<?php
declare(strict_types=1);

/**
 * Independent verifier of an EUROBABYSHOP prize-draw protocol (algorithms ebs-prizedraw-v1 and v2).
 * v1 — attendance bands of the offer edition 07.09.2026, wave EBS-G1; v2 — edition 06.10.2026, waves from EBS-G2.
 * The two versions differ only in the attendance bands.
 * Needs only PHP 8 (hash, json; curl for --online).
 *
 *   php verify.php EBS-G1-production-v1.json [--online]
 *
 * Checks: SHA-256(secret) equals the published commitment; drand randomness equals
 * SHA-256(signature) and the round is the first after the close of applications
 * (with --online the signature is also fetched from public drand relays);
 * snapshot hash; seed; full replay of the draw; result hash.
 * Exit code 0 only if every check passes.
 */

if (PHP_SAPI !== 'cli') {
    http_response_code(404);
    exit;
}

const V_BANDS = [
    'ebs-prizedraw-v1' => [1, 10, 30, 70, 150, 300, 500, 1000],
    'ebs-prizedraw-v2' => [1, 31, 71, 251, 501, 1001, 2501, 5001],
];

function v_algo_for_wave(string $wave): string
{
    return $wave === 'EBS-G1' ? 'ebs-prizedraw-v1' : 'ebs-prizedraw-v2';
}
const V_TABLE = [
    'cybex_priam_v' => [0, 0, 0, 0, 0, 0, 1, 2],
    'cybex_balios_s_lux' => [0, 0, 0, 0, 0, 1, 1, 2],
    'cybex_eezy_s_twist2' => [0, 0, 0, 0, 1, 1, 2, 2],
    'ebs_cert_50000' => [0, 0, 0, 0, 2, 3, 4, 6],
    'pp_tatamia' => [0, 0, 0, 0, 1, 1, 2, 2],
    'esspero_tour_s' => [0, 0, 0, 0, 1, 2, 3, 4],
    'cybex_solution_t' => [0, 0, 0, 1, 1, 1, 2, 2],
    'esspero_seat_profix' => [0, 0, 0, 1, 2, 3, 4, 5],
    'antemi_classic_sleep' => [0, 0, 0, 1, 1, 2, 2, 3],
    'esspero_air' => [0, 0, 0, 3, 3, 4, 5, 6],
    'esspero_summer_line' => [0, 0, 1, 2, 3, 4, 5, 6],
    'bb_lettino' => [0, 0, 1, 1, 2, 3, 4, 5],
    'pp_backpack' => [0, 0, 1, 1, 2, 3, 4, 5],
    'ramili_baby' => [0, 0, 1, 1, 2, 3, 4, 5],
    'bb_cuore' => [0, 1, 1, 1, 2, 3, 4, 5],
    'esspero_egg' => [0, 1, 1, 2, 2, 3, 4, 5],
    'esspero_transformer_lux' => [1, 1, 2, 3, 4, 6, 8, 10],
    'cybex_cupholder' => [0, 1, 2, 3, 4, 5, 6, 8],
];
const V_CHAIN = '8990e7a9aaed2ffed73dbd7092123d6f289930540d7651336225dc172e51b2ce';
const V_GENESIS = 1595431050;
const V_PERIOD = 30;
const V_RELAYS = ['https://api.drand.sh', 'https://drand.cloudflare.com'];

function v_canonical($x): string
{
    return json_encode($x, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE | JSON_THROW_ON_ERROR);
}

final class VStream
{
    private string $seed;
    public int $counter = 0;

    public function __construct(string $seed)
    {
        $this->seed = $seed;
    }

    public function uniform(int $total): int
    {
        if ($total < 1 || $total > (1 << 62)) {
            throw new RangeException('total out of range');
        }
        $bits = 1;
        while ($bits < 62 && (1 << $bits) < $total) {
            $bits++;
        }
        $mask = (1 << $bits) - 1;
        while (true) {
            $v = unpack('J', substr(hash('sha256', $this->seed.pack('J', $this->counter++), true), 0, 8))[1] & $mask;
            if ($v < $total) {
                return $v;
            }
        }
    }
}

function v_pick(array $weights, int $r): int
{
    $acc = 0;
    foreach (array_values($weights) as $i => $w) {
        $acc += $w;
        if ($r < $acc) {
            return $i;
        }
    }
    throw new OutOfRangeException('r >= total');
}

function v_weighted(array $pool, VStream $s): array
{
    $ids = array_keys($pool);
    $weights = array_values($pool);
    $total = array_sum($weights);
    $r = $s->uniform($total);
    $i = v_pick($weights, $r);
    return [$ids[$i], $weights[$i], $total, $r];
}

function v_draw(array $snap, string $seed, array $manual): array
{
    $s = new VStream($seed);
    $balance = [];
    foreach ($snap['balance'] as [$c, $q]) {
        $balance[$c] = $q;
    }
    if (array_keys($balance) !== array_keys(V_TABLE)) {
        throw new RuntimeException('balance positions differ from the offer table');
    }
    $pool = [];
    $win = [];
    foreach ($snap['entries'] as [$id, $w, $cat]) {
        if ($cat === 'R') {
            if (!is_int($w) || $w < 1 || $w > 5) {
                throw new RuntimeException('bad weight for entry '.$id);
            }
            $pool[$id] = $w;
        } else {
            $win[] = $id;
        }
    }
    ksort($pool);
    sort($win);
    $n = count($pool);
    $col = null;
    if (!isset(V_BANDS[$snap['algo'] ?? ''])) {
        throw new RuntimeException('unknown algorithm in the snapshot');
    }
    foreach (V_BANDS[$snap['algo']] as $i => $lb) {
        if ($n >= $lb) {
            $col = $i;
        }
    }
    $quota = [];
    foreach (V_TABLE as $c => $row) {
        $quota[$c] = $col === null ? 0 : min($row[$col], $balance[$c]);
    }
    $slots = [];
    foreach ($quota as $c => $q) {
        for ($u = 1; $u <= $q; $u++) {
            $slots[$c.'#'.$u] = null;
        }
    }
    $mr = $manual['random'] ?? [];
    ksort($mr);
    foreach ($mr as $id => $c) {
        foreach ($slots as $k => $e) {
            if ($e === null && str_starts_with($k, $c.'#')) {
                $slots[$k] = [$id, $pool[$id], null, null, 'manual'];
                unset($pool[$id]);
                break;
            }
        }
    }
    foreach ($slots as $k => $e) {
        if ($e === null && $pool !== []) {
            [$id, $w, $t, $r] = v_weighted($pool, $s);
            $slots[$k] = [$id, $w, $t, $r, 'weighted'];
            unset($pool[$id]);
        }
    }
    $awarded = array_fill_keys(array_keys($balance), 0);
    $winners = [];
    foreach ($slots as $k => $e) {
        [$c, $u] = explode('#', $k);
        if ($e === null) {
            $winners[] = [$c, (int)$u, null, null, null, null, 'unfilled'];
        } else {
            $winners[] = [$c, (int)$u, $e[0], $e[1], $e[2], $e[3], $e[4]];
            $awarded[$c]++;
        }
    }
    $reserve = [];
    for ($rank = 1; $rank <= $snap['reserve_size'] && $pool !== []; $rank++) {
        [$id, $w, $t, $r] = v_weighted($pool, $s);
        $reserve[] = [$rank, $id, $w, $t, $r];
        unset($pool[$id]);
    }
    $rem = [];
    $remOut = [];
    foreach ($balance as $c => $q) {
        $rem[$c] = $q - $quota[$c];
        $remOut[] = [$c, $rem[$c]];
    }
    $w100 = [];
    $unitNo = array_fill_keys(array_keys($balance), 0);
    $mw = $manual['win100'] ?? [];
    foreach ($win as $id) {
        if (isset($mw[$id])) {
            [$c, $t, $r, $type] = [$mw[$id], null, null, 'manual'];
        } else {
            if (!in_array($snap['roulette_rule'], ['by_unit', 'by_position'], true)) {
                throw new RuntimeException('roulette rule is not set for a win100 entry');
            }
            $codes = [];
            $ws = [];
            foreach ($rem as $c => $q) {
                if ($q > 0) {
                    $codes[] = $c;
                    $ws[] = $snap['roulette_rule'] === 'by_unit' ? $q : 1;
                }
            }
            $t = array_sum($ws);
            $r = $s->uniform($t);
            $c = $codes[v_pick($ws, $r)];
            $type = 'roulette';
        }
        $rem[$c]--;
        $unitNo[$c]++;
        $awarded[$c]++;
        $w100[] = [$id, $c, $unitNo[$c], $t, $r, $type];
    }
    $nb = [];
    $qo = [];
    foreach ($balance as $c => $q) {
        $nb[] = [$c, $q - $awarded[$c]];
        $qo[] = [$c, $quota[$c]];
    }
    return [
        'n_random' => $n, 'n_win100' => count($win), 'column' => $col, 'quotas' => $qo,
        'winners' => $winners, 'reserve' => $reserve, 'remainder_after_quota' => $remOut,
        'win100' => $w100, 'new_balance' => $nb, 'stream_blocks' => $s->counter,
    ];
}

function v_fetch(string $url): ?array
{
    $ctx = stream_context_create(['http' => ['timeout' => 15], 'ssl' => ['verify_peer' => true]]);
    $body = @file_get_contents($url, false, $ctx);
    $j = is_string($body) ? json_decode($body, true) : null;
    return is_array($j) ? $j : null;
}

$file = $argv[1] ?? '';
$online = in_array('--online', $argv, true);
if ($file === '' || !is_file($file)) {
    fwrite(STDERR, "Использование: php verify.php protocol.json [--online]\n");
    exit(2);
}
$p = json_decode((string)file_get_contents($file), true, 512, JSON_THROW_ON_ERROR);
$fail = 0;
$check = static function (string $name, bool $ok, string $detail = '') use (&$fail): void {
    echo ($ok ? 'OK   ' : 'FAIL ').$name.($detail !== '' ? ' — '.$detail : '')."\n";
    if (!$ok) {
        $fail++;
    }
};

$algo = v_algo_for_wave((string)($p['wave'] ?? ''));
$check('алгоритм '.$algo.' для волны '.($p['wave'] ?? '?'), ($p['algo'] ?? '') === $algo
    && ($p['snapshot']['algo'] ?? '') === $algo && ($p['snapshot']['wave'] ?? '') === ($p['wave'] ?? ''));
$prod = ($p['run_type'] ?? '') === 'production';
if (!$prod) {
    echo "ВНИМАНИЕ: тестовый протокол, не итог волны. Проверяется только воспроизводимость по seed.\n";
}

$snapHash = hash('sha256', v_canonical($p['snapshot']));
$check('хеш снимка заявок', $snapHash === $p['snapshot_hash'], $snapHash);

if ($prod) {
    $secret = hex2bin((string)$p['secret_hex']);
    $check('секрет соответствует обязательству', strlen((string)$secret) === 32 && hash('sha256', $secret) === $p['commit']['hash']);
    $close = (new DateTimeImmutable($p['wave_close'], new DateTimeZone('Europe/Moscow')))->getTimestamp();
    $commitTs = (new DateTimeImmutable($p['commit']['committed_at'], new DateTimeZone('Europe/Moscow')))->getTimestamp();
    $check('обязательство опубликовано до закрытия приёма', $commitTs < $close, $p['commit']['committed_at'].' < '.$p['wave_close']);
    $b = $p['beacon'];
    $expectedRound = intdiv($close - V_GENESIS, V_PERIOD) + 2;
    $check('раунд маяка — первый после закрытия приёма', (int)$b['round'] === $expectedRound, 'раунд '.$b['round'].', ожидался '.$expectedRound);
    $check('цепочка drand default', $b['chain_hash'] === V_CHAIN);
    $check('randomness = SHA-256(signature)', hash('sha256', hex2bin($b['signature'])) === $b['randomness']);
    if ($online) {
        $seen = 0;
        foreach (V_RELAYS as $relay) {
            $j = v_fetch($relay.'/public/'.$b['round']);
            if ($j !== null) {
                $seen++;
                $check('подпись раунда у '.$relay, ($j['signature'] ?? '') === $b['signature']);
            }
        }
        $check('маяк доступен онлайн', $seen > 0, $seen === 0 ? 'нет данных маяка' : '');
    }
    $seed = hash('sha256', $secret.hex2bin($b['randomness']).$p['wave'].hex2bin($snapHash), true);
    $check('зерно', bin2hex($seed) === $p['seed_hex']);
    $manual = [];
    $check('ручных назначений нет', empty($p['manual']));
} else {
    $seed = hex2bin((string)$p['seed_hex']);
    $manual = $p['manual'] ?? [];
}

try {
    $replay = v_draw($p['snapshot'], $seed, is_array($manual) ? $manual : []);
    $check('повтор розыгрыша совпадает с протоколом', v_canonical($replay) === v_canonical($p['results']));
    $check('хеш результата', hash('sha256', v_canonical($replay)) === $p['result_hash']);
} catch (Throwable $e) {
    $check('повтор розыгрыша', false, $e->getMessage());
}

$entries = [];
foreach (array_merge(
    array_column($p['results']['winners'], 2),
    array_column($p['results']['reserve'], 1),
    array_column($p['results']['win100'], 0)
) as $id) {
    if ($id !== null) {
        $entries[] = $id;
    }
}
$check('одна заявка — не более одного приза или места в резерве', count($entries) === count(array_unique($entries)));

if (!empty($p['corrections'])) {
    echo 'Исправлений: '.count($p['corrections']).' (версия протокола '.$p['protocol_version'].")\n";
}
echo $fail === 0 ? "ИТОГ: протокол подтверждён\n" : "ИТОГ: найдено расхождений: {$fail}\n";
exit($fail === 0 ? 0 : 1);