<?php
declare(strict_types=1);

/**
 * Privacy-conscious approximate IP geolocation for the "closest campus"
 * recommendation. Results are city-level, cached briefly by hashed IP, and
 * never stored with a lead.
 *
 * GEOIP_PROVIDER:
 *   none        – disabled (visitor always chooses manually)
 *   header      – trust a CDN header (Cloudflare: CF-IPCountry/CF-IPLatitude/CF-IPLongitude)
 *   ipapi_co    – https://ipapi.co (no key needed for low volume; GEOIP_API_KEY optional)
 *   ipinfo      – https://ipinfo.io (GEOIP_API_KEY required)
 *   ip_api_com  – http(s)://ip-api.com (GEOIP_API_KEY required for HTTPS/commercial use)
 */
final class GeoIp
{
    /** @return array{lat:float,lng:float,city:?string,region:?string}|null */
    public static function locate(string $ip): ?array
    {
        $provider = strtolower(Config::get('GEOIP_PROVIDER', 'ipapi_co') ?? 'none');
        if ($provider === 'none' || self::isPrivate($ip)) {
            return null;
        }
        if ($provider === 'header') {
            return self::fromHeaders();
        }
        $cacheKey = 'geoip:' . substr(hash('sha256', $ip . (Config::get('HASH_SALT') ?? '')), 0, 40);
        $cached = Db::cacheGet($cacheKey);
        if ($cached !== null) {
            $c = json_decode($cached, true);
            return is_array($c) && $c ? $c : null;
        }
        $result = null;
        try {
            $result = match ($provider) {
                'ipapi_co' => self::ipapiCo($ip),
                'ipinfo' => self::ipinfo($ip),
                'ip_api_com' => self::ipApiCom($ip),
                default => null,
            };
        } catch (Throwable $e) {
            Log::warn('GeoIP provider failed', ['provider' => $provider, 'error' => $e->getMessage()]);
        }
        Db::cacheSet($cacheKey, json_encode($result ?? []), Config::int('GEOIP_CACHE_TTL', 3600));
        return $result;
    }

    private static function fromHeaders(): ?array
    {
        $lat = $_SERVER['HTTP_CF_IPLATITUDE'] ?? null;
        $lng = $_SERVER['HTTP_CF_IPLONGITUDE'] ?? null;
        if ($lat === null || $lng === null) {
            return null;
        }
        return self::result((float)$lat, (float)$lng, $_SERVER['HTTP_CF_IPCITY'] ?? null, $_SERVER['HTTP_CF_REGION_CODE'] ?? null);
    }

    private static function ipapiCo(string $ip): ?array
    {
        $key = Config::get('GEOIP_API_KEY');
        $base = rtrim(Config::get('GEOIP_BASE_URL_OVERRIDE') ?: 'https://ipapi.co', '/'); // override is for the test-suite only
        $url = "$base/" . rawurlencode($ip) . "/json/" . ($key ? "?key=" . rawurlencode($key) : '');
        $r = Http::request('GET', $url, null, ['Accept' => 'application/json'], 3);
        $j = $r['json'];
        if ($r['status'] !== 200 || !is_array($j) || !isset($j['latitude'], $j['longitude'])) {
            return null;
        }
        return self::result((float)$j['latitude'], (float)$j['longitude'], $j['city'] ?? null, $j['region_code'] ?? null);
    }

    private static function ipinfo(string $ip): ?array
    {
        $key = Config::require('GEOIP_API_KEY');
        $r = Http::request('GET', "https://ipinfo.io/" . rawurlencode($ip) . "/json?token=" . rawurlencode($key), null, ['Accept' => 'application/json'], 3);
        $j = $r['json'];
        if ($r['status'] !== 200 || !is_array($j) || empty($j['loc'])) {
            return null;
        }
        [$lat, $lng] = array_map('floatval', explode(',', (string)$j['loc']) + [0, 0]);
        return self::result($lat, $lng, $j['city'] ?? null, $j['region'] ?? null);
    }

    private static function ipApiCom(string $ip): ?array
    {
        $key = Config::get('GEOIP_API_KEY');
        $base = $key ? "https://pro.ip-api.com/json/" : "http://ip-api.com/json/";
        $r = Http::request('GET', $base . rawurlencode($ip) . "?fields=status,lat,lon,city,region" . ($key ? "&key=" . rawurlencode($key) : ''), null, [], 3);
        $j = $r['json'];
        if ($r['status'] !== 200 || !is_array($j) || ($j['status'] ?? '') !== 'success') {
            return null;
        }
        return self::result((float)$j['lat'], (float)$j['lon'], $j['city'] ?? null, $j['region'] ?? null);
    }

    private static function result(float $lat, float $lng, ?string $city, ?string $region): ?array
    {
        if ($lat === 0.0 && $lng === 0.0 || abs($lat) > 90 || abs($lng) > 180) {
            return null;
        }
        // Round to ~1 km so we never hold anything close to a precise location.
        return ['lat' => round($lat, 2), 'lng' => round($lng, 2), 'city' => $city ? Validator::clean($city, 60) : null, 'region' => $region ? Validator::clean($region, 20) : null];
    }

    public static function isPrivate(string $ip): bool
    {
        return filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_NO_PRIV_RANGE | FILTER_FLAG_NO_RES_RANGE) === false;
    }
}