Move LinkResolving code to its own class

It has become sufficiently complex that a number of edge cases need to
be tested.

lib/utils/link_resolver.dart

@@ -0,0 +1,57 @@
+import 'package:gitjournal/core/note.dart';
+
+class LinkResolver {
+  final Note inputNote;
+
+  LinkResolver(this.inputNote);
+
+  Note resolve(String link) {
+    var spec = link;
+    var parent = inputNote.parent;
+
+    if (link.startsWith('[[') && link.endsWith(']]') && link.length > 4) {
+      // FIXME: What if the case is different?
+      spec = link.substring(2, link.length - 2) + ".md";
+    }
+
+    if (link.startsWith('./')) {
+      spec = link.substring(2);
+    }
+
+    var linkedNote = parent.getNoteWithSpec(spec);
+    if (linkedNote != null) {
+      return linkedNote;
+    }
+
+    if (!spec.endsWith('.md')) {
+      linkedNote = parent.getNoteWithSpec(spec + '.md');
+      if (linkedNote != null) {
+        return linkedNote;
+      }
+    }
+
+    if (!spec.endsWith('.txt')) {
+      linkedNote = parent.getNoteWithSpec(spec + '.txt');
+      if (linkedNote != null) {
+        return linkedNote;
+      }
+    }
+
+    return null;
+  }
+}
+
+// Test to write
+// 1. [[Fire]] resolves to base folder [[Fire.md]]
+// 2. [[Fire.md]] resolve to base folder [[Fire.md]]
+// 3. [[Hello/Fire]] resolves to Hello/Fire.md
+// 4. [[Hello | pipe]] resolves correctly
+// 5. [[Hello Dear]] should resolve correctly
+// 6. [[Hello Dear ]] check how it works in Obsidian (ignored extra spaces)
+// 7. Should resolve to 'txt' files as well
+
+// Normal Links
+// 4. ./Fire.md -> resovles
+// 5. Fire.md -> resolves
+// 6. Fire2.md -> fails to resolve
+// 7. Complex path ../../Foo/../bar/d.md

lib/widgets/note_viewer.dart

@@ -16,6 +16,7 @@ import 'package:gitjournal/core/notes_folder_fs.dart';
 import 'package:gitjournal/folder_views/common.dart';
 import 'package:gitjournal/settings.dart';
 import 'package:gitjournal/utils.dart';
+import 'package:gitjournal/utils/link_resolver.dart';
 import 'package:gitjournal/utils/logger.dart';
 import 'package:gitjournal/widgets/editor_scroll_view.dart';
 import 'package:gitjournal/widgets/notes_backlinks.dart';
@@ -67,40 +68,15 @@ class NoteViewer extends StatelessWidget {
               // selectable: false, -> making this true breaks link navigation
               styleSheet: markdownStyleSheet,
               onTapLink: (String link) async {
-                var spec = link;
+                final linkResolver = LinkResolver(note);
 
-                if (link.startsWith('[[') &&
-                    link.endsWith(']]') &&
-                    link.length > 4) {
-                  // FIXME: What if the case is different?
-                  spec = link.substring(2, link.length - 2) + ".md";
-                }
-
-                if (link.startsWith('./')) {
-                  spec = link.substring(2);
-                }
-
-                var linkedNote = note.parent.getNoteWithSpec(spec);
+                var linkedNote = linkResolver.resolve(link);
                 if (linkedNote != null) {
                   openNoteEditor(context, linkedNote);
                   return;
                 }
 
-                if (!spec.endsWith('.md')) {
-                  linkedNote = note.parent.getNoteWithSpec(spec + '.md');
-                  if (linkedNote != null) {
-                    openNoteEditor(context, linkedNote);
-                    return;
-                  }
-                }
-                if (!spec.endsWith('.txt')) {
-                  linkedNote = note.parent.getNoteWithSpec(spec + '.txt');
-                  if (linkedNote != null) {
-                    openNoteEditor(context, linkedNote);
-                    return;
-                  }
-                }
-
+                // External Link
                 try {
                   await launch(link);
                 } catch (e, stackTrace) {

test/link_resolver_test.dart

@@ -0,0 +1,52 @@
+import 'dart:io';
+
+import 'package:path/path.dart' as p;
+import 'package:test/test.dart';
+
+import 'package:gitjournal/core/notes_folder_fs.dart';
+import 'package:gitjournal/utils/link_resolver.dart';
+
+void main() {
+  Directory tempDir;
+  NotesFolderFS rootFolder;
+
+  setUpAll(() async {
+    tempDir = await Directory.systemTemp.createTemp('__link_resolver__');
+
+    rootFolder = NotesFolderFS(null, tempDir.path);
+
+    await generateNote(tempDir.path, "Hello.md");
+    await generateNote(tempDir.path, "Fire.md");
+
+    await rootFolder.loadRecursively();
+  });
+
+  tearDownAll(() async {
+    tempDir.deleteSync(recursive: true);
+  });
+
+  test('Should process simple wiki links', () {
+    var note = rootFolder.notes[0];
+    var linkResolver = LinkResolver(note);
+
+    var resolvedNote = linkResolver.resolve('[[Hello]]');
+    expect(resolvedNote.filePath, p.join(tempDir.path, 'Hello.md'));
+  });
+}
+
+Future<void> generateNote(String basePath, String path) async {
+  var filePath = p.join(basePath, path);
+
+  // Ensure directory exists
+  var dirPath = p.basename(filePath);
+  await Directory(dirPath).create(recursive: true);
+
+  var content = """---
+title:
+modified: 2017-02-15T22:41:19+01:00
+---
+
+Hello""";
+
+  return File(filePath).writeAsString(content, flush: true);
+}

test/markdown_rendering_test.dart

@@ -1,5 +1,5 @@
-import 'package:test/test.dart';
 import 'package:markdown/markdown.dart' as md;
+import 'package:test/test.dart';
 
 import 'package:gitjournal/widgets/note_viewer.dart';