Add an explicit serializer from Note -> NoteData

This is so that we can start configuring what the yaml metadata keys
should be called, and not have them hardcoded.

This also allows the note.created to be null. Earlier we were always
setting it to some value. That's doesn't seem right.

lib/core/note.dart

@@ -3,9 +3,8 @@ import 'dart:io';
 import 'package:flutter/material.dart';
 import 'package:path/path.dart' as p;
 
-import 'package:gitjournal/utils/datetime.dart';
-
 import 'note_fileName.dart';
+import 'note_serializer.dart';
 import 'notes_folder.dart';
 import 'serializers.dart';
 
@@ -30,13 +29,10 @@ class Note with ChangeNotifier implements Comparable<Note> {
   var _loadState = NoteLoadState.None;
   var _serializer = MarkdownYAMLSerializer();
 
-  Note(this.parent, this._filePath) {
-    _created = DateTime(0, 0, 0, 0, 0, 0, 0, 0);
-  }
+  Note(this.parent, this._filePath);
 
   Note.newNote(this.parent) {
     _created = DateTime.now();
-    _data.props['created'] = toIso8601WithTimezone(created);
     _filePath = p.join(parent.folderPath, getFileName(this));
   }
 
@@ -54,12 +50,6 @@ class Note with ChangeNotifier implements Comparable<Note> {
 
   set created(DateTime dt) {
     _created = dt;
-
-    if (hasValidDate()) {
-      _data.props['created'] = toIso8601WithTimezone(created);
-    } else {
-      _data.props.remove('created');
-    }
     notifyListeners();
   }
 
@@ -69,25 +59,20 @@ class Note with ChangeNotifier implements Comparable<Note> {
 
   set modified(DateTime dt) {
     _modified = dt;
-
-    if (hasValidDate()) {
-      _data.props['modified'] = toIso8601WithTimezone(_modified);
-    } else {
-      _data.props.remove('modified');
-    }
     notifyListeners();
   }
 
   void updateModified() {
     modified = DateTime.now();
+    notifyListeners();
   }
 
   String get body {
-    return data.body;
+    return _data.body;
   }
 
   set body(String newBody) {
-    data.body = newBody;
+    _data.body = newBody;
     notifyListeners();
   }
 
@@ -97,41 +82,26 @@ class Note with ChangeNotifier implements Comparable<Note> {
 
   set title(String title) {
     _title = title;
-
-    if (_title.isEmpty) {
-      _data.props.remove('title');
-    } else {
-      _data.props['title'] = title;
-    }
     notifyListeners();
   }
 
   NoteData get data {
+    var serializer = NoteSerializer();
+    serializer.encode(this, _data);
+
     return _data;
   }
 
   set data(NoteData data) {
     _data = data;
 
-    if (data.props.containsKey("created")) {
-      _created = parseDateTime(data.props['created'].toString());
-    }
-    if (data.props.containsKey("modified")) {
-      _modified = parseDateTime(data.props['modified'].toString());
-    }
-    if (data.props.containsKey("title")) {
-      _title = data.props['title'].toString();
-    }
+    // Fill the note's attributes from the data
+    var serializer = NoteSerializer();
+    serializer.decode(_data, this);
 
-    _created ??= DateTime(0, 0, 0, 0, 0, 0, 0, 0);
     notifyListeners();
   }
 
-  bool hasValidDate() {
-    // Arbitrary number, when we set the year = 0, it becomes 1, somehow
-    return created.year > 10;
-  }
-
   bool isEmpty() {
     return body.isEmpty;
   }
@@ -183,9 +153,8 @@ class Note with ChangeNotifier implements Comparable<Note> {
     await file.delete();
   }
 
-  // FIXME: Can't this part be auto-generated?
   @override
-  int get hashCode => filePath.hashCode ^ created.hashCode ^ data.hashCode;
+  int get hashCode => filePath.hashCode;
 
   @override
   bool operator ==(Object other) =>
@@ -193,11 +162,11 @@ class Note with ChangeNotifier implements Comparable<Note> {
       other is Note &&
           runtimeType == other.runtimeType &&
           filePath == other.filePath &&
-          data == other.data;
+          _data == other._data;
 
   @override
   String toString() {
-    return 'Note{filePath: $filePath, created: $created, modified: $modified, data: $data}';
+    return 'Note{filePath: $filePath, created: $created, modified: $modified, data: $_data}';
   }
 
   @override

lib/core/note_serializer.dart

@@ -0,0 +1,45 @@
+import 'package:gitjournal/utils/datetime.dart';
+
+import 'note.dart';
+import 'serializers.dart';
+
+abstract class NoteSerializerInterface {
+  void encode(Note note, NoteData data);
+  void decode(NoteData data, Note note);
+}
+
+class NoteSerializationSettings {
+  String modifiedKey = "modified";
+  String createdKey = "created";
+  String titleKey = "title";
+}
+
+class NoteSerializer implements NoteSerializerInterface {
+  var settings = NoteSerializationSettings();
+
+  @override
+  void encode(Note note, NoteData data) {
+    if (note.created != null)
+      data.props[settings.createdKey] = toIso8601WithTimezone(note.created);
+    else
+      data.props.remove(settings.createdKey);
+
+    if (note.modified != null)
+      data.props[settings.modifiedKey] = toIso8601WithTimezone(note.modified);
+    else
+      data.props.remove(settings.modifiedKey);
+
+    if (note.title != null && note.title.isNotEmpty)
+      data.props[settings.titleKey] = note.title;
+
+    data.body = note.body;
+  }
+
+  @override
+  void decode(NoteData data, Note note) {
+    note.body = data.body;
+    note.created = parseDateTime(data.props[settings.createdKey]?.toString());
+    note.modified = parseDateTime(data.props[settings.modifiedKey]?.toString());
+    note.title = data.props[settings.titleKey]?.toString();
+  }
+}

lib/screens/journal_browsing.dart

@@ -146,7 +146,7 @@ class NoteViewer extends StatelessWidget {
     var view = SingleChildScrollView(
       child: Column(
         children: <Widget>[
-          if (note.hasValidDate() && showJournalHeader)
+          if (note.created != null && showJournalHeader)
             JournalEditorHeader(note),
           if (showTitle && note.title.isNotEmpty)
             NoteTitleHeader(note.title),

lib/utils/datetime.dart

@@ -37,6 +37,8 @@ String toIso8601WithTimezone(DateTime dt, [Duration offset]) {
 }
 
 DateTime parseDateTime(String str) {
+  if (str == null) return null;
+
   DateTime dt;
   try {
     dt = DateTime.parse(str).toLocal();