Adds undo redo

components/canvas/canvas.tsx

 import styled from "styles"
-import { getPointerEventInfo } from "utils/utils"
 import React, { useCallback, useRef } from "react"
 import useZoomEvents from "hooks/useZoomEvents"
 import useCamera from "hooks/useCamera"

components/canvas/shape.tsx

 import React, { useCallback, useRef, memo } from "react"
 import state, { useSelector } from "state"
-import { getPointerEventInfo } from "utils/utils"
 import inputs from "state/inputs"
 import shapes from "lib/shapes"
 import styled from "styles"

hooks/useKeyboardEvents.ts

 import { useEffect } from "react"
 import state from "state"
-import { getKeyboardEventInfo } from "utils/utils"
+import { getKeyboardEventInfo, isDarwin } from "utils/utils"
 
 export default function useKeyboardEvents() {
   useEffect(() => {
     function handleKeyDown(e: KeyboardEvent) {
       if (e.key === "Escape") {
         state.send("CANCELLED")
+      } else if (e.key === "z" && (isDarwin() ? e.metaKey : e.ctrlKey)) {
+        if (e.shiftKey) {
+          state.send("REDO")
+        } else {
+          state.send("UNDO")
+        }
       }
 
       state.send("PRESSED_KEY", getKeyboardEventInfo(e))

hooks/useZoomEvents.ts

 import React, { useEffect, useRef } from "react"
 import state from "state"
-import { getPointerEventInfo } from "utils/utils"
+import inputs from "state/inputs"
 import * as vec from "utils/vec"
 
 /**
       if (e.ctrlKey) {
         state.send("ZOOMED_CAMERA", {
           delta: e.deltaY,
-          ...getPointerEventInfo(e),
+          ...inputs.wheel(e),
         })
         return
       }
 
       state.send("PANNED_CAMERA", {
         delta: [e.deltaX, e.deltaY],
-        ...getPointerEventInfo(e),
+        ...inputs.wheel(e),
       })
     }
 

state/commands/translate-command.ts

 import Command from "./command"
-import history from "./history"
+import history from "../history"
 import { TranslateSnapshot } from "state/sessions/translate-session"
 import { Data } from "types"
 

state/commands/history.ts → state/history.ts

 import { Data } from "types"
-import { BaseCommand } from "./command"
+import { BaseCommand } from "./commands/command"
 
 // A singleton to manage history changes.
 

state/inputs.tsx

 import { PointerInfo } from "types"
+import { isDarwin } from "utils/utils"
 
 class Inputs {
   points: Record<string, PointerInfo> = {}
   pointerDown(e: PointerEvent | React.PointerEvent) {
     const { shiftKey, ctrlKey, metaKey, altKey } = e
 
-    this.points[e.pointerId] = {
+    const info = {
       pointerId: e.pointerId,
       origin: [e.clientX, e.clientY],
       point: [e.clientX, e.clientY],
       shiftKey,
       ctrlKey,
-      metaKey,
+      metaKey: isDarwin() ? metaKey : ctrlKey,
       altKey,
     }
 
-    return this.points[e.pointerId]
+    this.points[e.pointerId] = info
+
+    return info
   }
 
   pointerMove(e: PointerEvent | React.PointerEvent) {
-    if (this.points[e.pointerId]) {
-      this.points[e.pointerId].point = [e.clientX, e.clientY]
-      return this.points[e.pointerId]
-    }
-
     const { shiftKey, ctrlKey, metaKey, altKey } = e
 
-    return {
+    const prev = this.points[e.pointerId]
+
+    const info = {
       pointerId: e.pointerId,
-      origin: [e.clientX, e.clientY],
+      origin: prev?.origin || [e.clientX, e.clientY],
       point: [e.clientX, e.clientY],
       shiftKey,
       ctrlKey,
-      metaKey,
+      metaKey: isDarwin() ? metaKey : ctrlKey,
       altKey,
     }
+
+    if (this.points[e.pointerId]) {
+      this.points[e.pointerId] = info
+    }
+
+    return info
   }
 
   pointerUp(e: PointerEvent | React.PointerEvent) {
-    this.points[e.pointerId].point = [e.clientX, e.clientY]
+    const { shiftKey, ctrlKey, metaKey, altKey } = e
 
-    const info = this.points[e.pointerId]
+    const prev = this.points[e.pointerId]
+
+    const info = {
+      pointerId: e.pointerId,
+      origin: prev?.origin || [e.clientX, e.clientY],
+      point: [e.clientX, e.clientY],
+      shiftKey,
+      ctrlKey,
+      metaKey: isDarwin() ? metaKey : ctrlKey,
+      altKey,
+    }
 
     delete this.points[e.pointerId]
 
     return info
   }
+
+  wheel(e: WheelEvent) {
+    const { shiftKey, ctrlKey, metaKey, altKey } = e
+    return { point: [e.clientX, e.clientY], shiftKey, ctrlKey, metaKey, altKey }
+  }
 }
 
 export default new Inputs()

state/state.ts

 import { Bounds, Data, PointerInfo, Shape, ShapeType } from "types"
 import { defaultDocument } from "./data"
 import Shapes from "lib/shapes"
+import history from "state/history"
 import * as Sessions from "./sessions"
 
 const initialData: Data = {
   initial: "selecting",
   states: {
     selecting: {
+      on: {
+        UNDO: { do: "undo" },
+        REDO: { do: "redo" },
+      },
       initial: "notPointing",
       states: {
         notPointing: {
     },
   },
   actions: {
+    // History
+    enableHistory() {
+      history.enable()
+    },
+    disableHistory() {
+      history.disable()
+    },
+    undo(data) {
+      history.undo(data)
+    },
+    redo(data) {
+      history.redo(data)
+    },
+
+    // Sessions
     cancelSession(data) {
       session.cancel(data)
       session = undefined
       session.complete(data)
       session = undefined
     },
+
     // Brushing
     startBrushSession(data, payload: { point: number[] }) {
       session = new Sessions.BrushSession(

utils/utils.ts

   return await d.json()
 }
 
-export function getPointerEventInfo(
-  e: PointerEvent | React.PointerEvent | WheelEvent
-) {
+export function getKeyboardEventInfo(e: KeyboardEvent | React.KeyboardEvent) {
   const { shiftKey, ctrlKey, metaKey, altKey } = e
-  return { point: [e.clientX, e.clientY], shiftKey, ctrlKey, metaKey, altKey }
+  return {
+    key: e.key,
+    shiftKey,
+    ctrlKey,
+    metaKey: isDarwin() ? metaKey : ctrlKey,
+    altKey,
+  }
 }
 
-export function getKeyboardEventInfo(e: KeyboardEvent | React.KeyboardEvent) {
-  const { shiftKey, ctrlKey, metaKey, altKey } = e
-  return { key: e.key, shiftKey, ctrlKey, metaKey, altKey }
+export function isDarwin() {
+  return /Mac|iPod|iPhone|iPad/.test(window.navigator.platform)
 }