<?php declare(strict_types=1);

namespace Aviat\Kilo;

use FFI;
use FFI\CData;

use Aviat\Kilo\Enum\C;

/**
 * An implicit singleton wrapper around terminal settings to simplify enabling/disabling raw mode
 */
class Termios {
	private CData $originalTermios;

	private function __construct()
	{
		$ffi = get_ffi();
		$termios = $ffi->new('struct termios');
		if ($termios === NULL)
		{
			throw new TermiosException('Failed to create termios struct');
		}

		$termiosAddr = FFI::addr($termios);
		$res = $ffi->tcgetattr(C::STDIN_FILENO, $termiosAddr);

		if ($res === -1)
		{
			throw new TermiosException('Failed to get existing terminal settings');
		}

		$this->originalTermios = $termios;
	}

	/**
	 * Put the current terminal into raw input mode
	 *
	 * Returns TRUE if successful. Will return NULL if run more than once, as
	 * raw mode is pretty binary...there's no point in reapplying raw mode!
	 *
	 * @return bool|null
	 */
	public static function enableRawMode(): ?bool
	{
		static $run = FALSE;

		// Don't run this more than once!
		if ($run === TRUE)
		{
			return NULL;
		}

		$run = TRUE;

		$instance = self::getInstance();

		// Make sure to restore normal mode on exit/die/crash
		register_shutdown_function([static::class, 'disableRawMode']);

		$termios = clone $instance->originalTermios;
		$termios->c_iflag &= ~(C::BRKINT | C::ICRNL | C::INPCK | C::ISTRIP | C::IXON);
		$termios->c_oflag &= ~(C::OPOST);
		$termios->c_cflag |= (C::CS8);
		$termios->c_lflag &= ~( C::ECHO | C::ICANON | C::IEXTEN | C::ISIG );
		$termios->c_cc[C::VMIN] = 0;
		$termios->c_cc[C::VTIME] = 1;

		// Turn on raw mode
		$res = get_ffi()->tcsetattr(C::STDIN_FILENO, C::TCSAFLUSH, FFI::addr($termios));

		return $res !== -1;
	}

	/**
	 * Restores terminal settings that were changed when going into raw mode.
	 *
	 * Returns TRUE if settings are applied successfully. If raw mode was not
	 * enabled, this will output a line of escape codes and a new line.
	 *
	 * @return bool
	 */
	public static function disableRawMode(): bool
	{
		$instance = self::getInstance();

		// Cleanup
		write_stdout(ANSI::CLEAR_SCREEN);
		write_stdout(ANSI::RESET_CURSOR);
		write_stdout("\n"); // New line, please

		$res = get_ffi()->tcsetattr(C::STDIN_FILENO, C::TCSAFLUSH, FFI::addr($instance->originalTermios));

		return $res !== -1;
	}

	private static function getInstance(): self
	{
		static $instance;

		if ($instance === NULL)
		{
			$instance = new self();
		}

		return $instance;
	}
}