import { die, IFFI, importForRuntime, ITerminalSize } from './mod.ts';

export const STDIN_FILENO = 0;
export const TCSANOW = 0;

export const TERMIOS_SIZE = 60;

export const defaultTerminalSize: ITerminalSize = {
	rows: 24,
	cols: 80,
};

/**
 * Implementation to toggle raw mode
 */
class Termios {
	/**
	 * The ffi implementation for the current runtime
	 * @private
	 */
	#ffi: IFFI;

	/**
	 * Are we in raw mode?
	 * @private
	 */
	#inRawMode: boolean;

	/**
	 * The saved version of the termios struct for cooked/canonical mode
	 * @private
	 */
	#cookedTermios: Uint8Array;

	/**
	 * The data for the termios struct we are manipulating
	 * @private
	 */
	#termios: Uint8Array;

	/**
	 * The pointer to the termios struct
	 * @private
	 */
	#ptr;

	constructor(ffi: IFFI) {
		this.#ffi = ffi;
		this.#inRawMode = false;

		// These are the TypedArrays linked to the raw pointer data
		this.#cookedTermios = new Uint8Array(TERMIOS_SIZE);
		this.#termios = new Uint8Array(TERMIOS_SIZE);

		// The current pointer for C
		this.#ptr = ffi.getPointer(this.#termios);
	}

	cleanup() {
		this.#ptr = null;
		this.#cookedTermios = new Uint8Array(0);
		this.#termios = new Uint8Array(0);
		this.#ffi.close();
	}

	enableRawMode() {
		if (this.#inRawMode) {
			throw new Error('Can not enable raw mode when in raw mode');
		}

		// Get the current termios settings
		let res = this.#ffi.tcgetattr(STDIN_FILENO, this.#ptr);
		if (res === -1) {
			die('Failed to get terminal settings');
		}

		// The #ptr property is pointing to the #termios TypedArray. As the pointer
		// is manipulated, the TypedArray is as well. We will use this to save
		// the original canonical/cooked terminal settings for disabling raw mode later.
		// @ts-ignore: bad type definition
		this.#cookedTermios = new Uint8Array(this.#termios, 0, 60);

		// Update termios struct with (most of the) raw settings
		this.#ffi.cfmakeraw(this.#ptr);

		// Actually set the new termios settings
		res = this.#ffi.tcsetattr(STDIN_FILENO, TCSANOW, this.#ptr);
		if (res === -1) {
			die('Failed to update terminal settings. Can\'t enter raw mode');
		}

		this.#inRawMode = true;
	}

	disableRawMode() {
		// Don't even bother throwing an error if we try to disable raw mode
		// and aren't in raw mode. It just doesn't really matter.
		if (!this.#inRawMode) {
			return;
		}

		const oldTermiosPtr = this.#ffi.getPointer(this.#cookedTermios);
		const res = this.#ffi.tcsetattr(STDIN_FILENO, TCSANOW, oldTermiosPtr);
		if (res === -1) {
			die('Failed to restore canonical mode.');
		}

		this.#inRawMode = false;
	}
}

let termiosSingleton: Termios | null = null;

export const getTermios = async () => {
	if (termiosSingleton !== null) {
		return termiosSingleton;
	}

	// Get the runtime-specific ffi wrappers
	const ffi = await importForRuntime('ffi');
	termiosSingleton = new Termios(ffi);

	return termiosSingleton;
};