feat: add undo and redo logic for eraser stroke

Memola/Canvas/Contexts/GraphicContext.swift

@@ -10,7 +10,6 @@ import MetalKit
 import CoreData
 import Foundation
 
-#warning("TODO: to update history undo and redo logic")
 final class GraphicContext: @unchecked Sendable {
     var tree: RTree = RTree<AnyStroke>(maxEntries: 8)
     var eraserStrokes: Set<EraserStroke> = []
@@ -46,26 +45,59 @@ final class GraphicContext: @unchecked Sendable {
     func undoGraphic(for event: HistoryEvent) {
         switch event {
         case .stroke(let stroke):
-            guard let _stroke = stroke.stroke(as: PenStroke.self) else { return }
-            let deletedStroke = tree.remove(_stroke.anyStroke, in: _stroke.strokeBox)
-            withPersistence(\.backgroundContext) { [stroke = deletedStroke] context in
-                stroke?.stroke(as: PenStroke.self)?.object?.graphicContext = nil
-                try context.saveIfNeeded()
+            switch stroke.style {
+            case .marker:
+                guard let penStroke = stroke.stroke(as: PenStroke.self) else { return }
+                let deletedStroke = tree.remove(penStroke.anyStroke, in: penStroke.strokeBox)
+                withPersistence(\.backgroundContext) { [stroke = deletedStroke] context in
+                    stroke?.stroke(as: PenStroke.self)?.object?.graphicContext = nil
+                    try context.saveIfNeeded()
+                }
+            case .eraser:
+                guard let eraserStroke = stroke.stroke(as: EraserStroke.self) else { return }
+                eraserStrokes.remove(eraserStroke)
+                let penStrokes = eraserStroke.penStrokes
+                withPersistence(\.backgroundContext) { [penStrokes] context in
+                    for penStroke in penStrokes {
+                        penStroke.eraserStrokes.remove(eraserStroke)
+                        if let object = eraserStroke.object {
+                            penStroke.object?.erasers.remove(object)
+                        }
+                    }
+                }
             }
             previousStroke = nil
         }
-
     }
 
     func redoGraphic(for event: HistoryEvent) {
         switch event {
         case .stroke(let stroke):
-            if let stroke = stroke.stroke(as: PenStroke.self) {
-                tree.insert(stroke.anyStroke, in: stroke.strokeBox)
-            }
-            withPersistence(\.backgroundContext) { [weak self, stroke] context in
-                stroke.stroke(as: PenStroke.self)?.object?.graphicContext = self?.object
-                try context.saveIfNeeded()
+            switch stroke.style {
+            case .marker:
+                guard let penStroke = stroke.stroke(as: PenStroke.self) else {
+                    break
+                }
+                tree.insert(penStroke.anyStroke, in: penStroke.strokeBox)
+                withPersistence(\.backgroundContext) { [weak self, penStroke] context in
+                    penStroke.object?.graphicContext = self?.object
+                    try context.saveIfNeeded()
+                }
+            case .eraser:
+                guard let eraserStroke = stroke.stroke(as: EraserStroke.self) else {
+                    break
+                }
+                eraserStrokes.insert(eraserStroke)
+                let penStrokes = eraserStroke.penStrokes
+                withPersistence(\.backgroundContext) { [eraserStroke, penStrokes] context in
+                    for penStroke in penStrokes {
+                        penStroke.eraserStrokes.insert(eraserStroke)
+                        if let object = eraserStroke.object {
+                            penStroke.object?.erasers.add(object)
+                        }
+                    }
+                    try context.saveIfNeeded()
+                }
             }
             previousStroke = nil
         }

Memola/Canvas/Geometries/Stroke/Strokes/EraserStroke.swift

@@ -34,6 +34,7 @@ final class EraserStroke: Stroke, @unchecked Sendable {
     weak var graphicContext: GraphicContext?
 
     var finishesSaving: Bool = false
+    var penStrokes: Set<PenStroke> = []
 
     init(
         bounds: [CGFloat],
@@ -58,7 +59,7 @@ final class EraserStroke: Stroke, @unchecked Sendable {
             bounds: object.bounds,
             color: object.color,
             style: style,
-            createdAt: object.createdAt,
+            createdAt: object.createdAt ?? .now,
             thickness: object.thickness
         )
         self.object = object
@@ -111,6 +112,7 @@ final class EraserStroke: Stroke, @unchecked Sendable {
                 for stroke in graphicContext.tree.search(box: _quad.quadBox) {
                     if let _penStroke = stroke.stroke(as: PenStroke.self), !_penStroke.eraserStrokes.contains(self) {
                         _penStroke.eraserStrokes.insert(self)
+                        penStrokes.insert(_penStroke)
                         if let penStroke = _penStroke.object {
                             penStroke.erasers.add(eraser)
                             eraser.strokes.add(penStroke)

Memola/Canvas/Geometries/Stroke/Strokes/PenStroke.swift

@@ -61,11 +61,12 @@ final class PenStroke: Stroke, @unchecked Sendable {
 
     convenience init(object: StrokeObject) {
         let style = StrokeStyle(rawValue: object.style) ?? .marker
+        #warning("TODO: revisit here and check if there is any crash")
         self.init(
             bounds: object.bounds,
             color: object.color,
             style: style,
-            createdAt: object.createdAt, // sometimes crash here
+            createdAt: object.createdAt ?? .now, // sometimes crash here
             thickness: object.thickness
         )
         self.object = object

Memola/Canvas/History/History.swift

@@ -52,11 +52,23 @@ class History: ObservableObject {
         for event in redoStack {
             switch event {
             case .stroke(let _stroke):
-                withPersistence(\.backgroundContext) { context in
-                    if let stroke = _stroke.stroke(as: PenStroke.self)?.object {
-                        context.delete(stroke)
+                switch _stroke.style {
+                case .marker:
+                    guard let penStroke = _stroke.stroke(as: PenStroke.self) else { return }
+                    withPersistence(\.backgroundContext) { context in
+                        if let stroke = penStroke.object {
+                            context.delete(stroke)
+                        }
+                        try context.saveIfNeeded()
+                    }
+                case .eraser:
+                    guard let eraserStroke = _stroke.stroke(as: EraserStroke.self) else { return }
+                    withPersistence(\.backgroundContext) { context in
+                        if let stroke = eraserStroke.object {
+                            context.delete(stroke)
+                        }
+                        try context.saveIfNeeded()
                     }
-                    try context.saveIfNeeded()
                 }
             }
         }

Memola/Persistence/Objects/EraserObject.swift

@@ -13,7 +13,7 @@ final class EraserObject: NSManagedObject {
     @NSManaged var bounds: [CGFloat]
     @NSManaged var color: [CGFloat]
     @NSManaged var style: Int16
-    @NSManaged var createdAt: Date
+    @NSManaged var createdAt: Date?
     @NSManaged var thickness: CGFloat
     @NSManaged var quads: NSMutableOrderedSet
     @NSManaged var strokes: NSMutableSet

Memola/Persistence/Objects/StrokeObject.swift

@@ -13,7 +13,7 @@ final class StrokeObject: NSManagedObject {
     @NSManaged var bounds: [CGFloat]
     @NSManaged var color: [CGFloat]
     @NSManaged var style: Int16
-    @NSManaged var createdAt: Date
+    @NSManaged var createdAt: Date?
     @NSManaged var thickness: CGFloat
     @NSManaged var quads: NSMutableOrderedSet
     @NSManaged var erasers: NSMutableSet