#include "quam/pack.h"

struct PackHeader {
	quint32 dirOffset;
	quint32 dirNum;
};

struct PackEntry {
	std::string name;
	Arc::File   file;
};

static constexpr quint32 sizeOfPackEntry = 64;

static PackHeader readPackHeader(std::istream &st) {
	auto magic = readBytes<4>(st);

	if(magic != std::array{'P', 'A', 'C', 'K'}) {
		throw FileFormatError("not a pak file (invalid magic number)");
	}

	auto dirOffset = readLE<quint32>(st);
	auto dirSize   = readLE<quint32>(st);

	if(dirSize % sizeOfPackEntry != 0) {
		throw FileFormatError("invalid directory size");
	}

	PackHeader hdr;
	hdr.dirOffset = dirOffset;
	hdr.dirNum    = dirSize / sizeOfPackEntry;
	return hdr;
}

static PackEntry readPackEntry(std::istream &st) {
	auto entName   = readBytes<56>(st);
	auto entOffset = readLE<quint32>(st);
	auto entSize   = readLE<quint32>(st);

	auto pos = st.tellg();

	st.seekg(entOffset);

	Arc::File file;
	file.resize(entSize);
	st.read(file.data(), entSize);

	st.seekg(pos);

	std::string name = ntbsToString(entName);

	if(name.front() == '/') {
		throw FileFormatError("empty root directory name");
	}

	PackEntry ent;
	ent.name = std::move(name);
	ent.file = std::move(file);
	return ent;
}

static void insertFile(Arc::Dir &dir, std::string &name, Arc::File &file) {
	Option<std::string> next;

	if(auto slash = name.find('/'); slash != std::string::npos) {
		next = name.substr(slash + 1);
		name = name.substr(0, slash);
	}

	auto existing = dir.findNode(name);
	if(next) {
		auto &ref = existing ? *existing
		                     : dir.emplace_back(Arc::Dir{}, std::move(name));
		insertFile(std::get<Arc::Dir>(ref), *next, file);
	} else if(!existing) {
		dir.emplace_back(std::move(file), std::move(name));
	} else {
		throw FileFormatError("duplicate file");
	}
}

Arc::Dir readPack(std::istream &st) {
	auto hdr = readPackHeader(st);
	st.seekg(hdr.dirOffset);

	Arc::Dir root;

	for(quint32 i = 0; i < hdr.dirNum; i++) {
		auto ent = readPackEntry(st);
		insertFile(root, ent.name, ent.file);
	}

	return root;
}

// EOF