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

#include <QIcon>
#include <QMetaEnum>

struct PakHeader {
	quint32 dirOffset;
	quint32 dirNum;
};

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

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 file;
	file.resize(entSize);
	st.read(file.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.file = std::move(file);
	return ent;
}

void insertFile(PakDir &dir, std::string name, PakFile file) {
	std::optional<std::string> next;

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

	auto existingNode = std::find_if(dir.begin(), dir.end(),
		[&name](PakNode const &node) {
			return node.name == name;
		});

	if(next) {
		auto ref =
			existingNode != dir.end()
				? *existingNode
				: dir.emplace_back(PakDir{}, std::move(name));
		insertFile(std::get<PakDir>(ref), *std::move(next), std::move(file));
	} else {
		if(existingNode != dir.end()) {
			throw std::runtime_error("duplicate file");
		}
		dir.emplace_back(std::move(file), std::move(name));
	}
}

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.file));
	}

	return root;
}

PakDirRoot::PakDirRoot(PakDir &&root, QObject *parent) :
	QObject{parent},
	PakDir{std::move(root)}
{
}

PakDirRoot::~PakDirRoot() {
}

PakDirModel::PakDirModel(PakDir const *root, QObject *parent) :
	QAbstractItemModel{parent},
	m_root{root}
{
}

PakDirModel::~PakDirModel() {
}

QVariant PakDirModel::data(QModelIndex const &index, int role) const {
	if(!index.isValid()) {
		return QVariant{};
	}

	auto node = static_cast<PakNode *>(index.internalPointer());
	auto col  = Pak::Column(index.column());

	switch(role) {
		case Qt::DecorationRole:
			if(col == Pak::Column::Name) {
				auto icon =
					std::holds_alternative<PakDir>(*node) ? "folder"
					                                      : "text-x-generic";
				return QVariant{QIcon::fromTheme(icon)};
			}
			break;
		case Qt::DisplayRole:
			switch(col) {
				case Pak::Column::Size:
					if(auto file = std::get_if<PakFile>(node)) {
						return QVariant{QString::number(file->size())};
					}
					break;
				case Pak::Column::Name:
					return QVariant{tr(node->name.data())};
			}
		default:
			break;
	}
	return QVariant{};
}

Qt::ItemFlags PakDirModel::flags(QModelIndex const &index) const {
	if(!index.isValid()) {
		return Qt::NoItemFlags;
	} else {
		return Qt::ItemIsSelectable  |
		       Qt::ItemIsDragEnabled |
		       Qt::ItemIsEnabled     |
		       Qt::ItemNeverHasChildren;
	}
}

QVariant PakDirModel::headerData(int section,
                                Qt::Orientation orientation,
                                int role) const {
	if(orientation == Qt::Horizontal && role == Qt::DisplayRole) {
		switch(Pak::Column(section)) {
			case Pak::Column::Size: return QVariant{tr("Size")};
			case Pak::Column::Name: return QVariant{tr("Name")};
		}
	}
	return QVariant{};
}

QModelIndex PakDirModel::index(int row,
                               int col,
                               QModelIndex const &parent) const {
	if(!hasIndex(row, col, parent) || row > m_root->size()) {
		return QModelIndex{};
	} else {
		// despite index data being const, this function does not take a const
		// pointer, which is very annoying!
		return createIndex(row, col, const_cast<PakNode *>(&m_root->at(row)));
	}
}

QModelIndex PakDirModel::parent(QModelIndex const &) const {
	return QModelIndex{};
}

int PakDirModel::rowCount(QModelIndex const &) const {
	return m_root->size();
}

int PakDirModel::columnCount(QModelIndex const &) const {
	return QMetaEnum::fromType<Pak::Column>().keyCount();
}

PakDirModelSorter::~PakDirModelSorter() {
}

// EOF