From 303f9b7cddcd13039a1730c0249f2534a701b6b1 Mon Sep 17 00:00:00 2001
From: Andreas Neumann <a.neumann@carto.net>
Date: Sat, 5 Aug 2017 21:49:56 +0200
Subject: [PATCH] [FEATURE] expression function array_reverse

---
 resources/function_help/json/array_reverse    | 7 +++++++
 src/core/expression/qgsexpressionfunction.cpp | 9 ++++++++-
 tests/src/core/testqgsexpression.cpp          | 4 ++++
 3 files changed, 19 insertions(+), 1 deletion(-)
 create mode 100644 resources/function_help/json/array_reverse

diff --git a/resources/function_help/json/array_reverse b/resources/function_help/json/array_reverse
new file mode 100644
index 00000000000..06e64dc3186
--- /dev/null
+++ b/resources/function_help/json/array_reverse
@@ -0,0 +1,7 @@
+{
+  "name": "array_reverse",
+  "type": "function",
+  "description": "Returns the given array with array values in reversed order.",
+  "arguments": [ {"arg":"array","description":"an array"} ],
+  "examples": [ { "expression":"array_reverse(array(2,4,0,10))", "returns":"array: 10,0,4,2"}]
+}
diff --git a/src/core/expression/qgsexpressionfunction.cpp b/src/core/expression/qgsexpressionfunction.cpp
index d687de8bdba..770acbfe640 100644
--- a/src/core/expression/qgsexpressionfunction.cpp
+++ b/src/core/expression/qgsexpressionfunction.cpp
@@ -3602,6 +3602,13 @@ static QVariant fcnArrayCat( const QVariantList &values, const QgsExpressionCont
   return convertToSameType( list, values.at( 0 ).type() );
 }
 
+static QVariant fcnArrayReverse( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent )
+{
+  QVariantList list = QgsExpressionUtils::getListValue( values.at( 0 ), parent );
+  for ( int k = 0, s = list.size(), max = ( s / 2 ); k < max; k++ ) list.swap( k, s - ( 1 + k ) );
+  return list;
+}
+
 static QVariant fcnArrayIntersect( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent )
 {
   const QVariantList array1 = QgsExpressionUtils::getListValue( values.at( 0 ), parent );
@@ -3613,7 +3620,6 @@ static QVariant fcnArrayIntersect( const QVariantList &values, const QgsExpressi
   return QVariant( false );
 }
 
-
 static QVariant fcnArrayDistinct( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent )
 {
   QVariantList array = QgsExpressionUtils::getListValue( values.at( 0 ), parent );
@@ -4257,6 +4263,7 @@ const QList<QgsExpressionFunction *> &QgsExpression::Functions()
         << new QgsStaticExpressionFunction( QStringLiteral( "array_remove_at" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "array" ) ) << QgsExpressionFunction::Parameter( QStringLiteral( "pos" ) ), fcnArrayRemoveAt, QStringLiteral( "Arrays" ) )
         << new QgsStaticExpressionFunction( QStringLiteral( "array_remove_all" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "array" ) ) << QgsExpressionFunction::Parameter( QStringLiteral( "value" ) ), fcnArrayRemoveAll, QStringLiteral( "Arrays" ) )
         << new QgsStaticExpressionFunction( QStringLiteral( "array_cat" ), -1, fcnArrayCat, QStringLiteral( "Arrays" ) )
+        << new QgsStaticExpressionFunction( QStringLiteral( "array_reverse" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "array" ) ), fcnArrayReverse, QStringLiteral( "Arrays" ) )
         << new QgsStaticExpressionFunction( QStringLiteral( "array_intersect" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "array1" ) ) << QgsExpressionFunction::Parameter( QStringLiteral( "array2" ) ), fcnArrayIntersect, QStringLiteral( "Arrays" ) )
         << new QgsStaticExpressionFunction( QStringLiteral( "array_distinct" ), 1, fcnArrayDistinct, QStringLiteral( "Arrays" ) )
         << new QgsStaticExpressionFunction( QStringLiteral( "array_to_string" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "array" ) ) << QgsExpressionFunction::Parameter( QStringLiteral( "delimiter" ), true, "," ) << QgsExpressionFunction::Parameter( QStringLiteral( "emptyvalue" ), true, "" ), fcnArrayToString, QStringLiteral( "Arrays" ) )
diff --git a/tests/src/core/testqgsexpression.cpp b/tests/src/core/testqgsexpression.cpp
index ecb760809d8..996ee1f3a8b 100644
--- a/tests/src/core/testqgsexpression.cpp
+++ b/tests/src/core/testqgsexpression.cpp
@@ -2420,6 +2420,8 @@ class TestQgsExpression: public QObject
 
       QCOMPARE( QgsExpression( "array_intersect(array('1', '2', '3', '4'), array('4', '0', '2', '5'))" ).evaluate( &context ), QVariant( true ) );
       QCOMPARE( QgsExpression( "array_intersect(array('1', '2', '3', '4'), array('0', '5'))" ).evaluate( &context ), QVariant( false ) );
+
+      QCOMPARE( QgsExpression( "array_reverse(array('Dufour','Valmiera','Chugiak','Wien','Pisa','Lyon','Essen','Nødebo','Las Palmas')) = array('Las Palmas','Nødebo','Essen','Lyon','Pisa','Wien','Chugiak','Valmiera','Dufour')" ).evaluate( &context ), QVariant( true ) );
     }
 
     void eval_int_array()
@@ -2482,6 +2484,8 @@ class TestQgsExpression: public QObject
       QCOMPARE( QgsExpression( "array_intersect(array(1, 2, 3, 4), array(4, 0, 2, 5))" ).evaluate( &context ), QVariant( true ) );
       QCOMPARE( QgsExpression( "array_intersect(array(1, 2, 3, 4), array(0, 5))" ).evaluate( &context ), QVariant( false ) );
 
+      QCOMPARE( QgsExpression( "array_reverse(array(2,4,0,10)) = array(10,0,4,2)" ).evaluate( &context ), QVariant( true ) );
+
       QgsExpression badArray( QStringLiteral( "array_get('not an array', 0)" ) );
       QCOMPARE( badArray.evaluate( &context ), QVariant() );
       QVERIFY( badArray.hasEvalError() );