From bd70fbc4168a432c93fbf849810e88d4bb5a4558 Mon Sep 17 00:00:00 2001
From: Lars <behethangames@gmail.com>
Date: Sat, 19 Aug 2023 02:27:42 +0200
Subject: [PATCH] `Entity` now implements `IComparable<Entity>`.

---
 src/Arch/Core/Entity.cs | 29 +++++++++++++++++++++++++++--
 1 file changed, 27 insertions(+), 2 deletions(-)

diff --git a/src/Arch/Core/Entity.cs b/src/Arch/Core/Entity.cs
index 8b9843af..f89cd21b 100644
--- a/src/Arch/Core/Entity.cs
+++ b/src/Arch/Core/Entity.cs
@@ -13,7 +13,7 @@ namespace Arch.Core;
 ///     represents a general-purpose object and can be assigned a set of components that act as data.
 /// </summary>
 [SkipLocalsInit]
-public readonly struct Entity : IEquatable<Entity>
+public readonly struct Entity : IEquatable<Entity>, IComparable<Entity>
 {
     /// <summary>
     ///     Its Id, unique in its <see cref="World"/>.
@@ -58,6 +58,18 @@ public override bool Equals(object? obj)
         return obj is Entity other && Equals(other);
     }
 
+    /// <summary>
+    ///     Compares this <see cref="Entity"/> instace to another one for sorting and ordering.
+    ///     <remarks>Orders them by id. Ascending.</remarks>
+    /// </summary>
+    /// <param name="other">The other <see cref="Entity"/>.</param>
+    /// <returns>A int indicating their order.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public int CompareTo(Entity other)
+    {
+        return Id.CompareTo(other.Id);
+    }
+
     /// <summary>
     ///     Calculates the hash of this <see cref="Entity"/>.
     /// </summary>
@@ -115,7 +127,7 @@ public override string ToString()
 /// </summary>
 [DebuggerTypeProxy(typeof(EntityDebugView))]
 [SkipLocalsInit]
-public readonly struct Entity : IEquatable<Entity>
+public readonly struct Entity : IEquatable<Entity>, IComparable<Entity>
 {
     /// <summary>
     ///      Its Id, unique in its <see cref="World"/>.
@@ -175,6 +187,19 @@ public override bool Equals(object obj)
         return obj is Entity other && Equals(other);
     }
 
+
+    /// <summary>
+    ///     Compares this <see cref="Entity"/> instace to another one for sorting and ordering.
+    ///     <remarks>Orders them by id and world. Ascending.</remarks>
+    /// </summary>
+    /// <param name="other">The other <see cref="Entity"/>.</param>
+    /// <returns>A int indicating their order.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public int CompareTo(Entity other)
+    {
+        return WorldId != other.WorldId ? WorldId.CompareTo(other.WorldId) : Id.CompareTo(other.Id);
+    }
+
     /// <summary>
     ///     Calculates the hash of this <see cref="Entity"/>.
     /// </summary>