/* 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>


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

	auto checker = MMC->updateChecker();

	// This runs after we've tried loading the channel list.
	// If the channel list doesn't need to be loaded, this will be called immediately.
	// If the channel list does need to be loaded, this will be called when it's done.
	auto processFunc = [this, &checker] () -> void
	{
		// 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 = channel.url;
				break;
			}
		}

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

	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, processFunc);
		checker->updateChanList();
	}
	else
	{
		processFunc();
	}
}

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."));

	parseVersionInfo(NEW_VERSION, &m_nVersionFileList);

	// 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)
	{
		parseVersionInfo(CURRENT_VERSION, &m_cVersionFileList);
	}

	// 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();
}

void DownloadUpdateTask::parseVersionInfo(VersionInfoFileEnum vfile, VersionFileList* list)
{
	if (vfile == CURRENT_VERSION)  setStatus(tr("Reading file list for current version."));
	else if (vfile == NEW_VERSION) setStatus(tr("Reading file list for new version."));

	QLOG_DEBUG() << "Reading file list for" << (vfile == NEW_VERSION ? "new" : "current") << "version.";
	
	QByteArray data;
	{
		ByteArrayDownloadPtr dl = std::dynamic_pointer_cast<ByteArrayDownload>(
				vfile == NEW_VERSION ? m_vinfoNetJob->first() : m_vinfoNetJob->operator[](1));
		data = dl->m_data;
	}

	QJsonParseError jsonError;
	QJsonDocument jsonDoc = QJsonDocument::fromJson(data, &jsonError);
	if (jsonError.error != QJsonParseError::NoError)
	{
		QLOG_ERROR() << "Failed to parse version info JSON:" << jsonError.errorString() << "at" << jsonError.offset;
		return;
	}

	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("Executable").toBool(false),
			FileSourceList(),
			fileObj.value("MD5").toString(),
		};
		
		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", sourceObj.value("Url").toString()));
			}
			else if (type == "httpc")
			{
				file.sources.append(FileSource("httpc", 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);
	}
}

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)
	{
		for (VersionFileEntry newEntry : m_nVersionFileList)
		{ 
			if (newEntry.path == entry.path)
				continue;
		}
		// If the loop reaches the end, we didn't find a match. Delete the file.
		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(), entry.path.replace("/", "_"));

					// We need to download the file to the updatefiles folder and add a task to copy it to its install path.
					FileDownloadPtr download = FileDownload::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));
				}
			}
		}
	}

	// 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();

	// TODO: Write update operations to a file for the update installer.
}

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));
}