scroll/src/common/editor.ts

import Ansi, { KeyCommand } from './ansi.ts';
import Buffer from './buffer.ts';
import Document from './document.ts';
import Row from './row.ts';

import { SCROLL_QUIT_TIMES, SCROLL_VERSION } from './config.ts';
import {
	ctrlKey,
	isControl,
	maxAdd,
	none,
	posSub,
	readKey,
	some,
	truncate,
} from './fns.ts';
import { getRuntime, log, LogLevel } from './runtime.ts';
import { ITerminalSize, Position } from './types.ts';

class Editor {
	/**
	 * The document being edited
	 * @private
	 */
	#document: Document;
	/**
	 * The output buffer for the terminal
	 * @private
	 */
	#buffer: Buffer;
	/**
	 * The size of the screen in rows/columns
	 * @private
	 */
	#screen: ITerminalSize;
	/**
	 * The current location of the mouse cursor
	 * @private
	 */
	#cursor: Position;
	/**
	 * The current scrolling offset
	 */
	#offset: Position;
	/**
	 * The scrolling offset for the rendered row
	 * @private
	 */
	#renderX: number = 0;
	/**
	 * The name of the currently open file
	 * @private
	 */
	#filename: string = '';
	/**
	 * A message to display at the bottom of the screen
	 * @private
	 */
	#statusMessage: string = '';
	/**
	 * Timeout for status messages
	 * @private
	 */
	#statusTimeout: number = 0;
	/**
	 * The number of times required to quit a dirty document
	 * @private
	 */
	#quitTimes: number = SCROLL_QUIT_TIMES;

	constructor(terminalSize: ITerminalSize) {
		this.#buffer = new Buffer();

		// Subtract two rows from the terminal size
		// for displaying the status bar
		// and message bar
		this.#screen = terminalSize;
		this.#screen.rows -= 2;

		this.#cursor = Position.default();
		this.#offset = Position.default();
		this.#document = Document.default();
	}

	private get numRows(): number {
		return this.#document.numRows;
	}

	private get currentRow(): Row | null {
		return this.#document.row(this.#cursor.y);
	}

	public async open(filename: string): Promise<Editor> {
		await this.#document.open(filename);
		this.#filename = filename;

		return this;
	}

	public async save(): Promise<void> {
		if (this.#filename === '') {
			const filename = await this.prompt('Save as: %s (ESC to cancel)');
			if (filename === null) {
				this.setStatusMessage('Save aborted');
				return;
			}

			this.#filename = filename;
		}

		await this.#document.save(this.#filename);
		this.setStatusMessage(`${this.#filename} was saved to disk.`);
	}

	// --------------------------------------------------------------------------
	// Command/input mapping
	// --------------------------------------------------------------------------

	/**
	 * Determine what to do based on input
	 * @param input - the decoded chunk of stdin
	 */
	public async processKeyPress(input: string): Promise<boolean> {
		switch (input) {
			// ----------------------------------------------------------------------
			// Ctrl-key chords
			// ----------------------------------------------------------------------
			case ctrlKey('f'):
				await this.find();
				break;

			case ctrlKey('s'):
				await this.save();
				break;

			case ctrlKey('q'):
				if (this.#quitTimes > 0 && this.#document.dirty) {
					this.setStatusMessage(
						'WARNING!!! File has unsaved changes. ' +
							`Press Ctrl-Q ${this.#quitTimes} more times to quit.`,
					);
					this.#quitTimes--;
					return true;
				}
				await this.clearScreen();
				return false;

			// ----------------------------------------------------------------------
			// Movement keys
			// ----------------------------------------------------------------------

			case KeyCommand.Home:
				this.#cursor.x = 0;
				break;

			case KeyCommand.End:
				if (this.currentRow !== null) {
					this.#cursor.x = this.currentRow.size;
				}
				break;

			case KeyCommand.PageUp:
			case KeyCommand.PageDown:
				{
					if (input === KeyCommand.PageUp) {
						this.#cursor.y = this.#offset.y;
					} else if (input === KeyCommand.PageDown) {
						this.#cursor.y = maxAdd(
							this.#offset.y,
							this.#screen.rows - 1,
							this.numRows,
						);
					}

					let times = this.#screen.rows;
					while (times--) {
						this.moveCursor(
							input === KeyCommand.PageUp
								? KeyCommand.ArrowUp
								: KeyCommand.ArrowDown,
						);
					}
				}
				break;

			case KeyCommand.ArrowUp:
			case KeyCommand.ArrowDown:
			case KeyCommand.ArrowRight:
			case KeyCommand.ArrowLeft:
				this.moveCursor(input);
				break;

			// ----------------------------------------------------------------------
			// Text manipulation keys
			// ----------------------------------------------------------------------

			case KeyCommand.Enter:
				this.#document.insertNewline(this.#cursor);
				this.#cursor.x = 0;
				this.#cursor.y++;
				break;

			case KeyCommand.Delete:
				this.#document.delete(this.#cursor);
				break;

			case KeyCommand.Backspace:
				{
					if (this.#cursor.x > 0 || this.#cursor.y > 0) {
						this.moveCursor(KeyCommand.ArrowLeft);
						this.#document.delete(this.#cursor);
					}
				}
				break;

			// ----------------------------------------------------------------------
			// Direct input
			// ----------------------------------------------------------------------

			default: {
				if (!this.shouldFilter(input)) {
					this.#document.insert(this.#cursor, input);
					this.#cursor.x++;
				}
			}
		}

		if (this.#quitTimes < SCROLL_QUIT_TIMES) {
			this.#quitTimes = SCROLL_QUIT_TIMES;
			this.setStatusMessage('');
		}

		return true;
	}

	public async prompt(
		p: string,
		callback?: (query: string, char: string) => void,
	): Promise<string | null> {
		const { term } = await getRuntime();

		let res = '';
		const maybeCallback = (query: string, char: string) => {
			if (callback !== undefined) {
				callback(query, char);
			}
		};

		outer: while (true) {
			if (p.includes('%s')) {
				this.setStatusMessage(p.replace('%s', res));
			} else {
				this.setStatusMessage(`${p}${res}`);
			}

			await this.refreshScreen();
			for await (const chunk of term.inputLoop()) {
				const char = readKey(chunk);
				if (none(char)) {
					continue;
				}

				switch (char) {
					// Remove the last character from the prompt input
					case KeyCommand.Backspace:
					case KeyCommand.Delete:
						res = truncate(res, res.length - 1);
						maybeCallback(res, char);
						continue outer;

					// End the prompt
					case KeyCommand.Escape:
						this.setStatusMessage('');
						maybeCallback(res, char);

						return null;

					// Return the input and end the prompt
					case KeyCommand.Enter:
						if (res.length > 0) {
							this.setStatusMessage('');
							maybeCallback(res, char);
							return res;
						}
						break;

					// Add to the prompt result
					default:
						if (!isControl(char)) {
							res += char;
						}
				}

				maybeCallback(res, char);
			}
		}
	}

	/**
	 * Find text within the document. This is roughly equivalent to the
	 * `editorFindCallback` function in the kilo tutorial.
	 */
	public async find(): Promise<void> {
		const savedCursor = Position.from(this.#cursor);
		const savedOffset = Position.from(this.#offset);

		const query = await this.prompt(
			'Search: %s (Use ESC/Arrows/Enter)',
			(query: string, key: string) => {
				if (key === KeyCommand.Enter || key === KeyCommand.Escape) {
					if (key === KeyCommand.Escape) {
						this.#document.resetFind();
					}
					return null;
				}

				if (some(query) && query.length > 0) {
					const pos = this.#document.find(query, key);
					if (pos !== null) {
						// We have a match here
						this.#cursor = pos;
						this.scroll();
					} else {
						this.setStatusMessage('Not found');
					}
				}
			},
		);

		// Return to document position before search
		// when you cancel the search (press the escape key)
		if (query === null) {
			this.#cursor = Position.from(savedCursor);
			this.#offset = Position.from(savedOffset);
		}
	}

	/**
	 * Filter out any additional unwanted keyboard input
	 *
	 * @param input
	 * @private
	 */
	private shouldFilter(input: string): boolean {
		const isEscapeSequence = input[0] === KeyCommand.Escape;
		const isCtrl = isControl(input);
		const shouldFilter = isEscapeSequence || isCtrl;
		const whitelist = ['\t'];

		if (shouldFilter && !whitelist.includes(input)) {
			log({
				'msg': `Ignoring input: ${input}`,
				isEscapeSequence,
				isCtrl,
			}, LogLevel.Debug);

			return true;
		}

		return false;
	}

	private moveCursor(char: string): void {
		switch (char) {
			case KeyCommand.ArrowLeft:
				if (this.#cursor.x > 0) {
					this.#cursor.x--;
				} else if (this.#cursor.y > 0) {
					this.#cursor.y--;
					this.#cursor.x = (this.currentRow !== null)
						? this.currentRow.size
						: 0;
				}
				break;
			case KeyCommand.ArrowRight:
				if (
					this.currentRow !== null && this.#cursor.x < this.currentRow.size
				) {
					this.#cursor.x++;
				} else if (
					this.currentRow !== null &&
					this.#cursor.x === this.currentRow.size
				) {
					this.#cursor.y++;
					this.#cursor.x = 0;
				}
				break;
			case KeyCommand.ArrowUp:
				if (this.#cursor.y > 0) {
					this.#cursor.y--;
				}
				break;
			case KeyCommand.ArrowDown:
				if (this.#cursor.y < this.numRows) {
					this.#cursor.y++;
				}
				break;
		}

		const rowLen = this.currentRow?.size ?? 0;
		if (this.#cursor.x > rowLen) {
			this.#cursor.x = rowLen;
		}
	}

	private scroll(): void {
		this.#renderX = 0;
		if (this.currentRow !== null) {
			this.#renderX = this.currentRow.cxToRx(this.#cursor.x);
		}

		if (this.#cursor.y < this.#offset.y) {
			this.#offset.y = this.#cursor.y;
		}
		if (this.#cursor.y >= this.#offset.y + this.#screen.rows) {
			this.#offset.y = this.#cursor.y - this.#screen.rows + 1;
		}
		if (this.#renderX < this.#offset.x) {
			this.#offset.x = this.#renderX;
		}
		if (this.#renderX >= this.#offset.x + this.#screen.cols) {
			this.#offset.x = this.#renderX - this.#screen.cols + 1;
		}
	}

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

	public setStatusMessage(msg: string): void {
		// TODO: consider some sort of formatting for passed strings
		this.#statusMessage = msg;
		this.#statusTimeout = Date.now();
	}

	/**
	 * Clear the screen and write out the buffer
	 */
	public async refreshScreen(): Promise<void> {
		this.scroll();
		this.#buffer.append(Ansi.HideCursor);
		this.#buffer.append(Ansi.ResetCursor);
		this.drawRows();
		this.drawStatusBar();
		this.drawMessageBar();
		this.#buffer.append(
			Ansi.moveCursor(
				this.#cursor.y - this.#offset.y,
				this.#renderX - this.#offset.x,
			),
		);
		this.#buffer.append(Ansi.ShowCursor);

		await this.#buffer.flush();
	}

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

		await this.#buffer.flush();
	}

	private drawRows(): void {
		for (let y = 0; y < this.#screen.rows; y++) {
			this.#buffer.append(Ansi.ClearLine);
			const fileRow = y + this.#offset.y;
			if (fileRow >= this.numRows) {
				this.drawPlaceholderRow(fileRow);
			} else {
				this.drawFileRow(fileRow);
			}

			this.#buffer.appendLine();
		}
	}

	private drawFileRow(y: number): void {
		const row = this.#document.row(y);
		if (row === null) {
			log(`Trying to draw non-existent row '${y}'`, LogLevel.Warning);
			return this.drawPlaceholderRow(y);
		}

		const len = Math.min(
			posSub(row.rsize, this.#offset.x),
			this.#screen.cols,
		);

		this.#buffer.append(row.render(this.#offset.x, len));
	}

	private drawPlaceholderRow(y: number): void {
		if (y === Math.trunc(this.#screen.rows / 2) && this.#document.isEmpty()) {
			const message = `Scroll editor -- version ${SCROLL_VERSION}`;
			const messageLen = (message.length > this.#screen.cols)
				? this.#screen.cols
				: message.length;
			let padding = Math.trunc((this.#screen.cols - messageLen) / 2);
			if (padding > 0) {
				this.#buffer.append('~');
				padding -= 1;

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

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

	private drawStatusBar(): void {
		this.#buffer.append(Ansi.InvertColor);
		const name = (this.#filename !== '') ? this.#filename : '[No Name]';
		const modified = (this.#document.dirty) ? '(modified)' : '';
		const status = `${truncate(name, 20)} - ${this.numRows} lines ${modified}`;
		const rStatus = `${this.#cursor.y + 1}/${this.numRows}`;
		let len = Math.min(status.length, this.#screen.cols);
		this.#buffer.append(status, len);

		while (len < this.#screen.cols) {
			if (this.#screen.cols - len === rStatus.length) {
				this.#buffer.append(rStatus);
				break;
			} else {
				this.#buffer.append(' ');
				len++;
			}
		}
		this.#buffer.appendLine(Ansi.ResetFormatting);
	}

	private drawMessageBar(): void {
		this.#buffer.append(Ansi.ClearLine);
		const msgLen = this.#statusMessage.length;
		if (msgLen > 0 && (Date.now() - this.#statusTimeout < 5000)) {
			this.#buffer.append(this.#statusMessage, this.#screen.cols);
		}
	}
}

export default Editor;