Add a sample download dialog and upload sub-system

Samples are  downloaded from a  web server, currently the  SF download
server.   The samples  are  stored in  the  source controlled  samples
directory and the CMake script  there builds a suitable directory tree
for upload to the web  server under samples/web containing the samples
hierarchy and the  generated JSON contents database  file. The samples
CMake script also  defines an 'upload-samples' target  that uses rsync
to efficiently upload  the samples and the  accompanying contents JSON
database file.

Any directory structure under the samples directory may be created, to
add a new sample file simply add  the file to source control and amend
the list of sample files (SAMPLE_FILES) in samples/CMakeLists.txt.

git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6308 ab8295b8-cf94-4d9e-aec4-7959e3be5d79

SampleDownloader/RemoteFile.hpp

@@ -0,0 +1,78 @@
+#ifndef REMOTE_FILE_HPP__
+#define REMOTE_FILE_HPP__
+
+#include <QObject>
+#include <QString>
+#include <QUrl>
+#include <QFileInfo>
+#include <QSaveFile>
+
+class QNetworkAccessManager;
+class QNetworkReply;
+
+//
+// Synchronize an individual file specified by a URL to the local file
+// system
+//
+class RemoteFile final
+  : public QObject
+{
+  Q_OBJECT
+
+public:
+  //
+  // Clients  of   RemoteFile  must   provide  an  instance   of  this
+  // interface. It  may be  used to  receive information  and requests
+  // from the RemoteFile instance as it does its work.
+  //
+  class ListenerInterface
+  {
+  protected:
+    ListenerInterface () {}
+
+  public:
+    virtual void error (QString const& title, QString const& message) = 0;
+    virtual bool redirect_request (QUrl const&) {return false;} // disallow
+    virtual void download_progress (qint64 /* bytes_received */, qint64 /* total_bytes */) {}
+    virtual void download_finished (bool /* success */) {}
+  };
+
+  explicit RemoteFile (ListenerInterface * listener, QNetworkAccessManager * network_manager
+                       , QString const& local_file_path, QObject * parent = nullptr);
+
+  // true if local file exists or will do very soon
+  bool local () const;
+
+  // download/remove the local file
+  bool sync (QUrl const& url, bool local = true, bool force = false);
+
+  // abort an active download
+  void abort ();
+
+  // change the local location, this will rename if the file exists locally
+  void local_file_path (QString const&);
+
+  QString local_file_path () const {return local_file_.absoluteFilePath ();}
+  QUrl url () const {return url_;}
+
+private:
+  void download (QUrl const& url);
+  void reply_finished ();
+
+  Q_SLOT void store ();
+
+  Q_SIGNAL void redirect (QUrl const&, unsigned redirect_count);
+  Q_SIGNAL void downloadProgress (qint64 bytes_received, qint64 total_bytes);
+  Q_SIGNAL void finished ();
+
+  ListenerInterface * listener_;
+  QNetworkAccessManager * network_manager_;
+  QFileInfo local_file_;
+  QUrl url_;
+  QNetworkReply * reply_;
+  bool is_valid_;
+  unsigned redirect_count_;
+  QSaveFile file_;
+};
+
+#endif