<?php

namespace App\Services\Hosting\Terminal;

use phpseclib3\Net\SSH2;

class RemoteSshShellSession implements ShellSession
{
    private const STARTUP_TIMEOUT_SECONDS = 10;
    private const READ_TIMEOUT_SECONDS = 0.1;

    private bool $closed = false;

    public function __construct(
        private SSH2 $ssh,
        private string $launchCommand,
        private int $cols = 120,
        private int $rows = 30,
    ) {}

    public function boot(): void
    {
        $this->ssh->setWindowSize($this->cols, $this->rows);
        $this->ssh->setTimeout(self::STARTUP_TIMEOUT_SECONDS);
        $this->ssh->enablePTY();

        if ($this->ssh->exec($this->launchCommand, false) !== true) {
            throw new \RuntimeException('Unable to start remote terminal shell.');
        }
    }

    public function read(): string
    {
        if (! $this->isAlive()) {
            return '';
        }

        $output = '';
        $this->ssh->setTimeout(self::READ_TIMEOUT_SECONDS);

        while (true) {
            $chunk = $this->ssh->read('', SSH2::READ_NEXT);

            if ($chunk === true) {
                if ($this->ssh->isTimeout()) {
                    break;
                }

                $this->closed = true;
                break;
            }

            if (! is_string($chunk) || $chunk === '') {
                break;
            }

            $output .= $chunk;
        }

        return $output;
    }

    public function write(string $input): void
    {
        if ($input === '' || ! $this->isAlive()) {
            return;
        }

        $this->ssh->write($input);
    }

    public function resize(int $cols, int $rows): void
    {
        // phpseclib applies the PTY size during shell creation; runtime resize is left as a no-op
        // to avoid injecting visible shell commands into the user session.
    }

    public function isAlive(): bool
    {
        return ! $this->closed && $this->ssh->isConnected();
    }

    public function close(): void
    {
        if ($this->ssh->isConnected()) {
            try {
                $this->ssh->write("exit\n");
            } catch (\Throwable) {
                // Ignore shutdown write failures.
            }

            $this->ssh->disconnect();
        }

        $this->closed = true;
    }
}