KubernetesScheme.cs

using System;
using System.Collections.Generic;
using System.Reflection;
using k8s.Models;

namespace k8s.Fluent
{
	/// <summary>Represents a map between object types and Kubernetes group, version, and kind triplets.</summary>
	public sealed class KubernetesScheme
	{
		/// <summary>Gets the Kubernetes group, version, and kind for the given type of object.</summary>
		public void GetGVK(Type type, out string group, out string version, out string kind) =>
			GetGVK(type, out group, out version, out kind, out string path);

		/// <summary>Gets the Kubernetes group, version, kind, and API path segment for the given type of object.</summary>
		public void GetGVK(Type type, out string group, out string version, out string kind, out string path)
		{
			if(!TryGetGVK(type, out group, out version, out kind, out path))
			{
				throw new ArgumentException($"The GVK of type {type.Name} is unknown.");
			}
		}

		/// <summary>Gets the Kubernetes group, version, and kind for the given type of object.</summary>
		public void GetGVK<T>(out string group, out string version, out string kind) =>
			GetGVK(typeof(T), out group, out version, out kind, out string path);

		/// <summary>Gets the Kubernetes group, version, kind, and API path segment for the given type of object.</summary>
		public void GetGVK<T>(out string group, out string version, out string kind, out string path) =>
			GetGVK(typeof(T), out group, out version, out kind, out path);

		/// <summary>Gets the Kubernetes API version (including the group, if any), and kind for the given type of object.</summary>
		public void GetVK(Type type, out string apiVersion, out string kind) => GetVK(type, out apiVersion, out kind, out string path);

		/// <summary>Gets the Kubernetes API version (including the group, if any), kind, and API path segment for the given type of
		/// object.
		/// </summary>
		public void GetVK(Type type, out string apiVersion, out string kind, out string path)
		{
			string group, version;
			GetGVK(type, out group, out version, out kind, out path);
			apiVersion = string.IsNullOrEmpty(group) ? version : group + "/" + version;
		}

		/// <summary>Gets the Kubernetes API version (including the group, if any) and kind for the given type of object.</summary>
		public void GetVK<T>(out string apiVersion, out string kind) => GetVK(typeof(T), out apiVersion, out kind, out string path);

		/// <summary>Gets the Kubernetes API version (including the group, if any), kind, and API path segment for the given type of
		/// object.
		/// </summary>
		public void GetVK<T>(out string apiVersion, out string kind, out string path) =>
			GetVK(typeof(T), out apiVersion, out kind, out path);

		/// <summary>Creates a new Kubernetes object of the given type and sets its <see cref="IKubernetesObject.ApiVersion"/> and
		/// <see cref="IKubernetesObject.Kind"/>.
		/// </summary>
		public T New<T>() where T : IKubernetesObject, new()
		{
			string apiVersion, kind;
			GetVK(typeof(T), out apiVersion, out kind);
			return new T() { ApiVersion = apiVersion, Kind = kind };
		}

		/// <summary>Creates a new Kubernetes object of the given type and sets its <see cref="IKubernetesObject.ApiVersion"/>,
		/// <see cref="IKubernetesObject.Kind"/>, and <see cref="V1ObjectMeta.Name"/>.
		/// </summary>
		public T New<T>(string name) where T : IKubernetesObject<V1ObjectMeta>, new() => New<T>(null, name);

		/// <summary>Creates a new Kubernetes object of the given type and sets its <see cref="IKubernetesObject.ApiVersion"/>,
		/// <see cref="IKubernetesObject.Kind"/>, <see cref="V1ObjectMeta.NamespaceProperty"/>, and <see cref="V1ObjectMeta.Name"/>.
		/// </summary>
		public T New<T>(string ns, string name) where T : IKubernetesObject<V1ObjectMeta>, new()
		{
			T obj = New<T>();
			obj.Metadata = new V1ObjectMeta() { NamespaceProperty = ns, Name = name };
			return obj;
		}

		/// <summary>Removes GVK information about the given type of object.</summary>
		public void RemoveGVK(Type type)
		{
			lock(gvks) gvks.Remove(type);
		}

		/// <summary>Removes GVK information about the given type of object.</summary>
		public void RemoveGVK<T>() => RemoveGVK(typeof(T));

		/// <summary>Sets GVK information for the given type of object.</summary>
		public void SetGVK(Type type, string group, string version, string kind, string path)
		{
			if(type == null) throw new ArgumentNullException(nameof(type));
			if(string.IsNullOrEmpty(version)) throw new ArgumentNullException(nameof(version));
			if(string.IsNullOrEmpty(kind)) throw new ArgumentNullException(nameof(kind));
			if(string.IsNullOrEmpty(path)) throw new ArgumentNullException(nameof(path));
			lock(gvks) gvks[type] = Tuple.Create(group ?? string.Empty, version, kind, path);
		}

		/// <summary>Sets GVK information for the given type of object.</summary>
		public void SetGVK<T>(string group, string version, string kind, string path) =>
			SetGVK(typeof(T), group, version, kind, path);

		/// <summary>Gets the Kubernetes group, version, and kind for the given type of object.</summary>
		public bool TryGetGVK(Type type, out string group, out string version, out string kind)
			=> TryGetGVK(type, out group, out version, out kind, out string path);

		/// <summary>Gets the Kubernetes group, version, kind, and API path segment for the given type of object.</summary>
		public bool TryGetGVK(Type type, out string group, out string version, out string kind, out string path)
		{
			if(type == null) throw new ArgumentNullException(nameof(type));
			lock(gvks)
			{
				if(!gvks.TryGetValue(type, out Tuple<string, string, string, string> gvk))
				{
					var attr = type.GetCustomAttribute<k8s.Models.KubernetesEntityAttribute>(); // newer types have this attribute
					if(attr != null)
					{
						gvk = Tuple.Create(attr.Group, attr.ApiVersion, attr.Kind, attr.PluralName);
					}
					else // some older types (and ours) just have static/const fields
					{
						const BindingFlags Flags = BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Static;
						FieldInfo kindf = type.GetField("KubeKind", Flags), versionf = type.GetField("KubeApiVersion", Flags);
						if(kindf != null && versionf != null)
						{
							FieldInfo groupf = type.GetField("KubeGroup", Flags);
							string k = (string)kindf.GetValue(null);
							gvk = Tuple.Create(
								(string)groupf?.GetValue(null) ?? string.Empty, (string)versionf.GetValue(null), k, GuessPath(k));
						}
					}
					gvks[type] = gvk;
				}

				if(gvk != null)
				{
					(group, version, kind, path) = gvk;
					return true;
				}
				else
				{
					group = version = kind = path = null;
					return false;
				}
			}
		}

		/// <summary>Gets the Kubernetes group, version, and kind for the given type of object.</summary>
		public bool TryGetGVK<T>(out string group, out string version, out string kind) =>
			TryGetGVK(typeof(T), out group, out version, out kind, out string path);

		/// <summary>Gets the Kubernetes group, version, kind, and API path segment for the given type of object.</summary>
		public bool TryGetGVK<T>(out string group, out string version, out string kind, out string path) =>
			TryGetGVK(typeof(T), out group, out version, out kind, out path);

		/// <summary>Gets the Kubernetes API version (including the group, if any) and kind for the given type of object.</summary>
		public bool TryGetVK(Type type, out string apiVersion, out string kind) =>
			TryGetVK(type, out apiVersion, out kind, out string path);

		/// <summary>Gets the Kubernetes API version (including the group, if any), kind, and API path segment for the given type of
		/// object.
		/// </summary>
		public bool TryGetVK(Type type, out string apiVersion, out string kind, out string path)
		{
			if(TryGetGVK(type, out string group, out string version, out kind, out path))
			{
				apiVersion = string.IsNullOrEmpty(group) ? version : group + "/" + version;
				return true;
			}
			else
			{
				apiVersion = null;
				return false;
			}
		}

		/// <summary>Gets the Kubernetes API version (including the group, if any) and kind for the given type of object.</summary>
		public bool TryGetVK<T>(out string apiVersion, out string kind) => TryGetVK(typeof(T), out apiVersion, out kind, out string path);

		/// <summary>Gets the Kubernetes API version (including the group, if any), kind, and API path segment for the given type of
		/// object.
		/// </summary>
		public bool TryGetVK<T>(out string apiVersion, out string kind, out string path) =>
			TryGetVK(typeof(T), out apiVersion, out kind, out path);

		/// <summary>Gets the default <see cref="KubernetesScheme"/>.</summary>
		public static readonly KubernetesScheme Default = new KubernetesScheme();

		/// <summary>Attempts to guess a type's API path segment based on its kind.</summary>
		internal static string GuessPath(string kind)
		{
			if(string.IsNullOrEmpty(kind)) return null;
			if(kind.Length > 4 && kind.EndsWith("List")) kind = kind.Substring(0, kind.Length-4); // e.g. PodList -> Pod
			kind = kind.ToLowerInvariant(); // e.g. Pod -> pod
			return kind + (kind[kind.Length-1] == 's' ? "es" : "s"); // e.g. pod -> pods
		}

		readonly Dictionary<Type, Tuple<string, string, string, string>> gvks = new Dictionary<Type, Tuple<string, string, string, string>>();
	}
}