<?php
declare(strict_types=1);

header('Content-Type: application/json; charset=utf-8');
header('Cache-Control: no-store, no-cache, must-revalidate, max-age=0');
header('X-Content-Type-Options: nosniff');

const ACHIEVEMENT_IDS = [
    'first_birth',
    'natural_zunchi_slave',
    'natural_tarinai_king',
    'self_zunchi_death',
    'natural_zunchi_slave_5_generations',
    'natural_tarinai_king_3_generations',
    'death_50_in_10_seconds',
    'birth_50_in_60_seconds',
    'great_mother_1000_births',
    'lifespan_completed',
    'soccer_ball_death',
    'fight_pair_danger_kill',
    'all_non_sleep_diseased_25',
    'colony_happy',
    'direct_feed_33',
    'ignite_during_birth_ritual',
    'laxative_starvation',
    'idle_observer_5_minutes',
    'placed_objects_100',
    'mechanized_industry',
    'safe_colony_25_5_minutes',
    'ants_alive_25',
    'ants_killed_100',
    'secret_collection_9_slots',
    'pause_spam_4_in_1_second',
    'continuous_play_1_hour',
    'below_absolute_zero_item',
    'undo_mass_revival',
    'robot_cleaner_100',
    'held_30_seconds',
    'minimalist_happy',
    'overprotective',
    'self_sufficient',
    'unplanned_city_30',
    'sauna_cold_plunge',
    'rain_shelter_all',
    'medicine_ledger_all',
    'mercury_lifespan',
    'enemy_enemy_friend',
    'revolution',
    'fuel_to_fire',
    'undo_20',
    'redo_20',
    'eternal_history_generation_10',
    'king_full_satisfaction',
    'slave_zero_satisfaction',
    'town_doctor_50',
    'poke_plushie_fling',
    'chaos_seeker_666_fights',
    'clean_freak_robot_only',
    'true_tarinai_observer',
    'sniper_333_shots',
    'megalopolis',
    'fertility_seeker_721_love_births',
    'low_fps_single_digit',
    'continuous_play_24_hours',
    'sandbox_five_toilets',
    'park_ground_changed',
    'ground_change_4_in_1_second',
    'ant_nest_without_tarinai',
    'sticky_bomb_15_passes',
    'daily_play_7_days',
    'wire_shock_7_tarinai',
    'information_industry',
];
const DATA_DIR_NAME = '.achievement_data';
const DATA_FILE_NAME = 'state.json';
const LOCK_FILE_NAME = 'state.lock';
const STATE_SCHEMA_VERSION = 3;
const MAX_REQUEST_BYTES = 131072;

function respond(array $payload, int $status = 200): never {
    http_response_code($status);
    echo json_encode($payload, JSON_UNESCAPED_SLASHES | JSON_INVALID_UTF8_SUBSTITUTE);
    exit;
}

function valid_player_id(string $value): bool {
    return preg_match('/^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/i', $value) === 1;
}

function empty_state(): array {
    return ['players' => [], 'unlocks' => []];
}

function compact_player_id(string $value): string {
    $hex = str_replace('-', '', strtolower($value));
    if (strlen($hex) !== 32 || !ctype_xdigit($hex)) return '';
    $binary = hex2bin($hex);
    if ($binary === false) return '';
    return rtrim(strtr(base64_encode($binary), '+/', '-_'), '=');
}

function expand_player_id(string $value): string {
    if (strlen($value) !== 22 || preg_match('/^[A-Za-z0-9_-]{22}$/', $value) !== 1) return '';
    $binary = base64_decode(strtr($value, '-_', '+/') . '==', true);
    if ($binary === false || strlen($binary) !== 16) return '';
    $hex = bin2hex($binary);
    return substr($hex, 0, 8) . '-' . substr($hex, 8, 4) . '-' . substr($hex, 12, 4) . '-' . substr($hex, 16, 4) . '-' . substr($hex, 20, 12);
}

function detect_state_format(mixed $value): string {
    if (!is_array($value)) return 'invalid';
    if ($value === []) return 'empty';
    if (array_is_list($value)) {
        return (($value[0] ?? null) === STATE_SCHEMA_VERSION
            && isset($value[1], $value[2], $value[3], $value[4])
            && is_array($value[2]) && is_array($value[3]) && is_array($value[4]))
            ? 'v3' : 'invalid';
    }
    if (($value['v'] ?? null) === 2 && isset($value['p'], $value['u']) && is_array($value['p']) && is_array($value['u'])) {
        return 'v2';
    }
    if (array_key_exists('players', $value) || array_key_exists('unlocks', $value)) return 'verbose';
    return 'invalid';
}

function normalize_state(mixed $value): array {
    if (!is_array($value)) return empty_state();
    $players = [];
    $unlocks = [];

    // v3 positional form: [version, baseTime, versions, players, unlocks].
    if (($value[0] ?? null) === STATE_SCHEMA_VERSION && isset($value[1], $value[2], $value[3], $value[4])
        && is_array($value[2]) && is_array($value[3]) && is_array($value[4])) {
        $baseTime = max(1, (int)$value[1]);
        $versions = array_map(static fn($entry): string => substr((string)$entry, 0, 32), $value[2]);
        $playerIds = [];
        foreach ($value[3] as $row) {
            if (!is_array($row) || !isset($row[0]) || !is_string($row[0])) continue;
            $id = expand_player_id($row[0]);
            if (!valid_player_id($id)) continue;
            $firstSeen = $baseTime + max(0, (int)($row[1] ?? 0));
            $lastSeen = $firstSeen + max(0, (int)($row[2] ?? 0));
            $versionIndex = max(0, (int)($row[3] ?? 0));
            $playerIds[] = $id;
            $players[$id] = [
                'firstSeen' => max(1, $firstSeen),
                'lastSeen' => max(1, $lastSeen),
                'gameVersion' => $versions[$versionIndex] ?? '',
            ];
        }
        foreach ($value[4] as $row) {
            if (!is_array($row) || count($row) < 3) continue;
            $achievementIndex = (int)$row[0];
            $achievementId = ACHIEVEMENT_IDS[$achievementIndex] ?? '';
            if ($achievementId === '') continue;
            $records = [];
            $count = count($row);
            for ($i = 1; $i + 1 < $count; $i += 2) {
                $playerIndex = (int)$row[$i];
                if (!isset($playerIds[$playerIndex])) continue;
                $records[$playerIds[$playerIndex]] = $baseTime + max(0, (int)$row[$i + 1]);
            }
            if ($records) $unlocks[$achievementId] = $records;
        }
    // v2 is an on-read migration source and is always rewritten as v3.
    } elseif (($value['v'] ?? null) === 2 && isset($value['p'], $value['u']) && is_array($value['p']) && is_array($value['u'])) {
        $playerIds = [];
        foreach ($value['p'] as $row) {
            if (!is_array($row) || !isset($row[0]) || !is_string($row[0]) || !valid_player_id($row[0])) continue;
            $id = strtolower($row[0]);
            $playerIds[] = $id;
            $players[$id] = [
                'firstSeen' => max(1, (int)($row[1] ?? 1)),
                'lastSeen' => max(1, (int)($row[2] ?? ($row[1] ?? 1))),
                'gameVersion' => substr((string)($row[3] ?? ''), 0, 32),
            ];
        }
        foreach ($value['u'] as $achievementId => $flat) {
            if (!is_string($achievementId) || (!in_array($achievementId, ACHIEVEMENT_IDS, true) && !in_array($achievementId, ['signal_automation_first', 'link_craftsman'], true)) || !is_array($flat)) continue;
            $records = [];
            $count = count($flat);
            for ($i = 0; $i + 1 < $count; $i += 2) {
                $playerIndex = (int)$flat[$i];
                if (!isset($playerIds[$playerIndex])) continue;
                $records[$playerIds[$playerIndex]] = max(1, (int)$flat[$i + 1]);
            }
            if ($records) $unlocks[$achievementId] = $records;
        }
    } else {
        $rawPlayers = isset($value['players']) && is_array($value['players']) ? $value['players'] : [];
        foreach ($rawPlayers as $id => $player) {
            if (!is_string($id) || !valid_player_id($id) || !is_array($player)) continue;
            $players[strtolower($id)] = [
                'firstSeen' => max(1, (int)($player['firstSeen'] ?? 1)),
                'lastSeen' => max(1, (int)($player['lastSeen'] ?? ($player['firstSeen'] ?? 1))),
                'gameVersion' => substr((string)($player['gameVersion'] ?? ''), 0, 32),
            ];
        }
        $rawUnlocks = isset($value['unlocks']) && is_array($value['unlocks']) ? $value['unlocks'] : [];
        foreach ($rawUnlocks as $achievementId => $records) {
            if (!is_string($achievementId) || (!in_array($achievementId, ACHIEVEMENT_IDS, true) && !in_array($achievementId, ['signal_automation_first', 'link_craftsman'], true)) || !is_array($records)) continue;
            foreach ($records as $id => $timestamp) {
                $normalizedId = strtolower((string)$id);
                if (!isset($players[$normalizedId])) continue;
                $unlocks[$achievementId][$normalizedId] = max(1, (int)$timestamp);
            }
        }
    }

    $legacySignal = isset($unlocks['signal_automation_first']) && is_array($unlocks['signal_automation_first'])
        ? $unlocks['signal_automation_first'] : [];
    $legacyLinks = isset($unlocks['link_craftsman']) && is_array($unlocks['link_craftsman'])
        ? $unlocks['link_craftsman'] : [];
    if ($legacySignal && $legacyLinks) {
        if (!isset($unlocks['mechanized_industry']) || !is_array($unlocks['mechanized_industry'])) {
            $unlocks['mechanized_industry'] = [];
        }
        foreach ($legacySignal as $playerId => $signalTime) {
            if (!isset($legacyLinks[$playerId])) continue;
            $unlocks['mechanized_industry'][$playerId] = max((int)$signalTime, (int)$legacyLinks[$playerId]);
        }
    }
    unset($unlocks['signal_automation_first'], $unlocks['link_craftsman']);

    return ['players' => $players, 'unlocks' => $unlocks];
}

function compact_state(array $state): array {
    $playerIds = array_keys($state['players']);
    sort($playerIds, SORT_STRING);
    $playerIndex = [];
    $timestamps = [];
    $versionCounts = [];
    foreach ($playerIds as $id) {
        $player = is_array($state['players'][$id] ?? null) ? $state['players'][$id] : [];
        $timestamps[] = max(1, (int)($player['firstSeen'] ?? 1));
        $timestamps[] = max(1, (int)($player['lastSeen'] ?? ($player['firstSeen'] ?? 1)));
        $version = substr((string)($player['gameVersion'] ?? ''), 0, 32);
        $versionCounts[$version] = ($versionCounts[$version] ?? 0) + 1;
    }
    foreach ($state['unlocks'] as $achievementId => $records) {
        if (!is_string($achievementId) || !in_array($achievementId, ACHIEVEMENT_IDS, true) || !is_array($records)) continue;
        foreach ($records as $timestamp) $timestamps[] = max(1, (int)$timestamp);
    }
    $baseTime = $timestamps ? min($timestamps) : 1;
    uksort($versionCounts, static function (string $a, string $b) use ($versionCounts): int {
        $countOrder = ($versionCounts[$b] ?? 0) <=> ($versionCounts[$a] ?? 0);
        return $countOrder !== 0 ? $countOrder : strcmp($a, $b);
    });
    $versions = array_keys($versionCounts);
    if (!$versions) $versions = [''];
    $versionIndex = array_flip($versions);

    $players = [];
    foreach ($playerIds as $index => $id) {
        $playerIndex[$id] = $index;
        $player = is_array($state['players'][$id] ?? null) ? $state['players'][$id] : [];
        $firstSeen = max(1, (int)($player['firstSeen'] ?? 1));
        $lastSeen = max($firstSeen, (int)($player['lastSeen'] ?? $firstSeen));
        $version = substr((string)($player['gameVersion'] ?? ''), 0, 32);
        $row = [compact_player_id($id), $firstSeen - $baseTime, $lastSeen - $firstSeen];
        $indexValue = (int)($versionIndex[$version] ?? 0);
        if ($indexValue !== 0) $row[] = $indexValue;
        $players[] = $row;
    }

    $unlocks = [];
    foreach (ACHIEVEMENT_IDS as $achievementIndex => $achievementId) {
        $records = $state['unlocks'][$achievementId] ?? null;
        if (!is_array($records) || !$records) continue;
        $pairs = [];
        foreach ($records as $id => $timestamp) {
            if (!isset($playerIndex[$id])) continue;
            $pairs[] = [$playerIndex[$id], max(1, (int)$timestamp) - $baseTime];
        }
        usort($pairs, static fn(array $a, array $b): int => $a[0] <=> $b[0]);
        if (!$pairs) continue;
        $row = [$achievementIndex];
        foreach ($pairs as [$indexValue, $timestampDelta]) {
            $row[] = $indexValue;
            $row[] = max(0, $timestampDelta);
        }
        $unlocks[] = $row;
    }
    return [STATE_SCHEMA_VERSION, $baseTime, $versions, $players, $unlocks];
}

function encode_compact_state(array $state): string {
    try {
        return json_encode(compact_state($state), JSON_UNESCAPED_SLASHES | JSON_INVALID_UTF8_SUBSTITUTE | JSON_THROW_ON_ERROR);
    } catch (JsonException $error) {
        throw new RuntimeException('storage_encode_failed', 0, $error);
    }
}

function decode_stored_state(string $contents): array {
    if (trim($contents) === '') return [empty_state(), 'empty'];
    try {
        $decoded = json_decode($contents, true, 512, JSON_THROW_ON_ERROR);
    } catch (JsonException $error) {
        throw new RuntimeException('storage_corrupt', 0, $error);
    }
    $format = detect_state_format($decoded);
    if ($format === 'invalid') throw new RuntimeException('storage_corrupt');
    return [normalize_state($decoded), $format];
}

function atomic_write_state(string $dataPath, string $encoded): void {
    $dataDir = dirname($dataPath);
    $tempPath = tempnam($dataDir, DATA_FILE_NAME . '.tmp.');
    if ($tempPath === false) throw new RuntimeException('storage_unavailable');
    $handle = @fopen($tempPath, 'wb');
    if ($handle === false) {
        @unlink($tempPath);
        throw new RuntimeException('storage_unavailable');
    }
    try {
        $length = strlen($encoded);
        $offset = 0;
        while ($offset < $length) {
            $written = fwrite($handle, substr($encoded, $offset));
            if ($written === false || $written === 0) throw new RuntimeException('storage_write_failed');
            $offset += $written;
        }
        if (!fflush($handle)) throw new RuntimeException('storage_write_failed');
        if (function_exists('fsync') && !fsync($handle)) throw new RuntimeException('storage_write_failed');
    } catch (Throwable $error) {
        fclose($handle);
        @unlink($tempPath);
        throw $error;
    }
    fclose($handle);
    @chmod($tempPath, 0664);
    if (!@rename($tempPath, $dataPath)) {
        @unlink($tempPath);
        throw new RuntimeException('storage_write_failed');
    }
}

function build_summary(array $state): array {
    $total = count($state['players']);
    $achievements = [];
    foreach (ACHIEVEMENT_IDS as $id) {
        $unlocked = isset($state['unlocks'][$id]) && is_array($state['unlocks'][$id])
            ? count($state['unlocks'][$id])
            : 0;
        $percentage = $total > 0 ? round(($unlocked / $total) * 100, 1) : 0.0;
        $achievements[$id] = [
            'unlockedPlayers' => $unlocked,
            'percentage' => $percentage,
        ];
    }
    return [
        'ok' => true,
        'totalPlayers' => $total,
        'achievements' => $achievements,
    ];
}

$method = strtoupper($_SERVER['REQUEST_METHOD'] ?? 'GET');
if (!in_array($method, ['GET', 'POST'], true)) respond(['ok' => false, 'error' => 'method_not_allowed'], 405);

$payload = [];
if ($method === 'POST') {
    $declaredLength = max(0, (int)($_SERVER['CONTENT_LENGTH'] ?? 0));
    if ($declaredLength > MAX_REQUEST_BYTES) respond(['ok' => false, 'error' => 'request_too_large'], 413);
    $raw = file_get_contents('php://input', false, null, 0, MAX_REQUEST_BYTES + 1);
    if (!is_string($raw) || strlen($raw) > MAX_REQUEST_BYTES) respond(['ok' => false, 'error' => 'request_too_large'], 413);
    try {
        $decoded = json_decode($raw, true, 64, JSON_THROW_ON_ERROR);
    } catch (JsonException) {
        respond(['ok' => false, 'error' => 'invalid_json'], 400);
    }
    if (!is_array($decoded)) respond(['ok' => false, 'error' => 'invalid_json'], 400);
    $payload = $decoded;
}

$action = $method === 'POST'
    ? (string)($payload['action'] ?? '')
    : (string)($_GET['action'] ?? 'summary');
$playerId = $method === 'POST'
    ? (string)($payload['playerId'] ?? '')
    : (string)($_GET['playerId'] ?? '');

if (!in_array($action, ['session', 'unlock', 'sync', 'reset', 'summary'], true)) {
    respond(['ok' => false, 'error' => 'invalid_action'], 400);
}
if ($method === 'GET' && $action !== 'summary') {
    respond(['ok' => false, 'error' => 'method_not_allowed'], 405);
}
if (!valid_player_id($playerId)) {
    respond(['ok' => false, 'error' => 'invalid_player'], 400);
}
$playerId = strtolower($playerId);
$syncUnlocks = [];
$completionistEligible = null;
if ($action === 'unlock') {
    $achievementId = (string)($payload['achievementId'] ?? '');
    if (!in_array($achievementId, ACHIEVEMENT_IDS, true)) {
        respond(['ok' => false, 'error' => 'invalid_achievement'], 400);
    }
} elseif ($action === 'sync') {
    $submittedUnlocks = $payload['unlocked'] ?? null;
    if (!is_array($submittedUnlocks) || count($submittedUnlocks) > count(ACHIEVEMENT_IDS)) {
        respond(['ok' => false, 'error' => 'invalid_unlocks'], 400);
    }
    if (array_key_exists('completionistEligible', $payload)) {
        if (!is_bool($payload['completionistEligible'])) {
            respond(['ok' => false, 'error' => 'invalid_completionist_state'], 400);
        }
        $completionistEligible = $payload['completionistEligible'];
    }
    foreach ($submittedUnlocks as $achievementId => $timestamp) {
        if (!is_string($achievementId) || !in_array($achievementId, ACHIEVEMENT_IDS, true)) {
            respond(['ok' => false, 'error' => 'invalid_achievement'], 400);
        }
        if (!is_int($timestamp) && !is_float($timestamp) && !is_string($timestamp)) {
            respond(['ok' => false, 'error' => 'invalid_timestamp'], 400);
        }
        $numericTimestamp = filter_var($timestamp, FILTER_VALIDATE_FLOAT);
        if ($numericTimestamp === false || !is_finite((float)$numericTimestamp) || $numericTimestamp <= 0) {
            respond(['ok' => false, 'error' => 'invalid_timestamp'], 400);
        }
        $syncUnlocks[$achievementId] = (float)$numericTimestamp;
    }
    if ($completionistEligible === false) unset($syncUnlocks['true_tarinai_observer']);
}

$dataDir = __DIR__ . DIRECTORY_SEPARATOR . DATA_DIR_NAME;
if (!is_dir($dataDir) && !mkdir($dataDir, 0775, true) && !is_dir($dataDir)) {
    respond(['ok' => false, 'error' => 'storage_unavailable'], 503);
}
$dataPath = $dataDir . DIRECTORY_SEPARATOR . DATA_FILE_NAME;
$lockPath = $dataDir . DIRECTORY_SEPARATOR . LOCK_FILE_NAME;
$lockHandle = @fopen($lockPath, 'c');
if ($lockHandle === false || !flock($lockHandle, LOCK_EX)) {
    if (is_resource($lockHandle)) fclose($lockHandle);
    respond(['ok' => false, 'error' => 'storage_locked'], 503);
}

$summary = null;
$storageError = null;
try {
    $contents = is_file($dataPath) ? file_get_contents($dataPath) : '';
    if ($contents === false) throw new RuntimeException('storage_unavailable');
    [$state, $sourceFormat] = decode_stored_state($contents);
    $now = time();
    $mutatesPlayer = $action !== 'summary';

    if ($mutatesPlayer) {
        $player = isset($state['players'][$playerId]) && is_array($state['players'][$playerId])
            ? $state['players'][$playerId]
            : ['firstSeen' => $now];
        $player['lastSeen'] = $now;
        $submittedGameVersion = substr((string)($payload['gameVersion'] ?? ''), 0, 32);
        if ($submittedGameVersion !== '' || !isset($player['gameVersion'])) $player['gameVersion'] = $submittedGameVersion;
        $state['players'][$playerId] = $player;
    }

    if ($action === 'unlock') {
        $achievementId = (string)$payload['achievementId'];
        if (!isset($state['unlocks'][$achievementId]) || !is_array($state['unlocks'][$achievementId])) {
            $state['unlocks'][$achievementId] = [];
        }
        if (!isset($state['unlocks'][$achievementId][$playerId])) {
            $state['unlocks'][$achievementId][$playerId] = $now;
        }
    } elseif ($action === 'sync') {
        if ($completionistEligible === false && isset($state['unlocks']['true_tarinai_observer'][$playerId])) {
            unset($state['unlocks']['true_tarinai_observer'][$playerId]);
        }
        foreach ($syncUnlocks as $achievementId => $submittedTimestamp) {
            if (!isset($state['unlocks'][$achievementId]) || !is_array($state['unlocks'][$achievementId])) {
                $state['unlocks'][$achievementId] = [];
            }
            if (isset($state['unlocks'][$achievementId][$playerId])) continue;
            $timestampSeconds = $submittedTimestamp >= 100000000000
                ? (int)floor($submittedTimestamp / 1000)
                : (int)floor($submittedTimestamp);
            $state['unlocks'][$achievementId][$playerId] = max(1, min($now, $timestampSeconds));
        }
    } elseif ($action === 'reset') {
        foreach ($state['unlocks'] as $achievementId => $records) {
            if (is_array($records)) unset($state['unlocks'][$achievementId][$playerId]);
        }
    }

    $encoded = encode_compact_state($state);
    if (trim($contents) !== $encoded || $sourceFormat !== 'v3' || $mutatesPlayer) {
        atomic_write_state($dataPath, $encoded);
    }
    $summary = build_summary($state);
} catch (RuntimeException $error) {
    $known = ['storage_corrupt', 'storage_unavailable', 'storage_write_failed', 'storage_encode_failed'];
    $storageError = in_array($error->getMessage(), $known, true) ? $error->getMessage() : 'storage_unavailable';
} finally {
    flock($lockHandle, LOCK_UN);
    fclose($lockHandle);
}

if ($storageError !== null) respond(['ok' => false, 'error' => $storageError], 503);
respond(is_array($summary) ? $summary : ['ok' => false, 'error' => 'storage_unavailable'], is_array($summary) ? 200 : 503);