using System;
using System.Collections.Generic;

namespace IslaApocalypse.Core
{
	/// <summary>
	/// ⭐ THE TRANSFORMATION / RECIPE SEAM — the bridge between the two material schemas.
	/// → `Design - Data - Material Schema.md` §3, D-054.
	///
	/// Terrain materials are RESOURCES that refine and combine into BUILDING materials —
	/// e.g. sand + clay + rock → concrete. That relationship is the survival loop, and keeping the
	/// two schemas distinct with a transformation between them is what stops it collapsing into
	/// "the same material tagged differently".
	///
	/// ⚠⚠ THIS REGISTRY IS DELIBERATELY EMPTY, AND THAT IS THE POINT.
	///
	/// The recipes themselves are DEFERRED. Designing the resource tree now would be a
	/// biomes-premature-style over-commitment — the exact mistake the rewrite exists to undo.
	/// But the SEAM EXISTS NOW: the architecture has the hole, so filling it later is new ROWS and
	/// never a rewrite.
	///
	/// Do not add recipes here without a design decision that says the tree is ready.
	/// </summary>
	public static class RecipeRegistry
	{
		private static readonly List<Recipe> _recipes = new();

		// ===== NO SEED ROWS. See the class comment — the emptiness is the design. =====

		/// <summary>Append a recipe. Append-only, same as the material registries.</summary>
		public static void Register(Recipe recipe)
		{
			if (recipe == null) throw new ArgumentNullException(nameof(recipe));
			_recipes.Add(recipe);
		}

		public static IReadOnlyList<Recipe> All => _recipes;
		public static int Count => _recipes.Count;
	}

	/// <summary>
	/// One transformation: some quantity of terrain-derived inputs produces a building material.
	///
	/// ⚠ SHAPE ONLY. The exact recipe FORMAT is an open note in the design doc — inputs may grow
	/// tools, stations, time or byproducts. This is the minimum that makes the seam real enough to
	/// compile against, not a committed format.
	/// </summary>
	public sealed class Recipe
	{
		/// <summary>Input material keys and their amounts. Terrain-derived resources.</summary>
		public IReadOnlyList<RecipeInput> Inputs { get; }

		/// <summary>The building material produced.</summary>
		public MaterialKey Output { get; }

		/// <summary>How much of <see cref="Output"/> one application yields.</summary>
		public int OutputAmount { get; }

		public Recipe(IReadOnlyList<RecipeInput> inputs, MaterialKey output, int outputAmount)
		{
			Inputs = inputs ?? throw new ArgumentNullException(nameof(inputs));
			Output = output;
			OutputAmount = outputAmount;
		}
	}

	/// <summary>One input line of a <see cref="Recipe"/>.</summary>
	public readonly struct RecipeInput
	{
		public readonly MaterialKey Material;
		public readonly int Amount;

		public RecipeInput(MaterialKey material, int amount)
		{
			Material = material;
			Amount = amount;
		}
	}
}