Define IWorld and IWorldService, and implement them. (#58)

src/Orion/Npcs/INpcService.cs

@@ -20,7 +20,7 @@
 
 namespace Orion.Npcs {
     /// <summary>
-    /// Represents an item service. Provides access to NPC-related properties and methods.
+    /// Represents an NPC service. Provides access to NPC-related properties and methods.
     /// </summary>
     public interface INpcService {
         /// <summary>

src/Orion/World/IWorld.cs

@@ -0,0 +1,46 @@
+// Copyright (c) 2020 Pryaxis & Orion Contributors
+// 
+// This file is part of Orion.
+// 
+// Orion is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+// 
+// Orion is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+// 
+// You should have received a copy of the GNU General Public License
+// along with Orion.  If not, see <https://www.gnu.org/licenses/>.
+
+using Orion.Entities;
+using Orion.World.Tiles;
+
+namespace Orion.World {
+    /// <summary>
+    /// Represents a Terraria world.
+    /// </summary>
+    public interface IWorld : IAnnotatable {
+        /// <summary>
+        /// Gets a reference to the tile at the given coordinates.
+        /// </summary>
+        /// <param name="x">The X coordinate.</param>
+        /// <param name="y">The Y coordinate.</param>
+        /// <returns>A reference to the tile at the given coordinates.</returns>
+        ref Tile this[int x, int y] { get; }
+
+        /// <summary>
+        /// Gets the world width.
+        /// </summary>
+        /// <value>The world width.</value>
+        int Width { get; }
+
+        /// <summary>
+        /// Gets the world height.
+        /// </summary>
+        /// <value>The world height.</value>
+        int Height { get; }
+    }
+}

src/Orion/World/IWorldService.cs

@@ -0,0 +1,29 @@
+// Copyright (c) 2020 Pryaxis & Orion Contributors
+// 
+// This file is part of Orion.
+// 
+// Orion is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+// 
+// Orion is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+// 
+// You should have received a copy of the GNU General Public License
+// along with Orion.  If not, see <https://www.gnu.org/licenses/>.
+
+namespace Orion.World {
+    /// <summary>
+    /// Represents a world service. Provides access to world-related properties and methods.
+    /// </summary>
+    public interface IWorldService {
+        /// <summary>
+        /// Gets the world.
+        /// </summary>
+        /// <value>The world.</value>
+        IWorld World { get; }
+    }
+}

src/Orion/World/OrionWorld.cs

@@ -0,0 +1,61 @@
+// Copyright (c) 2020 Pryaxis & Orion Contributors
+// 
+// This file is part of Orion.
+// 
+// Orion is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+// 
+// Orion is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+// 
+// You should have received a copy of the GNU General Public License
+// along with Orion.  If not, see <https://www.gnu.org/licenses/>.
+
+using System;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using Orion.Entities;
+using Orion.World.Tiles;
+
+namespace Orion.World {
+    internal sealed unsafe class OrionWorld : AnnotatableObject, IDisposable, IWorld {
+        // Store a pointer to the `Tile` array in unmanaged memory so that the array doesn't need to be pinned.
+        private readonly unsafe Tile* _tiles;
+
+        public OrionWorld(int width, int height) {
+            Debug.Assert(width > 0);
+            Debug.Assert(height > 0);
+
+            Width = width;
+            Height = height;
+
+            _tiles = (Tile*)Marshal.AllocHGlobal(sizeof(Tile) * width * height);
+        }
+
+        ~OrionWorld() {
+            Marshal.FreeHGlobal((IntPtr)_tiles);
+        }
+
+        public ref Tile this[int x, int y] {
+            get {
+                Debug.Assert(x >= 0 && x < Width);
+                Debug.Assert(y >= 0 && y < Height);
+
+                var offset = y * Width + x;
+                return ref _tiles[offset];
+            }
+        }
+
+        public int Width { get; }
+        public int Height { get; }
+
+        public void Dispose() {
+            Marshal.FreeHGlobal((IntPtr)_tiles);
+            GC.SuppressFinalize(this);
+        }
+    }
+}