/* Copyright 2013-2017 MultiMC Contributors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "LegacyModList.h"
#include <FileSystem.h>
#include <QString>
#include <QDebug>

LegacyModList::LegacyModList(const QString &dir, const QString &list_file)
	: m_dir(dir), m_list_file(list_file)
{
	FS::ensureFolderPathExists(m_dir.absolutePath());
	m_dir.setFilter(QDir::Readable | QDir::NoDotAndDotDot | QDir::Files | QDir::Dirs |
					QDir::NoSymLinks);
	m_dir.setSorting(QDir::Name | QDir::IgnoreCase | QDir::LocaleAware);
}

	struct OrderItem
	{
		QString id;
		bool enabled = false;
	};
	typedef QList<OrderItem> OrderList;

static void internalSort(QList<Mod> &what)
{
	auto predicate = [](const Mod &left, const Mod &right)
	{
		if (left.name() == right.name())
		{
			return left.mmc_id().localeAwareCompare(right.mmc_id()) < 0;
		}
		return left.name().localeAwareCompare(right.name()) < 0;
	};
	std::sort(what.begin(), what.end(), predicate);
}

static OrderList readListFile(const QString &m_list_file)
{
	OrderList itemList;
	if (m_list_file.isNull() || m_list_file.isEmpty())
		return itemList;

	QFile textFile(m_list_file);
	if (!textFile.open(QIODevice::ReadOnly | QIODevice::Text))
		return OrderList();

	QTextStream textStream;
	textStream.setAutoDetectUnicode(true);
	textStream.setDevice(&textFile);
	while (true)
	{
		QString line = textStream.readLine();
		if (line.isNull() || line.isEmpty())
			break;
		else
		{
			OrderItem it;
			it.enabled = !line.endsWith(".disabled");
			if (!it.enabled)
			{
				line.chop(9);
			}
			it.id = line;
			itemList.append(it);
		}
	}
	textFile.close();
	return itemList;
}

bool LegacyModList::update()
{
	if (!m_dir.exists() || !m_dir.isReadable())
		return false;

	QList<Mod> orderedMods;
	QList<Mod> newMods;
	m_dir.refresh();
	auto folderContents = m_dir.entryInfoList();
	bool orderOrStateChanged = false;

	// first, process the ordered items (if any)
	OrderList listOrder = readListFile(m_list_file);
	for (auto item : listOrder)
	{
		QFileInfo infoEnabled(m_dir.filePath(item.id));
		QFileInfo infoDisabled(m_dir.filePath(item.id + ".disabled"));
		int idxEnabled = folderContents.indexOf(infoEnabled);
		int idxDisabled = folderContents.indexOf(infoDisabled);
		bool isEnabled;
		// if both enabled and disabled versions are present, it's a special case...
		if (idxEnabled >= 0 && idxDisabled >= 0)
		{
			// we only process the one we actually have in the order file.
			// and exactly as we have it.
			// THIS IS A CORNER CASE
			isEnabled = item.enabled;
		}
		else
		{
			// only one is present.
			// we pick the one that we found.
			// we assume the mod was enabled/disabled by external means
			isEnabled = idxEnabled >= 0;
		}
		int idx = isEnabled ? idxEnabled : idxDisabled;
		QFileInfo &info = isEnabled ? infoEnabled : infoDisabled;
		// if the file from the index file exists
		if (idx != -1)
		{
			// remove from the actual folder contents list
			folderContents.takeAt(idx);
			// append the new mod
			orderedMods.append(Mod(info));
			if (isEnabled != item.enabled)
				orderOrStateChanged = true;
		}
		else
		{
			orderOrStateChanged = true;
		}
	}
	// if there are any untracked files...
	if (folderContents.size())
	{
		// the order surely changed!
		for (auto entry : folderContents)
		{
			newMods.append(Mod(entry));
		}
		internalSort(newMods);
		orderedMods.append(newMods);
		orderOrStateChanged = true;
	}
	// otherwise, if we were already tracking some mods
	else if (mods.size())
	{
		// if the number doesn't match, order changed.
		if (mods.size() != orderedMods.size())
			orderOrStateChanged = true;
		// if it does match, compare the mods themselves
		else
			for (int i = 0; i < mods.size(); i++)
			{
				if (!mods[i].strongCompare(orderedMods[i]))
				{
					orderOrStateChanged = true;
					break;
				}
			}
	}
	mods.swap(orderedMods);
	if (orderOrStateChanged && !m_list_file.isEmpty())
	{
		qDebug() << "Mod list " << m_list_file << " changed!";
	}
	return true;
}