Proof-of-concept of JSON export limited to PrimeMeridian (refs #1545)

4 files changed, 207 insertions, 0 deletions

diff --git a/src/iso19111/common.cpp b/src/iso19111/common.cpp
index d46da0da..f2a51032 100644
--- a/src/iso19111/common.cpp
+++ b/src/iso19111/common.cpp
@@ -236,6 +236,54 @@ void UnitOfMeasure::_exportToWKT(
     }
     formatter->endNode();
 }
+
+// ---------------------------------------------------------------------------
+
+void UnitOfMeasure::_exportToJSON(
+    JSONFormatter *formatter) const // throw(FormattingException)
+{
+    auto &writer = formatter->writer();
+    PROJ::CPLJSonStreamingWriter::ObjectContext objContext(writer);
+    writer.AddObjKey("type");
+    const auto l_type = type();
+    if (l_type == Type::LINEAR) {
+        writer.Add("LinearUnit");
+    } else if (l_type == Type::ANGULAR) {
+        writer.Add("AngularUnit");
+    } else if (l_type == Type::SCALE) {
+        writer.Add("ScaleUnit");
+    } else if (l_type == Type::TIME) {
+        writer.Add("TimeUnit");
+    } else if (l_type == Type::PARAMETRIC) {
+        writer.Add("ParametericUnit");
+    } else {
+        writer.Add("Unit");
+    }
+
+    writer.AddObjKey("name");
+    const auto &l_name = name();
+    writer.Add(l_name);
+
+    const auto &factor = conversionToSI();
+    writer.AddObjKey("conversion_factor");
+    writer.Add(factor, 15);
+
+    const auto &l_codeSpace = codeSpace();
+    if (!l_codeSpace.empty() && formatter->outputId()) {
+        writer.AddObjKey("id");
+        PROJ::CPLJSonStreamingWriter::ObjectContext idContext(writer);
+        writer.AddObjKey("authority");
+        writer.Add(l_codeSpace);
+        writer.AddObjKey("code");
+        const auto &l_code = code();
+        try {
+            writer.Add(std::stoi(l_code));
+        } catch (const std::exception &) {
+            writer.Add(l_code);
+        }
+    }
+}
+
 //! @endcond
 
 // ---------------------------------------------------------------------------
@@ -815,6 +863,23 @@ void IdentifiedObject::formatRemarks(WKTFormatter *formatter) const {
 
 // ---------------------------------------------------------------------------
 
+void IdentifiedObject::formatID(JSONFormatter *formatter) const {
+    const auto &ids(identifiers());
+    auto &writer = formatter->writer();
+    if (ids.size() == 1) {
+        writer.AddObjKey("id");
+        ids.front()->_exportToJSON(formatter);
+    } else if (!ids.empty()) {
+        writer.AddObjKey("ids");
+        PROJ::CPLJSonStreamingWriter::ArrayContext arrayContext(writer);
+        for (const auto &id : ids) {
+            id->_exportToJSON(formatter);
+        }
+    }
+}
+
+// ---------------------------------------------------------------------------
+
 bool IdentifiedObject::_isEquivalentTo(
     const util::IComparable *other,
     util::IComparable::Criterion criterion) const {
diff --git a/src/iso19111/datum.cpp b/src/iso19111/datum.cpp
index bf3092c1..6ba219d4 100644
--- a/src/iso19111/datum.cpp
+++ b/src/iso19111/datum.cpp
@@ -348,6 +348,41 @@ void PrimeMeridian::_exportToWKT(
 // ---------------------------------------------------------------------------
 
 //! @cond Doxygen_Suppress
+void PrimeMeridian::_exportToJSON(
+    io::JSONFormatter *formatter) const // throw(FormattingException)
+{
+    auto &writer = formatter->writer();
+    PROJ::CPLJSonStreamingWriter::ObjectContext objectContext(writer);
+
+    writer.AddObjKey("type");
+    writer.Add("PrimeMeridian");
+
+    writer.AddObjKey("name");
+    std::string l_name =
+        name()->description().has_value() ? nameStr() : "Greenwich";
+    writer.Add(l_name);
+
+    const auto &l_long = longitude();
+    writer.AddObjKey("longitude");
+    {
+        PROJ::CPLJSonStreamingWriter::ObjectContext longitudeContext(writer);
+        writer.AddObjKey("value");
+        writer.Add(l_long.value(), 15);
+
+        const auto &unit = l_long.unit();
+        writer.AddObjKey("unit");
+        unit._exportToJSON(formatter);
+    }
+
+    if (formatter->outputId()) {
+        formatID(formatter);
+    }
+}
+//! @endcond
+
+// ---------------------------------------------------------------------------
+
+//! @cond Doxygen_Suppress
 std::string
 PrimeMeridian::getPROJStringWellKnownName(const common::Angle &angle) {
     const double valRad = angle.getSIValue();
diff --git a/src/iso19111/io.cpp b/src/iso19111/io.cpp
index 0db97d0b..0c9f8a0c 100644
--- a/src/iso19111/io.cpp
+++ b/src/iso19111/io.cpp
@@ -60,6 +60,7 @@
 
 #include "proj_constants.h"
 
+#include "proj_json_streaming_writer.hpp"
 #include "wkt1_parser.h"
 #include "wkt2_parser.h"
 
@@ -8016,5 +8017,91 @@ PROJStringParser::createFromPROJString(const std::string &projString) {
                                                        nullptr, nullptr, {});
 }
 
+// ---------------------------------------------------------------------------
+
+//! @cond Doxygen_Suppress
+struct JSONFormatter::Private {
+    PROJ::CPLJSonStreamingWriter writer_{nullptr, nullptr};
+    DatabaseContextPtr dbContext_{};
+    std::string result_{};
+};
+//! @endcond
+
+// ---------------------------------------------------------------------------
+
+/** \brief Constructs a new formatter.
+ *
+ * A formatter can be used only once (its internal state is mutated)
+ *
+ * @return new formatter.
+ */
+JSONFormatterNNPtr JSONFormatter::create( // cppcheck-suppress passedByValue
+    DatabaseContextPtr dbContext) {
+    auto ret = NN_NO_CHECK(JSONFormatter::make_unique<JSONFormatter>());
+    ret->d->dbContext_ = dbContext;
+    return ret;
+}
+
+// ---------------------------------------------------------------------------
+
+/** \brief Whether to use multi line output or not. */
+JSONFormatter &JSONFormatter::setMultiLine(bool multiLine) noexcept {
+    d->writer_.SetPrettyFormatting(multiLine);
+    return *this;
+}
+
+// ---------------------------------------------------------------------------
+
+/** \brief Set number of spaces for each indentation level (defaults to 4).
+ */
+JSONFormatter &JSONFormatter::setIndentationWidth(int width) noexcept {
+    d->writer_.SetIndentationSize(width);
+    return *this;
+}
+
+// ---------------------------------------------------------------------------
+
+//! @cond Doxygen_Suppress
+
+JSONFormatter::JSONFormatter() : d(internal::make_unique<Private>()) {}
+
+// ---------------------------------------------------------------------------
+
+JSONFormatter::~JSONFormatter() = default;
+
+// ---------------------------------------------------------------------------
+
+PROJ::CPLJSonStreamingWriter &JSONFormatter::writer() const {
+    return d->writer_;
+}
+
+// ---------------------------------------------------------------------------
+
+bool JSONFormatter::outputId() const { return true; }
+
+//! @endcond
+
+// ---------------------------------------------------------------------------
+
+/** \brief Return the serialized JSON.
+ */
+const std::string &JSONFormatter::toString() const {
+    return d->writer_.GetString();
+}
+
+// ---------------------------------------------------------------------------
+
+//! @cond Doxygen_Suppress
+IJSONExportable::~IJSONExportable() = default;
+
+// ---------------------------------------------------------------------------
+
+std::string IJSONExportable::exportToJSON(JSONFormatter *formatter) const {
+    _exportToJSON(formatter);
+    return formatter->toString();
+}
+
+//! @endcond
+
 } // namespace io
 NS_PROJ_END
diff --git a/src/iso19111/metadata.cpp b/src/iso19111/metadata.cpp
index 3725b072..761b909b 100644
--- a/src/iso19111/metadata.cpp
+++ b/src/iso19111/metadata.cpp
@@ -1088,6 +1088,26 @@ void Identifier::_exportToWKT(WKTFormatter *formatter) const {
         }
     }
 }
+
+// ---------------------------------------------------------------------------
+
+void Identifier::_exportToJSON(JSONFormatter *formatter) const {
+    const std::string &l_code = code();
+    const std::string &l_codeSpace = *codeSpace();
+    if (!l_codeSpace.empty() && !l_code.empty()) {
+        auto &writer = formatter->writer();
+        PROJ::CPLJSonStreamingWriter::ObjectContext objContext(writer);
+        writer.AddObjKey("authority");
+        writer.Add(l_codeSpace);
+        writer.AddObjKey("code");
+        try {
+            writer.Add(std::stoi(l_code));
+        } catch (const std::exception &) {
+            writer.Add(l_code);
+        }
+    }
+}
+
 //! @endcond
 
 // ---------------------------------------------------------------------------