/* Copyright 2013 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 "DownloadUpdateTask.h"

#include "MultiMC.h"
#include "logic/updater/UpdateChecker.h"
#include "logic/net/NetJob.h"
#include "pathutils.h"

#include <QFile>
#include <QTemporaryDir>
#include <QCryptographicHash>

#include <QDomDocument>


DownloadUpdateTask::DownloadUpdateTask(QString repoUrl, int versionId, QObject* parent) :
	Task(parent)
{
	m_cVersionId = MMC->version().build;

	m_nRepoUrl = repoUrl;
	m_nVersionId = versionId;

	m_updateFilesDir.setAutoRemove(false);
}

void DownloadUpdateTask::executeTask()
{
	// GO!
	// This will call the next step when it's done.
	findCurrentVersionInfo();
}

void DownloadUpdateTask::processChannels()
{
	auto checker = MMC->updateChecker();

	// Now, check the channel list again.
	if (!checker->hasChannels())
	{
		// We still couldn't load the channel list. Give up. Call loadVersionInfo and return.
		QLOG_INFO() << "Reloading the channel list didn't work. Giving up.";
		loadVersionInfo();
		return;
	}

	QList<UpdateChecker::ChannelListEntry> channels = checker->getChannelList();
	QString channelId = MMC->version().channel;

	// Search through the channel list for a channel with the correct ID.
	for (auto channel : channels)
	{
		if (channel.id == channelId)
		{
			QLOG_INFO() << "Found matching channel.";
			m_cRepoUrl = preparePath(channel.url);
			break;
		}
	}

	// Now that we've done that, load version info.
	loadVersionInfo();
}

void DownloadUpdateTask::findCurrentVersionInfo()
{
	setStatus(tr("Finding information about the current version."));

	auto checker = MMC->updateChecker();

	if (!checker->hasChannels())
	{
		// Load the channel list and wait for it to finish loading.
		QLOG_INFO() << "No channel list entries found. Will try reloading it.";

		QObject::connect(checker.get(), &UpdateChecker::channelListLoaded, this, &DownloadUpdateTask::processChannels);
		checker->updateChanList();
	}
	else
	{
		processChannels();
	}
}

void DownloadUpdateTask::loadVersionInfo()
{
	setStatus(tr("Loading version information."));

	// Create the net job for loading version info.
	NetJob* netJob = new NetJob("Version Info");
	
	// Find the index URL.
	QUrl newIndexUrl = QUrl(m_nRepoUrl).resolved(QString::number(m_nVersionId) + ".json");
	
	// Add a net action to download the version info for the version we're updating to.
	netJob->addNetAction(ByteArrayDownload::make(newIndexUrl));

	// If we have a current version URL, get that one too.
	if (!m_cRepoUrl.isEmpty())
	{
		QUrl cIndexUrl = QUrl(m_cRepoUrl).resolved(QString::number(m_cVersionId) + ".json");
		netJob->addNetAction(ByteArrayDownload::make(cIndexUrl));
	}

	// Connect slots so we know when it's done.
	QObject::connect(netJob, &NetJob::succeeded, this, &DownloadUpdateTask::vinfoDownloadFinished);
	QObject::connect(netJob, &NetJob::failed, this, &DownloadUpdateTask::vinfoDownloadFailed);

	// Store the NetJob in a class member. We don't want to lose it!
	m_vinfoNetJob.reset(netJob);

	// Finally, we start the network job and the thread's event loop to wait for it to finish.
	netJob->start();
}

void DownloadUpdateTask::vinfoDownloadFinished()
{
	// Both downloads succeeded. OK. Parse stuff.
	parseDownloadedVersionInfo();
}

void DownloadUpdateTask::vinfoDownloadFailed()
{
	// Something failed. We really need the second download (current version info), so parse downloads anyways as long as the first one succeeded.
	if (m_vinfoNetJob->first()->m_status != Job_Failed)
	{
		parseDownloadedVersionInfo();
		return;
	}

	// TODO: Give a more detailed error message.
	QLOG_ERROR() << "Failed to download version info files.";
	emitFailed(tr("Failed to download version info files."));
}

void DownloadUpdateTask::parseDownloadedVersionInfo()
{
	setStatus(tr("Reading file lists."));

	setStatus(tr("Reading file list for new version."));
	QLOG_DEBUG() << "Reading file list for new version.";
	QString error;
	if (!parseVersionInfo(std::dynamic_pointer_cast<ByteArrayDownload>(
							  m_vinfoNetJob->first())->m_data, &m_nVersionFileList, &error))
	{
		emitFailed(error);
		return;
	}

	// If there is a second entry in the network job's list, load it as the current version's info.
	if (m_vinfoNetJob->size() >= 2 && m_vinfoNetJob->operator[](1)->m_status != Job_Failed)
	{
		setStatus(tr("Reading file list for current version."));
		QLOG_DEBUG() << "Reading file list for current version.";
		QString error;
		parseVersionInfo(std::dynamic_pointer_cast<ByteArrayDownload>(
							 m_vinfoNetJob->operator[](1))->m_data, &m_cVersionFileList, &error);
	}

	// We don't need this any more.
	m_vinfoNetJob.reset();

	// Now that we're done loading version info, we can move on to the next step. Process file lists and download files.
	processFileLists();
}

bool DownloadUpdateTask::parseVersionInfo(const QByteArray &data, VersionFileList* list, QString *error)
{
	QJsonParseError jsonError;
	QJsonDocument jsonDoc = QJsonDocument::fromJson(data, &jsonError);
	if (jsonError.error != QJsonParseError::NoError)
	{
		*error = QString("Failed to parse version info JSON: %1 at %2").arg(jsonError.errorString()).arg(jsonError.offset);
		QLOG_ERROR() << error;
		return false;
	}

	QJsonObject json = jsonDoc.object();

	QLOG_DEBUG() << "Loading version info from JSON.";
	QJsonArray filesArray = json.value("Files").toArray();
	for (QJsonValue fileValue : filesArray)
	{
		QJsonObject fileObj = fileValue.toObject();

		VersionFileEntry file{
			fileObj.value("Path").toString(),
			fileObj.value("Perms").toVariant().toInt(),
			FileSourceList(),
			fileObj.value("MD5").toString(),
		};
		QLOG_DEBUG() << "File" << file.path << "with perms" << file.mode;
		
		QJsonArray sourceArray = fileObj.value("Sources").toArray();
		for (QJsonValue val : sourceArray)
		{
			QJsonObject sourceObj = val.toObject();

			QString type = sourceObj.value("SourceType").toString();
			if (type == "http")
			{
				file.sources.append(FileSource("http", preparePath(sourceObj.value("Url").toString())));
			}
			else if (type == "httpc")
			{
				file.sources.append(FileSource("httpc", preparePath(sourceObj.value("Url").toString()), sourceObj.value("CompressionType").toString()));
			}
			else
			{
				QLOG_WARN() << "Unknown source type" << type << "ignored.";
			}
		}

		QLOG_DEBUG() << "Loaded info for" << file.path;

		list->append(file);
	}

	return true;
}

void DownloadUpdateTask::processFileLists()
{
	setStatus(tr("Processing file lists. Figuring out how to install the update."));

	// First, if we've loaded the current version's file list, we need to iterate through it and 
	// delete anything in the current one version's list that isn't in the new version's list.
	for (VersionFileEntry entry : m_cVersionFileList)
	{
		bool keep = false;
		for (VersionFileEntry newEntry : m_nVersionFileList)
		{
			if (newEntry.path == entry.path)
			{
				QLOG_DEBUG() << "Not deleting" << entry.path << "because it is still present in the new version.";
				keep = true;
				break;
			}
		}
		// If the loop reaches the end and we didn't find a match, delete the file.
		if(!keep)
			m_operationList.append(UpdateOperation::DeleteOp(entry.path));
	}

	// Create a network job for downloading files.
	NetJob* netJob = new NetJob("Update Files");

	// Next, check each file in MultiMC's folder and see if we need to update them.
	for (VersionFileEntry entry : m_nVersionFileList)
	{
		// TODO: Let's not MD5sum a ton of files on the GUI thread. We should probably find a way to do this in the background.
		QString fileMD5;
		QFile entryFile(entry.path);
		if (entryFile.open(QFile::ReadOnly))
		{
			QCryptographicHash hash(QCryptographicHash::Md5);
			hash.addData(entryFile.readAll());
			fileMD5 = hash.result().toHex();
		}

		if (!entryFile.exists() || fileMD5.isEmpty() || fileMD5 != entry.md5)
		{
			QLOG_DEBUG() << "Found file" << entry.path << "that needs updating.";

			// Go through the sources list and find one to use.
			// TODO: Make a NetAction that takes a source list and tries each of them until one works. For now, we'll just use the first http one.
			for (FileSource source : entry.sources)
			{
				if (source.type == "http")
				{
					QLOG_DEBUG() << "Will download" << entry.path << "from" << source.url;

					// Download it to updatedir/<filepath>-<md5> where filepath is the file's path with slashes replaced by underscores.
					QString dlPath = PathCombine(m_updateFilesDir.path(), QString(entry.path).replace("/", "_"));

					// We need to download the file to the updatefiles folder and add a task to copy it to its install path.
					auto download = MD5EtagDownload::make(source.url, dlPath);
					download->m_check_md5 = true;
					download->m_expected_md5 = entry.md5;
					netJob->addNetAction(download);

					// Now add a copy operation to our operations list to install the file.
					m_operationList.append(UpdateOperation::CopyOp(dlPath, entry.path, entry.mode));
				}
			}
		}
	}

	// Add listeners to wait for the downloads to finish.
	QObject::connect(netJob, &NetJob::succeeded, this, &DownloadUpdateTask::fileDownloadFinished);
	QObject::connect(netJob, &NetJob::progress, this, &DownloadUpdateTask::fileDownloadProgressChanged);
	QObject::connect(netJob, &NetJob::failed, this, &DownloadUpdateTask::fileDownloadFailed);

	// Now start the download.
	setStatus(tr("Downloading %1 update files.").arg(QString::number(netJob->size())));
	QLOG_DEBUG() << "Begin downloading update files to" << m_updateFilesDir.path();
	m_filesNetJob.reset(netJob);
	netJob->start();

	writeInstallScript(m_operationList, PathCombine(m_updateFilesDir.path(), "file_list.xml"));
}

bool DownloadUpdateTask::writeInstallScript(UpdateOperationList& opsList, QString scriptFile)
{
	// Build the base structure of the XML document.
	QDomDocument doc;

	QDomElement root = doc.createElement("update");
	root.setAttribute("version", "3");
	doc.appendChild(root);

	QDomElement installFiles = doc.createElement("install");
	root.appendChild(installFiles);

	QDomElement removeFiles = doc.createElement("uninstall");
	root.appendChild(removeFiles);

	// Write the operation list to the XML document.
	for (UpdateOperation op : opsList)
	{
		QDomElement file = doc.createElement("file");

		switch (op.type)
		{
			case UpdateOperation::OP_COPY:
				{
				// Install the file.
				QDomElement name = doc.createElement("source");
				QDomElement path = doc.createElement("dest");
				QDomElement mode = doc.createElement("mode");
				name.appendChild(doc.createTextNode(op.file));
				path.appendChild(doc.createTextNode(op.dest));
				// We need to add a 0 at the beginning here, because Qt doesn't convert to octal correctly.
				mode.appendChild(doc.createTextNode("0" + QString::number(op.mode, 8)));
				file.appendChild(name);
				file.appendChild(path);
				file.appendChild(mode);
				installFiles.appendChild(file);
				QLOG_DEBUG() << "Will install file" << op.file;
				}
				break;

			case UpdateOperation::OP_DELETE:
				{
				// Delete the file.
				file.appendChild(doc.createTextNode(op.file));
				removeFiles.appendChild(file);
				QLOG_DEBUG() << "Will remove file" << op.file;
				}
				break;

			default:
				QLOG_WARN() << "Can't write update operation of type" << op.type << "to file. Not implemented.";
				continue;
		}
	}

	// Write the XML document to the file.
	QFile outFile(scriptFile);

	if (outFile.open(QIODevice::WriteOnly))
	{
		outFile.write(doc.toByteArray());
	}
	else
	{
		emitFailed(tr("Failed to write update script file."));
		return false;
	}

	return true;
}

QString DownloadUpdateTask::preparePath(const QString &path)
{
	return QString(path).replace("$PWD", qApp->applicationDirPath());
}

void DownloadUpdateTask::fileDownloadFinished()
{
	emitSucceeded();
}

void DownloadUpdateTask::fileDownloadFailed()
{
	// TODO: Give more info about the failure.
	QLOG_ERROR() << "Failed to download update files.";
	emitFailed(tr("Failed to download update files."));
}

void DownloadUpdateTask::fileDownloadProgressChanged(qint64 current, qint64 total)
{
	setProgress((int)(((float)current / (float)total)*100));
}

QString DownloadUpdateTask::updateFilesDir()
{
	return m_updateFilesDir.path();
}