<?php

declare(strict_types=1);

namespace Box\Mod\Mailgateway;

use FOSSBilling\InformationException;
use Pimple\Container;

class Poller
{
    private const LOCK = 'fossbilling_mailgateway_poll';

    public function __construct(
        private Container $di,
        private Service $service,
        private ?\Closure $factory = null,
        private ?\Closure $clock = null,
        private ?\Closure $lock = null,
    ) {}

    public function poll(bool $force = false): array
    {
        if (!$this->locking(true)) {
            return ['status' => 'busy', 'mailboxes' => []];
        }
        try {
            $store = $this->di['mailgateway_settings'] ?? new Settings($this->di);
            $mailboxes = array_filter($store->getAll(), fn ($settings) => $settings['enabled']);
            if ($mailboxes === []) {
                return ['status' => 'disabled', 'mailboxes' => []];
            }
            $system = $this->di['mod_service']('system');
            $now = $this->now();
            $last = (int) $system->getParamValue('mailgateway_last_poll', 0);
            if (!$force && $last > $now - RuntimeConfig::get('poll_interval_seconds')) {
                return ['status' => 'not_due', 'mailboxes' => []];
            }
            // Record the attempt before network work, so a failing server is not hammered.
            $system->setParamValue('mailgateway_last_poll', (string) $now, true);
            $results = [];
            $deadline = microtime(true) + RuntimeConfig::get('poll_budget_seconds');
            foreach ($mailboxes as $id => $settings) {
                if (microtime(true) >= $deadline) {
                    break;
                }
                $results[$id] = $this->mailbox($id, $settings, $deadline);
            }
            return ['status' => 'completed', 'mailboxes' => $results];
        } finally {
            $this->locking(false);
        }
    }

    private function mailbox(string $id, array $settings, float $deadline): array
    {
        $counts = ['ticket' => 0, 'reply' => 0, 'ignored' => 0, 'duplicate' => 0, 'failed' => 0, 'retry_pending' => 0, 'move_pending' => 0];
        $transport = null;
        $errors = [];
        $stage = 'connecting';
        try {
            $transport = $this->factory !== null ? ($this->factory)($settings) : new ImapMailbox($settings);
            $transport->connect();
            $stage = 'listing messages';
            foreach ($transport->uids(RuntimeConfig::get('messages_per_mailbox')) as $uid) {
                if (microtime(true) >= $deadline) {
                    break;
                }
                try {
                    $stage = 'reading email';
                    $data = $transport->read((int) $uid);
                    $stage = 'importing email';
                    $result = (new MessageTracker($this->di['dbal']))->process($data, $this->service);
                    $counts[$result['duplicate'] ? 'duplicate' : $result['action']]++;
                    $destination = $result['action'] === 'ignored' ? 'ignored_folder' : 'processed_folder';
                } catch (InformationException $error) {
                    $errors[] = $this->diagnostic($error, $stage, (int) $uid);
                    $counts['failed']++;
                    $destination = 'failed_folder';
                    $this->warning($id, (int) $uid, 'message rejected; moving to Failed');
                } catch (\Throwable $error) {
                    $errors[] = $this->diagnostic($error, $stage, (int) $uid);
                    // Infrastructure/fetch failures stay in the inbox for a later attempt.
                    $counts['retry_pending']++;
                    $this->warning($id, (int) $uid, 'import unavailable; left in inbox for retry');
                    continue;
                }
                try {
                    $stage = 'moving email';
                    $transport->move((int) $uid, $destination);
                } catch (\Throwable $error) {
                    $errors[] = $this->diagnostic($error, $stage, (int) $uid);
                    // Import already committed. Tracking prevents a second ticket on retry.
                    $counts['move_pending']++;
                    $this->warning($id, (int) $uid, 'folder move failed; retry will use message tracking');
                }
            }
            return ['status' => 'completed'] + $counts + ($errors === [] ? [] : ['errors' => $errors]);
        } catch (\Throwable $error) {
            $errors[] = $this->diagnostic($error, $stage, null);
            $this->warning($id, null, 'mailbox poll failed; check credentials, TLS, folders, network access, and server MOVE support');
            return ['status' => 'failed'] + $counts + ['errors' => $errors];
        } finally {
            if ($transport !== null) {
                try { $transport->disconnect(); } catch (\Throwable) {
                    $this->warning($id, null, 'IMAP logout failed');
                }
            }
        }
    }

    private function diagnostic(\Throwable $error, string $stage, ?int $uid): array
    {
        // A location identifies code faults without exposing exception messages/arguments.
        return ['uid' => $uid, 'stage' => $stage, 'exception' => $error::class,
            'file' => basename($error->getFile()), 'line' => $error->getLine()];
    }

    private function warning(string $id, ?int $uid, string $text): void
    {
        // Never log IMAP exception messages/traces, credentials, sender, subject or body.
        $this->di['logger']->warning('Mail Gateway mailbox ' . $id . ($uid !== null ? ' UID ' . $uid : '') . ': ' . $text);
    }

    private function now(): int
    {
        return $this->clock !== null ? ($this->clock)() : time();
    }

    private function locking(bool $acquire): bool
    {
        if ($this->lock !== null) {
            return ($this->lock)($acquire);
        }
        $sql = $acquire ? 'SELECT GET_LOCK(?, 0)' : 'SELECT RELEASE_LOCK(?)';
        return (int) $this->di['dbal']->fetchOne($sql, [self::LOCK]) === 1;
    }
}