Medusa System Added

Read about the medusa system [here](https://nadekobot.readthedocs.io/en/latest/medusa/creating-a-medusa/)

src/NadekoBot/Common/Medusa/Adapters/BehaviorAdapter.cs

@@ -0,0 +1,76 @@
+#nullable enable
+
+[DontAddToIocContainer]
+public sealed class BehaviorAdapter : ICustomBehavior
+{
+    private readonly WeakReference<Snek> _snekWr;
+    private readonly IMedusaStrings _strings;
+    private readonly IServiceProvider _services;
+    private readonly string _name;
+
+    // unused
+    public int Priority
+        => 0;
+
+    public BehaviorAdapter(WeakReference<Snek> snekWr, IMedusaStrings strings, IServiceProvider services)
+    {
+        _snekWr = snekWr;
+        _strings = strings;
+        _services = services;
+
+        _name = snekWr.TryGetTarget(out var snek)
+            ? $"snek/{snek.GetType().Name}"
+            : "unknown";
+    }
+
+    public async Task<bool> ExecPreCommandAsync(ICommandContext context, string moduleName, CommandInfo command)
+    {
+        if (!_snekWr.TryGetTarget(out var snek))
+            return false;
+
+        return await snek.ExecPreCommandAsync(ContextAdapterFactory.CreateNew(context, _strings, _services),
+            moduleName,
+            command.Name);
+    }
+
+    public async Task<bool> ExecOnMessageAsync(IGuild? guild, IUserMessage msg)
+    {
+        if (!_snekWr.TryGetTarget(out var snek))
+            return false;
+
+        return await snek.ExecOnMessageAsync(guild, msg);
+    }
+
+    public async Task<string?> TransformInput(
+        IGuild guild,
+        IMessageChannel channel,
+        IUser user,
+        string input)
+    {
+        if (!_snekWr.TryGetTarget(out var snek))
+            return null;
+        
+        return await snek.ExecInputTransformAsync(guild, channel, user, input);
+    }
+
+    public async Task ExecOnNoCommandAsync(IGuild? guild, IUserMessage msg)
+    {
+        if (!_snekWr.TryGetTarget(out var snek))
+            return;
+
+        await snek.ExecOnNoCommandAsync(guild, msg);
+    }
+
+    public async ValueTask ExecPostCommandAsync(ICommandContext context, string moduleName, string commandName)
+    {
+        if (!_snekWr.TryGetTarget(out var snek))
+            return;
+        
+        await snek.ExecPostCommandAsync(ContextAdapterFactory.CreateNew(context, _strings, _services),
+            moduleName,
+            commandName);
+    }
+
+    public override string ToString()
+        => _name;
+}

src/NadekoBot/Common/Medusa/Adapters/ContextAdapterFactory.cs

@@ -0,0 +1,7 @@
+internal class ContextAdapterFactory
+{
+    public static AnyContext CreateNew(ICommandContext context, IMedusaStrings strings, IServiceProvider services)
+        => context.Guild is null
+            ? new DmContextAdapter(context, strings, services)
+            : new GuildContextAdapter(context, strings, services);
+}

src/NadekoBot/Common/Medusa/Adapters/DmContextAdapter.cs

@@ -0,0 +1,48 @@
+using Microsoft.Extensions.DependencyInjection;
+
+public sealed class DmContextAdapter : DmContext
+{
+    public override IMedusaStrings Strings { get; }
+    public override IDMChannel Channel { get; }
+    public override IUserMessage Message { get; }
+    public override IUser User
+        => Message.Author;
+    
+    private readonly IServiceProvider _services;
+    private readonly Lazy<IEmbedBuilderService> _ebs;
+    private readonly Lazy<IBotStrings> _botStrings;
+    private readonly Lazy<ILocalization> _localization;
+
+    public DmContextAdapter(ICommandContext ctx, IMedusaStrings strings, IServiceProvider services)
+    {
+        if (ctx is not { Channel: IDMChannel ch })
+        {
+            throw new ArgumentException("Can't use non-dm context to create DmContextAdapter", nameof(ctx));
+        }
+
+        Strings = strings;
+
+        _services = services;
+
+        Channel = ch;
+        Message = ctx.Message;
+        
+        
+        _ebs = new(_services.GetRequiredService<IEmbedBuilderService>());
+        _botStrings = new(_services.GetRequiredService<IBotStrings>);
+        _localization = new(_services.GetRequiredService<ILocalization>());
+    }
+
+    public override IEmbedBuilder Embed()
+        => _ebs.Value.Create();
+
+    public override string GetText(string key, object[]? args = null)
+    {
+        var cultureInfo = _localization.Value.GetCultureInfo(default(ulong?));
+        var output = Strings.GetText(key, cultureInfo, args ?? Array.Empty<object>());
+        if (!string.IsNullOrWhiteSpace(output))
+            return output;
+        
+        return _botStrings.Value.GetText(key, cultureInfo, args);
+    }
+}

src/NadekoBot/Common/Medusa/Adapters/GuildContextAdapter.cs

@@ -0,0 +1,51 @@
+using Microsoft.Extensions.DependencyInjection;
+
+public sealed class GuildContextAdapter : GuildContext
+{
+    private readonly IServiceProvider _services;
+    private readonly ICommandContext _ctx;
+    private readonly Lazy<IEmbedBuilderService> _ebs;
+    private readonly Lazy<IBotStrings> _botStrings;
+    private readonly Lazy<ILocalization> _localization;
+    
+    public override IMedusaStrings Strings { get; }
+    public override IGuild Guild { get; }
+    public override ITextChannel Channel { get; }
+    public override IUserMessage Message
+        => _ctx.Message;
+
+    public override IGuildUser User { get; } 
+
+    public override IEmbedBuilder Embed()
+        => _ebs.Value.Create();
+
+    public GuildContextAdapter(ICommandContext ctx, IMedusaStrings strings, IServiceProvider services)
+    {
+        if (ctx.Guild is not IGuild guild || ctx.Channel is not ITextChannel channel)
+        {
+            throw new ArgumentException("Can't use non-guild context to create GuildContextAdapter", nameof(ctx));
+        }
+
+        Strings = strings;
+        User = (IGuildUser)ctx.User;
+
+        _services = services;
+        _ebs = new(_services.GetRequiredService<IEmbedBuilderService>());
+        _botStrings = new(_services.GetRequiredService<IBotStrings>);
+        _localization = new(_services.GetRequiredService<ILocalization>());
+
+        (_ctx, Guild, Channel) = (ctx, guild, channel);
+    }
+
+    public override string GetText(string key, object[]? args = null)
+    {
+        args ??= Array.Empty<object>();
+        
+        var cultureInfo = _localization.Value.GetCultureInfo(_ctx.Guild.Id);
+        var output = Strings.GetText(key, cultureInfo, args);
+        if (!string.IsNullOrWhiteSpace(output))
+            return output;
+        
+        return _botStrings.Value.GetText(key, cultureInfo, args);
+    }
+}

src/NadekoBot/Common/Medusa/Adapters/ParamParserAdapter.cs

@@ -0,0 +1,32 @@
+public sealed class ParamParserAdapter<T> : TypeReader
+{
+    private readonly ParamParser<T> _parser;
+    private readonly IMedusaStrings _strings;
+    private readonly IServiceProvider _services;
+
+    public ParamParserAdapter(ParamParser<T> parser,
+        IMedusaStrings strings,
+        IServiceProvider services)
+    {
+        _parser = parser;
+        _strings = strings;
+        _services = services;
+    }
+
+    public override async Task<Discord.Commands.TypeReaderResult> ReadAsync(
+        ICommandContext context,
+        string input,
+        IServiceProvider services)
+    {
+        var medusaContext = ContextAdapterFactory.CreateNew(context,
+            _strings,
+            _services);
+        
+        var result = await _parser.TryParseAsync(medusaContext, input);
+        
+        if(result.IsSuccess)
+            return Discord.Commands.TypeReaderResult.FromSuccess(result.Data);
+        
+        return Discord.Commands.TypeReaderResult.FromError(CommandError.Unsuccessful, "Invalid input");
+    }
+}