<?php declare(strict_types=1);

namespace Aviat\Kilo;

use FFI;
use FFI\CData;

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

	private function __construct()
	{
		$ffi = self::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 = 0; // &= ~(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
		$res = self::ffi()
			->tcsetattr(C::STDIN_FILENO, C::TCSAFLUSH, FFI::addr($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
		Terminal::clear();
		Terminal::write("\n"); // New line, please

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

		return $res !== -1;
	}

	/**
	 * Get the size of the current terminal window
	 *
	 * @codeCoverageIgnore
	 * @return array|null
	 */
	public static function getWindowSize(): ?array
	{
		// First, try to get the answer from ioctl
		$ffi = self::ffi();
		$ws = $ffi->new('struct winsize');
		if ($ws !== NULL)
		{
			$res = $ffi->ioctl(C::STDOUT_FILENO, C::TIOCGWINSZ, FFI::addr($ws));
			if ($res === 0 && $ws->ws_col !== 0 && $ws->ws_row !== 0)
			{
				return [$ws->ws_row, $ws->ws_col];
			}
		}

		return null;
	}

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

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

		return $instance;
	}

	/**
	 * A 'singleton' function to replace a global variable
	 *
	 * @return FFI
	 */
	private static function ffi(): FFI
	{
		static $ffi;

		if ($ffi === NULL)
		{
			$ffi = FFI::load(__DIR__ . '/ffi.h');
		}

		return $ffi;
	}
}