<?php

declare(strict_types=1);

namespace Box\Mod\Mailgateway;

use FOSSBilling\InformationException;
use Webklex\PHPIMAP\IMAP;

/** IMAP transport; deliberately never uses Webklex's MOVE fallback (global EXPUNGE). */
class ImapMailbox
{
    private $client;
    private $inbox;
    private array $folders = [];

    public function __construct(private array $settings, private ?\Closure $factory = null) {}

    public function connect(): void
    {
        if ($this->settings['password'] === '') {
            throw new InformationException('Mailbox password is missing');
        }
        if ($this->factory === null) {
            if (!is_file(__DIR__ . '/vendor/autoload.php')) {
                throw new InformationException('Mail Gateway Composer dependencies are missing');
            }
            require_once __DIR__ . '/vendor/autoload.php';
        }
        $config = [
            'host' => $this->settings['host'], 'port' => (int) $this->settings['port'],
            'protocol' => 'imap', 'encryption' => $this->settings['encryption'],
            'validate_cert' => true, 'username' => $this->settings['username'],
            'password' => $this->settings['password'], 'authentication' => null, 'timeout' => RuntimeConfig::get('imap_timeout_seconds'),
        ];
        $this->client = $this->factory !== null ? ($this->factory)($config)
            : (new \Webklex\PHPIMAP\ClientManager(['options' => ['debug' => false]]))->make($config);
        $this->client->connect();
        $capabilities = $this->client->getConnection()->getCapabilities()->validatedData();
        if (!in_array('MOVE', array_map('strtoupper', $capabilities), true)) {
            throw new InformationException('IMAP server must support MOVE');
        }
        foreach (['inbox_folder', 'processed_folder', 'ignored_folder', 'failed_folder'] as $field) {
            $folder = $this->client->getFolderByPath($this->settings[$field]);
            if ($folder === null || $folder->no_select) {
                throw new InformationException('A configured IMAP folder is missing or cannot be selected');
            }
            $this->folders[$field] = $folder;
        }
        $this->inbox = $this->folders['inbox_folder'];
    }

    public function uids(int $limit): array
    {
        $query = $this->inbox->query()->leaveUnread()->setSequence(IMAP::ST_UID)->whereUndeleted();
        $uids = array_map('intval', $query->search()->toArray());
        sort($uids, SORT_NUMERIC);
        return array_slice($uids, 0, $limit);
    }

    public function read(int $uid): array
    {
        $message = $this->inbox->query()->leaveUnread()->fetchBody(false)->setFetchFlags(false)->getMessageByUid($uid);
        $header = $message->getHeader();
        $headers = self::rawHeaders($header->raw);
        $policy = new InboundPolicy();
        $ignored = $policy->ignoreReason($policy->headers(['headers' => $headers])) !== null;
        if (!$ignored) {
            if ((int) $message->getSize() > RuntimeConfig::get('max_message_bytes')) {
                throw new InformationException('Email exceeds the configured import size limit');
            }
            // Webklex parseBody() fetches RFC822.TEXT then restores Seen flags.
            // Fetch with true PEEK instead: even a crash cannot mark mail as read.
            $bodies = $this->client->getConnection()->fetch(['BODY.PEEK[TEXT]', 'UID'], [$uid], null, IMAP::ST_UID)->validatedData();
            $body = $bodies[$uid]['BODY[TEXT]'] ?? null;
            if (!is_string($body)) {
                throw new \RuntimeException('IMAP body was not returned');
            }
            $message->parseRawBody($body);
        }
        return self::data($message, $this->settings['mailbox'], $headers, $ignored);
    }

    /** Keep repeated values and the literal null Return-Path lost by address parsers. */
    public static function rawHeaders(string $raw): array
    {
        $raw = preg_replace('/\r?\n[ \t]+/', ' ', $raw);
        $headers = [];
        foreach (preg_split('/\r?\n/', $raw) as $line) {
            if (preg_match('/^([A-Za-z0-9-]+):[ \t]*(.*)$/D', $line, $match)) {
                $headers[strtolower($match[1])][] = trim($match[2]);
            }
        }
        return $headers;
    }

    public static function data(object $message, string $mailbox, array $headers, bool $ignored): array
    {
        $ids = $headers['message-id'] ?? [];
        if (count($ids) > 1) {
            throw new InformationException('Email has multiple Message-ID headers');
        }
        // A stable MIME fingerprint also deduplicates messages without a Message-ID.
        $id = $ids[0] ?? '<' . hash('sha256', $message->getHeader()->raw . ($ignored ? '' : $message->getRawBody())) . '@mailgateway.invalid>';
        $data = ['mailbox' => $mailbox, 'message_id' => $id, 'headers' => $headers];
        if ($ignored) {
            return $data;
        }
        $senders = $message->getFrom()->toArray();
        if (count($headers['from'] ?? []) !== 1 || count($senders) !== 1) {
            throw new InformationException('Email must have exactly one From address');
        }
        $sender = $senders[0];
        $content = trim($message->getTextBody());
        if ($content === '') {
            $html = preg_replace('/<(script|style)\b[^>]*>.*?<\/\1\s*>/is', '', $message->getHTMLBody());
            $html = preg_replace('/<br\s*\/?\s*>|<\/(?:p|div|li|tr|h[1-6])\s*>/i', "\n", $html);
            $content = trim(html_entity_decode(strip_tags($html), ENT_QUOTES | ENT_HTML5, 'UTF-8'));
        }
        $subject = trim(mb_decode_mimeheader((string) $message->getSubject()));
        return $data + [
            'sender_email' => $sender->mail,
            'sender_name' => trim(mb_decode_mimeheader($sender->personal)) ?: $sender->mail,
            'subject' => $subject === '' ? '(No subject)' : $subject,
            'content' => $content,
        ];
    }

    public function move(int $uid, string $destination): void
    {
        $this->client->openFolder($this->inbox->path);
        $protocol = $this->client->getConnection();
        // Native UID MOVE touches only this message. No COPY/STORE/EXPUNGE fallback.
        $response = $protocol->requestAndResponse('UID MOVE', [(string) $uid,
            $protocol->escapeString($this->folders[$destination]->path)], true);
        if (!$response->boolean()) {
            throw new \RuntimeException('IMAP MOVE failed');
        }
    }

    public function disconnect(): void
    {
        if ($this->client !== null) {
            $this->client->disconnect();
        }
    }
}