Improve the terminal's navigation

wasm/demo/package.json

@@ -5,6 +5,7 @@
     "main": "index.js",
     "dependencies": {
         "codemirror": "^5.42.0",
+        "local-echo": "^0.2.0",
         "xterm": "^3.8.0"
     },
     "devDependencies": {
@@ -14,11 +15,11 @@
         "html-webpack-plugin": "^3.2.0",
         "mini-css-extract-plugin": "^0.5.0",
         "raw-loader": "^1.0.0",
+        "serve": "^11.0.2",
+        "start-server-and-test": "^1.7.11",
         "webpack": "^4.16.3",
         "webpack-cli": "^3.1.0",
-        "webpack-dev-server": "^3.1.5",
-        "start-server-and-test": "^1.7.11",
-        "serve": "^11.0.2"
+        "webpack-dev-server": "^3.1.5"
     },
     "scripts": {
         "dev": "webpack-dev-server -d",

wasm/demo/src/main.js

@@ -3,6 +3,7 @@ import CodeMirror from 'codemirror';
 import 'codemirror/mode/python/python';
 import 'codemirror/addon/comment/comment';
 import { Terminal } from 'xterm';
+import LocalEchoController from 'local-echo';
 
 // so people can play around with it
 window.rp = rp;
@@ -35,7 +36,7 @@ function runCodeFromTextarea() {
 
     const code = editor.getValue();
     try {
-        const result = rp.pyEval(code, {
+        rp.pyEval(code, {
             stdout: output => {
                 const shouldScroll =
                     consoleElement.scrollHeight - consoleElement.scrollTop ===
@@ -46,9 +47,6 @@ function runCodeFromTextarea() {
                 }
             }
         });
-        if (result !== null) {
-            consoleElement.value += `\n${result}\n`;
-        }
     } catch (err) {
         if (err instanceof WebAssembly.RuntimeError) {
             err = window.__RUSTPYTHON_ERROR || err;
@@ -82,24 +80,16 @@ snippets.addEventListener('change', updateSnippet);
 // option selected for the `select`, but the textarea won't be updated)
 updateSnippet();
 
-function removeNonAscii(str) {
-    if (str === null || str === '') return false;
-    else str = str.toString();
-
-    return str.replace(/[^\x20-\x7E]/g, '');
-}
-
-function printToConsole(data) {
-    term.write(removeNonAscii(data) + '\r\n');
-}
-
 const term = new Terminal();
 term.open(document.getElementById('terminal'));
 
-const terminalVM = rp.vmStore.init('term_vm');
-terminalVM.setStdout(printToConsole);
+const localEcho = new LocalEchoController(term);
 
-function getPrompt(name = 'ps1') {
+const terminalVM = rp.vmStore.init('term_vm');
+
+terminalVM.setStdout(data => localEcho.println(data));
+
+function getPrompt(name) {
     terminalVM.exec(`
 try:
     import sys as __sys
@@ -112,64 +102,37 @@ finally:
     return String(terminalVM.eval('__prompt'));
 }
 
-term.write(getPrompt());
+async function readPrompts() {
+    let continuing = false;
 
-function resetInput() {
-    continuedInput = [];
-    input = '';
-    continuing = false;
-}
-
-let continuedInput, input, continuing;
-resetInput();
-
-let ps2;
-
-term.on('data', data => {
-    const code = data.charCodeAt(0);
-    if (code == 13) {
-        // CR
-        term.write('\r\n');
-        continuedInput.push(input);
+    while (true) {
+        const ps1 = getPrompt('ps1');
+        const ps2 = getPrompt('ps2');
+        let input;
         if (continuing) {
-            if (input === '') {
-                continuing = false;
-            } else {
-                input = '';
-                term.write(ps2);
-                return;
-            }
+            const prom = localEcho.read(ps2, ps2);
+            localEcho._activePrompt.prompt = ps1;
+            localEcho._input = localEcho.history.entries.pop() + '\n';
+            localEcho._cursor = localEcho._input.length;
+            localEcho._active = true;
+            input = await prom;
+            if (!input.endsWith('\n')) continue;
+        } else {
+            input = await localEcho.read(ps1, ps2);
         }
         try {
-            terminalVM.execSingle(continuedInput.join('\n'));
+            terminalVM.execSingle(input);
         } catch (err) {
             if (err instanceof SyntaxError && err.message.includes('EOF')) {
-                ps2 = getPrompt('ps2');
-                term.write(ps2);
                 continuing = true;
-                input = '';
-                return;
+                continue;
             } else if (err instanceof WebAssembly.RuntimeError) {
                 err = window.__RUSTPYTHON_ERROR || err;
             }
-            printToConsole(err);
+            localEcho.println(err);
         }
-        resetInput();
-        term.write(getPrompt());
-    } else if (code == 127 || code == 8) {
-        // Backspace
-        if (input.length > 0) {
-            term.write('\b \b');
-            input = input.slice(0, -1);
-        }
-    } else if (code < 32) {
-        // Control
-        term.write('\r\n' + getPrompt());
-        input = '';
-        continuedInput = [];
-    } else {
-        // Visible
-        term.write(data);
-        input += data;
+        continuing = false;
     }
-});
+}
+
+readPrompts().catch(err => console.error(err));