factory-hole-core/include/Core/Chunk.h

#pragma once

#include <stdint.h>
#include <array>
#include <memory>
#include <vector>
#include <unordered_map>

#include "Util/Span.h"

#include "config.h"
#include "Types/Tile.h"
#include "Components/Misc.hpp"

struct Chunk
{
public:
	typedef uint8_t CoordinateType;
	static constexpr int ChunkSizePowerOfTwo = 6;
	static constexpr int ChunkSize = 1 << ChunkSizePowerOfTwo;
	static constexpr int TotalChunkTiles = ChunkSize * ChunkSize;
	static constexpr int ChunkMask = (1 << ChunkSizePowerOfTwo) - 1;
	static_assert(sizeof(CoordinateType) * 8 >= ChunkSizePowerOfTwo, "CoordinateType is too small to support chunk size");

	static constexpr uint8_t WorldToLocal(int world) { return world & ChunkMask; }

	std::array<Tile, TotalChunkTiles> Tiles;

public:
	static void Assert(int x, int y) { DEV_ASSERT(x < ChunkSize && x >= 0 && y < ChunkSize && y >= 0); }
public:
	Tile GetTile(int x, int y) const { Assert(x, y); return Tiles[y * ChunkSize + x]; }
	Tile GetTile(Vector2 pos) const { return GetTile(pos.X, pos.Y); }
	const Tile& GetTileRef(int x, int y) const { Assert(x, y); return Tiles[y * ChunkSize + x]; }
	Tile& GetTile(int x, int y) { Assert(x, y); return Tiles[y * ChunkSize + x]; }
	Tile& GetTile(Vector2 pos) { return GetTile(pos.X, pos.Y); }
};

struct ChunkCoordinate
{
	ChunkCoordinate() = default;
	ChunkCoordinate(int x, int y) : X{ static_cast<uint8_t>(x) }, Y{ static_cast<uint8_t>(y) } { DEV_ASSERT(x >= 0 && x < Chunk::ChunkSize && y >= 0 && y < Chunk::ChunkSize); }
	ChunkCoordinate(Vector2 pos) : ChunkCoordinate{pos.X, pos.Y} {}

	uint8_t X{};
	uint8_t Y{};

	operator Vector2() const { return Vector2(X, Y); }
};

static_assert(sizeof(ChunkCoordinate) / 2 >= Chunk::ChunkSizePowerOfTwo / 8);

struct EntityTile final
{
public:
	EntityTile() = default;
	EntityTile(flecs::entity entity, int worldX, int worldY)
		: Entity{ entity }
		, ChunkX{ Chunk::WorldToLocal(worldX) }
		, ChunkY{ Chunk::WorldToLocal(worldY) }
		{}
	
public:
	flecs::entity Entity{};
	Chunk::CoordinateType ChunkX{};
	Chunk::CoordinateType ChunkY{};
};

struct ChunkKey
{
public:
	static constexpr int16_t WorldToChunk(int pos) { return static_cast<int16_t>(pos >> Chunk::ChunkSizePowerOfTwo); }
	static constexpr int32_t ChunkToWorld(int16_t pos) { return pos << Chunk::ChunkSizePowerOfTwo; }

public:
	int16_t X{}, Y{};

public:
	ChunkKey() = default;
	ChunkKey(int WorldX, int WorldY) : X{ WorldToChunk(WorldX) }, Y{ WorldToChunk(WorldY) } {}

public:
	uint64_t hash64() const { static_assert(sizeof(uint32_t) == sizeof(ChunkKey)); return std::hash<uint32_t>{}(*reinterpret_cast<const uint32_t*>(this)); }
	uint32_t hash() const { return static_cast<uint32_t>(hash64()); }
	static uint32_t hash(ChunkKey key) { return key.hash(); }

	Bounds GetBounds() const { return Bounds{Vector2{ChunkToWorld(X), ChunkToWorld(Y)}, Vector2{ChunkToWorld(X + 1), ChunkToWorld(Y + 1)}}; }

public:
	bool operator==(const ChunkKey& rhs) const { return hash() == rhs.hash(); }
};

static_assert(sizeof(ChunkKey) == 4);

struct ChunkData
{
public:
	void MarkAsPersistant(flecs::entity entity);
	void RemovePersistance(flecs::entity entity);
	void Clear()
	{
		TileData = {};
		Entities.resize(0);
	}

public:
	std::unique_ptr<Chunk> TileData{};
	std::vector<EntityTile> Entities{};
	std::vector<EntityTile> PersistantEntities{};
};

struct ChunkCollection
{
public:
	const Chunk& GetChunk(int x, int y);
	const Chunk& GetChunk(ChunkKey key);
	Chunk const* TryGetChunk(int x, int y) const;
	Chunk const* TryGetChunk(ChunkKey key) const;
	ChunkData& GetChunkData(int x, int y);
	ChunkData& GetChunkData(ChunkKey key);

	Tile GetTile(int x, int y);
	Tile const* TryGetTile(int x, int y) const;
	flecs::entity GetEntity(int x, int y) const;

	void SetChunkTiles(int x, int y, std::unique_ptr<Chunk>&& chunk);
	void SetChunkTiles(ChunkKey key, std::unique_ptr<Chunk>&& chunk);
	void AddEntity(flecs::entity entity, tcb::span<Vector2> claimedPositions);
	void AddPersistantEntity(flecs::entity entity, tcb::span<Vector2> claimedPositions);

	void MarkAsPersistant(flecs::entity entity);
	void RemovePersistance(flecs::entity entity);
	
	void RemoveEntity(flecs::entity entity);
	void RemoveChunk(int x, int y);
	void RemoveChunk(ChunkKey key);

private:
	int GetChunkIndex(int x, int y);
	int GetChunkIndex(ChunkKey key);
	int TryGetChunkIndex(int x, int y) const;
	int TryGetChunkIndex(ChunkKey key) const;
	Chunk& GetChunkInternal(int x, int y);
	Chunk& GetChunkInternal(ChunkKey key);
	Tile& GetTileInternal(int x, int y);

	void SetTile(Tile tile, int x, int y);

	void InvalidateCachedChunk();
	
private:
	std::vector<ChunkData> ChunkDatas;
	std::unordered_map<ChunkKey, int, ChunkKey> ChunkMap{};
	ChunkKey CachedChunkKey{};
	int CachedChunk{-1};
};

// struct LightValue
// {
// 	constexpr static uint8_t LightLevelBits = 5;
// 	constexpr static uint8_t PenetrationBits = 8 - LightLevelBits;
// 	constexpr static uint8_t MaxLightVal = (1 << LightLevelBits) - 1;
// 	constexpr static uint8_t MaxPenetration = (1 << PenetrationBits) - 1;

// 	uint8_t Penetration : PenetrationBits;
// 	uint8_t Val : LightLevelBits;

// 	LightValue()
// 	{
// 		Penetration = 1;
// 		Val = 0;
// 	}
// };

//static_assert(sizeof(LightValue) == 1);

// struct LightChunk
// {
// 	std::array<LightValue, Chunk::TotalChunkTiles> Tiles;

// public:
// 	LightValue GetTile(int x, int y) const { Chunk::Assert(x, y); return Tiles[y * Chunk::ChunkSize + x]; }
// 	LightValue& GetTile(int x, int y) { Chunk::Assert(x, y); return Tiles[y * Chunk::ChunkSize + x]; }
// };