GH-1697 always stale files tolerate errors if a local copy is present

This fixes the situation when liteloader snapshot site is broken
and there's an older local snapshot already present.

10 files changed, 64 insertions, 11 deletions

diff --git a/api/logic/minecraft/Library.cpp b/api/logic/minecraft/Library.cpp
index 8bbd5503..5a75fe79 100644
--- a/api/logic/minecraft/Library.cpp
+++ b/api/logic/minecraft/Library.cpp
@@ -131,6 +131,11 @@ QList< std::shared_ptr< NetAction > > Library::getDownloads(OpSys system, class
 			}
 			return true;
 		}
+		Net::Download::Options options;
+		if(isAlwaysStale)
+		{
+			options |= Net::Download::Option::AcceptLocalFiles;
+		}
 		if (isForge)
 		{
 			out.append(ForgeXzDownload::make(storage, entry));
@@ -140,13 +145,13 @@ QList< std::shared_ptr< NetAction > > Library::getDownloads(OpSys system, class
 			if(sha1.size())
 			{
 				auto rawSha1 = QByteArray::fromHex(sha1.toLatin1());
-				auto dl = Net::Download::makeCached(url, entry);
+				auto dl = Net::Download::makeCached(url, entry, options);
 				dl->addValidator(new Net::ChecksumValidator(QCryptographicHash::Sha1, rawSha1));
 				out.append(dl);
 			}
 
 			else
-				out.append(Net::Download::makeCached(url, entry));
+				out.append(Net::Download::makeCached(url, entry, options));
 		}
 		return true;
 	};
diff --git a/api/logic/net/ByteArraySink.h b/api/logic/net/ByteArraySink.h
index 3deef1ed..03b77fcc 100644
--- a/api/logic/net/ByteArraySink.h
+++ b/api/logic/net/ByteArraySink.h
@@ -51,6 +51,11 @@ public:
 		return Job_Failed;
 	}
 
+	bool hasLocalData() override
+	{
+		return false;
+	}
+
 private:
 	QByteArray * m_output;
 };
diff --git a/api/logic/net/Download.cpp b/api/logic/net/Download.cpp
index 7610cae3..3d53ded0 100644
--- a/api/logic/net/Download.cpp
+++ b/api/logic/net/Download.cpp
@@ -31,10 +31,11 @@ Download::Download():NetAction()
 	m_status = Job_NotStarted;
 }
 
-Download::Ptr Download::makeCached(QUrl url, MetaEntryPtr entry)
+Download::Ptr Download::makeCached(QUrl url, MetaEntryPtr entry, Options options)
 {
 	Download * dl = new Download();
 	dl->m_url = url;
+	dl->m_options = options;
 	auto md5Node = new ChecksumValidator(QCryptographicHash::Md5);
 	auto cachedNode = new MetaCacheSink(entry, md5Node);
 	dl->m_sink.reset(cachedNode);
@@ -42,18 +43,20 @@ Download::Ptr Download::makeCached(QUrl url, MetaEntryPtr entry)
 	return std::shared_ptr<Download>(dl);
 }
 
-Download::Ptr Download::makeByteArray(QUrl url, QByteArray *output)
+Download::Ptr Download::makeByteArray(QUrl url, QByteArray *output, Options options)
 {
 	Download * dl = new Download();
 	dl->m_url = url;
+	dl->m_options = options;
 	dl->m_sink.reset(new ByteArraySink(output));
 	return std::shared_ptr<Download>(dl);
 }
 
-Download::Ptr Download::makeFile(QUrl url, QString path)
+Download::Ptr Download::makeFile(QUrl url, QString path, Options options)
 {
 	Download * dl = new Download();
 	dl->m_url = url;
+	dl->m_options = options;
 	dl->m_sink.reset(new FileSink(path));
 	return std::shared_ptr<Download>(dl);
 }
@@ -118,6 +121,14 @@ void Download::downloadError(QNetworkReply::NetworkError error)
 	}
 	else
 	{
+		if(m_options & Option::AcceptLocalFiles)
+		{
+			if(m_sink->hasLocalData())
+			{
+				m_status = Job_Failed_Proceed;
+				return;
+			}
+		}
 		// error happened during download.
 		qCritical() << "Failed " << m_url.toString() << " with reason " << error;
 		m_status = Job_Failed;
@@ -162,7 +173,15 @@ void Download::downloadFinished()
 	}
 
 	// if the download failed before this point ...
-	if (m_status == Job_Failed)
+	if (m_status == Job_Failed_Proceed)
+	{
+		qDebug() << "Download failed but we are allowed to proceed:" << m_url.toString();
+		m_sink->abort();
+		m_reply.reset();
+		emit succeeded(m_index_within_job);
+		return;
+	}
+	else if (m_status == Job_Failed)
 	{
 		qDebug() << "Download failed in previous step:" << m_url.toString();
 		m_sink->abort();
diff --git a/api/logic/net/Download.h b/api/logic/net/Download.h
index fab39ffe..d417f660 100644
--- a/api/logic/net/Download.h
+++ b/api/logic/net/Download.h
@@ -28,14 +28,20 @@ class MULTIMC_LOGIC_EXPORT Download : public NetAction
 
 public: /* types */
 	typedef std::shared_ptr<class Download> Ptr;
+	enum class Option
+	{
+		NoOptions = 0,
+		AcceptLocalFiles = 1
+	};
+	Q_DECLARE_FLAGS(Options, Option)
 
 protected: /* con/des */
 	explicit Download();
 public:
 	virtual ~Download(){};
-	static Download::Ptr makeCached(QUrl url, MetaEntryPtr entry);
-	static Download::Ptr makeByteArray(QUrl url, QByteArray *output);
-	static Download::Ptr makeFile(QUrl url, QString path);
+	static Download::Ptr makeCached(QUrl url, MetaEntryPtr entry, Options options = Option::NoOptions);
+	static Download::Ptr makeByteArray(QUrl url, QByteArray *output, Options options = Option::NoOptions);
+	static Download::Ptr makeFile(QUrl url, QString path, Options options = Option::NoOptions);
 
 public: /* methods */
 	QString getTargetFilepath()
@@ -62,5 +68,8 @@ private: /* data */
 	// FIXME: remove this, it has no business being here.
 	QString m_target_path;
 	std::unique_ptr<Sink> m_sink;
+	Options m_options;
 };
-}
\ No newline at end of file
+}
+
+Q_DECLARE_OPERATORS_FOR_FLAGS(Net::Download::Options)
diff --git a/api/logic/net/FileSink.cpp b/api/logic/net/FileSink.cpp
index e912b1c9..7dfc4336 100644
--- a/api/logic/net/FileSink.cpp
+++ b/api/logic/net/FileSink.cpp
@@ -97,4 +97,9 @@ JobStatus FileSink::finalizeCache(QNetworkReply &)
 	return Job_Finished;
 }
 
+bool FileSink::hasLocalData()
+{
+	QFileInfo info(m_filename);
+	return info.exists() && info.size() != 0;
+}
 }
diff --git a/api/logic/net/FileSink.h b/api/logic/net/FileSink.h
index 7adc9c47..035d5bfd 100644
--- a/api/logic/net/FileSink.h
+++ b/api/logic/net/FileSink.h
@@ -14,6 +14,7 @@ public: /* methods */
 	JobStatus write(QByteArray & data) override;
 	JobStatus abort() override;
 	JobStatus finalize(QNetworkReply & reply) override;
+	bool hasLocalData() override;
 
 protected: /* methods */
 	virtual JobStatus initCache(QNetworkRequest &);
diff --git a/api/logic/net/MetaCacheSink.cpp b/api/logic/net/MetaCacheSink.cpp
index 539b4bb3..c9d75310 100644
--- a/api/logic/net/MetaCacheSink.cpp
+++ b/api/logic/net/MetaCacheSink.cpp
@@ -56,4 +56,10 @@ JobStatus MetaCacheSink::finalizeCache(QNetworkReply & reply)
 	ENV.metacache()->updateEntry(m_entry);
 	return Job_Finished;
 }
+
+bool MetaCacheSink::hasLocalData()
+{
+	QFileInfo info(m_filename);
+	return info.exists() && info.size() != 0;
+}
 }
diff --git a/api/logic/net/MetaCacheSink.h b/api/logic/net/MetaCacheSink.h
index 98e9bba1..0f3bbdf6 100644
--- a/api/logic/net/MetaCacheSink.h
+++ b/api/logic/net/MetaCacheSink.h
@@ -9,6 +9,7 @@ class MetaCacheSink : public FileSink
 public: /* con/des */
 	MetaCacheSink(MetaEntryPtr entry, ChecksumValidator * md5sum);
 	virtual ~MetaCacheSink();
+	bool hasLocalData() override;
 
 protected: /* methods */
 	JobStatus initCache(QNetworkRequest & request) override;
diff --git a/api/logic/net/NetAction.h b/api/logic/net/NetAction.h
index 07456ce1..aee68230 100644
--- a/api/logic/net/NetAction.h
+++ b/api/logic/net/NetAction.h
@@ -29,7 +29,8 @@ enum JobStatus
 	Job_InProgress,
 	Job_Finished,
 	Job_Failed,
-	Job_Aborted
+	Job_Aborted,
+	Job_Failed_Proceed
 };
 
 typedef std::shared_ptr<class NetAction> NetActionPtr;
diff --git a/api/logic/net/Sink.h b/api/logic/net/Sink.h
index 53f2b221..de9b1722 100644
--- a/api/logic/net/Sink.h
+++ b/api/logic/net/Sink.h
@@ -17,6 +17,7 @@ public: /* methods */
 	virtual JobStatus write(QByteArray & data) = 0;
 	virtual JobStatus abort() = 0;
 	virtual JobStatus finalize(QNetworkReply & reply) = 0;
+	virtual bool hasLocalData() = 0;
 
 	void addValidator(Validator * validator)
 	{