TileUtils.cs

using Terraria;
using Terraria.DataStructures;

namespace Eggpack;

public static class TileUtils
{
	/// <summary>
	/// Gets the top-left tile of a multitile
	/// </summary>
	/// <param name="i">The tile X-coordinate</param>
	/// <param name="j">The tile Y-coordinate</param>
	public static Point16 GetTileOrigin(int i, int j)
	{
		//Framing.GetTileSafely ensures that the returned Tile instance is not null
		//Do note that neither this method nor Framing.GetTileSafely check if the wanted coordiates are in the world!
		Tile tile = Framing.GetTileSafely(i, j);

		Point16 coord = new(i, j);
		Point16 frame = new(tile.TileFrameX / 18, tile.TileFrameY / 18);

		return coord - frame;
	}

	/// <summary>
	/// Uses <seealso cref="GetTileOrigin(int, int)"/> to try to get the entity bound to the multitile at (<paramref name="i"/>, <paramref name="j"/>).
	/// </summary>
	/// <typeparam name="T">The type to get the entity as</typeparam>
	/// <param name="i">The tile X-coordinate</param>
	/// <param name="j">The tile Y-coordinate</param>
	/// <param name="entity">The found <typeparamref name="T"/> instance, if there was one.</param>
	/// <returns><see langword="true"/> if there was a <typeparamref name="T"/> instance, or <see langword="false"/> if there was no entity present OR the entity was not a <typeparamref name="T"/> instance.</returns>
	public static bool TryGetTileEntityAs<T>(int i, int j, out T entity) where T : TileEntity
	{
		Point16 origin = GetTileOrigin(i, j);

		//TileEntity.ByPosition is a Dictionary<Point16, TileEntity> which contains all placed TileEntity instances in the world
		//TryGetValue is used to both check if the dictionary has the key, origin, and get the value from that key if it's there
		if (TileEntity.ByPosition.TryGetValue(origin, out TileEntity existing) && existing is T existingAsT)
		{
			entity = existingAsT;
			return true;
		}

		entity = null;
		return false;
	}
}