Import: support importing the single file argument as a CSV file

This will allow associating DB4S to CSV files and dropping a CSV file to be
importing into a new in-memory database, when there is no DB open yet.

See issue #2589

src/Application.cpp

@@ -127,9 +127,10 @@ Application::Application(int& argc, char** argv) :
         if(arguments().at(i) == "-h" || arguments().at(i) == "--help")
         {
             // Help
-            qWarning() << qPrintable(QString("%1: %2 [%3] [<%4>|<%5>]\n").
+            qWarning() << qPrintable(QString("%1: %2 [%3] [<%4>|<%5>|%6]\n").
                                      arg(tr("Usage")).arg(QFileInfo(argv[0]).fileName()).
-                                     arg(tr("options")).arg(tr("database")).arg(tr("project")));
+                                     arg(tr("options")).arg(tr("database")).arg(tr("project")).
+                                     arg(tr("csv-file")));
 
             qWarning() << qPrintable(tr("Possible command line arguments:"));
             printArgument(QString("-h, --help"),
@@ -156,6 +157,8 @@ Application::Application(int& argc, char** argv) :
                           tr("Open this SQLite database"));
             printArgument(QString("<%1>").arg(tr("project")),
                           tr("Open this project file (*.sqbpro)"));
+            printArgument(QString("<%1>").arg(tr("csv-file")),
+                          tr("Import this CSV file into an in-memory database"));
             m_showMainWindow = false;
         } else if(arguments().at(i) == "-v" || arguments().at(i) == "--version") {
             qWarning() << qPrintable(versionInformation());

src/Data.cpp

@@ -5,6 +5,7 @@
 #include <QImageReader>
 #include <QLocale>
 #include <QTextCodec>
+#include <QFile>
 
 #include <algorithm>
 
@@ -59,6 +60,17 @@ bool isTextOnly(QByteArray data, const QString& encoding, bool quickTest)
     }
 }
 
+bool isTextOnlyFile(const QString& fileName)
+{
+    QFile file(fileName);
+    if (file.open(QFile::ReadOnly)) {
+        QByteArray data = file.read(512);
+        return isTextOnly(data);
+    } else {
+        return false;
+    }
+}
+
 bool containsRightToLeft(const QString& text) {
 
     for(QChar ch : text) {

src/Data.h

@@ -10,6 +10,9 @@
 // text but makes it less reliable
 bool isTextOnly(QByteArray data, const QString& encoding = QString(), bool quickTest = false);
 
+// Determine if file is a text file reading first 512 bytes and calling isTextOnly().
+bool isTextOnlyFile(const QString& fileName);
+
 // This returns true if text contains some character whose direction is right-to-left.
 bool containsRightToLeft(const QString& text);
 

src/MainWindow.cpp

@@ -530,6 +530,10 @@ bool MainWindow::fileOpen(const QString& fileName, bool openFromProject, bool re
         if(loadProject(wFile, readOnly))
         {
             retval = true;
+        } else if(isTextOnlyFile(wFile)) {
+            // If it's a text file, cannot be an SQLite/SQLCipher database,
+            // so try to import it as CSV.
+            importCSVfiles({wFile});
         } else {
             // Close the database. If the user didn't want to close it, though, stop here
             if (db.isOpen())