COMPLUMP: Choose completion number by largest overlap in cell

When several perforation intervals cut the same cell, the completion number
was taken from the first contribution, which depended on the order events
were applied. Unrelated event changes (e.g. group tree members) could then
change COMPLUMP numbers on boundary cells.

Pick the number with the largest summed MD overlap in the cell, with ties
going to the lowest number. Also use stable_sort for same-date events so
they keep file order.

ApplicationLibCode/UnitTests/RicWellPathExportCompletionDataFeatureImpl-Test.cpp

@@ -0,0 +1,100 @@
+/////////////////////////////////////////////////////////////////////////////////
+//
+//  Copyright (C) 2026     Equinor ASA
+//
+//  ResInsight 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 3 of the License, or
+//  (at your option) any later version.
+//
+//  ResInsight is distributed in the hope that it will be useful, but WITHOUT ANY
+//  WARRANTY; without even the implied warranty of MERCHANTABILITY or
+//  FITNESS FOR A PARTICULAR PURPOSE.
+//
+//  See the GNU General Public License at <http://www.gnu.org/licenses/gpl.html>
+//  for more details.
+//
+/////////////////////////////////////////////////////////////////////////////////
+
+#include "gtest/gtest.h"
+
+#include "Commands/CompletionExportCommands/RicWellPathExportCompletionDataFeatureImpl.h"
+
+#include "RigCompletionData.h"
+
+#include <algorithm>
+#include <optional>
+
+namespace
+{
+RigCompletionData makeCompletion( double startMD, double endMD, std::optional<int> completionNumber )
+{
+    RigCompletionData completion( "W", RigCompletionDataGridCell( 0, nullptr ), startMD );
+    completion.setDepthRange( startMD, endMD );
+    if ( completionNumber ) completion.setCompletionNumber( *completionNumber );
+    return completion;
+}
+
+std::optional<int> numberForAllOrders( std::vector<RigCompletionData> completions )
+{
+    std::vector<size_t> order( completions.size() );
+    for ( size_t i = 0; i < order.size(); ++i )
+        order[i] = i;
+
+    std::optional<int> first;
+    bool               firstSet = false;
+    do
+    {
+        std::vector<RigCompletionData> permuted;
+        for ( size_t i : order )
+            permuted.push_back( completions[i] );
+
+        auto number = RicWellPathExportCompletionDataFeatureImpl::completionNumberForCell( permuted );
+        if ( !firstSet )
+        {
+            first    = number;
+            firstSet = true;
+        }
+        EXPECT_EQ( first, number );
+    } while ( std::next_permutation( order.begin(), order.end() ) );
+
+    return first;
+}
+} // namespace
+
+//--------------------------------------------------------------------------------------------------
+/// A cell cut by two perforation intervals gets the number of the interval with the largest overlap,
+/// regardless of the order the contributions arrive in.
+//--------------------------------------------------------------------------------------------------
+TEST( RicWellPathExportCompletionDataFeatureImpl, CompletionNumberUsesLargestOverlap )
+{
+    EXPECT_EQ( 2, numberForAllOrders( { makeCompletion( 100.0, 101.0, 1 ), makeCompletion( 101.0, 105.0, 2 ) } ) );
+    EXPECT_EQ( 1, numberForAllOrders( { makeCompletion( 100.0, 104.0, 1 ), makeCompletion( 104.0, 105.0, 2 ) } ) );
+}
+
+//--------------------------------------------------------------------------------------------------
+///
+//--------------------------------------------------------------------------------------------------
+TEST( RicWellPathExportCompletionDataFeatureImpl, CompletionNumberTieGoesToLowestNumber )
+{
+    EXPECT_EQ( 3, numberForAllOrders( { makeCompletion( 100.0, 102.0, 5 ), makeCompletion( 102.0, 104.0, 3 ) } ) );
+}
+
+//--------------------------------------------------------------------------------------------------
+/// The same interval can cross a cell more than once; its lengths are summed.
+//--------------------------------------------------------------------------------------------------
+TEST( RicWellPathExportCompletionDataFeatureImpl, CompletionNumberSumsOverlapPerNumber )
+{
+    EXPECT_EQ( 1,
+               numberForAllOrders(
+                   { makeCompletion( 100.0, 102.0, 1 ), makeCompletion( 102.0, 105.0, 2 ), makeCompletion( 110.0, 112.0, 1 ) } ) );
+}
+
+//--------------------------------------------------------------------------------------------------
+///
+//--------------------------------------------------------------------------------------------------
+TEST( RicWellPathExportCompletionDataFeatureImpl, CompletionNumberIgnoresContributionsWithoutNumber )
+{
+    EXPECT_EQ( 4, numberForAllOrders( { makeCompletion( 100.0, 110.0, std::nullopt ), makeCompletion( 110.0, 111.0, 4 ) } ) );
+    EXPECT_EQ( std::nullopt, numberForAllOrders( { makeCompletion( 100.0, 110.0, std::nullopt ) } ) );
+}