From 561fbbed3ec97adeb23867a0394f7eb8e6bc3b09 Mon Sep 17 00:00:00 2001
From: singerdmx <singerdmx@gmail.com>
Date: Thu, 24 Dec 2020 21:38:40 -0800
Subject: [PATCH] Add history

---
 lib/models/documents/document.dart |  18 ++++-
 lib/models/documents/history.dart  | 116 +++++++++++++++++++++++++++++
 lib/widgets/controller.dart        |  12 +++
 3 files changed, 144 insertions(+), 2 deletions(-)
 create mode 100644 lib/models/documents/history.dart

diff --git a/lib/models/documents/document.dart b/lib/models/documents/document.dart
index d249926a..62a59c05 100644
--- a/lib/models/documents/document.dart
+++ b/lib/models/documents/document.dart
@@ -9,6 +9,7 @@ import 'package:tuple/tuple.dart';
 
 import '../rules/rule.dart';
 import 'attribute.dart';
+import 'history.dart';
 import 'nodes/embed.dart';
 import 'nodes/node.dart';
 
@@ -30,6 +31,8 @@ class Document {
   final StreamController<Tuple3<Delta, Delta, ChangeSource>> _observer =
   StreamController.broadcast();
 
+  final History _history = History();
+
   Stream<Tuple3> get changes => _observer.stream;
 
   Document() : _delta = Delta()
@@ -115,7 +118,7 @@ class Document {
     return block.queryChild(res.offset, true);
   }
 
-  compose(Delta delta, ChangeSource changeSource) {
+  compose(Delta delta, ChangeSource changeSource, {bool history}) {
     assert(!_observer.isClosed);
     delta.trim();
     assert(delta.isNotEmpty);
@@ -148,7 +151,17 @@ class Document {
     if (_delta != _root.toDelta()) {
       throw ('Compose failed');
     }
-    _observer.add(Tuple3(originalDelta, delta, changeSource));
+    final change = Tuple3(originalDelta, delta, changeSource);
+    _observer.add(change);
+    _history.handleDocChange(change);
+  }
+
+  void undo() {
+    _history.undo(this);
+  }
+
+  void redo() {
+    _history.redo(this);
   }
 
   static Delta _transform(Delta delta) {
@@ -172,6 +185,7 @@ class Document {
 
   close() {
     _observer.close();
+    _history.clear();
   }
 
   String toPlainText() => _root.children.map((e) => e.toPlainText()).join('');
diff --git a/lib/models/documents/history.dart b/lib/models/documents/history.dart
new file mode 100644
index 00000000..f672ba68
--- /dev/null
+++ b/lib/models/documents/history.dart
@@ -0,0 +1,116 @@
+import 'package:quill_delta/quill_delta.dart';
+import 'package:tuple/tuple.dart';
+
+import 'document.dart';
+
+class History {
+  final HistoryStack stack = HistoryStack.empty();
+
+  /// used for disable redo or undo function
+  bool ignoreChange;
+
+  int lastRecorded;
+
+  /// Collaborative editing's conditions should be true
+  final bool userOnly;
+
+  ///max operation count for undo
+  final int maxStack;
+
+  ///record delay
+  final int interval;
+
+  History(
+      {this.ignoreChange = false,
+      this.interval = 400,
+      this.maxStack = 100,
+      this.userOnly = false,
+      this.lastRecorded = 0});
+
+  void handleDocChange(Tuple3<Delta, Delta, ChangeSource> change) {
+    if (ignoreChange) return;
+    if (!userOnly || change.item3 == ChangeSource.LOCAL) {
+      record(change.item2, change.item1);
+    } else {
+      transform(change.item2);
+    }
+  }
+
+  void clear() {
+    stack.clear();
+  }
+
+  void record(Delta change, Delta before) {
+    if (change.isEmpty) return;
+    stack.redo.clear();
+    Delta undoDelta = change.invert(before);
+    final timeStamp = DateTime.now().millisecondsSinceEpoch;
+
+    if (lastRecorded + interval > timeStamp && stack.undo.isNotEmpty) {
+      final lastDelta = stack.undo.removeLast();
+      undoDelta = undoDelta.compose(lastDelta);
+    } else {
+      lastRecorded = timeStamp;
+    }
+
+    if (undoDelta.isEmpty) return;
+    stack.undo.add(undoDelta);
+
+    if (stack.undo.length > maxStack) {
+      stack.undo.removeAt(0);
+    }
+  }
+
+  ///
+  ///It will override pre local undo delta,replaced by remote change
+  ///
+  void transform(Delta delta) {
+    transformStack(this.stack.undo, delta);
+    transformStack(this.stack.redo, delta);
+  }
+
+  void transformStack(List<Delta> stack, Delta delta) {
+    for (int i = stack.length - 1; i >= 0; i -= 1) {
+      final oldDelta = stack[i];
+      stack[i] = delta.transform(oldDelta, true);
+      delta = oldDelta.transform(delta, false);
+      if (stack[i].length == 0) {
+        stack.removeAt(i);
+      }
+    }
+  }
+
+  void _change(Document doc, List<Delta> source, List<Delta> dest) {
+    if (source.length == 0) return;
+    Delta delta = source.removeLast();
+    Delta base = doc.toDelta();
+    Delta inverseDelta = delta.invert(base);
+    dest.add(inverseDelta);
+    this.lastRecorded = 0;
+    this.ignoreChange = true;
+    doc.compose(delta, ChangeSource.LOCAL, history: true);
+    this.ignoreChange = false;
+  }
+
+  void undo(Document doc) {
+    _change(doc, stack.undo, stack.redo);
+  }
+
+  void redo(Document doc) {
+    _change(doc, stack.redo, stack.undo);
+  }
+}
+
+class HistoryStack {
+  final List<Delta> undo;
+  final List<Delta> redo;
+
+  HistoryStack.empty()
+      : undo = [],
+        redo = [];
+
+  void clear() {
+    undo.clear();
+    redo.clear();
+  }
+}
diff --git a/lib/widgets/controller.dart b/lib/widgets/controller.dart
index 486f93cf..aeffe1fd 100644
--- a/lib/widgets/controller.dart
+++ b/lib/widgets/controller.dart
@@ -34,6 +34,18 @@ class QuillController extends ChangeNotifier {
         .mergeAll(toggledStyle);
   }
 
+  void undo() {
+    document.undo();
+    updateSelection(
+        TextSelection.collapsed(offset: document.length), ChangeSource.REMOTE);
+  }
+
+  void redo() {
+    document.redo();
+    updateSelection(
+        TextSelection.collapsed(offset: document.length), ChangeSource.REMOTE);
+  }
+
   replaceText(int index, int len, Object data, TextSelection textSelection) {
     assert(data is String || data is Embeddable);