using System.Net;
using MaxMind.Db;

namespace PlaytimeHistory;

// Country and city for an IP, from DB-IP's City Lite database (MaxMind DB format, CC BY 4.0:
// "IP Geolocation by DB-IP", https://db-ip.com). Only the result is kept; the IP never is.
public sealed class Geo : IDisposable
{
    public sealed record Location(string? CountryIso, string? CountryName, string? City);

    private readonly Reader _reader;

    private Geo(Reader reader) => _reader = reader;

    public string DatabaseType => _reader.Metadata.DatabaseType;
    public DateTime BuildDate => _reader.Metadata.BuildDate;

    // Null when the file isn't there.
    public static Geo? Open(string path) =>
        File.Exists(path) ? new Geo(new Reader(path, FileAccessMode.MemoryMapped)) : null;

    // `address` is "ip" or "ip:port", as CCSPlayerController.IpAddress gives it.
    public Location? Lookup(string? address)
    {
        if (string.IsNullOrEmpty(address))
            return null;
        var colon = address.LastIndexOf(':');
        var host = colon > 0 && address.IndexOf(':') == colon ? address[..colon] : address;
        if (!IPAddress.TryParse(host, out var ip))
            return null;

        var data = _reader.Find<Dictionary<string, object>>(ip);
        if (data == null)
            return null;

        string? iso = null, country = null, city = null;
        if (data.TryGetValue("country", out var c) && c is Dictionary<string, object> countryData)
        {
            iso = countryData.TryGetValue("iso_code", out var code) ? code as string : null;
            country = EnglishName(countryData);
        }
        if (data.TryGetValue("city", out var ct) && ct is Dictionary<string, object> cityData)
            city = EnglishName(cityData);
        return iso == null && city == null ? null : new Location(iso, country, city);
    }

    private static string? EnglishName(Dictionary<string, object> data) =>
        data.TryGetValue("names", out var n) && n is Dictionary<string, object> names &&
        names.TryGetValue("en", out var en) ? en as string : null;

    public void Dispose() => _reader.Dispose();
}