Watch buffer file for changes, and automatically reload it if changed (#76)

* Implement Buffer class in main process that watches for changes to the file, and notifies the editor in the renderer process so that it can update the buffer.

* Add Editor.setReadOnly() method

* Add dummy onChangeCallback function

* Remove debug logging

electron/main/buffer.js

@@ -1,6 +1,8 @@
 import fs from "fs"
-import { join } from "path"
+import { join, dirname, basename } from "path"
 import { app } from "electron"
+import * as jetpack from "fs-jetpack";
+
 import CONFIG from "../config"
 import { isDev } from "../detect-platform"
 
@@ -21,3 +23,60 @@ export function getBufferFilePath() {
         return bufferFilePath
     }
 }
+
+
+export class Buffer {
+    constructor({filePath, onChange}) {
+        this.filePath = filePath
+        this.onChange = onChange
+        this.watcher = null
+        this.setupWatcher()
+        this._lastSavedContent = null
+    }
+
+    async load() {
+        const content = await jetpack.read(this.filePath, 'utf8')
+        this.setupWatcher()
+        return content
+    }
+
+    async save(content) {
+        this._lastSavedContent = content
+        const saveResult = await jetpack.write(this.filePath, content, {
+            atomic: true,
+            mode: '600',
+        })
+        return saveResult
+    }
+
+    exists() {
+        return jetpack.exists(this.filePath) === "file"
+    }
+
+    setupWatcher() {
+        if (!this.watcher && this.exists()) {
+            this.watcher = fs.watch(
+                dirname(this.filePath), 
+                {
+                    persistent: true,
+                    recursive: false,
+                    encoding: "utf8",
+                },
+                async (eventType, filename) => {
+                    if (filename !== basename(this.filePath)) {
+                        return
+                    }
+                    
+                    // read the file content and compare it to the last saved content
+                    // (if the content is the same, then we can ignore the event)
+                    const content = await jetpack.read(this.filePath, 'utf8')
+
+                    if (this._lastSavedContent !== content) {
+                        // file has changed on disk, trigger onChange
+                        this.onChange({filename, eventType, content})
+                    }
+                }
+            )
+        }
+    }
+}

electron/main/index.ts

@@ -11,7 +11,7 @@ import { onBeforeInputEvent } from "../keymap"
 import { isDev } from '../detect-platform';
 import { initializeAutoUpdate, checkForUpdates } from './auto-update';
 import { fixElectronCors } from './cors';
-import { getBufferFilePath } from './buffer';
+import { getBufferFilePath, Buffer } from './buffer';
 
 
 // The built directory structure
@@ -210,20 +210,24 @@ ipcMain.handle('dark-mode:set', (event, mode) => {
 
 ipcMain.handle('dark-mode:get', () => nativeTheme.themeSource)
 
+
+const buffer = new Buffer({
+    filePath: getBufferFilePath(), 
+    onChange: (eventData) => {
+        win?.webContents.send("buffer-content:change", eventData)
+    },
+})
+
 ipcMain.handle('buffer-content:load', async () => {
-    let bufferPath = getBufferFilePath()
-    if (jetpack.exists(bufferPath) === "file") {
-        return await jetpack.read(bufferPath, 'utf8')
+    if (buffer.exists()) {
+        return await buffer.load()
     } else {
         return isDev? initialDevContent : initialContent
     }
 });
 
 async function save(content) {
-    return await jetpack.write(getBufferFilePath(), content, {
-        atomic: true,
-        mode: '600',
-    })
+    return await buffer.save(content)
 }
 
 ipcMain.handle('buffer-content:save', async (event, content) =>  {

electron/preload/index.ts

@@ -53,6 +53,10 @@ contextBridge.exposeInMainWorld("heynote", {
         async saveAndQuit(content) {
             return await ipcRenderer.invoke("buffer-content:saveAndQuit", content)
         },
+
+        onChangeCallback(callback) {
+            ipcRenderer.on("buffer-content:change", callback)
+        },
     },
 
     settings: CONFIG.get("settings"),

src/components/Editor.vue

@@ -21,6 +21,8 @@
             },
         },
 
+        components: {},
+
         data() {
             return {
                 syntaxTreeDebugContent: null,
@@ -44,11 +46,16 @@
 
             // load buffer content and create editor
             window.heynote.buffer.load().then((content) => {
+                let diskContent = content
                 this.editor = new HeynoteEditor({
                     element: this.$refs.editor,
                     content: content,
                     theme: this.theme,
                     saveFunction: (content) => {
+                        if (content === diskContent) {
+                            return
+                        }
+                        diskContent = content
                         window.heynote.buffer.save(content)
                     },
                     keymap: this.keymap,
@@ -57,6 +64,12 @@
                 })
                 window._heynote_editor = this.editor
                 window.document.addEventListener("currenciesLoaded", this.onCurrenciesLoaded)
+
+                // set up buffer change listener
+                window.heynote.buffer.onChangeCallback((event, {filename, content, eventType}) => {
+                    diskContent = content
+                    this.editor.setContent(content)
+                })
             })
             // set up window close handler that will save the buffer and quit
             window.heynote.onWindowClose(() => {
@@ -142,7 +155,7 @@
     </div>
 </template>
 
-<style lang="sass">
+<style lang="sass" scoped>
     .debug-syntax-tree
         position: absolute
         top: 0

src/editor/editor.js

@@ -48,6 +48,7 @@ export class HeynoteEditor {
         this.lineNumberCompartmentPre = new Compartment
         this.lineNumberCompartment = new Compartment
         this.foldGutterCompartment = new Compartment
+        this.readOnlyCompartment = new Compartment
         this.deselectOnCopy = keymap === "emacs"
 
         const state = EditorState.create({
@@ -60,6 +61,8 @@ export class HeynoteEditor {
                 this.lineNumberCompartment.of(showLineNumberGutter ? [lineNumbers(), blockLineNumbers] : []),
                 customSetup, 
                 this.foldGutterCompartment.of(showFoldGutter ? [foldGutter()] : []),
+
+                this.readOnlyCompartment.of([]),
                 
                 this.themeCompartment.of(theme === "dark" ? heynoteDark : heynoteLight),
                 heynoteBase,
@@ -135,6 +138,12 @@ export class HeynoteEditor {
         this.view.focus()
     }
 
+    setReadOnly(readOnly) {
+        this.view.dispatch({
+            effects: this.readOnlyCompartment.reconfigure(readOnly ? [EditorState.readOnly.of(true)] : []),
+        })
+    }
+
     setTheme(theme) {
         this.view.dispatch({
             effects: this.themeCompartment.reconfigure(theme === "dark" ? heynoteDark : heynoteLight),

webapp/bridge.js

@@ -47,6 +47,10 @@ const Heynote = {
         async saveAndQuit(content) {
             
         },
+
+        onChangeCallback(callback) {
+            
+        },
     },
 
     onWindowClose(callback) {