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,
	posSub,
	readKey,
	truncate,
} from './fns.ts';
import Option, { None, Some } from './option.ts';
import { getRuntime, logDebug, logWarning } from './runtime.ts';
import { ITerminalSize, Position, SearchDirection } from './types.ts';

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

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

	protected row(at: number): Option<Row> {
		return this.document.row(at);
	}

	protected get currentRow(): Option<Row> {
		return this.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.isNone()) {
				this.setStatusMessage('Save aborted');
				return;
			}

			this.filename = filename.unwrap();
		}

		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('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;

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

			case ctrlKey('f'):
				await this.find();
				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;

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

			case KeyCommand.ArrowUp:
			case KeyCommand.ArrowDown:
			case KeyCommand.ArrowRight:
			case KeyCommand.ArrowLeft:
			case KeyCommand.Home:
			case KeyCommand.End:
			case KeyCommand.PageUp:
			case KeyCommand.PageDown:
				this.moveCursor(input);
				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?: (char: string, query: string) => void,
	): Promise<Option<string>> {
		const { term } = await getRuntime();

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

		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 (chunk.length === 0 || char.length === 0) {
					continue;
				}

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

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

						return None;

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

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

				maybeCallback(char, res);
			}
		}
	}

	/**
	 * 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);
		let direction = SearchDirection.Forward;

		const result = await this.prompt(
			'Search: %s (Use ESC/Arrows/Enter)',
			(key: string, query: string) => {
				let moved = false;

				switch (key) {
					case KeyCommand.ArrowRight:
					case KeyCommand.ArrowDown:
						direction = SearchDirection.Forward;
						this.moveCursor(KeyCommand.ArrowRight);
						moved = true;
						break;

					case KeyCommand.ArrowLeft:
					case KeyCommand.ArrowUp:
						direction = SearchDirection.Backward;
						break;

					default:
						direction = SearchDirection.Forward;
				}

				if (query.length > 0) {
					const pos = this.document.find(query, this.cursor, direction);
					if (pos.isSome()) {
						// We have a match here
						this.cursor = Position.from(pos.unwrap());
						this.scroll();
					} else if (moved) {
						this.moveCursor(KeyCommand.ArrowLeft);
					}

					this.document.highlight(Some(query));
				}
			},
		);

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

		this.document.highlight(None);
	}

	/**
	 * Filter out any additional unwanted keyboard input
	 *
	 * @param input
	 */
	protected 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)) {
			logDebug('Ignoring input:', {
				input,
				isEscapeSequence,
				isCtrl,
			});

			return true;
		}

		return false;
	}

	protected moveCursor(char: string): void {
		const screenHeight = this.screen.rows;
		let { x, y } = this.cursor;
		const height = this.numRows;
		let width = (this.row(y).isSome()) ? this.row(y).unwrap().size : 0;

		logDebug('Editor.moveCursor - start', {
			char,
			cursor: this.cursor,
			renderX: this.renderX,
			screen: this.screen,
			height,
			width,
		});

		switch (char) {
			case KeyCommand.ArrowUp:
				if (y > 0) {
					y -= 1;
				}
				break;
			case KeyCommand.ArrowDown:
				if (y < height) {
					y += 1;
				}
				break;
			case KeyCommand.ArrowLeft:
				if (x > 0) {
					x -= 1;
				} else if (y > 0) {
					y -= 1;
					x = (this.row(y).isSome()) ? this.row(y).unwrap().size : 0;
				}
				break;
			case KeyCommand.ArrowRight:
				if (
					this.row(y).isSome() && x < width
				) {
					x += 1;
				} else if (y < height) {
					y += 1;
					x = 0;
				}
				break;
			case KeyCommand.PageUp:
				y = (y > screenHeight) ? posSub(y, screenHeight) : 0;
				break;
			case KeyCommand.PageDown:
				y = maxAdd(y, screenHeight, height);
				break;
			case KeyCommand.Home:
				x = 0;
				break;
			case KeyCommand.End:
				x = width;
				break;
		}

		width = (this.row(y).isSome()) ? this.row(y).unwrap().size : 0;

		if (x > width) {
			x = width;
		}

		this.cursor = Position.at(x, y);

		logDebug('Editor.moveCursor - end', {
			cursor: this.cursor,
			renderX: this.renderX,
			screen: this.screen,
			height,
			width,
		});
	}

	protected scroll(): void {
		this.renderX = (this.row(this.cursor.y).isSome())
			? this.document.row(this.cursor.y).unwrap().cxToRx(this.cursor.x)
			: 0;

		logDebug('Editor.scroll - start', {
			cursor: this.cursor,
			renderX: this.renderX,
			offset: this.offset,
		});

		const { y } = this.cursor;
		const offset = this.offset;
		const width = this.screen.cols;
		const height = this.screen.rows;

		if (y < offset.y) {
			offset.y = y;
		} else if (y >= offset.y + height) {
			offset.y = y - height + 1;
		}

		if (this.renderX < offset.x) {
			offset.x = this.renderX;
		} else if (this.renderX >= offset.x + width) {
			offset.x = this.renderX - width + 1;
		}

		logDebug('Editor.scroll - end', {
			cursor: this.cursor,
			renderX: this.renderX,
			offset: this.offset,
		});
	}

	// --------------------------------------------------------------------------
	// 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();
	}

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

		await this.buffer.flush();
	}

	protected 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();
		}
	}

	protected drawFileRow(y: number): void {
		const maybeRow = this.document.row(y);
		if (maybeRow.isNone()) {
			logWarning(`Trying to draw non-existent row '${y}'`);
			return this.drawPlaceholderRow(y);
		}

		const row = maybeRow.unwrap();

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

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

	protected 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('~');
		}
	}

	protected 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, 25)} - ${this.numRows} lines ${modified}`;
		const rStatus = `${this.cursor.y + 1},${this.cursor.x + 1}/${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);
	}

	protected 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);
		}
	}
}