scroll/src/common/editor/editor.ts

import Ansi from './ansi.ts';
import Buffer from './buffer.ts';
import {
	ctrl_key,
	importDefaultForRuntime,
	ITerminalSize,
	truncate,
	VERSION,
} from '../mod.ts';

export class Editor {
	#buffer: Buffer;
	#screenRows: number;
	#screenCols: number;
	constructor(terminalSize: ITerminalSize) {
		this.#buffer = new Buffer();
		this.#screenRows = terminalSize.rows;
		this.#screenCols = terminalSize.cols;
	}

	/**
	 * Determine what to do based on input
	 * @param input - the decoded chunk of stdin
	 */
	public processKeyPress(input: string): boolean {
		switch (input) {
			case ctrl_key('q'):
				this.clearScreen().then(() => {});
				return false;

			default:
				return true;
		}
	}

	// -------------------------------------------------------------------------------------------------------------------
	// Terminal Output / Drawing
	// -------------------------------------------------------------------------------------------------------------------

	/**
	 * Clear the screen and write out the buffer
	 */
	public async refreshScreen(): Promise<void> {
		this.#buffer.append(Ansi.HideCursor);
		this.#buffer.append(Ansi.ResetCursor);
		this.drawRows();
		this.#buffer.append(Ansi.ShowCursor);

		await this.writeToScreen();
	}

	private async clearScreen(): Promise<void> {
		this.#buffer.append(Ansi.ClearScreen);
		this.#buffer.append(Ansi.ResetCursor);

		await this.writeToScreen();
	}

	private drawRows(): void {
		this.drawPlaceholderRows();
	}

	private drawPlaceholderRows(): void {
		for (let y = 0; y < this.#screenRows; y++) {
			if (y === Math.trunc(this.#screenRows / 2)) {
				const message = `Kilo editor -- version ${VERSION}`;
				const messageLen = (message.length > this.#screenCols) ? this.#screenCols : message.length;
				let padding = Math.trunc((this.#screenCols - messageLen) / 2);
				if (padding > 0) {
					this.#buffer.append('~');
					padding -= 1;

					this.#buffer.append(' '.repeat(padding));
				}

				this.#buffer.append(truncate(message, messageLen));
			} else {
				this.#buffer.append('~');
			}

			this.#buffer.append(Ansi.ClearLine);
			if (y < this.#screenRows - 1) {
				this.#buffer.appendLine('');
			}
		}
	}

	private async writeToScreen(): Promise<void> {
		const io = await importDefaultForRuntime('terminal_io');

		await io.write(this.#buffer.getBuffer());
		this.#buffer.clear();
	}
}