co-mono/packages/tui/test/editor.test.ts

import assert from "node:assert";
import { describe, it } from "node:test";
import { Editor } from "../src/components/editor.js";

describe("Editor component", () => {
	describe("Unicode text editing behavior", () => {
		it("inserts mixed ASCII, umlauts, and emojis as literal text", () => {
			const editor = new Editor();

			editor.handleInput("H");
			editor.handleInput("e");
			editor.handleInput("l");
			editor.handleInput("l");
			editor.handleInput("o");
			editor.handleInput(" ");
			editor.handleInput("ä");
			editor.handleInput("ö");
			editor.handleInput("ü");
			editor.handleInput(" ");
			editor.handleInput("😀");

			const text = editor.getText();
			assert.strictEqual(text, "Hello äöü 😀");
		});

		it("deletes single-code-unit unicode characters (umlauts) with Backspace", () => {
			const editor = new Editor();

			editor.handleInput("ä");
			editor.handleInput("ö");
			editor.handleInput("ü");

			// Delete the last character (ü)
			editor.handleInput("\x7f"); // Backspace

			const text = editor.getText();
			assert.strictEqual(text, "äö");
		});

		it("deletes multi-code-unit emojis with repeated Backspace", () => {
			const editor = new Editor();

			editor.handleInput("😀");
			editor.handleInput("👍");

			// Delete the last emoji (👍) - requires 2 backspaces since emojis are 2 code units
			editor.handleInput("\x7f"); // Backspace
			editor.handleInput("\x7f"); // Backspace

			const text = editor.getText();
			assert.strictEqual(text, "😀");
		});

		it("inserts characters at the correct position after cursor movement over umlauts", () => {
			const editor = new Editor();

			editor.handleInput("ä");
			editor.handleInput("ö");
			editor.handleInput("ü");

			// Move cursor left twice
			editor.handleInput("\x1b[D"); // Left arrow
			editor.handleInput("\x1b[D"); // Left arrow

			// Insert 'x' in the middle
			editor.handleInput("x");

			const text = editor.getText();
			assert.strictEqual(text, "äxöü");
		});

		it("moves cursor in code units across multi-code-unit emojis before insertion", () => {
			const editor = new Editor();

			editor.handleInput("😀");
			editor.handleInput("👍");
			editor.handleInput("🎉");

			// Move cursor left over last emoji (🎉)
			editor.handleInput("\x1b[D"); // Left arrow
			editor.handleInput("\x1b[D"); // Left arrow

			// Move cursor left over second emoji (👍)
			editor.handleInput("\x1b[D");
			editor.handleInput("\x1b[D");

			// Insert 'x' between first and second emoji
			editor.handleInput("x");

			const text = editor.getText();
			assert.strictEqual(text, "😀x👍🎉");
		});

		it("preserves umlauts across line breaks", () => {
			const editor = new Editor();

			editor.handleInput("ä");
			editor.handleInput("ö");
			editor.handleInput("ü");
			editor.handleInput("\n"); // new line
			editor.handleInput("Ä");
			editor.handleInput("Ö");
			editor.handleInput("Ü");

			const text = editor.getText();
			assert.strictEqual(text, "äöü\nÄÖÜ");
		});

		it("replaces the entire document with unicode text via setText (paste simulation)", () => {
			const editor = new Editor();

			// Simulate bracketed paste / programmatic replacement
			editor.setText("Hällö Wörld! 😀 äöüÄÖÜß");

			const text = editor.getText();
			assert.strictEqual(text, "Hällö Wörld! 😀 äöüÄÖÜß");
		});

		it("moves cursor to document start on Ctrl+A and inserts at the beginning", () => {
			const editor = new Editor();

			editor.handleInput("a");
			editor.handleInput("b");
			editor.handleInput("\x01"); // Ctrl+A (move to start)
			editor.handleInput("x"); // Insert at start

			const text = editor.getText();
			assert.strictEqual(text, "xab");
		});
	});
});