<?php

namespace App\Services\Hosting\Terminal;

class LocalPtyShellSession implements ShellSession
{
    /** @var resource|null */
    private $process = null;

    /** @var array<int, resource> */
    private array $pipes = [];

    public function __construct(
        private string $command,
    ) {}

    public function boot(): void
    {
        $spec = [
            0 => ['pipe', 'r'],
            1 => ['pty'],
            2 => ['pty'],
        ];

        $process = proc_open($this->command, $spec, $pipes, base_path());

        if (! is_resource($process)) {
            throw new \RuntimeException('Unable to start local PTY shell.');
        }

        $this->process = $process;
        $this->pipes = $pipes;

        foreach ($this->pipes as $pipe) {
            stream_set_blocking($pipe, false);
        }
    }

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

        $output = '';
        $stream = $this->outputStream();

        if (! $stream) {
            return '';
        }

        $read = [$stream];

        $write = null;
        $except = null;
        $available = @stream_select($read, $write, $except, 0, 200000);

        if ($available === false || $available === 0) {
            return '';
        }

        $chunk = @stream_get_contents($stream);

        if ($chunk !== false && $chunk !== '') {
            $output .= $chunk;
        }

        return $output;
    }

    public function write(string $input): void
    {
        $stream = $this->inputStream();

        if ($input === '' || ! $stream) {
            return;
        }

        @fwrite($stream, $input);
        @fflush($stream);
    }

    public function resize(int $cols, int $rows): void
    {
        // proc_open PTYs do not expose a portable runtime resize API.
    }

    public function isAlive(): bool
    {
        return is_resource($this->process) && (proc_get_status($this->process)['running'] ?? false);
    }

    public function close(): void
    {
        $input = $this->inputStream();

        if ($input) {
            @fwrite($input, "exit\n");
            @fflush($input);
        }

        foreach ($this->pipes as $pipe) {
            if (is_resource($pipe)) {
                @fclose($pipe);
            }
        }

        $this->pipes = [];

        if (is_resource($this->process)) {
            @proc_terminate($this->process);
            @proc_close($this->process);
        }

        $this->process = null;
    }

    /** @return resource|null */
    private function inputStream()
    {
        return isset($this->pipes[0]) && is_resource($this->pipes[0]) ? $this->pipes[0] : null;
    }

    /** @return resource|null */
    private function outputStream()
    {
        if (isset($this->pipes[1]) && is_resource($this->pipes[1])) {
            return $this->pipes[1];
        }

        if (isset($this->pipes[2]) && is_resource($this->pipes[2])) {
            return $this->pipes[2];
        }

        return isset($this->pipes[0]) && is_resource($this->pipes[0]) ? $this->pipes[0] : null;
    }
}