From a258592054140b9fa524208c0bdbcc2d141d00fa Mon Sep 17 00:00:00 2001
From: Michael Peters <michael@styx>
Date: Sat, 27 Jan 2024 12:40:13 -0800
Subject: [PATCH] undo/redo

---
 src/components/grid/grid.tsx | 97 ++++++++++++++++++++++++++----------
 1 file changed, 72 insertions(+), 25 deletions(-)

diff --git a/src/components/grid/grid.tsx b/src/components/grid/grid.tsx
index 3974165..35c2ffb 100644
--- a/src/components/grid/grid.tsx
+++ b/src/components/grid/grid.tsx
@@ -1,5 +1,12 @@
 import { useMouse, useWindowSize } from '@uidotdev/usehooks';
-import { FC, MouseEvent, useCallback, useMemo, useState } from 'react';
+import {
+    FC,
+    KeyboardEvent,
+    MouseEvent,
+    useCallback,
+    useMemo,
+    useState,
+} from 'react';
 
 import './grid.scss';
 
@@ -51,7 +58,6 @@ function useMouseInRange(range: Range): Point {
 const Grid: FC = () => {
     const GAP = 20;
 
-    // const [offset, setOffset] = useState<Point>({ x: GAP / 2, y: GAP / 2 });
     const [offset, setOffset] = useState<Point>({ x: 10, y: 10 });
     const range = useRange(offset);
     const mousePoint = useMouseInRange(range);
@@ -71,8 +77,68 @@ const Grid: FC = () => {
     }, [range, GAP]);
 
     const [userLines, setUserLines] = useState<Range[]>([]);
+    const [userRedoLines, setUserRedoLines] = useState<Range[]>([]);
     const [userStartPoint, setUserStartPoint] = useState<Point | null>(null);
 
+    // mouse clicks create lines
+    const onGridClick = useCallback(
+        (event: MouseEvent<SVGSVGElement>) => {
+            const point = snapToGrid(mousePoint, GAP);
+
+            setUserRedoLines([]);
+
+            if (lodash.isEqual(userStartPoint, point)) return;
+            if (lodash.isNull(userStartPoint)) {
+                setUserStartPoint(point);
+                return;
+            }
+
+            const line = pointsToRange(userStartPoint, point);
+            setUserLines([...userLines, line]);
+
+            if (event.shiftKey == false) {
+                setUserStartPoint(null);
+            } else {
+                setUserStartPoint(point);
+            }
+        },
+        [userStartPoint, setUserStartPoint, setUserLines, GAP, mousePoint]
+    );
+
+    const onGridRightClick = useCallback(
+        (event: MouseEvent<SVGSVGElement>) => {
+            event.preventDefault(); // disable default context menu
+
+            setUserStartPoint(null);
+        },
+        [setUserStartPoint]
+    );
+
+    // ctrl+z/ctrl+y for undo/redo
+    const onUndo = useCallback(() => {
+        const line = userLines.at(-1);
+        if (!line) return;
+
+        setUserLines(userLines.slice(0, -1));
+        setUserRedoLines([...userRedoLines, line]);
+    }, [userLines, setUserLines, userRedoLines, setUserRedoLines]);
+
+    const onRedo = useCallback(() => {
+        const line = userRedoLines.at(-1);
+        if (!line) return;
+
+        setUserRedoLines(userRedoLines.slice(0, -1));
+        setUserLines([...userLines, line]);
+    }, [userLines, setUserLines, userRedoLines, setUserRedoLines]);
+
+    const onGridKeyDown = useCallback(
+        (event: KeyboardEvent<SVGSVGElement>) => {
+            if (event.key == 'z' && event.ctrlKey) onUndo();
+            if (event.key == 'y' && event.ctrlKey) onRedo();
+        },
+        [onUndo, onRedo]
+    );
+
     const gridLineElements = useMemo(() => {
         return gridLines.map((line, idx) => (
             <line
@@ -130,28 +196,6 @@ const Grid: FC = () => {
         ));
     }, [userLines]);
 
-    const onGridClick = useCallback(
-        (event: MouseEvent<SVGSVGElement>) => {
-            const point = snapToGrid(mousePoint, GAP);
-
-            if (lodash.isEqual(userStartPoint, point)) return;
-            if (lodash.isNull(userStartPoint)) {
-                setUserStartPoint(point);
-                return;
-            }
-
-            const line = pointsToRange(userStartPoint, point);
-            setUserLines([...userLines, line]);
-
-            if (event.shiftKey == false) {
-                setUserStartPoint(null);
-            } else {
-                setUserStartPoint(point);
-            }
-        },
-        [userStartPoint, setUserStartPoint, setUserLines, GAP, mousePoint]
-    );
-
     return (
         <svg
             className="grid"
@@ -159,7 +203,10 @@ const Grid: FC = () => {
             viewBox={`${range.x0} ${range.y0} ${range.x1 - range.x0} ${
                 range.y1 - range.y0
             }`}
-            onClick={onGridClick}
+            tabIndex={0} // to support onKeyDown event
+            onMouseDown={onGridClick}
+            onContextMenu={onGridRightClick}
+            onKeyDown={onGridKeyDown}
         >
             {gridLineElements}
             {userLineElements}