Medusa System Added

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

src/Nadeko.Medusa/Strings/CommandStrings.cs

@@ -0,0 +1,24 @@
+using YamlDotNet.Serialization;
+
+namespace Nadeko.Snake;
+
+public readonly struct CommandStrings
+{
+    public CommandStrings(string? desc, string[]? args)
+    {
+        Desc = desc;
+        Args = args;
+    }
+
+    [YamlMember(Alias = "desc")]
+    public string? Desc { get; init; }
+    
+    [YamlMember(Alias = "args")]
+    public string[]? Args { get; init; }
+
+    public void Deconstruct(out string? desc, out string[]? args)
+    {
+        desc = Desc;
+        args = Args;
+    }
+}

src/Nadeko.Medusa/Strings/IMedusaStrings.cs

@@ -0,0 +1,15 @@
+using System.Globalization;
+
+namespace Nadeko.Snake;
+
+/// <summary>
+///     Defines methods to retrieve and reload medusa strings
+/// </summary>
+public interface IMedusaStrings
+{
+    // string GetText(string key, ulong? guildId = null, params object[] data);
+    string? GetText(string key, CultureInfo locale, params object[] data);
+    void Reload();
+    CommandStrings GetCommandStrings(string commandName, CultureInfo cultureInfo);
+    string? GetDescription(CultureInfo? locale);
+}

src/Nadeko.Medusa/Strings/IMedusaStringsProvider.cs

@@ -0,0 +1,28 @@
+namespace Nadeko.Snake;
+
+/// <summary>
+///     Implemented by classes which provide localized strings in their own ways
+/// </summary>
+public interface IMedusaStringsProvider
+{
+    /// <summary>
+    ///     Gets localized string
+    /// </summary>
+    /// <param name="localeName">Language name</param>
+    /// <param name="key">String key</param>
+    /// <returns>Localized string</returns>
+    string? GetText(string localeName, string key);
+
+    /// <summary>
+    ///     Reloads string cache
+    /// </summary>
+    void Reload();
+
+    // /// <summary>
+    // ///     Gets command arg examples and description
+    // /// </summary>
+    // /// <param name="localeName">Language name</param>
+    // /// <param name="commandName">Command name</param>
+    // CommandStrings GetCommandStrings(string localeName, string commandName);
+    CommandStrings? GetCommandStrings(string localeName, string commandName);
+}

src/Nadeko.Medusa/Strings/LocalMedusaStringsProvider.cs

@@ -0,0 +1,40 @@
+namespace Nadeko.Snake;
+
+public class LocalMedusaStringsProvider : IMedusaStringsProvider
+{
+    private readonly StringsLoader _source;
+    private IReadOnlyDictionary<string, IReadOnlyDictionary<string, string>> _responseStrings;
+    private IReadOnlyDictionary<string, IReadOnlyDictionary<string, CommandStrings>> _commandStrings;
+
+    public LocalMedusaStringsProvider(StringsLoader source)
+    {
+        _source = source;
+        _responseStrings = _source.GetResponseStrings();
+        _commandStrings = _source.GetCommandStrings();
+    }
+
+    public void Reload()
+    {
+        _responseStrings = _source.GetResponseStrings();
+        _commandStrings = _source.GetCommandStrings();
+    }
+    
+
+    public string? GetText(string localeName, string key)
+    {
+        if (_responseStrings.TryGetValue(localeName.ToLowerInvariant(), out var langStrings)
+            && langStrings.TryGetValue(key.ToLowerInvariant(), out var text))
+            return text;
+
+        return null;
+    }
+
+    public CommandStrings? GetCommandStrings(string localeName, string commandName)
+    {
+        if (_commandStrings.TryGetValue(localeName.ToLowerInvariant(), out var langStrings)
+            && langStrings.TryGetValue(commandName.ToLowerInvariant(), out var strings))
+            return strings;
+    
+        return null;
+    }
+} 

src/Nadeko.Medusa/Strings/MedusaStrings.cs

@@ -0,0 +1,79 @@
+using System.Globalization;
+using Serilog;
+
+namespace Nadeko.Snake;
+
+public class MedusaStrings : IMedusaStrings
+{
+    /// <summary>
+    ///     Used as failsafe in case response key doesn't exist in the selected or default language.
+    /// </summary>
+    private readonly CultureInfo _usCultureInfo = new("en-US");
+    
+    private readonly IMedusaStringsProvider _stringsProvider;
+
+    public MedusaStrings(IMedusaStringsProvider stringsProvider)
+    {
+        _stringsProvider = stringsProvider;
+    }
+
+    private string? GetString(string key, CultureInfo cultureInfo)
+        => _stringsProvider.GetText(cultureInfo.Name, key);
+
+    public string? GetText(string key, CultureInfo cultureInfo)
+        => GetString(key, cultureInfo)
+           ?? GetString(key, _usCultureInfo);
+
+    public string? GetText(string key, CultureInfo cultureInfo, params object[] data)
+    {
+        var text = GetText(key, cultureInfo);
+
+        if (string.IsNullOrWhiteSpace(text))
+            return null;
+        
+        try
+        {
+            return string.Format(text, data);
+        }
+        catch (FormatException)
+        {
+            Log.Warning(" Key '{Key}' is not properly formatted in '{LanguageName}' response strings",
+                key,
+                cultureInfo.Name);
+            
+            return $"⚠️ Response string key '{key}' is not properly formatted. Please report this.\n\n{text}";
+        }
+    }
+    
+    public CommandStrings GetCommandStrings(string commandName, CultureInfo cultureInfo)
+    {
+        var cmdStrings = _stringsProvider.GetCommandStrings(cultureInfo.Name, commandName);
+        if (cmdStrings is null)
+        {
+            if (cultureInfo.Name == _usCultureInfo.Name)
+            {
+                Log.Warning("'{CommandName}' doesn't exist in 'en-US' command strings for one of the medusae",
+                    commandName);
+
+                return new(null, null);
+            }
+
+            Log.Information("Missing '{CommandName}' command strings for the '{LocaleName}' locale",
+                commandName,
+                cultureInfo.Name);
+            
+            return GetCommandStrings(commandName, _usCultureInfo);
+        }
+
+        return cmdStrings.Value;
+    }
+
+    public string? GetDescription(CultureInfo? locale = null)
+        => GetText("medusa.description", locale ?? _usCultureInfo);
+
+    public static MedusaStrings CreateDefault(string basePath)
+        => new MedusaStrings(new LocalMedusaStringsProvider(new(basePath)));
+    
+    public void Reload()
+        => _stringsProvider.Reload();
+}

src/Nadeko.Medusa/Strings/StringsLoader.cs

@@ -0,0 +1,137 @@
+using System.Diagnostics.CodeAnalysis;
+using Serilog;
+using YamlDotNet.Serialization;
+
+namespace Nadeko.Snake;
+
+/// <summary>
+///     Loads strings from the shortcut or localizable path
+/// </summary>
+public class StringsLoader
+{
+    private readonly string _localizableResponsesPath;
+    private readonly string _shortcutResponsesFile;
+    
+    private readonly string _localizableCommandsPath;
+    private readonly string _shortcutCommandsFile;
+
+    public StringsLoader(string basePath)
+    {
+        _localizableResponsesPath = Path.Join(basePath, "strings/res");
+        _shortcutResponsesFile = Path.Join(basePath, "res.yml");
+        
+        _localizableCommandsPath = Path.Join(basePath, "strings/cmds");
+        _shortcutCommandsFile = Path.Join(basePath, "cmds.yml");
+    }
+
+    public IReadOnlyDictionary<string, IReadOnlyDictionary<string, CommandStrings>> GetCommandStrings()
+    {
+        var outputDict = new Dictionary<string, IReadOnlyDictionary<string, CommandStrings>>();
+
+        if (File.Exists(_shortcutCommandsFile))
+        {
+            if (TryLoadCommandsFromFile(_shortcutCommandsFile, out var dict, out _))
+            {
+                outputDict["en-us"] = dict;
+            }
+
+            return outputDict;
+        }
+
+        if (Directory.Exists(_localizableCommandsPath))
+        {
+            foreach (var cmdsFile in Directory.EnumerateFiles(_localizableCommandsPath))
+            {
+                if (TryLoadCommandsFromFile(cmdsFile, out var dict, out var locale) && locale is not null)
+                {
+                    outputDict[locale.ToLowerInvariant()] = dict;
+                }
+            }
+        }
+
+        return outputDict;
+    }
+
+    
+    private static readonly IDeserializer _deserializer = new DeserializerBuilder().Build();
+    private static bool TryLoadCommandsFromFile(string file,
+        [NotNullWhen(true)] out IReadOnlyDictionary<string, CommandStrings>? strings,
+        out string? localeName)
+    {
+        try
+        {
+            var text = File.ReadAllText(file);
+            strings = _deserializer.Deserialize<Dictionary<string, CommandStrings>?>(text)
+                      ?? new();
+            localeName = GetLocaleName(file);
+            return true;
+        }
+        catch (Exception ex)
+        {
+            Log.Error(ex, "Error loading {FileName} command strings: {ErrorMessage}", file, ex.Message);
+        }
+
+        strings = null;
+        localeName = null;
+        return false;
+    }
+
+
+    public IReadOnlyDictionary<string, IReadOnlyDictionary<string, string>> GetResponseStrings()
+    {
+        var outputDict = new Dictionary<string, IReadOnlyDictionary<string, string>>();
+
+        // try to load a shortcut file
+        if (File.Exists(_shortcutResponsesFile))
+        {
+            if (TryLoadResponsesFromFile(_shortcutResponsesFile, out var dict, out _))
+            {
+                outputDict["en-us"] = dict;
+            }
+
+            return outputDict;
+        }
+
+        if (!Directory.Exists(_localizableResponsesPath))
+            return outputDict;
+        
+        // if shortcut file doesn't exist, try to load localizable files
+        foreach (var file in Directory.GetFiles(_localizableResponsesPath))
+        {
+            if (TryLoadResponsesFromFile(file, out var strings, out var localeName) && localeName is not null)
+            {
+                outputDict[localeName.ToLowerInvariant()] = strings;
+            }
+        }
+
+        return outputDict;
+    }
+
+    private static bool TryLoadResponsesFromFile(string file,
+        [NotNullWhen(true)] out IReadOnlyDictionary<string, string>? strings,
+        out string? localeName)
+    {
+        try
+        {
+            strings = _deserializer.Deserialize<Dictionary<string, string>?>(File.ReadAllText(file));
+            if (strings is null)
+            {
+                localeName = null;
+                return false;
+            }
+
+            localeName = GetLocaleName(file).ToLowerInvariant();
+            return true;
+        }
+        catch (Exception ex)
+        {
+            Log.Error(ex, "Error loading {FileName} response strings: {ErrorMessage}", file, ex.Message);
+            strings = null;
+            localeName = null;
+            return false;
+        }
+    }
+
+    private static string GetLocaleName(string fileName)
+        => Path.GetFileNameWithoutExtension(fileName);
+}