<?php

declare(strict_types=1);

/** Atomic incremental installer for the confirmed-feedback update. */
function v4ConfirmedWrite(string $path, string $content, int $mode = 0644): void
{
    if (is_link($path)) {
        throw new RuntimeException('Symlink wird nicht ersetzt.');
    }
    $temp = tempnam(dirname($path), '.v4-confirmed-');
    if ($temp === false) {
        throw new RuntimeException('Temporaere Datei nicht verfuegbar.');
    }
    try {
        if (file_put_contents($temp, $content, LOCK_EX) !== strlen($content)
            || !chmod($temp, $mode)
            || !rename($temp, $path)) {
            throw new RuntimeException('Atomarer Dateitausch fehlgeschlagen.');
        }
    } finally {
        if (is_file($temp)) {
            unlink($temp);
        }
    }
}

function v4ConfirmedFiles(string $stage, string $target): array
{
    $allowed = [
        'libs/NetzfahrplanV4Rueckmeldung.php',
        'libs/NetzfahrplanV4Geraeteabruf.php',
        'libs/BatterieNetzfahrplanV4RueckmeldungTrait.php',
    ];
    $manifest = json_decode((string) file_get_contents($stage . '/MANIFEST.json'), true, 32, JSON_THROW_ON_ERROR);
    if (($manifest['scope'] ?? null) !== 'confirmed_feedback_trial_disabled'
        || count($manifest['files'] ?? []) !== count($allowed)
        || array_diff(array_keys($manifest['files']), $allowed)
        || array_diff($allowed, array_keys($manifest['files']))) {
        throw new RuntimeException('Unerwarteter Dateiumfang.');
    }
    if (realpath($target) !== $target || is_link($target)) {
        throw new RuntimeException('Modulpfad unerwartet.');
    }
    foreach ($manifest['dependencies'] as $name => $hash) {
        if (!preg_match('~^(libs/[A-Za-z0-9]+\\.php|Batterie/module\\.php|Manager/module\\.php)$~D', $name)
            || is_link($target . '/' . $name)
            || hash_file('sha256', $target . '/' . $name) !== $hash) {
            throw new RuntimeException('Abhaengigkeit wurde parallel geaendert: ' . $name);
        }
    }

    $before = [];
    $source = [];
    $already = true;
    foreach ($allowed as $name) {
        $path = $target . '/' . $name;
        $candidate = $stage . '/source/' . $name;
        if (is_link($path) || is_link($candidate) || realpath(dirname($path)) !== $target . '/' . dirname($name)) {
            throw new RuntimeException('Unerwarteter Dateipfad.');
        }
        $source[$name] = (string) file_get_contents($candidate);
        if (hash('sha256', $source[$name]) !== $manifest['files'][$name]['after']) {
            throw new RuntimeException('Paketpruefsumme geaendert: ' . $name);
        }
        token_get_all($source[$name], TOKEN_PARSE);
        $before[$name] = is_file($path) ? file_get_contents($path) : null;
        $hash = $before[$name] === null ? null : hash('sha256', $before[$name]);
        if (!in_array($hash, [$manifest['files'][$name]['before'], $manifest['files'][$name]['after']], true)) {
            throw new RuntimeException('Paralleler Modulstand; nichts ueberschrieben: ' . $name);
        }
        if ($hash !== $manifest['files'][$name]['after']) {
            $already = false;
        }
    }
    if ($already) {
        return ['status' => 'already_installed', 'backup' => null, 'filesChanged' => []];
    }

    $backup = $stage . '/backups/' . gmdate('Ymd\\THis\\Z') . '-' . bin2hex(random_bytes(4));
    if (!mkdir($backup, 0700, true)) {
        throw new RuntimeException('Sicherung fehlgeschlagen.');
    }
    foreach ($allowed as $name) {
        if ($before[$name] !== null) {
            $destination = $backup . '/' . $name;
            if (!is_dir(dirname($destination))) {
                mkdir(dirname($destination), 0700, true);
            }
            v4ConfirmedWrite($destination, $before[$name], 0600);
        }
    }
    v4ConfirmedWrite(
        $backup . '/MANIFEST.json',
        json_encode($manifest, JSON_THROW_ON_ERROR | JSON_PRETTY_PRINT) . "\n",
        0600
    );

    $written = [];
    try {
        foreach ($allowed as $name) {
            if ((is_file($target . '/' . $name) ? file_get_contents($target . '/' . $name) : null) !== $before[$name]) {
                throw new RuntimeException('Parallele Aenderung waehrend Installation.');
            }
            if ($before[$name] === $source[$name]) {
                continue;
            }
            v4ConfirmedWrite($target . '/' . $name, $source[$name]);
            $written[] = $name;
        }
    } catch (Throwable $error) {
        foreach (array_reverse($written) as $name) {
            $path = $target . '/' . $name;
            if (!is_link($path) && is_file($path)
                && hash_file('sha256', $path) === $manifest['files'][$name]['after']) {
                if ($before[$name] === null) {
                    unlink($path);
                } else {
                    v4ConfirmedWrite($path, $before[$name]);
                }
            }
        }
        throw $error;
    }

    return ['status' => 'installed', 'backup' => $backup, 'filesChanged' => $written];
}