<?php

namespace App\Ops;

/**
 * Runs an external command, or says plainly that it cannot.
 *
 * `proc_open` is disabled on a lot of shared hosting, and that is not an edge case to discover
 * halfway through an update - it is the first thing the updater has to ask. The command is passed
 * as an array, so there is no shell and nothing to quote: an argument can contain a space, a
 * quote or a semicolon without becoming a second command.
 */
final class CommandRunner
{
    /** @var array<string, list<string>|null> */
    private array $resolved = [];

    public function available(): bool
    {
        if (!function_exists('proc_open')) {
            return false;
        }
        $disabled = array_map('trim', explode(',', (string) ini_get('disable_functions')));

        return !in_array('proc_open', $disabled, true);
    }

    /**
     * Was ein Kindprozess von der Umgebung sehen darf: Pfade, ein Zuhause fuer Composer und Git,
     * aber kein APP_ENV, das einen Konsolenbefehl gegen die falsche Umgebung laufen liesse.
     *
     * @return array<string, string>
     */
    private function environment(): array
    {
        $environment = ['PATH' => getenv('PATH') ?: '', 'SystemRoot' => getenv('SystemRoot') ?: '', 'TEMP' => sys_get_temp_dir(), 'TMP' => sys_get_temp_dir()];
        // Composer verlangt HOME (Linux) oder APPDATA (Windows) - ohne sie bricht `composer
        // install` ab, waehrend `composer --version` noch laeuft. Git braucht HOME fuer .gitconfig.
        foreach (['HOME', 'USERPROFILE', 'APPDATA', 'LOCALAPPDATA', 'COMPOSER_HOME', 'PATHEXT', 'LANG', 'LC_ALL'] as $name) {
            $value = getenv($name);
            if (is_string($value) && '' !== $value) {
                $environment[$name] = $value;
            }
        }
        if (!isset($environment['HOME']) && !isset($environment['USERPROFILE'])) {
            // Unter php-fpm ist HOME oft leer; ein Ordner in var/ tut es fuer Composer und Git.
            $environment['HOME'] = sys_get_temp_dir();
        }
        if (!isset($environment['COMPOSER_HOME'])) {
            $environment['COMPOSER_HOME'] = $environment['HOME'] ?? sys_get_temp_dir();
        }

        return $environment;
    }

    /**
     * Die PHP-Kommandozeile, mit der Konsolenbefehle laufen.
     *
     * Aus einem Webprozess ist PHP_BINARY der Server selbst (php-fpm) oder leer (mod_php) - und
     * `php-fpm bin/console` startet keinen Befehl. Dann wird die Kommandozeile im Pfad gesucht.
     */
    public function php(): string
    {
        if (isset($this->resolved['php'])) {
            return $this->resolved['php'][0];
        }
        $candidates = [];
        if ('cli' === \PHP_SAPI && '' !== \PHP_BINARY) {
            $candidates[] = \PHP_BINARY;
        }
        $suffix = '\\' === \DIRECTORY_SEPARATOR ? '.exe' : '';
        foreach ([\PHP_BINDIR.'/php'.$suffix, \PHP_BINDIR.'/php'.\PHP_MAJOR_VERSION.'.'.\PHP_MINOR_VERSION.$suffix, 'php'.$suffix, 'php'.\PHP_MAJOR_VERSION.'.'.\PHP_MINOR_VERSION.$suffix, \PHP_BINARY] as $candidate) {
            if ('' !== $candidate && !\in_array($candidate, $candidates, true)) {
                $candidates[] = $candidate;
            }
        }
        foreach ($candidates as $candidate) {
            if ($this->run([$candidate, '-r', 'echo PHP_VERSION;'], sys_get_temp_dir(), 30)['ok']) {
                $this->resolved['php'] = [$candidate];

                return $candidate;
            }
        }

        return $candidates[0] ?? 'php';
    }

    /**
     * @param list<string> $command
     *
     * @return array{ok: bool, exit: int, output: string}
     */
    public function run(array $command, string $cwd, int $timeout = 300): array
    {
        if (!$this->available()) {
            return ['ok' => false, 'exit' => -1, 'output' => 'proc_open ist auf diesem Server abgeschaltet.'];
        }
        $pipes = [];
        $process = @proc_open(
            $command,
            [1 => ['pipe', 'w'], 2 => ['pipe', 'w']],
            $pipes,
            $cwd,
            // A minimal, predictable environment: no inherited APP_ENV that would make a console
            // command run against the wrong environment.
            $this->environment(),
        );
        if (!is_resource($process)) {
            return ['ok' => false, 'exit' => -1, 'output' => sprintf('%s konnte nicht gestartet werden.', $command[0])];
        }
        foreach ($pipes as $pipe) {
            stream_set_blocking($pipe, false);
        }
        $output = '';
        $deadline = microtime(true) + $timeout;
        while (true) {
            $status = proc_get_status($process);
            foreach ($pipes as $pipe) {
                $output .= stream_get_contents($pipe) ?: '';
            }
            if (!$status['running']) {
                break;
            }
            if (microtime(true) > $deadline) {
                proc_terminate($process);
                foreach ($pipes as $pipe) {
                    fclose($pipe);
                }
                proc_close($process);

                return ['ok' => false, 'exit' => -1, 'output' => trim($output)."\n".sprintf('Abgebrochen nach %d Sekunden.', $timeout)];
            }
            usleep(50000);
        }
        foreach ($pipes as $pipe) {
            $output .= stream_get_contents($pipe) ?: '';
            fclose($pipe);
        }
        proc_close($process);
        $exit = $status['exitcode'];

        return ['ok' => 0 === $exit, 'exit' => $exit, 'output' => trim($output)];
    }

    /**
     * Whether an executable can be found at all, so a missing one is reported, not guessed at.
     *
     * On Windows several of these are batch files, and proc_open without a shell cannot start a
     * .bat - which reported "composer is not available" on a machine that has it. The variants are
     * tried in order, and the one that answers is remembered for the next call.
     */
    public function has(string $executable, string $cwd): bool
    {
        return null !== $this->resolve($executable, $cwd);
    }

    /** The spelling of a command that actually starts here, or null. */
    public function resolve(string $executable, string $cwd): ?array
    {
        if (array_key_exists($executable, $this->resolved)) {
            return $this->resolved[$executable];
        }
        $candidates = [[$executable]];
        if ('\\' === DIRECTORY_SEPARATOR) {
            // On Windows composer is a .bat, and CreateProcess cannot start a batch file on its
            // own - it needs the command interpreter. The argument list stays fixed, nothing from
            // a request ever reaches it.
            $candidates[] = [getenv('COMSPEC') ?: 'cmd.exe', '/c', $executable];
        }
        // A phar in the project is the way on hosting where nothing is installed globally.
        if (is_file($cwd.'/'.$executable.'.phar')) {
            $candidates[] = [$this->php(), $cwd.'/'.$executable.'.phar'];
        }
        foreach ($candidates as $candidate) {
            if ($this->run([...$candidate, '--version'], $cwd, 30)['ok']) {
                return $this->resolved[$executable] = $candidate;
            }
        }

        return $this->resolved[$executable] = null;
    }
}