Add method to merge a list of possibly non-contigous date/datetime ranges

python/core/auto_generated/qgsrange.sip.in

@@ -375,6 +375,7 @@ If the range is empty and ``other`` is not, the range is changed and set to ``ot
 .. versionadded:: 3.12
 %End
 
+
     bool operator==( const QgsTemporalRange<T> &other ) const;
 
     bool operator!=( const QgsTemporalRange<T> &other ) const;

src/core/qgsrange.h

@@ -599,6 +599,53 @@ class QgsTemporalRange
       return changed;
     }
 
+#ifndef SIP_RUN
+
+    /**
+     * Merges a list of temporal ranges.
+     *
+     * Any overlapping ranges will be converted to a single range which covers the entire
+     * range of the input ranges.
+     *
+     * The returned value will be a list of non-contiguous ranges which completely encompass
+     * the input \a ranges, sorted in ascending order.
+     *
+     * \note Not available in Python bindings
+     *
+     * \since QGIS 3.20
+     */
+    static QList< QgsTemporalRange<T> > mergeRanges( const QList< QgsTemporalRange<T> > &ranges )
+    {
+      QList< QgsTemporalRange<T > > res;
+
+      QList< QgsTemporalRange<T> > queue = ranges;
+      while ( !queue.empty() )
+      {
+        QgsTemporalRange<T> range = queue.back();
+        queue.pop_back();
+
+        bool extended = false;
+        for ( int i = 0; i < res.count(); ++i )
+        {
+          if ( res[i].overlaps( range ) )
+          {
+            QgsTemporalRange< T > other = res.takeAt( i );
+            other.extend( range );
+            queue.push_back( other );
+            extended = true;
+            break;
+          }
+        }
+
+        if ( !extended )
+          res.push_back( range );
+      }
+
+      std::sort( res.begin(), res.end(), []( const QgsTemporalRange< T > &a, const QgsTemporalRange< T > &b ) -> bool { return a.begin() < b.begin(); } );
+      return res;
+    }
+#endif
+
     bool operator==( const QgsTemporalRange<T> &other ) const
     {
       return mLower == other.mLower &&

tests/src/core/CMakeLists.txt

@@ -171,6 +171,7 @@ set(TESTS
  testqgsproperty.cpp
  testqgsprovidermetadata.cpp
  testqgis.cpp
+ testqgsrange.cpp
  testqgsrasterfilewriter.cpp
  testqgsrasterfill.cpp
  testqgsrastermarker.cpp

tests/src/core/testqgsrange.cpp

@@ -0,0 +1,92 @@
+/***************************************************************************
+     testqgsrange.cpp
+     -------------------
+    Date                 : March 2021
+    Copyright            : (C) 2021 Nyall Dawson
+    Email                : nyall dot dawson at gmail dot com
+ ***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+#include "qgstest.h"
+#include <QObject>
+
+#include "qgsrange.h"
+
+class TestQgsRange: public QObject
+{
+    Q_OBJECT
+
+  private slots:
+    void initTestCase();// will be called before the first testfunction is executed.
+    void cleanupTestCase();// will be called after the last testfunction was executed.
+    void init();// will be called before each testfunction is executed.
+    void cleanup();// will be called after every testfunction.
+    void testMergeRangesDate();
+    void testMergeRangesDateTime();
+
+  private:
+
+};
+
+void TestQgsRange::initTestCase()
+{
+}
+
+void TestQgsRange::cleanupTestCase()
+{
+}
+
+void TestQgsRange::init()
+{
+
+}
+
+void TestQgsRange::cleanup()
+{
+
+}
+
+void TestQgsRange::testMergeRangesDate()
+{
+  QList< QgsDateRange > ranges { QgsDateRange( QDate( 2020, 1, 10 ), QDate( 2020, 1, 15 ) ),
+                                 QgsDateRange( QDate( 2020, 1, 20 ), QDate( 2020, 1, 25 ) ),
+                                 QgsDateRange( QDate( 2020, 1, 9 ), QDate( 2020, 1, 11 ) ),
+                                 QgsDateRange( QDate( 2020, 1, 19 ), QDate( 2020, 1, 27 ) ),
+                                 QgsDateRange( QDate( 2020, 1, 1 ), QDate( 2020, 1, 3 ) ) };
+
+  QList< QgsDateRange > res = QgsDateRange::mergeRanges( ranges );
+  QCOMPARE( res.size(), 3 );
+  QCOMPARE( res.at( 0 ).begin(), QDate( 2020, 1, 1 ) );
+  QCOMPARE( res.at( 0 ).end(), QDate( 2020, 1, 3 ) );
+  QCOMPARE( res.at( 1 ).begin(), QDate( 2020, 1, 9 ) );
+  QCOMPARE( res.at( 1 ).end(), QDate( 2020, 1, 15 ) );
+  QCOMPARE( res.at( 2 ).begin(), QDate( 2020, 1, 19 ) );
+  QCOMPARE( res.at( 2 ).end(), QDate( 2020, 1, 27 ) );
+}
+
+void TestQgsRange::testMergeRangesDateTime()
+{
+  QList< QgsDateTimeRange > ranges { QgsDateTimeRange( QDateTime( QDate( 2020, 1, 10 ), QTime( 0, 0, 0 ) ), QDateTime( QDate( 2020, 1, 15 ), QTime( 0, 0, 0 ) ) ),
+                                     QgsDateTimeRange( QDateTime( QDate( 2020, 1, 20 ), QTime( 0, 0, 0 ) ), QDateTime( QDate( 2020, 1, 25 ), QTime( 0, 0, 0 ) ) ),
+                                     QgsDateTimeRange( QDateTime( QDate( 2020, 1, 9 ), QTime( 0, 0, 0 ) ), QDateTime( QDate( 2020, 1, 11 ), QTime( 0, 0, 0 ) ) ),
+                                     QgsDateTimeRange( QDateTime( QDate( 2020, 1, 19 ), QTime( 0, 0, 0 ) ), QDateTime( QDate( 2020, 1, 27 ), QTime( 0, 0, 0 ) ) ),
+                                     QgsDateTimeRange( QDateTime( QDate( 2020, 1, 1 ), QTime( 0, 0, 0 ) ), QDateTime( QDate( 2020, 1, 3 ), QTime( 0, 0, 0 ) ) ) };
+
+  QList< QgsDateTimeRange > res = QgsDateTimeRange::mergeRanges( ranges );
+  QCOMPARE( res.size(), 3 );
+  QCOMPARE( res.at( 0 ).begin(), QDateTime( QDate( 2020, 1, 1 ), QTime( 0, 0, 0 ) ) );
+  QCOMPARE( res.at( 0 ).end(), QDateTime( QDate( 2020, 1, 3 ), QTime( 0, 0, 0 ) ) );
+  QCOMPARE( res.at( 1 ).begin(), QDateTime( QDate( 2020, 1, 9 ), QTime( 0, 0, 0 ) ) );
+  QCOMPARE( res.at( 1 ).end(), QDateTime( QDate( 2020, 1, 15 ), QTime( 0, 0, 0 ) ) );
+  QCOMPARE( res.at( 2 ).begin(), QDateTime( QDate( 2020, 1, 19 ), QTime( 0, 0, 0 ) ) );
+  QCOMPARE( res.at( 2 ).end(), QDateTime( QDate( 2020, 1, 27 ), QTime( 0, 0, 0 ) ) );
+}
+
+
+QGSTEST_MAIN( TestQgsRange )
+#include "testqgsrange.moc"