Nuget support

LabApi/LabApi.csproj

@@ -62,12 +62,17 @@
 		<Reference Include="Mirror" HintPath="$(SL_REFERENCES)\Mirror.dll" />
 		<Reference Include="NorthwoodLib" HintPath="$(SL_REFERENCES)\NorthwoodLib.dll" />
 		<Reference Include="Pooling" HintPath="$(SL_REFERENCES)\Pooling.dll" />
+		<Reference Include="System.IO.Compression.FileSystem" HintPath="$(UNITY_REFERENCES)\System.IO.Compression.FileSystem.dll" />
+		<Reference Include="System.Net.Http" />
 		<Reference Include="UnityEngine.CoreModule" HintPath="$(UNITY_REFERENCES)\UnityEngine.CoreModule.dll" />
 		<Reference Include="UnityEngine.PhysicsModule" HintPath="$(UNITY_REFERENCES)\UnityEngine.PhysicsModule.dll" />
 		<Reference Include="UnityEngine.AudioModule" HintPath="$(UNITY_REFERENCES)\UnityEngine.AudioModule.dll" />
 		<Reference Include="mscorlib" HintPath="$(UNITY_REFERENCES)\mscorlib.dll" />
 		<Reference Include="System" HintPath="$(UNITY_REFERENCES)\System.dll" />
 		<Reference Include="System.Core" HintPath="$(UNITY_REFERENCES)\System.Core.dll" />
+		<Reference Include="System.IO.Compression" HintPath="$(UNITY_REFERENCES)\System.IO.Compression.dll" />
+		<Reference Include="System.Xml.Linq" HintPath="$(UNITY_REFERENCES)\System.Xml.Linq.dll" />
+		<Reference Include="System.Runtime.Serialization" HintPath="$(UNITY_REFERENCES)\System.Runtime.Serialization.dll" />
 		<Reference Include="netstandard" HintPath="$(UNITY_REFERENCES)\netstandard.dll" />
 	</ItemGroup>
 

LabApi/Loader/Features/Configuration/LabApiConfig.cs

@@ -27,4 +27,28 @@ public class LabApiConfig
     /// <seealso cref="LabApi.Loader.Features.Plugins.Configuration.Properties.UnsupportedLoading"/>
     [Description("Whether to allow loading plugins even if they were built for a different major version of LabAPI.")]
     public bool LoadUnsupportedPlugins { get; set; }
+
+    /// <summary>
+    /// Gets or sets the list of NuGet package source URLs used when resolving
+    /// and downloading dependencies from NuGet repositories.
+    /// </summary>
+    /// <remarks>
+    /// Each entry in this list represents a NuGet feed endpoint (for example,
+    /// the official <c>https://api.nuget.org/v3/index.json</c> source).
+    /// Multiple sources can be specified to support private or custom feeds.
+    /// </remarks>
+    [Description("List of NuGet package sources to use when resolving dependencies via NuGet.")]
+    public string[] NugetPackageSources { get; set; } = ["https://api.nuget.org/v3/index.json"];
+
+    /// <summary>
+    /// Gets or sets a value indicating whether dependencies should be automatically
+    /// downloaded from the configured NuGet sources when they are missing or outdated.
+    /// </summary>
+    /// <remarks>
+    /// When set to <see langword="true"/>, the system attempts to retrieve and install
+    /// required packages automatically during dependency resolution.
+    /// Disabling this option may require manual dependency management.
+    /// </remarks>
+    [Description("Automatically download dependencies from NuGet when missing or outdated.")]
+    public bool AutomaticallyDownloadDependencies { get; set; } = true;
 }

LabApi/Loader/Features/NuGet/Models/NuGetDependency.cs

@@ -0,0 +1,89 @@
+using LabApi.Features.Console;
+using System;
+using System.Reflection;
+
+namespace LabApi.Loader.Features.NuGet.Models;
+
+/// <summary>
+/// Represents a dependency entry within a NuGet package,
+/// including its identifier and version, and provides
+/// helper methods for installation and status checking.
+/// </summary>
+public class NuGetDependency
+{
+    /// <summary>
+    /// Gets or sets the unique identifier (name) of the NuGet dependency.
+    /// </summary>
+    public required string Id { get; set; }
+
+    /// <summary>
+    /// Gets or sets the semantic version string of the dependency (e.g. "1.2.3").
+    /// </summary>
+    public required string Version { get; set; }
+
+    /// <summary>
+    /// Installs this NuGet dependency by downloading it from the configured source.
+    /// </summary>
+    /// <returns>
+    /// A <see cref="NuGetPackage"/> instance representing the downloaded package,
+    /// or <see langword="null"/> if the installation failed or the package could not be found.
+    /// </returns>
+    /// <remarks>
+    /// This method delegates to <see cref="NuGetPackagesManager.DownloadNugetPackage(string, string)"/>.
+    /// </remarks>
+    public NuGetPackage? Install() => NuGetPackagesManager.DownloadNugetPackage(Id, Version);
+
+    /// <summary>
+    /// Determines whether this dependency is already installed
+    /// or loaded in the current AppDomain.
+    /// </summary>
+    /// <returns>
+    /// <c>true</c> if the dependency is installed or the corresponding assembly is already loaded;
+    /// otherwise, <c>false</c>.
+    /// </returns>
+    public bool IsInstalled()
+    {
+        if (NuGetPackagesManager.Packages.TryGetValue($"{Id}.{Version}", out NuGetPackage package))
+        {
+            return string.Equals(package.Version, Version, StringComparison.OrdinalIgnoreCase);
+        }
+
+        if (IsAssemblyAlreadyLoaded(Id))
+        {
+            return true;
+        }
+
+        return false;
+    }
+
+    /// <summary>
+    /// Checks whether an assembly with the given identifier is already loaded
+    /// into the current application domain.
+    /// </summary>
+    /// <param name="id">The dependency or assembly identifier to check.</param>
+    /// <returns>
+    /// <c>true</c> if an assembly with the specified ID is already loaded;
+    /// otherwise, <c>false</c>.
+    /// </returns>
+    private bool IsAssemblyAlreadyLoaded(string id)
+    {
+        try
+        {
+            foreach (Assembly? asm in AppDomain.CurrentDomain.GetAssemblies())
+            {
+                string asmName = asm.GetName().Name ?? string.Empty;
+
+                if (asmName.Equals(id, StringComparison.OrdinalIgnoreCase))
+                {
+                    return true;
+                }
+            }
+        }
+        catch (Exception ex)
+        {
+            Logger.Warn($"{NuGetPackagesManager.Prefix} Failed to check if assembly '{id}' is already loaded: {ex.Message}");
+        }
+
+        return false;
+    }
+}

LabApi/Loader/Features/NuGet/Models/NuGetPackage.cs

@@ -0,0 +1,173 @@
+using LabApi.Features.Console;
+using LabApi.Loader.Features.Misc;
+using LabApi.Loader.Features.Paths;
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Reflection;
+
+namespace LabApi.Loader.Features.NuGet.Models;
+
+/// <summary>
+/// Represents a NuGet package loaded by LabApi, including its metadata,
+/// content, and dependency information.
+/// </summary>
+public class NuGetPackage
+{
+    /// <summary>
+    /// Identifies the plugin tag used to mark NuGet package as plugin.
+    /// </summary>
+    private const string LabApiPluginTag = "labapi-plugin";
+
+    /// <summary>
+    /// Gets or sets the unique package identifier (name).
+    /// </summary>
+    public string Id { get; set; } = string.Empty;
+
+    /// <summary>
+    /// Gets or sets the package version string (e.g. "1.2.3").
+    /// </summary>
+    public string Version { get; set; } = string.Empty;
+
+    /// <summary>
+    /// Gets or sets the tag metadata from the .nuspec file (used to identify plugins, etc.).
+    /// </summary>
+    public string Tags { get; set; } = string.Empty;
+
+    /// <summary>
+    /// Gets or sets the compiled assembly content of the package (if applicable).
+    /// </summary>
+    public byte[]? RawAssembly { get; set; } = null;
+
+    /// <summary>
+    /// Gets or sets the full path of NuGet package.
+    /// </summary>
+    public string FilePath { get; set; } = string.Empty;
+
+    /// <summary>
+    /// Gets or sets the name of the NuGet package file (e.g. "MyPlugin.1.0.0.nupkg").
+    /// </summary>
+    public required string FileName { get; set; }
+
+    /// <summary>
+    /// Gets or sets the raw file contents of the NuGet package (.nupkg file).
+    /// </summary>
+    public required byte[] FileContent { get; set; }
+
+    /// <summary>
+    /// Gets or sets the list of dependencies defined by this package.
+    /// </summary>
+    public List<NuGetDependency> Dependencies { get; set; } = new List<NuGetDependency>();
+
+    /// <summary>
+    /// Gets a value indicating whether this package is marked as a LabApi plugin.
+    /// Determined by the presence of the "labapi-plugin" tag.
+    /// </summary>
+    public bool IsPlugin => Tags
+        .ToLower()
+        .Contains(LabApiPluginTag);
+
+    /// <summary>
+    /// Gets or sets a value indicating whether the package is already loaded.
+    /// </summary>
+    public bool IsLoaded { get; set; }
+
+    /// <summary>
+    /// Extracts the NuGet package file (.nupkg) to the appropriate directory
+    /// (plugins or dependencies), depending on whether it is a plugin.
+    /// </summary>
+    /// <returns>
+    /// The full path to the extracted file if successful; otherwise, <c>null</c>.
+    /// </returns>
+    public string? ExtractToFolder()
+    {
+        string? folder = GetFinalFolder();
+
+        if (folder == null)
+        {
+            Logger.Warn($"{NuGetPackagesManager.Prefix} Could not extract package '{Id}' v{Version} to {(IsPlugin ? "plugins" : "dependencies")} folder: no valid path found!");
+            return null;
+        }
+
+        string targetFile = Path.Combine(folder, FileName);
+
+        File.WriteAllBytes(targetFile, FileContent);
+
+        FilePath = targetFile;
+
+        return targetFile;
+    }
+
+    /// <summary>
+    /// Loads package.
+    /// </summary>
+    public void Load()
+    {
+        if (IsLoaded)
+        {
+            return;
+        }
+
+        if (RawAssembly?.Length == 0)
+        {
+            Logger.Warn($"{NuGetPackagesManager.Prefix} Package '{Id}' v{Version} does not contain a valid assembly, skipping...");
+            return;
+        }
+
+        Assembly assembly = Assembly.Load(RawAssembly);
+
+        if (IsPlugin)
+        {
+            try
+            {
+                AssemblyUtils.ResolveEmbeddedResources(assembly);
+            }
+            catch (Exception e)
+            {
+                Logger.Error($"{NuGetPackagesManager.Prefix} Failed to resolve embedded resources for package '{Id}' v{Version}");
+                Logger.Error(e);
+            }
+
+            try
+            {
+                PluginLoader.InstantiatePlugins(assembly.GetTypes(), assembly, FilePath);
+            }
+            catch (Exception e)
+            {
+                Logger.Error($"{NuGetPackagesManager.Prefix} Couldn't load the plugin inside package '{Id}' v{Version}");
+                Logger.Error(e);
+            }
+        }
+        else
+        {
+            PluginLoader.Dependencies.Add(assembly);
+        }
+
+        Logger.Info($"{NuGetPackagesManager.Prefix} Package '{Id}' v{Version} was loaded!");
+
+        IsLoaded = true;
+    }
+
+    /// <summary>
+    /// Resolves and returns the final folder path for the package extraction,
+    /// creating directories if necessary.
+    /// </summary>
+    /// <returns>
+    /// The full directory path where the package should be extracted,
+    /// or <c>null</c> if no valid path could be determined.
+    /// </returns>
+    private string? GetFinalFolder()
+    {
+        foreach (string path in IsPlugin ? PluginLoader.Config.PluginPaths : PluginLoader.Config.DependencyPaths)
+        {
+            string resolvedPath = PluginLoader.ResolvePath(path);
+            string fullPath = Path.Combine(IsPlugin ? PathManager.Plugins.FullName : PathManager.Dependencies.FullName, resolvedPath);
+
+            Directory.CreateDirectory(fullPath);
+
+            return fullPath;
+        }
+
+        return null;
+    }
+}

LabApi/Loader/Features/NuGet/Models/NuGetPackageIndex.cs

@@ -0,0 +1,26 @@
+using System.Runtime.Serialization;
+
+namespace LabApi.Loader.Features.NuGet.Models;
+
+/// <summary>
+/// Represents the root structure of a NuGet service index (<c>index.json</c>),
+/// which describes the available service endpoints for a NuGet source.
+/// </summary>
+/// <remarks>
+/// The NuGet service index (usually located at <c>https://api.nuget.org/v3/index.json</c>)
+/// provides metadata about the repository’s available APIs, such as
+/// <c>PackageBaseAddress</c>, <c>SearchQueryService</c>, and others.
+/// </remarks>
+public class NuGetPackageIndex
+{
+    /// <summary>
+    /// Gets or sets the list of service resources exposed by the NuGet source.
+    /// </summary>
+    /// <remarks>
+    /// Each resource entry describes an endpoint (for example,
+    /// a package base address or search service) and its supported version.
+    /// These are typically represented by the <see cref="NuGetPackageResource"/> type.
+    /// </remarks>
+    [DataMember(Name = "resources")]
+    public NuGetPackageResource[] Resources { get; set; } = [];
+}

LabApi/Loader/Features/NuGet/Models/NuGetPackageResource.cs

@@ -0,0 +1,37 @@
+using System.Runtime.Serialization;
+
+namespace LabApi.Loader.Features.NuGet.Models;
+
+/// <summary>
+/// Represents a single resource entry within a NuGet service index (<c>index.json</c>).
+/// </summary>
+/// <remarks>
+/// Each resource describes a specific NuGet service endpoint and its purpose,
+/// such as the <c>PackageBaseAddress</c> (used to download packages) or
+/// <c>SearchQueryService</c> (used to search packages).
+/// </remarks>
+public class NuGetPackageResource
+{
+    /// <summary>
+    /// Gets or sets the type of the NuGet service resource.
+    /// </summary>
+    /// <remarks>
+    /// The <c>@type</c> field defines the role of the resource, for example:
+    /// <list type="bullet">
+    /// <item><description><c>PackageBaseAddress/3.0.0</c> — base URL for downloading package files</description></item>
+    /// </list>
+    /// </remarks>
+    [DataMember(Name = "@type")]
+    public string Type { get; set; } = string.Empty;
+
+    /// <summary>
+    /// Gets or sets the absolute URL of the service endpoint.
+    /// </summary>
+    /// <remarks>
+    /// The <c>@id</c> value is typically a fully qualified HTTPS URL that identifies
+    /// the service’s base address. For example:
+    /// <c>https://api.nuget.org/v3-flatcontainer/</c> or
+    /// </remarks>
+    [DataMember(Name = "@id")]
+    public string Id { get; set; } = string.Empty;
+}