#!/usr/local/bin/php
<?php
declare(strict_types=1);

require_once dirname(__DIR__) . '/exec/lib/Settings.php';
require_once dirname(__DIR__) . '/exec/lib/MessageClassifier.php';
require_once dirname(__DIR__) . '/exec/lib/RepeatState.php';
require_once dirname(__DIR__) . '/exec/lib/MailSender.php';
require_once dirname(__DIR__) . '/exec/lib/MailboxDirectory.php';
require_once dirname(__DIR__) . '/exec/lib/RuleRepository.php';

final class GlobalAutoresponderWorker
{
    /** @param callable(string,string,string,string):bool $send */
    public function __construct(
        private Settings $settings,
        private RuleRepository $rules,
        private MailboxDirectory $mailboxes,
        private RepeatState $repeat,
        private $send,
        private ?int $now = null
    ) {
    }

    /** @param array<string,string> $env */
    public function handle(array $env, string $message): int
    {
        if ($this->settings->backendMode() !== 'exim') {
            return 0;
        }
        $sender = self::firstEnv($env, ['SENDER_ADDRESS', 'sender_address', 'SENDER', 'sender']);
        $recipient = self::recipientFromEnv($env);
        if ($sender === '' || $recipient === '' || !self::isEmail($sender) || !self::isEmail($recipient)) {
            return 0;
        }
        $headers = self::parseHeaders($message);
        if (MessageClassifier::shouldSuppress($headers, $sender)) {
            return 0;
        }
        $resolved = $this->mailboxes->resolveRecipient($recipient);
        if ($resolved === null) {
            return 0;
        }
        $sent = 0;
        $owner = $resolved['owner'];
        $recipient = $resolved['email'];
        foreach ($this->rules->all($owner) as $rule) {
            if (!$this->isActiveRule($rule)) {
                continue;
            }
            if (!$this->ruleIncludesRecipient($rule, $recipient)) {
                continue;
            }
            $ruleId = (string)($rule['id'] ?? '');
            if ($ruleId === '') {
                continue;
            }
            $repeatMinutes = !empty($rule['reply_every_message']) ? 0 : max(0, (int)($rule['repeat_minutes'] ?? 1440));
            if (!$this->repeat->shouldSend($owner, $ruleId, $recipient, $sender, $repeatMinutes)) {
                continue;
            }
            $replySubject = self::replySubject(
                (string)($rule['subject_prefix'] ?? $rule['subject'] ?? ''),
                self::headerValue($headers, 'subject')
            );
            $ok = (bool)call_user_func(
                $this->send,
                $recipient,
                strtolower($sender),
                $replySubject,
                (string)$rule['body']
            );
            if ($ok) {
                $this->repeat->record($owner, $ruleId, $recipient, $sender);
                $sent++;
            }
        }
        return $sent;
    }

    /** @param array<string,mixed> $rule */
    private function isActiveRule(array $rule): bool
    {
        if (empty($rule['enabled'])) {
            return false;
        }
        $now = $this->now ?? time();
        return (int)($rule['start_ts'] ?? 0) <= $now && (int)($rule['end_ts'] ?? 0) >= $now;
    }

    /** @param array<string,mixed> $rule */
    private function ruleIncludesRecipient(array $rule, string $recipient): bool
    {
        if (!array_key_exists('dynamic_scope', $rule) || !empty($rule['dynamic_scope'])) {
            return true;
        }
        $snapshot = $rule['mailbox_snapshot'] ?? [];
        if (!is_array($snapshot)) {
            return false;
        }
        foreach ($snapshot as $mailbox) {
            if (is_array($mailbox) && strtolower((string)($mailbox['email'] ?? '')) === strtolower($recipient)) {
                return true;
            }
        }
        return false;
    }

    /** @param array<string,string> $env @param string[] $keys */
    private static function firstEnv(array $env, array $keys): string
    {
        foreach ($keys as $key) {
            $value = trim((string)($env[$key] ?? ''));
            if ($value !== '') {
                return strtolower($value);
            }
        }
        return '';
    }

    /** @param array<string,string> $env */
    private static function recipientFromEnv(array $env): string
    {
        $direct = self::firstEnv($env, ['LOCAL_PART_DOMAIN', 'RECIPIENT', 'ORIGINAL_RECIPIENT', 'local_part_domain']);
        if ($direct !== '') {
            return $direct;
        }
        $local = self::firstEnv($env, ['LOCAL_PART', 'local_part']);
        $domain = self::firstEnv($env, ['DOMAIN', 'domain']);
        return ($local !== '' && $domain !== '') ? $local . '@' . $domain : '';
    }

    private static function isEmail(string $value): bool
    {
        return (bool)preg_match('/^[A-Za-z0-9._%+\-]+@[A-Za-z0-9.\-]+$/', $value);
    }

    /** @return array<string,string> */
    public static function parseHeaders(string $message): array
    {
        $headers = [];
        $current = '';
        foreach (preg_split('/\r\n|\n|\r/', $message) ?: [] as $line) {
            if ($line === '') {
                break;
            }
            if ($current !== '' && preg_match('/^[ \t]/', $line)) {
                $headers[$current] .= ' ' . trim($line);
                continue;
            }
            if (!str_contains($line, ':')) {
                continue;
            }
            [$key, $value] = explode(':', $line, 2);
            $current = trim($key);
            if ($current !== '') {
                $headers[$current] = trim($value);
            }
        }
        return $headers;
    }

    /** @param array<string,string> $headers */
    private static function headerValue(array $headers, string $name): string
    {
        foreach ($headers as $key => $value) {
            if (strcasecmp($key, $name) === 0) {
                return trim($value);
            }
        }
        return '';
    }

    private static function replySubject(string $prefix, string $originalSubject): string
    {
        $prefix = trim($prefix);
        $originalSubject = trim($originalSubject);
        if ($prefix !== '' && $originalSubject !== '') {
            return str_ends_with($prefix, ':') ? $prefix . ' ' . $originalSubject : $prefix . ': ' . $originalSubject;
        }
        if ($prefix !== '') {
            return $prefix;
        }
        return $originalSubject !== '' ? $originalSubject : 'Automatic reply';
    }
}

if (PHP_SAPI === 'cli' && realpath((string)($_SERVER['SCRIPT_FILENAME'] ?? '')) === __FILE__) {
    $settings = Settings::load(Settings::EXTERNAL_SETTINGS);
    $sender = new MailSender();
    $worker = new GlobalAutoresponderWorker(
        $settings,
        new RuleRepository(),
        new MailboxDirectory(),
        new RepeatState(),
        static fn (string $from, string $to, string $subject, string $body): bool => $sender->send('/usr/sbin/sendmail', $from, $to, $subject, $body)
    );
    $worker->handle(getenv(), stream_get_contents(STDIN) ?: '');
}