Add DatumEnsemble::asDatum() and use it in exportToWkt()

to allow exporting DatumEnsemble to WKT < 2019.

5 files changed, 119 insertions, 7 deletions

diff --git a/include/proj/datum.hpp b/include/proj/datum.hpp
index 35b8576e..bf3dbcb7 100644
--- a/include/proj/datum.hpp
+++ b/include/proj/datum.hpp
@@ -147,7 +147,10 @@ class PROJ_GCC_DLL DatumEnsemble final : public common::ObjectUsage,
 
     PROJ_INTERNAL void _exportToJSON(io::JSONFormatter *formatter)
         const override; // throw(io::FormattingException)
-                        //! @endcond
+
+    PROJ_FOR_TEST DatumNNPtr
+    asDatum(const io::DatabaseContextPtr &dbContext) const;
+    //! @endcond
 
   protected:
 #ifdef DOXYGEN_ENABLED
diff --git a/scripts/reference_exported_symbols.txt b/scripts/reference_exported_symbols.txt
index d864030a..f37dde16 100644
--- a/scripts/reference_exported_symbols.txt
+++ b/scripts/reference_exported_symbols.txt
@@ -234,6 +234,7 @@ osgeo::proj::cs::VerticalCS::~VerticalCS()
 osgeo::proj::datum::Datum::anchorDefinition() const
 osgeo::proj::datum::Datum::conventionalRS() const
 osgeo::proj::datum::Datum::~Datum()
+osgeo::proj::datum::DatumEnsemble::asDatum(std::shared_ptr<osgeo::proj::io::DatabaseContext> const&) const
 osgeo::proj::datum::DatumEnsemble::create(osgeo::proj::util::PropertyMap const&, std::vector<dropbox::oxygen::nn<std::shared_ptr<osgeo::proj::datum::Datum> >, std::allocator<dropbox::oxygen::nn<std::shared_ptr<osgeo::proj::datum::Datum> > > > const&, dropbox::oxygen::nn<std::shared_ptr<osgeo::proj::metadata::PositionalAccuracy> > const&)
 osgeo::proj::datum::DatumEnsemble::~DatumEnsemble()
 osgeo::proj::datum::DatumEnsemble::datums() const
diff --git a/src/iso19111/datum.cpp b/src/iso19111/datum.cpp
index d94d729c..9ec9fb62 100644
--- a/src/iso19111/datum.cpp
+++ b/src/iso19111/datum.cpp
@@ -1613,16 +1613,83 @@ DatumEnsemble::positionalAccuracy() const {
 // ---------------------------------------------------------------------------
 
 //! @cond Doxygen_Suppress
+DatumNNPtr
+DatumEnsemble::asDatum(const io::DatabaseContextPtr &dbContext) const {
+
+    const auto &l_datums = datums();
+    auto *grf = dynamic_cast<const GeodeticReferenceFrame *>(l_datums[0].get());
+
+    const auto &l_identifiers = identifiers();
+    if (dbContext) {
+        if (!l_identifiers.empty()) {
+            const auto &id = l_identifiers[0];
+            try {
+                auto factory = io::AuthorityFactory::create(
+                    NN_NO_CHECK(dbContext), *(id->codeSpace()));
+                if (grf) {
+                    return factory->createGeodeticDatum(id->code());
+                } else {
+                    return factory->createVerticalDatum(id->code());
+                }
+            } catch (const std::exception &) {
+            }
+        }
+    }
+
+    std::string l_name(nameStr());
+    if (grf) {
+        // Remap to traditional datum names
+        if (l_name == "World Geodetic System 1984 ensemble") {
+            l_name = "World Geodetic System 1984";
+        } else if (l_name ==
+                   "European Terrestrial Reference System 1989 ensemble") {
+            l_name = "European Terrestrial Reference System 1989";
+        }
+    }
+    auto props =
+        util::PropertyMap().set(common::IdentifiedObject::NAME_KEY, l_name);
+    if (isDeprecated()) {
+        props.set(common::IdentifiedObject::DEPRECATED_KEY, true);
+    }
+    if (!l_identifiers.empty()) {
+        const auto &id = l_identifiers[0];
+        props.set(metadata::Identifier::CODESPACE_KEY, *(id->codeSpace()))
+            .set(metadata::Identifier::CODE_KEY, id->code());
+    }
+    const auto &l_usages = domains();
+    if (!l_usages.empty()) {
+
+        auto array(util::ArrayOfBaseObject::create());
+        for (const auto &usage : l_usages) {
+            array->add(usage);
+        }
+        props.set(common::ObjectUsage::OBJECT_DOMAIN_KEY,
+                  util::nn_static_pointer_cast<util::BaseObject>(array));
+    }
+    const auto anchor = util::optional<std::string>();
+
+    if (grf) {
+        return GeodeticReferenceFrame::create(props, grf->ellipsoid(), anchor,
+                                              grf->primeMeridian());
+    } else {
+        assert(dynamic_cast<VerticalReferenceFrame *>(l_datums[0].get()));
+        return datum::VerticalReferenceFrame::create(props, anchor);
+    }
+}
+//! @endcond
+
+// ---------------------------------------------------------------------------
+
+//! @cond Doxygen_Suppress
 void DatumEnsemble::_exportToWKT(
     io::WKTFormatter *formatter) const // throw(FormattingException)
 {
     const bool isWKT2 = formatter->version() == io::WKTFormatter::Version::WKT2;
     if (!isWKT2 || !formatter->use2019Keywords()) {
-        throw io::FormattingException(
-            "DatumEnsemble can only be exported to WKT2:2019");
+        return asDatum(formatter->databaseContext())->_exportToWKT(formatter);
     }
 
-    auto l_datums = datums();
+    const auto &l_datums = datums();
     assert(!l_datums.empty());
 
     formatter->startNode(io::WKTConstants::ENSEMBLE, false);
@@ -1679,7 +1746,7 @@ void DatumEnsemble::_exportToJSON(
         writer->Add(l_name);
     }
 
-    auto l_datums = datums();
+    const auto &l_datums = datums();
     writer->AddObjKey("members");
     {
         auto membersContext(writer->MakeArrayContext(false));
diff --git a/test/unit/test_datum.cpp b/test/unit/test_datum.cpp
index adf0ae4b..26098d5c 100644
--- a/test/unit/test_datum.cpp
+++ b/test/unit/test_datum.cpp
@@ -409,8 +409,7 @@ TEST(datum, datum_ensemble) {
         PositionalAccuracy::create("100"));
     EXPECT_EQ(ensemble->datums().size(), 2U);
     EXPECT_EQ(ensemble->positionalAccuracy()->value(), "100");
-    EXPECT_THROW(ensemble->exportToWKT(WKTFormatter::create().get()),
-                 FormattingException);
+
     EXPECT_EQ(
         ensemble->exportToWKT(
             WKTFormatter::create(WKTFormatter::Convention::WKT2_2019).get()),
@@ -422,6 +421,14 @@ TEST(datum, datum_ensemble) {
         "        LENGTHUNIT[\"metre\",1],\n"
         "        ID[\"EPSG\",7030]],\n"
         "    ENSEMBLEACCURACY[100]]");
+
+    EXPECT_EQ(
+        ensemble->exportToWKT(
+            WKTFormatter::create(WKTFormatter::Convention::WKT2_2015).get()),
+        "DATUM[\"test\",\n"
+        "    ELLIPSOID[\"WGS 84\",6378137,298.257223563,\n"
+        "        LENGTHUNIT[\"metre\",1],\n"
+        "        ID[\"EPSG\",7030]]]");
 }
 
 // ---------------------------------------------------------------------------
diff --git a/test/unit/test_factory.cpp b/test/unit/test_factory.cpp
index 6b87fba6..b17a3077 100644
--- a/test/unit/test_factory.cpp
+++ b/test/unit/test_factory.cpp
@@ -334,6 +334,24 @@ TEST(factory, AuthorityFactory_createDatumEnsembleGeodetic) {
     auto extent = domain->domainOfValidity();
     ASSERT_TRUE(extent != nullptr);
     EXPECT_TRUE(extent->isEquivalentTo(factory->createExtent("1262").get()));
+
+    {
+        // Without using db
+        auto datum = ensemble->asDatum(nullptr);
+        EXPECT_EQ(datum->nameStr(), "World Geodetic System 1984");
+        auto grf = dynamic_cast<GeodeticReferenceFrame *>(datum.get());
+        ASSERT_TRUE(grf != nullptr);
+        EXPECT_TRUE(grf->isEquivalentTo(factory->createDatum("6326").get()));
+    }
+
+    {
+        // Using db
+        auto datum = ensemble->asDatum(DatabaseContext::create());
+        EXPECT_EQ(datum->nameStr(), "World Geodetic System 1984");
+        auto grf = dynamic_cast<GeodeticReferenceFrame *>(datum.get());
+        ASSERT_TRUE(grf != nullptr);
+        EXPECT_TRUE(grf->isEquivalentTo(factory->createDatum("6326").get()));
+    }
 }
 
 // ---------------------------------------------------------------------------
@@ -354,6 +372,22 @@ TEST(factory, AuthorityFactory_createDatumEnsembleVertical) {
     auto extent = domain->domainOfValidity();
     ASSERT_TRUE(extent != nullptr);
     EXPECT_TRUE(extent->isEquivalentTo(factory->createExtent("4606").get()));
+
+    {
+        // Without using db
+        auto datum = ensemble->asDatum(nullptr);
+        auto vrf = dynamic_cast<VerticalReferenceFrame *>(datum.get());
+        ASSERT_TRUE(vrf != nullptr);
+        EXPECT_TRUE(vrf->isEquivalentTo(factory->createDatum("1288").get()));
+    }
+
+    {
+        // Using db
+        auto datum = ensemble->asDatum(DatabaseContext::create());
+        auto vrf = dynamic_cast<VerticalReferenceFrame *>(datum.get());
+        ASSERT_TRUE(vrf != nullptr);
+        EXPECT_TRUE(vrf->isEquivalentTo(factory->createDatum("1288").get()));
+    }
 }
 
 // ---------------------------------------------------------------------------