#pragma once
#ifndef GRID_CACHE_IO_H
#define GRID_CACHE_IO_H

#include <string>
#include <fstream>
#include <iostream>

#include "pch.h"

class GridCacheIO
{
public:
	// 保存网格（写入 header + gridOutput2）
	// 注意：会自动“清洗”一些不稳定的 n 字段，避免写入垃圾值
	static bool saveGrid(const std::string& filename,
		HX_NWTM_GRID_OUTPUT2 grid,              // 这里用值传递：方便内部清洗
		const HX_NWTM_GRID_INPUT& gridInput);

	// 读取网格（读取后会检查 sceneKey 是否匹配）
	// 注意：读取后也会做一次“清洗”，保证 n 字段稳定
	static bool loadGrid(const std::string& filename,
		HX_NWTM_GRID_OUTPUT2& grid,
		const HX_NWTM_GRID_INPUT& expectedGridInput);

	// 只检查 header 的 sceneKey 是否匹配（不读完整网格）
	static bool isCacheMatch(const std::string& filename,
		const HX_NWTM_GRID_INPUT& expectedGridInput);

	static bool fileExists(const std::string& filename);

private:
	// ---------------- 文件头 ----------------
	struct GridCacheHeader
	{
		unsigned int magic;          // 'GCHX'
		unsigned int version;        // 格式版本
		unsigned int reserved;       // 保留
		unsigned long long sceneKey; // 串场景指纹
		unsigned int nCells;         // 快速检查
	};

	enum { MAGIC = 0x58484347 };  // 'GCHX' little-endian
	enum { VERSION = 1 };

private:
	// 计算串场景 key
	static unsigned long long computeSceneKey64(const HX_NWTM_GRID_INPUT& in);

	// FNV-1a 64
	static unsigned long long fnv1a64_init();
	static void fnv1a64_update(unsigned long long& h, const void* data, size_t len);

	// hash 辅助
	static void hashInt(unsigned long long& h, int v);
	static void hashUInt(unsigned long long& h, unsigned int v);
	static void hashDouble(unsigned long long& h, double v);
	static void hashVec1D(unsigned long long& h, const dVec1& v);
	static void hashIVec1D(unsigned long long& h, const iVec1& v);
	static void hashVec2D(unsigned long long& h, const dVec2& v);
	static void hashIVec2D(unsigned long long& h, const iVec2& v);
	static void hashVec3D(unsigned long long& h, const dVec3& v);

	// IO 基元
	static bool writeUInt(std::ofstream& fs, unsigned int v);
	static bool writeULL(std::ofstream& fs, unsigned long long v);
	static bool writeInt(std::ofstream& fs, int v);
	static bool writeDouble(std::ofstream& fs, double v);

	static bool readUInt(std::ifstream& fs, unsigned int& v);
	static bool readULL(std::ifstream& fs, unsigned long long& v);
	static bool readInt(std::ifstream& fs, int& v);
	static bool readDouble(std::ifstream& fs, double& v);

	static bool writeSafeSize(std::ofstream& fs, size_t sz);
	static bool readSafeSize(std::ifstream& fs, size_t& sz);

	static bool writeVec1D(std::ofstream& fs, const dVec1& v);
	static bool writeIVec1D(std::ofstream& fs, const iVec1& v);
	static bool writeVec2D(std::ofstream& fs, const dVec2& v);
	static bool writeIVec2D(std::ofstream& fs, const iVec2& v);
	static bool writeVec3D(std::ofstream& fs, const dVec3& v);

	static bool readVec1D(std::ifstream& fs, dVec1& v);
	static bool readIVec1D(std::ifstream& fs, iVec1& v);
	static bool readVec2D(std::ifstream& fs, dVec2& v);
	static bool readIVec2D(std::ifstream& fs, iVec2& v);
	static bool readVec3D(std::ifstream& fs, dVec3& v);

	// gridOutput2 序列化
	static bool writeGridOutput2(std::ofstream& fs, const HX_NWTM_GRID_OUTPUT2& g);
	static bool readGridOutput2(std::ifstream& fs, HX_NWTM_GRID_OUTPUT2& g);

	static bool readHeader(std::ifstream& fs, GridCacheHeader& hdr);
	static bool writeHeader(std::ofstream& fs, const GridCacheHeader& hdr);

	// “清洗”不稳定字段：用 vector size 统一覆盖 n，避免 DLL 未初始化导致的随机值
	static void sanitizeGridOutput2(HX_NWTM_GRID_OUTPUT2& g);
};

#endif // GRID_CACHE_IO_H