PlaytimeHistory 0.1.0: sessions and team/alive segments in MySQL, DB-IP locations

Geo.cs

@@ -0,0 +1,53 @@
+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();
+}