CommandHook/CommandHook/CommandHookModSystem.cs

using System.Collections.Frozen;
using System.Collections.Generic;
using HarmonyLib;
using Vintagestory.API.Common;
using Vintagestory.API.Server;

namespace CommandHook;

public class CommandHookModSystem : ModSystem
{
    internal static CommandHookModSystem? Instance;

    private FrozenDictionary<string, FrozenDictionary<string, CommandRegistration>> registrations =
        FrozenDictionary<string, FrozenDictionary<string, CommandRegistration>>.Empty;

    private Harmony? harmony;

    public override bool ShouldLoad(EnumAppSide forSide) => forSide == EnumAppSide.Server;

    public override void StartServerSide(ICoreServerAPI api)
    {
        Instance = this;
        harmony = new Harmony(Mod.Info.ModID);
        harmony.PatchAll();
        Mod.Logger.Notification("Loaded");
    }

    public override void Dispose()
    {
        harmony?.UnpatchAll(Mod.Info.ModID);
        Instance = null;
    }

    public void Register(
        string modId,
        CommandRegistration registration,
        params string[] commandNames
    )
    {
        var builder = Thaw();

        foreach (var commandName in commandNames)
        {
            if (!builder.TryGetValue(commandName, out var target))
            {
                target = new Dictionary<string, CommandRegistration>();
                builder[commandName] = target;
            }
            target[modId] = registration;
        }

        registrations = Freeze(builder);
    }

    public void Unregister(string modId, params string[] commandNames)
    {
        var builder = Thaw();

        if (commandNames.Length == 0)
        {
            foreach (var (_, mods) in builder)
                mods.Remove(modId);
        }
        else
        {
            foreach (var commandName in commandNames)
                if (builder.TryGetValue(commandName, out var mods))
                    mods.Remove(modId);
        }

        registrations = Freeze(builder);
    }

    public bool FireBefore(string commandName, ref CommandData data)
    {
        if (registrations.TryGetValue(commandName, out var mods))
            foreach (var (_, reg) in mods)
                reg.Before?.Invoke(ref data);

        return data.Cancel;
    }

    public void FireAfter(string commandName, ref CommandData data, TextCommandResult result)
    {
        if (registrations.TryGetValue(commandName, out var mods))
            foreach (var (_, reg) in mods)
                reg.After?.Invoke(ref data, result);
    }

    private Dictionary<string, Dictionary<string, CommandRegistration>> Thaw()
    {
        var builder = new Dictionary<string, Dictionary<string, CommandRegistration>>();

        foreach (var (cmd, mods) in registrations)
        {
            var inner = new Dictionary<string, CommandRegistration>();
            foreach (var (id, reg) in mods)
                inner[id] = reg;
            builder[cmd] = inner;
        }

        return builder;
    }

    private static FrozenDictionary<string, FrozenDictionary<string, CommandRegistration>> Freeze(
        Dictionary<string, Dictionary<string, CommandRegistration>> builder
    )
    {
        var pruned = new Dictionary<string, FrozenDictionary<string, CommandRegistration>>();

        foreach (var (cmd, mods) in builder)
            if (mods.Count > 0)
                pruned[cmd] = mods.ToFrozenDictionary();

        return pruned.ToFrozenDictionary();
    }
}