Add Python formatter button

index.html

@@ -64,6 +64,7 @@
                 <div id="editor-bar">
                     <button class="purple-button btn-new">New<i class="fa-solid fa-plus"></i></button>
                     <button class="purple-button btn-open">Open<i class="fa-solid fa-folder-open"></i></button>
+                    <button class="purple-button btn-format">Format<i class="fa-solid fa-wand-magic-sparkles"></i></button>
                     <button class="purple-button btn-save">Save<i class="fa-solid fa-floppy-disk"></i></button>
                     <button class="purple-button btn-save-as">Save As<i class="fa-solid fa-download"></i></button>
                     <div class="file-path"></div>
@@ -85,6 +86,7 @@
                         <ul>
                             <li><a class="btn-new">New<i class="fa-solid fa-plus"></i></a></li>
                             <li><a class="btn-open">Open<i class="fa-solid fa-folder-open"></i></a></li>
+                            <li><a class="btn-format">Format<i class="fa-solid fa-wand-magic-sparkles"></i></a></li>
                             <li><a class="btn-save">Save<i class="fa-solid fa-floppy-disk"></i></a></li>
                             <li><a class="btn-save-as">Save As<i class="fa-solid fa-download"></i></a></li>
                         </ul>

js/script.js

@@ -11,6 +11,7 @@ import { xml } from "@codemirror/lang-xml";
 import { markdown } from "@codemirror/lang-markdown";
 import { syntaxHighlighting, indentUnit } from "@codemirror/language";
 import { classHighlighter } from "@lezer/highlight";
+import initRuffFormatter, { PositionEncoding, Workspace } from "@astral-sh/ruff-wasm-web";
 import { circuitpythonHighlight } from "./common/circuitpython_highlight.js";
 import { getFileIcon } from "./common/file_dialog.js";
 
@@ -40,6 +41,9 @@ let workflow = null;
 let unchanged = 0;
 let connectionPromise = null;
 let debugMessageAnsi = null;
+let formatterInitPromise = null;
+let formatterWorkspace = null;
+let currentEditorPath = null;
 
 const btnRestart = document.querySelector('.btn-restart');
 const btnHalt = document.querySelector('.btn-halt');
@@ -48,6 +52,7 @@ const btnClear = document.querySelector('.btn-clear');
 const btnConnect = document.querySelectorAll('.btn-connect');
 const btnNew = document.querySelectorAll('.btn-new');
 const btnOpen = document.querySelectorAll('.btn-open');
+const btnFormat = document.querySelectorAll('.btn-format');
 const btnSave = document.querySelectorAll('.btn-save');
 const btnSaveAs = document.querySelectorAll('.btn-save-as');
 const btnSaveRun = document.querySelectorAll('.btn-save-run');
@@ -112,6 +117,21 @@ function getFileExtensionFromPath(path) {
     return base.split(".").pop().toLowerCase();
 }
 
+function isPythonFilePath(path) {
+    if (path === null || path === undefined) {
+        return true;
+    }
+    return getFileExtensionFromPath(path) === "py";
+}
+
+function updateFormatterButtonState(path) {
+    const enabled = isPythonFilePath(path);
+    btnFormat.forEach((element) => {
+        element.disabled = !enabled;
+        element.setAttribute("aria-disabled", enabled ? "false" : "true");
+    });
+}
+
 // Pick the CodeMirror language extensions to use for a given file path.
 // Returns an array so callers can spread it directly into the editor's
 // extension list. New (untitled) docs default to Python so the editor
@@ -211,6 +231,15 @@ btnOpen.forEach((element) => {
     });
 });
 
+// Format Link/Button (Mobile and Desktop Layout)
+btnFormat.forEach((element) => {
+    element.addEventListener('click', async function(e) {
+        e.preventDefault();
+        e.stopPropagation();
+        await formatCurrentFile();
+    });
+});
+
 // Save Link/Button (Mobile and Desktop Layout)
 btnSave.forEach((element) => {
     element.addEventListener('click', async function(e) {
@@ -301,6 +330,53 @@ async function openFile() {
     }
 }
 
+async function initFormatter() {
+    if (!formatterInitPromise) {
+        formatterInitPromise = initRuffFormatter().then(() => {
+            formatterWorkspace = new Workspace(
+                {
+                    "line-length": 88,
+                    "indent-width": 4,
+                    format: {
+                        "indent-style": "space",
+                        "quote-style": "double",
+                    },
+                },
+                PositionEncoding.Utf16,
+            );
+        });
+    }
+    return formatterInitPromise;
+}
+
+async function formatCurrentFile() {
+    if (!isPythonFilePath(currentEditorPath)) {
+        await showMessage("Format is only available for Python files.");
+        return false;
+    }
+
+    try {
+        await initFormatter();
+        const contents = editor.state.doc.sliceString(0);
+        const formatted = formatterWorkspace.format(contents);
+
+        if (formatted !== contents) {
+            editor.dispatch({
+                changes: {
+                    from: 0,
+                    to: editor.state.doc.length,
+                    insert: formatted,
+                },
+            });
+        }
+        return true;
+    } catch (e) {
+        console.error("Could not format Python file", e);
+        await showMessage(`Could not format Python file. ${e.message || e}`);
+        return false;
+    }
+}
+
 async function saveFile() {
     if (await checkConnected()) {
         await workflow.saveFile();
@@ -436,6 +512,9 @@ async function checkReadOnly() {
 
 /* Update the filename and update the UI */
 function setFilename(path) {
+    currentEditorPath = path;
+    updateFormatterButtonState(path);
+
     // Refresh the CodeMirror language plugin whenever the active file
     // changes — this is the single chokepoint that all filename
     // changes route through (Open File, New File, Save As, backend

package.json

@@ -16,6 +16,7 @@
   "dependencies": {
     "@adafruit/ble-file-transfer-js": "adafruit/ble-file-transfer-js#1.0.5",
     "@adafruit/circuitpython-repl-js": "adafruit/circuitpython-repl-js#3.3.0",
+    "@astral-sh/ruff-wasm-web": "^0.15.21",
     "@codemirror/lang-css": "^6.3.1",
     "@codemirror/lang-html": "^6.4.11",
     "@codemirror/lang-javascript": "^6.2.5",