<?php

namespace app\api\controller;

use think\Db;
use think\Env;
use PHPMailer\PHPMailer;
use think\Validate;

class EmailClient extends Base
{
    // ==================== SMTP Account Management ====================

    /**
     * Get SMTP accounts for a journal
     * Params: journal_id
     */
    public function getAccounts()
    {
        $journalId = intval($this->request->param('journal_id', 0));
        if (!$journalId) {
            return jsonError('journal_id is required');
        }

        $list = Db::name('journal_email')
            ->where('journal_id', $journalId)
            ->order('state asc, j_email_id asc')
            ->select();

        foreach ($list as &$item) {
            $item['smtp_password'] = '******';
            $item['remaining_today'] = max(0, $item['daily_limit'] - $item['today_sent']);
        }

        return jsonSuccess($list);
    }

    /**
     * Add SMTP account
     */
    public function addAccount()
    {
        $data = $this->request->post();

        if (empty($data['journal_id']) || empty($data['smtp_host']) || empty($data['smtp_user']) || empty($data['smtp_password'])) {
            return jsonError('journal_id, smtp_host, smtp_user, smtp_password are required');
        }

        $count = Db::name('journal_email')
            ->where('journal_id', intval($data['journal_id']))
            ->where('state', 0)
            ->count();
        if ($count >= 4) {
            return jsonError('Each journal allows at most 4 SMTP accounts');
        }

        $insert = [
            'journal_id'      => intval($data['journal_id']),
            'smtp_host'       => trim($data['smtp_host']),
            'smtp_port'       => intval($data['smtp_port'] ?? 465),
            'smtp_user'       => trim($data['smtp_user']),
            'smtp_password'   => trim($data['smtp_password']),
            'smtp_encryption' => in_array($data['smtp_encryption'] ?? 'ssl', ['ssl', 'tls']) ? $data['smtp_encryption'] : 'ssl',
            'smtp_from_name'  => trim($data['smtp_from_name'] ?? ''),
            'daily_limit'     => intval($data['daily_limit'] ?? 100),
            'today_sent'      => 0,
            'imap_host'       => trim($data['imap_host'] ?? ''),
            'imap_port'       => intval($data['imap_port'] ?? 993),
            'last_uid'        => 0,
            'state'           => 0,
        ];

        $id = Db::name('journal_email')->insertGetId($insert);

        return jsonSuccess(['j_email_id' => $id]);
    }

    /**
     * Update SMTP account
     */
    public function updateAccount()
    {
        $data = $this->request->post();
        $id   = intval($data['j_email_id'] ?? 0);

        if (!$id) {
            return jsonError('j_email_id is required');
        }

        $account = Db::name('journal_email')->where('j_email_id', $id)->find();
        if (!$account) {
            return jsonError('Account not found');
        }

        $update = [];
        $fields = ['smtp_host', 'smtp_port', 'smtp_user', 'smtp_password', 'smtp_encryption', 'smtp_from_name', 'daily_limit', 'imap_host', 'imap_port', 'state'];
        foreach ($fields as $field) {
            if (isset($data[$field])) {
                $update[$field] = $data[$field];
            }
        }

        if (isset($update['smtp_port'])) {
            $update['smtp_port'] = intval($update['smtp_port']);
        }
        if (isset($update['imap_port'])) {
            $update['imap_port'] = intval($update['imap_port']);
        }
        if (isset($update['daily_limit'])) {
            $update['daily_limit'] = intval($update['daily_limit']);
        }
        if (isset($update['state'])) {
            $update['state'] = intval($update['state']);
        }
        if (isset($update['smtp_encryption']) && !in_array($update['smtp_encryption'], ['ssl', 'tls'])) {
            $update['smtp_encryption'] = 'ssl';
        }

        if (empty($update)) {
            return jsonError('No fields to update');
        }

        Db::name('journal_email')->where('j_email_id', $id)->update($update);

        return jsonSuccess(['j_email_id' => $id]);
    }

    /**
     * Delete SMTP account
     */
    public function deleteAccount()
    {
        $id = intval($this->request->param('j_email_id', 0));
        if (!$id) {
            return jsonError('j_email_id is required');
        }

        Db::name('journal_email')->where('j_email_id', $id)->delete();

        return jsonSuccess(['deleted' => $id]);
    }

    /**
     * Test SMTP connection
     */
    public function testAccount()
    {
        $id        = intval($this->request->param('j_email_id', 0));
        $testEmail = trim($this->request->param('test_email', ''));

        if (!$id) {
            return jsonError('j_email_id is required');
        }
        if (empty($testEmail)) {
            return jsonError('test_email is required');
        }

        $account = Db::name('journal_email')->where('j_email_id', $id)->find();
        if (!$account) {
            return jsonError('Account not found');
        }

        $result = $this->doSendEmail($account, $testEmail, 'SMTP Test', '<p>This is a test email from your journal system.</p>');

        if ($result['status'] === 1) {
            return jsonSuccess(['msg' => 'Test email sent successfully']);
        } else {
            return jsonError('Send failed: ' . $result['data']);
        }
    }

    // ==================== Email Sending ====================

    /**
     * Send a single email using a specific journal's SMTP
     * Params: journal_id, to_email, subject, content, j_email_id(optional, auto-select if empty)
     */
    public function sendOne()
    {
        $journalId = intval($this->request->param('journal_id', 0));
        $toEmail   = trim($this->request->param('to_email', ''));
        $subject   = trim($this->request->param('subject', ''));
        $content   = $this->request->param('content', '');
        $accountId = intval($this->request->param('j_email_id', 0));

        if (!$journalId || empty($toEmail) || empty($subject) || empty($content)) {
            return jsonError('journal_id, to_email, subject, content are required');
        }

        if ($accountId) {
            $account = Db::name('journal_email')
                ->where('j_email_id', $accountId)
                ->where('journal_id', $journalId)
                ->where('state', 0)
                ->find();
        } else {
            $account = $this->pickSmtpAccount($journalId);
        }

        if (!$account) {
            return jsonError('No available SMTP account (all disabled or daily limit reached)');
        }

        $this->resetDailyCountIfNeeded($account);

        if ($account['today_sent'] >= $account['daily_limit']) {
            $account = $this->pickSmtpAccount($journalId);
            if (!$account) {
                return jsonError('All SMTP accounts have reached daily limit');
            }
        }

        $result = $this->doSendEmail($account, $toEmail, $subject, $content);

        if ($result['status'] === 1) {
            Db::name('journal_email')->where('j_email_id', $account['j_email_id'])->setInc('today_sent');
            return jsonSuccess([
                'msg'        => 'Email sent',
                'from'       => $account['smtp_user'],
                'to'         => $toEmail,
                'j_email_id' => $account['j_email_id'],
            ]);
        } else {
            return jsonError('Send failed: ' . $result['data']);
        }
    }

    /**
     * Send batch emails to multiple experts
     * Params: journal_id, expert_ids (comma separated), subject, content
     * Content supports variables: {name}, {email}, {affiliation}
     */
    public function sendBatch()
    {
        $journalId = intval($this->request->param('journal_id', 0));
        $expertIds = trim($this->request->param('expert_ids', ''));
        $subject   = trim($this->request->param('subject', ''));
        $content   = $this->request->param('content', '');

        if (!$journalId || empty($expertIds) || empty($subject) || empty($content)) {
            return jsonError('journal_id, expert_ids, subject, content are required');
        }

        $ids     = array_map('intval', explode(',', $expertIds));
        $experts = Db::name('expert')->where('expert_id', 'in', $ids)->where('state', 0)->select();

        if (empty($experts)) {
            return jsonError('No valid experts found (state must be 0)');
        }

        $sent    = 0;
        $failed  = 0;
        $skipped = 0;
        $errors  = [];

        foreach ($experts as $expert) {
            $account = $this->pickSmtpAccount($journalId);
            if (!$account) {
                $skipped += (count($experts) - $sent - $failed);
                $errors[] = 'All SMTP accounts reached daily limit, stopped at #' . ($sent + $failed + 1);
                break;
            }

            $personalContent = $this->replaceVariables($content, $expert);
            $personalSubject = $this->replaceVariables($subject, $expert);

            $result = $this->doSendEmail($account, $expert['email'], $personalSubject, $personalContent);

            if ($result['status'] === 1) {
                Db::name('journal_email')->where('j_email_id', $account['j_email_id'])->setInc('today_sent');
                Db::name('expert')->where('expert_id', $expert['expert_id'])->update(['state' => 1]);
                $sent++;
            } else {
                $failed++;
                $errors[] = $expert['email'] . ': ' . $result['data'];
            }

            $delay = rand(30, 60);
            sleep($delay);
        }

        return jsonSuccess([
            'sent'    => $sent,
            'failed'  => $failed,
            'skipped' => $skipped,
            'errors'  => $errors,
        ]);
    }

    /**
     * Get sending stats for a journal
     */
    public function getStats()
    {
        $journalId = intval($this->request->param('journal_id', 0));
        if (!$journalId) {
            return jsonError('journal_id is required');
        }

        $accounts = Db::name('journal_email')
            ->where('journal_id', $journalId)
            ->where('state', 0)
            ->select();

        $totalLimit = 0;
        $totalSent  = 0;
        $details    = [];

        foreach ($accounts as $acc) {
            $this->resetDailyCountIfNeeded($acc);
            $totalLimit += $acc['daily_limit'];
            $totalSent  += $acc['today_sent'];
            $details[]   = [
                'j_email_id'     => $acc['j_email_id'],
                'smtp_user'      => $acc['smtp_user'],
                'daily_limit'    => $acc['daily_limit'],
                'today_sent'     => $acc['today_sent'],
                'remaining'      => max(0, $acc['daily_limit'] - $acc['today_sent']),
            ];
        }

        return jsonSuccess([
            'total_daily_limit'  => $totalLimit,
            'total_today_sent'   => $totalSent,
            'total_remaining'    => max(0, $totalLimit - $totalSent),
            'accounts'           => $details,
        ]);
    }

    /**
     * Reset daily sent count (called by cron or manually)
     */
    public function resetDailyCount()
    {
        $journalId = intval($this->request->param('journal_id', 0));

        if ($journalId) {
            $count = Db::name('journal_email')
                ->where('journal_id', $journalId)
                ->update(['today_sent' => 0]);
        } else {
            $count = Db::name('journal_email')->update(['today_sent' => 0]);
        }

        return jsonSuccess(['reset_count' => $count]);
    }

    // ==================== Inbox - Sync ====================

    /**
     * Sync emails from IMAP to local database
     * Params: j_email_id (single account) or journal_id (all accounts)
     */
    public function syncInbox()
    {
        $accountId = intval($this->request->param('j_email_id', 0));
        $journalId = intval($this->request->param('journal_id', 0));

        if (!$accountId && !$journalId) {
            return jsonError('j_email_id or journal_id is required');
        }

        set_time_limit(300);

        if ($accountId) {
            $accounts = Db::name('journal_email')->where('j_email_id', $accountId)->where('state', 0)->select();
        } else {
            $accounts = Db::name('journal_email')->where('journal_id', $journalId)->where('state', 0)->select();
        }

        $report = [];
        foreach ($accounts as $account) {
            $report[] = $this->doSyncAccount($account);
        }

        return jsonSuccess(['report' => $report]);
    }

    private function doSyncAccount($account)
    {
        if (empty($account['imap_host'])) {
            return ['j_email_id' => $account['j_email_id'], 'error' => 'IMAP not configured'];
        }

        $imap = $this->connectImap($account);
        if (!$imap) {
            return ['j_email_id' => $account['j_email_id'], 'error' => 'IMAP connection failed'];
        }

        $lastUid = intval($account['last_uid']);
        $synced  = 0;
        $bounced = 0;
        $maxUid  = $lastUid;

        try {
            if ($lastUid > 0) {
                $searchRange = ($lastUid + 1) . ':*';
                $emails = imap_fetch_overview($imap, $searchRange, FT_UID);
            } else {
                $emails = imap_fetch_overview($imap, '1:*', FT_UID);
            }

            if (!$emails) {
                $emails = [];
            }

            foreach ($emails as $overview) {
                $uid = intval($overview->uid);
                if ($uid <= $lastUid) {
                    continue;
                }

                $messageId = isset($overview->message_id) ? trim($overview->message_id) : '';
                if ($messageId && Db::name('email_inbox')->where('message_id', $messageId)->find()) {
                    if ($uid > $maxUid) $maxUid = $uid;
                    continue;
                }

                $header  = imap_fetchheader($imap, $uid, FT_UID);
                $struct  = imap_fetchstructure($imap, $uid, FT_UID);
                $body    = $this->getEmailBody($imap, $uid, $struct);

                $fromParts = isset($overview->from) ? $this->parseAddress($overview->from) : ['email' => '', 'name' => ''];
                $subject   = isset($overview->subject) ? $this->decodeMimeStr($overview->subject) : '';
                $toEmail   = isset($overview->to) ? $this->parseAddress($overview->to)['email'] : $account['smtp_user'];
                $emailDate = isset($overview->date) ? strtotime($overview->date) : time();
                if (!$emailDate) $emailDate = time();

                $hasAttachment = $this->checkAttachment($struct);
                $isBounce      = $this->detectBounce($fromParts['email'], $subject, $header);
                $bounceEmail   = '';

                if ($isBounce) {
                    $bounceEmail = $this->extractBounceRecipient($body['text'], $header);
                    if ($bounceEmail) {
                        Db::name('expert')->where('email', strtolower($bounceEmail))->update(['state' => 4]);
                        $bounced++;
                    }
                }

                $insert = [
                    'j_email_id'     => $account['j_email_id'],
                    'journal_id'     => $account['journal_id'],
                    'message_id'     => mb_substr($messageId, 0, 255),
                    'uid'            => $uid,
                    'from_email'     => mb_substr($fromParts['email'], 0, 255),
                    'from_name'      => mb_substr($fromParts['name'], 0, 255),
                    'to_email'       => mb_substr($toEmail, 0, 255),
                    'subject'        => mb_substr($subject, 0, 512),
                    'content_html'   => $body['html'],
                    'content_text'   => $body['text'],
                    'email_date'     => $emailDate,
                    'has_attachment'  => $hasAttachment ? 1 : 0,
                    'is_read'        => 0,
                    'is_starred'     => 0,
                    'is_bounce'      => $isBounce ? 1 : 0,
                    'bounce_email'   => mb_substr($bounceEmail, 0, 128),
                    'folder'         => 'INBOX',
                    'ctime'          => time(),
                    'state'          => 0,
                ];

                try {
                    Db::name('email_inbox')->insert($insert);
                    $synced++;
                } catch (\Exception $e) {
                    // skip duplicate
                }

                if ($uid > $maxUid) {
                    $maxUid = $uid;
                }
            }

            if ($maxUid > $lastUid) {
                Db::name('journal_email')->where('j_email_id', $account['j_email_id'])->update(['last_uid' => $maxUid]);
            }
        } catch (\Exception $e) {
            imap_close($imap);
            return ['j_email_id' => $account['j_email_id'], 'error' => $e->getMessage()];
        }

        imap_close($imap);

        return [
            'j_email_id' => $account['j_email_id'],
            'smtp_user'  => $account['smtp_user'],
            'synced'     => $synced,
            'bounced'    => $bounced,
            'last_uid'   => $maxUid,
        ];
    }

    // ==================== Inbox - Read ====================

    /**
     * Get inbox list with pagination and filtering
     */
    public function getInboxList()
    {
        $journalId = intval($this->request->param('journal_id', 0));
        $accountId = intval($this->request->param('j_email_id', 0));
        $isRead    = $this->request->param('is_read', '-1');
        $isBounce  = $this->request->param('is_bounce', '-1');
        $keyword   = trim($this->request->param('keyword', ''));
        $folder    = trim($this->request->param('folder', 'INBOX'));
        $page      = max(1, intval($this->request->param('page', 1)));
        $perPage   = max(1, min(intval($this->request->param('per_page', 20)), 100));

        $where = ['state' => 0, 'folder' => $folder];

        if ($accountId) {
            $where['j_email_id'] = $accountId;
        } elseif ($journalId) {
            $where['journal_id'] = $journalId;
        } else {
            return jsonError('j_email_id or journal_id is required');
        }

        if ($isRead !== '-1' && $isRead !== '') {
            $where['is_read'] = intval($isRead);
        }
        if ($isBounce !== '-1' && $isBounce !== '') {
            $where['is_bounce'] = intval($isBounce);
        }

        $query = Db::name('email_inbox')->where($where);
        if ($keyword !== '') {
            $query->where('from_email|from_name|subject', 'like', '%' . $keyword . '%');
        }

        $total = Db::name('email_inbox')->where($where)->count();
        $list  = $query
            ->field('inbox_id,j_email_id,from_email,from_name,to_email,subject,email_date,has_attachment,is_read,is_starred,is_bounce,bounce_email,ctime')
            ->order('email_date desc')
            ->page($page, $perPage)
            ->select();

        return jsonSuccess([
            'list'        => $list,
            'total'       => $total,
            'page'        => $page,
            'per_page'    => $perPage,
            'total_pages' => $total > 0 ? ceil($total / $perPage) : 0,
        ]);
    }

    public function getOneEmail(){
        $data = $this->request->post();
        $rule = new Validate([
            "j_email_id"
        ]);
        if(!$rule->check($data)){
            return jsonError($rule->getError());
        }
        $email_info = DB::name("journal_email")->where("j_email_id",$data['j_email_id'])->find();
        $re['email'] = $email_info;
        return jsonSuccess($re);
    }

    /**
     * Get single email detail
     */
    public function getEmailDetail()
    {
        $inboxId = intval($this->request->param('inbox_id', 0));
        if (!$inboxId) {
            return jsonError('inbox_id is required');
        }

        $email = Db::name('email_inbox')->where('inbox_id', $inboxId)->where('state', 0)->find();
        if (!$email) {
            return jsonError('Email not found');
        }

        if (!$email['is_read']) {
            Db::name('email_inbox')->where('inbox_id', $inboxId)->update(['is_read' => 1]);
            $email['is_read'] = 1;
        }

        return jsonSuccess($email);
    }

    /**
     * Get unread count
     */
    public function getUnreadCount()
    {
        $journalId = intval($this->request->param('journal_id', 0));
        $accountId = intval($this->request->param('j_email_id', 0));

        $where = ['state' => 0, 'is_read' => 0, 'folder' => 'INBOX'];

        if ($accountId) {
            $where['j_email_id'] = $accountId;
        } elseif ($journalId) {
            $where['journal_id'] = $journalId;
        } else {
            return jsonError('j_email_id or journal_id is required');
        }

        $total  = Db::name('email_inbox')->where($where)->count();
        $bounce = Db::name('email_inbox')->where($where)->where('is_bounce', 1)->count();

        return jsonSuccess([
            'unread'        => $total,
            'unread_bounce' => $bounce,
        ]);
    }

    // ==================== Inbox - Actions ====================

    /**
     * Mark emails as read/unread
     * Params: inbox_ids (comma separated), is_read (0 or 1)
     */
    public function markRead()
    {
        $ids    = trim($this->request->param('inbox_ids', ''));
        $isRead = intval($this->request->param('is_read', 1));

        if (empty($ids)) {
            return jsonError('inbox_ids is required');
        }

        $idArr = array_map('intval', explode(',', $ids));
        $count = Db::name('email_inbox')->where('inbox_id', 'in', $idArr)->update(['is_read' => $isRead ? 1 : 0]);

        return jsonSuccess(['updated' => $count]);
    }

    /**
     * Star/unstar emails
     */
    public function markStar()
    {
        $ids       = trim($this->request->param('inbox_ids', ''));
        $isStarred = intval($this->request->param('is_starred', 1));

        if (empty($ids)) {
            return jsonError('inbox_ids is required');
        }

        $idArr = array_map('intval', explode(',', $ids));
        $count = Db::name('email_inbox')->where('inbox_id', 'in', $idArr)->update(['is_starred' => $isStarred ? 1 : 0]);

        return jsonSuccess(['updated' => $count]);
    }

    /**
     * Delete emails (soft delete)
     */
    public function deleteEmail()
    {
        $ids = trim($this->request->param('inbox_ids', ''));
        if (empty($ids)) {
            return jsonError('inbox_ids is required');
        }

        $idArr = array_map('intval', explode(',', $ids));
        $count = Db::name('email_inbox')->where('inbox_id', 'in', $idArr)->update(['state' => 1]);

        return jsonSuccess(['deleted' => $count]);
    }

    /**
     * Download attachment from IMAP in real time
     * Params: inbox_id, part_index (attachment index, starting from 0)
     */
    public function getAttachment()
    {
        $inboxId   = intval($this->request->param('inbox_id', 0));
        $partIndex = intval($this->request->param('part_index', 0));

        if (!$inboxId) {
            return jsonError('inbox_id is required');
        }

        $email = Db::name('email_inbox')->where('inbox_id', $inboxId)->where('state', 0)->find();
        if (!$email) {
            return jsonError('Email not found');
        }

        $account = Db::name('journal_email')->where('j_email_id', $email['j_email_id'])->find();
        if (!$account || empty($account['imap_host'])) {
            return jsonError('IMAP not configured for this account');
        }

        $imap = $this->connectImap($account);
        if (!$imap) {
            return jsonError('IMAP connection failed');
        }

        $struct      = imap_fetchstructure($imap, $email['uid'], FT_UID);
        $attachments = $this->listAttachments($struct);

        if (!isset($attachments[$partIndex])) {
            imap_close($imap);
            return jsonError('Attachment not found at index ' . $partIndex);
        }

        $att      = $attachments[$partIndex];
        $partNum  = $att['part_number'];
        $filename = $att['filename'];
        $encoding = $att['encoding'];

        $body = imap_fetchbody($imap, $email['uid'], $partNum, FT_UID);
        imap_close($imap);

        if ($encoding == 3) {
            $body = base64_decode($body);
        } elseif ($encoding == 4) {
            $body = quoted_printable_decode($body);
        }

        $dir = ROOT_PATH . 'public' . DS . 'attachments';
        if (!is_dir($dir)) {
            mkdir($dir, 0777, true);
        }
        $safeName = time() . '_' . preg_replace('/[^a-zA-Z0-9._\-]/', '_', $filename);
        $filepath = $dir . DS . $safeName;
        file_put_contents($filepath, $body);

        return jsonSuccess([
            'filename'  => $filename,
            'file_url'  => '/attachments/' . $safeName,
            'file_size' => strlen($body),
        ]);
    }

    /**
     * List attachments for an email (without downloading)
     */
    public function listEmailAttachments()
    {
        $inboxId = intval($this->request->param('inbox_id', 0));
        if (!$inboxId) {
            return jsonError('inbox_id is required');
        }

        $email = Db::name('email_inbox')->where('inbox_id', $inboxId)->where('state', 0)->find();
        if (!$email) {
            return jsonError('Email not found');
        }

        $account = Db::name('journal_email')->where('j_email_id', $email['j_email_id'])->find();
        if (!$account || empty($account['imap_host'])) {
            return jsonError('IMAP not configured');
        }

        $imap = $this->connectImap($account);
        if (!$imap) {
            return jsonError('IMAP connection failed');
        }

        $struct      = imap_fetchstructure($imap, $email['uid'], FT_UID);
        $attachments = $this->listAttachments($struct);
        imap_close($imap);

        $result = [];
        foreach ($attachments as $i => $att) {
            $result[] = [
                'index'    => $i,
                'filename' => $att['filename'],
                'size'     => $att['size'] ?? 0,
            ];
        }

        return jsonSuccess($result);
    }

    // ==================== IMAP Helpers ====================

    private function connectImap($account)
    {
        $host       = $account['imap_host'];
        $port       = intval($account['imap_port'] ?: 993);
        $user       = $account['smtp_user'];
        $password   = $account['smtp_password'];
        $encryption = ($port == 993) ? 'ssl' : '';

        $flags = '/imap';
        if ($encryption === 'ssl') {
            $flags .= '/ssl';
        }
        $flags .= '/novalidate-cert';

        $mailbox = '{' . $host . ':' . $port . $flags . '}INBOX';

        $imap = @imap_open($mailbox, $user, $password, 0, 1);
        if (!$imap) {
            return false;
        }

        return $imap;
    }

    private function getEmailBody($imap, $uid, $struct)
    {
        $html = '';
        $text = '';

        if (!isset($struct->parts) || empty($struct->parts)) {
            $body = imap_fetchbody($imap, $uid, '1', FT_UID);
            $body = $this->decodeBody($body, $struct->encoding ?? 0);
            $charset = $this->getCharset($struct);
            $body = $this->convertToUtf8($body, $charset);

            if (isset($struct->subtype) && strtoupper($struct->subtype) === 'HTML') {
                $html = $body;
            } else {
                $text = $body;
            }
        } else {
            foreach ($struct->parts as $index => $part) {
                $partNum = ($index + 1);
                if (isset($part->subtype)) {
                    $subtype = strtoupper($part->subtype);
                    if ($subtype === 'PLAIN' && empty($text)) {
                        $body = imap_fetchbody($imap, $uid, (string) $partNum, FT_UID);
                        $text = $this->decodeBody($body, $part->encoding ?? 0);
                        $text = $this->convertToUtf8($text, $this->getCharset($part));
                    } elseif ($subtype === 'HTML' && empty($html)) {
                        $body = imap_fetchbody($imap, $uid, (string) $partNum, FT_UID);
                        $html = $this->decodeBody($body, $part->encoding ?? 0);
                        $html = $this->convertToUtf8($html, $this->getCharset($part));
                    } elseif ($subtype === 'ALTERNATIVE' || $subtype === 'MIXED' || $subtype === 'RELATED') {
                        if (isset($part->parts)) {
                            foreach ($part->parts as $subIndex => $subPart) {
                                $subPartNum = $partNum . '.' . ($subIndex + 1);
                                $sub = strtoupper($subPart->subtype ?? '');
                                if ($sub === 'PLAIN' && empty($text)) {
                                    $body = imap_fetchbody($imap, $uid, $subPartNum, FT_UID);
                                    $text = $this->decodeBody($body, $subPart->encoding ?? 0);
                                    $text = $this->convertToUtf8($text, $this->getCharset($subPart));
                                } elseif ($sub === 'HTML' && empty($html)) {
                                    $body = imap_fetchbody($imap, $uid, $subPartNum, FT_UID);
                                    $html = $this->decodeBody($body, $subPart->encoding ?? 0);
                                    $html = $this->convertToUtf8($html, $this->getCharset($subPart));
                                }
                            }
                        }
                    }
                }
            }
        }

        if (empty($html) && !empty($text)) {
            $html = '<pre>' . htmlspecialchars($text) . '</pre>';
        }

        return ['html' => $html, 'text' => $text];
    }

    private function decodeBody($body, $encoding)
    {
        switch ($encoding) {
            case 3: return base64_decode($body);
            case 4: return quoted_printable_decode($body);
            default: return $body;
        }
    }

    private function getCharset($struct)
    {
        if (isset($struct->parameters)) {
            foreach ($struct->parameters as $param) {
                if (strtolower($param->attribute) === 'charset') {
                    return $param->value;
                }
            }
        }
        return 'UTF-8';
    }

    private function convertToUtf8($str, $charset)
    {
        $charset = strtoupper(trim($charset));
        if ($charset === 'UTF-8' || $charset === 'UTF8' || empty($charset)) {
            return $str;
        }
        $converted = @iconv($charset, 'UTF-8//IGNORE', $str);
        return $converted !== false ? $converted : $str;
    }

    private function decodeMimeStr($str)
    {
        $elements = imap_mime_header_decode($str);
        $decoded  = '';
        foreach ($elements as $el) {
            $charset = ($el->charset === 'default') ? 'ASCII' : $el->charset;
            $decoded .= $this->convertToUtf8($el->text, $charset);
        }
        return $decoded;
    }

    private function parseAddress($addressStr)
    {
        $decoded = $this->decodeMimeStr($addressStr);
        $email   = '';
        $name    = '';

        if (preg_match('/<?([a-zA-Z0-9._%+\-]+@[a-zA-Z0-9.\-]+\.[a-zA-Z]{2,})>?/', $decoded, $m)) {
            $email = strtolower($m[1]);
        }
        if (preg_match('/^"?([^"<]+)"?\s*</', $decoded, $m)) {
            $name = trim($m[1]);
        }

        return ['email' => $email, 'name' => $name];
    }

    private function checkAttachment($struct)
    {
        if (!isset($struct->parts)) {
            return false;
        }
        foreach ($struct->parts as $part) {
            $disposition = '';
            if (isset($part->disposition)) {
                $disposition = strtolower($part->disposition);
            }
            if ($disposition === 'attachment') {
                return true;
            }
            if (isset($part->ifdparameters) && $part->ifdparameters) {
                foreach ($part->dparameters as $dp) {
                    if (strtolower($dp->attribute) === 'filename') {
                        return true;
                    }
                }
            }
        }
        return false;
    }

    private function listAttachments($struct, $prefix = '')
    {
        $attachments = [];
        if (!isset($struct->parts)) {
            return $attachments;
        }

        foreach ($struct->parts as $index => $part) {
            $partNum = $prefix ? ($prefix . '.' . ($index + 1)) : (string) ($index + 1);
            $filename = '';

            if (isset($part->dparameters)) {
                foreach ($part->dparameters as $dp) {
                    if (strtolower($dp->attribute) === 'filename') {
                        $filename = $this->decodeMimeStr($dp->value);
                    }
                }
            }
            if (empty($filename) && isset($part->parameters)) {
                foreach ($part->parameters as $p) {
                    if (strtolower($p->attribute) === 'name') {
                        $filename = $this->decodeMimeStr($p->value);
                    }
                }
            }

            if (!empty($filename)) {
                $attachments[] = [
                    'filename'    => $filename,
                    'part_number' => $partNum,
                    'encoding'    => $part->encoding ?? 0,
                    'size'        => $part->bytes ?? 0,
                ];
            }

            if (isset($part->parts)) {
                $sub = $this->listAttachments($part, $partNum);
                $attachments = array_merge($attachments, $sub);
            }
        }

        return $attachments;
    }

    // ==================== Bounce Detection ====================

    private function detectBounce($fromEmail, $subject, $header)
    {
        $fromEmail = strtolower($fromEmail);
        if (strpos($fromEmail, 'mailer-daemon') !== false || strpos($fromEmail, 'postmaster') !== false) {
            return true;
        }

        $subjectLower = strtolower($subject);
        $bounceKeywords = ['undelivered', 'delivery status', 'delivery failed', 'mail delivery failed', 'returned mail', 'undeliverable', 'failure notice'];
        foreach ($bounceKeywords as $kw) {
            if (strpos($subjectLower, $kw) !== false) {
                return true;
            }
        }

        if (stripos($header, 'report-type=delivery-status') !== false) {
            return true;
        }

        return false;
    }

    private function extractBounceRecipient($bodyText, $header)
    {
        if (preg_match('/Final-Recipient:.*?;\s*<?([a-zA-Z0-9._%+\-]+@[a-zA-Z0-9.\-]+\.[a-zA-Z]{2,})>?/i', $header . "\n" . $bodyText, $m)) {
            return strtolower($m[1]);
        }

        if (preg_match('/Original-Recipient:.*?;\s*<?([a-zA-Z0-9._%+\-]+@[a-zA-Z0-9.\-]+\.[a-zA-Z]{2,})>?/i', $header . "\n" . $bodyText, $m)) {
            return strtolower($m[1]);
        }

        if (preg_match('/<?([a-zA-Z0-9._%+\-]+@[a-zA-Z0-9.\-]+\.[a-zA-Z]{2,})>?\s+was not delivered/i', $bodyText, $m)) {
            return strtolower($m[1]);
        }

        if (preg_match('/delivery to.*?<?([a-zA-Z0-9._%+\-]+@[a-zA-Z0-9.\-]+\.[a-zA-Z]{2,})>?.*?failed/i', $bodyText, $m)) {
            return strtolower($m[1]);
        }

        return '';
    }

    // ==================== Internal Methods ====================

    /**
     * Pick the best available SMTP account for a journal
     * Strategy: choose the account with the most remaining quota
     */
    private function pickSmtpAccount($journalId)
    {
        $accounts = Db::name('journal_email')
            ->where('journal_id', $journalId)
            ->where('state', 0)
            ->select();

        if (empty($accounts)) {
            return null;
        }

        $best = null;
        $bestRemaining = -1;

        foreach ($accounts as $acc) {
            $this->resetDailyCountIfNeeded($acc);
            $remaining = $acc['daily_limit'] - $acc['today_sent'];
            if ($remaining > 0 && $remaining > $bestRemaining) {
                $best = $acc;
                $bestRemaining = $remaining;
            }
        }

        return $best;
    }

    /**
     * Reset today_sent if the date has changed
     */
    private function resetDailyCountIfNeeded(&$account)
    {
        $todayDate = date('Y-m-d');
        $cacheKey  = 'smtp_reset_' . $account['j_email_id'];
        $lastReset = \think\Cache::get($cacheKey);

        if ($lastReset !== $todayDate) {
            Db::name('journal_email')
                ->where('j_email_id', $account['j_email_id'])
                ->update(['today_sent' => 0]);
            $account['today_sent'] = 0;
            \think\Cache::set($cacheKey, $todayDate, 86400);
        }
    }

    /**
     * Actually send an email using PHPMailer with given SMTP config
     */
    private function doSendEmail($account, $toEmail, $subject, $htmlContent)
    {
        try {
            $mail = new PHPMailer\PHPMailer(true);
            $mail->isSMTP();
            $mail->SMTPDebug  = 0;
            $mail->CharSet    = 'UTF-8';
            $mail->Host       = $account['smtp_host'];
            $mail->Port       = intval($account['smtp_port']);
            $mail->SMTPAuth   = true;
            $mail->Username   = $account['smtp_user'];
            $mail->Password   = $account['smtp_password'];

            if ($account['smtp_encryption'] === 'ssl') {
                $mail->SMTPSecure = 'ssl';
            } elseif ($account['smtp_encryption'] === 'tls') {
                $mail->SMTPSecure = 'tls';
            } else {
                $mail->SMTPSecure = false;
                $mail->SMTPAutoTLS = false;
            }

            $fromName = !empty($account['smtp_from_name']) ? $account['smtp_from_name'] : $account['smtp_user'];
            $mail->setFrom($account['smtp_user'], $fromName);
            $mail->addReplyTo($account['smtp_user'], $fromName);
            $mail->addAddress($toEmail);

            $mail->isHTML(true);
            $mail->Subject = $subject;
            $mail->Body    = $htmlContent;
            $mail->AltBody = strip_tags($htmlContent);

            $mail->send();

            return ['status' => 1, 'data' => 'success'];
        } catch (\Exception $e) {
            return ['status' => 0, 'data' => $e->getMessage()];
        }
    }

    /**
     * Replace template variables with expert data
     */
    private function replaceVariables($template, $expert)
    {
        $vars = [
            '{name}'        => $expert['name'] ?? '',
            '{email}'       => $expert['email'] ?? '',
            '{affiliation}' => $expert['affiliation'] ?? '',
            '{field}'       => $expert['field'] ?? '',
        ];

        return str_replace(array_keys($vars), array_values($vars), $template);
    }
}