#include "common.h"
#include "quam/pak.h"

struct PakHeader {
	quint32 dirOffset;
	quint32 dirNum;
};

struct PakEntry {
	std::string name;
	PakFile     data;
};

static constexpr quint32 sizeOfPakEntry = 64;

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

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

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

	if(dirSize % sizeOfPakEntry != 0) {
		throw std::runtime_error("invalid directory size");
	}

	PakHeader hdr;
	hdr.dirOffset = dirOffset;
	hdr.dirNum    = dirSize / sizeOfPakEntry;
	return hdr;
}

static PakEntry readPakEntry(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);

	PakFile bytes;
	bytes.resize(entSize);
	st.read(bytes.data(), entSize);

	st.seekg(pos);

	auto zero = std::find(entName.cbegin(), entName.cend(), '\0');

	std::string name;
	std::copy(entName.cbegin(), zero, std::back_inserter(name));

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

	PakEntry ent;
	ent.name = std::move(name);
	ent.data = std::move(bytes);
	return ent;
}

void insertFile(PakDir &dir, std::string name, PakFile file) {
	if(auto slash = name.find('/'); slash != std::string::npos) {
		auto folder = name.substr(0, slash);
		auto next   = name.substr(slash + 1);
		dir[folder] = PakNode{PakDir{}};
		insertFile(std::get<PakDir>(dir[folder]),
		           std::move(next),
		           std::move(file));
	} else {
		dir[name] = PakNode{std::move(file)};
	}
}

PakDir readPak(std::istream &st) {
	auto hdr = readPakHeader(st);
	st.seekg(hdr.dirOffset);

	PakDir root;

	for(quint32 i = 0; i < hdr.dirNum; i++) {
		auto ent = readPakEntry(st);
		insertFile(root, std::move(ent.name), std::move(ent.data));
	}

	return root;
}

// EOF