<?php

namespace App\Support\Link;

use GeoIp2\Database\Reader;
use GeoIp2\Exception\AddressNotFoundException;
use Illuminate\Http\Request;

final class LinkGeoResolver
{
    /** @var list<string> */
    private const HEADER_KEYS = ['CF-IPCountry', 'X-Country-Code', 'CloudFront-Viewer-Country'];

    private static ?Reader $reader = null;

    public static function countryCode(Request $request): ?string
    {
        if ($fromHeader = self::countryFromHeaders($request)) {
            return $fromHeader;
        }

        return self::countryFromIp($request->ip());
    }

    public static function countryFromIp(?string $ip): ?string
    {
        if (! self::isPublicIp($ip)) {
            return null;
        }

        $reader = self::reader();
        if ($reader === null) {
            return null;
        }

        try {
            $code = strtoupper((string) ($reader->country((string) $ip)->country->isoCode ?? ''));

            return strlen($code) === 2 && ! in_array($code, ['XX', 'T1'], true) ? $code : null;
        } catch (AddressNotFoundException) {
            return null;
        } catch (\Throwable) {
            return null;
        }
    }

    public static function countryLabel(?string $code): string
    {
        if ($code === null || $code === '') {
            return 'Unknown';
        }

        if (function_exists('locale_get_display_region')) {
            $name = locale_get_display_region('_'.$code, 'en');

            return is_string($name) && $name !== '' ? $name : $code;
        }

        return $code;
    }

    /** Visible for tests. */
    public static function resetReader(): void
    {
        self::$reader = null;
    }

    private static function countryFromHeaders(Request $request): ?string
    {
        foreach (self::HEADER_KEYS as $header) {
            $value = $request->header($header);
            if (! is_string($value) || strlen($value) !== 2) {
                continue;
            }

            $code = strtoupper($value);
            if (! in_array($code, ['XX', 'T1'], true)) {
                return $code;
            }
        }

        return null;
    }

    private static function isPublicIp(?string $ip): bool
    {
        return is_string($ip)
            && $ip !== ''
            && filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_NO_PRIV_RANGE | FILTER_FLAG_NO_RES_RANGE) !== false;
    }

    private static function reader(): ?Reader
    {
        if (self::$reader !== null) {
            return self::$reader;
        }

        $path = (string) config('link.geoip_database', '');
        if ($path === '' || ! is_readable($path)) {
            return null;
        }

        try {
            self::$reader = new Reader($path);

            return self::$reader;
        } catch (\Throwable) {
            return null;
        }
    }
}