
+  toMainSender.send(fromMainRec.sendPort);
+
+  fromMainRec.listen((data) async {
+    assert(data is _LoadingMessage);
+    var msg = data as _LoadingMessage;
+
+    var links = _parseLinks(msg.body, msg.parentFolderPath);
+    msg.sendPort.send(links);
+  });
+}
+
+List<Link> _parseLinks(String body, String parentFolderPath) {
+  final doc = md.Document(
+    encodeHtml: false,
+    extensionSet: md.ExtensionSet.gitHubFlavored,
+    inlineSyntaxes: [WikiLinkSyntax()],
+  );
+
+  var lines = body.replaceAll('\r\n', '\n').split('\n');
+  var nodes = doc.parseLines(lines);
+  var possibleLinks = LinkExtractor().visit(nodes);
+
+  var links = <Link>[];
+  for (var l in possibleLinks) {
+    var path = l.filePath;
+    if (path == null) {
+      links.add(l);
+      continue;
+    }
+
+    var isLocal = !path.contains('://');
+    if (isLocal) {
+      l.filePath = p.join(parentFolderPath, p.normalize(l.filePath));
+      links.add(l);
+    }
+  }
+
+  doc.linkReferences.forEach((key, value) {
+    var filePath = value.destination;
+    links.add(Link(term: key, filePath: filePath));
+  });
+
+  return links;
+}

lib/core/note.dart

@@ -1,6 +1,7 @@
 import 'dart:io';
 
 import 'package:gitjournal/core/md_yaml_doc_loader.dart';
+import 'package:gitjournal/core/links_loader.dart';
 import 'package:gitjournal/core/note_notifier.dart';
 import 'package:gitjournal/core/notes_folder_fs.dart';
 import 'package:gitjournal/error_reporting.dart';
@@ -11,7 +12,6 @@ import 'package:gitjournal/utils/datetime.dart';
 
 import 'package:path/path.dart' as p;
 
-import 'package:markdown/markdown.dart' as md;
 import 'package:uuid/uuid.dart';
 
 import 'link.dart';
@@ -64,6 +64,7 @@ class Note with NotesNotifier {
   List<Link> _links;
 
   static final _mdYamlDocLoader = MdYamlDocLoader();
+  static final _linksLoader = LinksLoader();
 
   Note(this.parent, this._filePath);
 
@@ -455,38 +456,8 @@ class Note with NotesNotifier {
       return _links;
     }
 
-    final doc = md.Document(
-      encodeHtml: false,
-      extensionSet: md.ExtensionSet.gitHubFlavored,
-      inlineSyntaxes: [WikiLinkSyntax()],
-    );
-
-    var lines = body.replaceAll('\r\n', '\n').split('\n');
-    var nodes = doc.parseLines(lines);
-    var possibleLinks = LinkExtractor().visit(nodes);
-
-    var links = <Link>[];
-    for (var l in possibleLinks) {
-      var path = l.filePath;
-      if (path == null) {
-        links.add(l);
-        continue;
-      }
-
-      var isLocal = !path.contains('://');
-      if (isLocal) {
-        l.filePath = p.join(parent.folderPath, p.normalize(l.filePath));
-        links.add(l);
-      }
-    }
-
-    doc.linkReferences.forEach((key, value) {
-      var filePath = value.destination;
-      links.add(Link(term: key, filePath: filePath));
-    });
-
-    _links = links;
-    return links;
+    _links = await _linksLoader.parseLinks(_body, parent.folderPath);
+    return _links;
   }
 
   List<Link> links() {

test/links_loader_test.dart

@@ -0,0 +1,35 @@
+import 'package:gitjournal/core/links_loader.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group('LinksLoader', () {
+    var contents = """[[GitJournal]]
+
+[GitJournal](./gitjournal.md)
+[GitJournal](gitjournal.md)
+[GitJournal](gitjournal)
+
+[Google](https://google.com)
+
+    """;
+
+    test('Should load links', () async {
+      var loader = LinksLoader();
+      var links = await loader.parseLinks(contents, "/tmp/foo");
+
+      expect(links[0].filePath, null);
+      expect(links[0].term, "GitJournal");
+
+      expect(links[1].filePath, "/tmp/foo/gitjournal.md");
+      expect(links[1].term, "GitJournal");
+
+      expect(links[2].filePath, "/tmp/foo/gitjournal.md");
+      expect(links[2].term, "GitJournal");
+
+      expect(links[3].filePath, "/tmp/foo/gitjournal");
+      expect(links[3].term, "GitJournal");
+
+      expect(links.length, 4);
+    });
+  });
+}