using System.Runtime.CompilerServices;
using System.Text;

namespace AcDream.Core.Net.Messages;

/// <summary>
/// Shared text encodings for the AC wire protocol.
///
/// <para>
/// Retail and holtburger both use Windows-1252 (CP1252) for every
/// String16L on the wire — chat, character names, item names,
/// system messages, popup text. Before Phase I.5 we used ASCII,
/// which was wrong: any non-ASCII byte (e.g. é = 0xE9, name accents
/// or chat punctuation from Latin-1 locales) decoded to '?'. Switching
/// to CP1252 matches what the server actually sends.
/// </para>
///
/// <para>
/// .NET 6+ ships only ASCII / Latin-1 / UTF8/16/32 in the base library;
/// Windows-1252 lives in <c>System.Text.Encoding.CodePages</c>. The
/// module initializer below registers that provider on first load of
/// any type in <c>AcDream.Core.Net.Messages</c>, so call sites can use
/// <see cref="Encoding.GetEncoding(int)"/> with id <c>1252</c> directly.
/// </para>
/// </summary>
public static class Encodings
{
    /// <summary>
    /// Module initializer — guaranteed by ECMA-335 to run before any
    /// other code in this module (in particular, before any static
    /// field initializer in user code that follows). Registers
    /// <c>CodePagesEncodingProvider</c> so
    /// <see cref="Encoding.GetEncoding(int)"/> with id 1252 returns a
    /// real encoding instance instead of throwing
    /// <see cref="System.NotSupportedException"/>.
    /// </summary>
#pragma warning disable CA2255 // Library-internal: registers CP1252 once
                              // before any wire-string parser is invoked.
    [ModuleInitializer]
    internal static void Register()
    {
        Encoding.RegisterProvider(CodePagesEncodingProvider.Instance);
    }
#pragma warning restore CA2255

    /// <summary>
    /// CP1252 (Windows-1252). Cached so callers don't look it up each frame.
    /// Initialized after <see cref="Register"/> via field-init ordering.
    /// </summary>
    public static readonly Encoding Windows1252 = Encoding.GetEncoding(1252);
}