<?php

declare(strict_types=1);

namespace app\common\service;

/** 一次 HTTP 请求只拉一页；只有归档成功后才推进游标。 */
final class ImChatSyncSession
{
    public static function start(array $accounts): array
    {
        return [
            'accounts' => array_values(array_unique($accounts)),
            'index' => 0, 'side' => 0, 'cursor' => [], 'inserted' => 0, 'errors' => [],
        ];
    }

    public static function step(array $state, callable $fetchPage, callable $archive): array
    {
        if ($state['index'] >= count($state['accounts'])) {
            return $state;
        }
        $account = $state['accounts'][$state['index']];
        try {
            $page = $fetchPage($account, $state['cursor']);
        } catch (\Throwable $e) {
            // 失败的会话不妨碍其他医生记录落库，下一轮仍从头补拉该会话。
            $state['errors'][] = $account . ($state['side'] === 0 ? '（医生侧）' : '（患者侧）') . '：' . $e->getMessage();
            return self::nextSide($state);
        }

        // 落库异常交由调用者处理，绝不能把未归档的页标记为已同步。
        $state['inserted'] += $archive($account, $page['msgList']);
        if ($page['completed']) {
            $state = self::nextSide($state);
        } else {
            $state['cursor'] = $page['cursor'];
        }
        return $state;
    }

    private static function nextSide(array $state): array
    {
        $state['cursor'] = [];
        if ($state['side'] === 0) {
            $state['side'] = 1;
        } else {
            $state['side'] = 0;
            $state['index']++;
        }
        return $state;
    }

    public static function progress(array $state): array
    {
        $checking = array_key_exists('accounts_verified', $state) && !$state['accounts_verified'];
        $check = $state['account_check'] ?? null;
        $completed = !$checking && $state['index'] >= count($state['accounts']);
        return [
            'completed' => $completed,
            'phase' => $checking ? 'checking_accounts' : ($completed ? 'completed' : 'syncing'),
            'checked_accounts' => $check['offset'] ?? 0,
            'candidate_accounts' => $check ? count($check['candidates']) : 0,
            'skipped_accounts' => $check ? count($check['missing']) : 0,
            'inserted' => $state['inserted'],
            'processed_peers' => $state['index'],
            'total_peers' => count($state['accounts']),
            'errors' => $state['errors'],
        ];
    }
}