#pragma once
// EterPack — reader/writer for this m2dev fork's single-file asset pack
// (PackLib/Pack.cpp). NOT the classic Metin2 .eix/.epk format.
//
// Layout:
//   [Header: u64 entry_num, u64 data_begin, u8 nonce[24]]        (40 bytes)
//   [Entry x entry_num]  each XChaCha20-encrypted with Header.nonce + PACK_KEY
//       Entry: char name[NAME_FIELD], u64 offset, u64 file_size,
//              u64 compressed_size, u8 encryption, u8 nonce[24]
//   [data blob @ data_begin]
//       per file @ data_begin+offset, compressed_size bytes:
//         encryption==0 -> zstd frame            -> zstd-decompress to file_size
//         encryption==1 -> XChaCha20(entry.nonce)-> zstd-decompress to file_size
//
// NAME_FIELD is FILENAME_MAX+1 on the packer's platform (MSVC PackMaker = 261).
// The reader derives it from (data_begin - 40) / entry_num, falling back to the
// known platform values, so it stays compatible with real packs.

#include <cstdint>
#include <string>
#include <unordered_map>
#include <vector>

namespace mtpack {

inline constexpr int PACK_NONCE_SIZE = 24;
inline constexpr int PACK_KEY_SIZE = 32;

// PackLib/config.h PACK_KEY — the fork ships this hardcoded.
inline constexpr uint8_t PACK_KEY[PACK_KEY_SIZE] = {
	0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77,
	0x88, 0x99, 0xAA, 0xBB, 0xCC, 0xDD, 0xEE, 0xFF,
	0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF,
	0xFE, 0xDC, 0xBA, 0x98, 0x76, 0x54, 0x32, 0x10
};

// MSVC PackMaker.exe: FILENAME_MAX == 260, so the name field is 261 bytes.
inline constexpr int PACK_NAME_FIELD_DEFAULT = 261;

struct Entry {
	std::string name;
	uint64_t offset = 0;
	uint64_t file_size = 0;
	uint64_t compressed_size = 0;
	uint8_t encryption = 0;
	uint8_t nonce[PACK_NONCE_SIZE] = {};
};

class EterPack {
public:
	// Load the index (mmaps the file; keeps it open for read()).
	bool open(const std::string &path, std::string *err = nullptr);
	void close();

	bool has(const std::string &name) const { return m_by_name.count(norm(name)) != 0; }
	std::vector<std::string> names() const;
	size_t count() const { return m_index.size(); }

	// Decompress (+decrypt) one file into `out`.
	bool read(const std::string &name, std::vector<uint8_t> &out, std::string *err = nullptr) const;

	int name_field() const { return m_name_field; }

private:
	static std::string norm(std::string s); // '\\'->'/', lowercase

	std::vector<uint8_t> m_file; // whole pack in memory (simple; mmap later)
	uint64_t m_data_begin = 0;
	std::vector<Entry> m_index;
	std::unordered_map<std::string, size_t> m_by_name;
	int m_name_field = PACK_NAME_FIELD_DEFAULT;
};

// Build a pack from (name, bytes) pairs. `encrypt` -> per-file encryption==1.
// Uses PACK_NAME_FIELD_DEFAULT so real clients / PackLib can read it back.
struct InputFile {
	std::string name;
	std::vector<uint8_t> data;
};
bool write_pack(const std::string &out_path, const std::vector<InputFile> &files, bool encrypt,
		std::string *err = nullptr);

} // namespace mtpack