From 16ae592157ce5f677221149699b64b747c7e7de0 Mon Sep 17 00:00:00 2001
From: Even Rouault <even.rouault@spatialys.com>
Date: Tue, 28 Nov 2023 22:56:13 +0100
Subject: [PATCH] FlatGeobuf: add support for reading and writing layer title,
 description and metadata

---
 autotest/ogr/ogr_flatgeobuf.py                |  40 +++++++
 doc/source/drivers/vector/flatgeobuf.rst      |  15 +++
 ogr/ogrsf_frmts/flatgeobuf/ogr_flatgeobuf.h   |  16 ++-
 .../flatgeobuf/ogrflatgeobufdataset.cpp       |   5 +-
 .../flatgeobuf/ogrflatgeobufeditablelayer.cpp |   5 +-
 .../flatgeobuf/ogrflatgeobuflayer.cpp         | 111 +++++++++++++++---
 6 files changed, 166 insertions(+), 26 deletions(-)

diff --git a/autotest/ogr/ogr_flatgeobuf.py b/autotest/ogr/ogr_flatgeobuf.py
index 40849801ac6d..bd6b1a4fc0b2 100644
--- a/autotest/ogr/ogr_flatgeobuf.py
+++ b/autotest/ogr/ogr_flatgeobuf.py
@@ -1217,3 +1217,43 @@ def test_ogr_flatgeobuf_issue_7401():
 
     ogr.GetDriverByName("FlatGeobuf").DeleteDataSource("/vsimem/test.fgb")
     assert not gdal.VSIStatL("/vsimem/test.fgb")
+
+
+###############################################################################
+# Test reading and writing layer title, description and metadata
+
+
+def test_ogr_flatgeobuf_title_description_metadata(tmp_vsimem):
+
+    filename = str(tmp_vsimem / "test.fgb")
+    ds = ogr.GetDriverByName("FlatGeobuf").CreateDataSource(filename)
+    lyr = ds.CreateLayer(
+        "test",
+        geom_type=ogr.wkbPoint,
+        options=["SPATIAL_INDEX=NO", "TITLE=title", "DESCRIPTION=description"],
+    )
+    lyr.SetMetadata({"foo": "bar", "bar": "baz"})
+    f = ogr.Feature(lyr.GetLayerDefn())
+    f.SetGeometry(ogr.CreateGeometryFromWkt("POINT (0 0)"))
+    lyr.CreateFeature(f)
+    ds = None
+
+    ds = ogr.Open(filename)
+    lyr = ds.GetLayer(0)
+    assert lyr.GetMetadata_Dict() == {
+        "TITLE": "title",
+        "DESCRIPTION": "description",
+        "foo": "bar",
+        "bar": "baz",
+    }
+
+    # Test that on FlatGeoBuf -> FlatGeoBuf TITLE and DESCRIPTION get properly propagated.
+    filename2 = str(tmp_vsimem / "test2.fgb")
+    ds = gdal.VectorTranslate(filename2, filename)
+    lyr = ds.GetLayer(0)
+    assert lyr.GetMetadata_Dict() == {
+        "TITLE": "title",
+        "DESCRIPTION": "description",
+        "foo": "bar",
+        "bar": "baz",
+    }
diff --git a/doc/source/drivers/vector/flatgeobuf.rst b/doc/source/drivers/vector/flatgeobuf.rst
index 0656c42668df..b3c289ddc166 100644
--- a/doc/source/drivers/vector/flatgeobuf.rst
+++ b/doc/source/drivers/vector/flatgeobuf.rst
@@ -34,6 +34,9 @@ On creation, passing a filename without a .fgb suffix will instruct the driver
 to create a directory of that name, and create layers as .fgb files in that
 directory.
 
+Starting with GDAL 3.9, metadata set at the layer level will be written in the
+FlatGeobuf header, and retrieved on reading as layer metadata.
+
 Open options
 ------------
 
@@ -65,6 +68,18 @@ Layer Creation Options
       the :cpp:func:`CPLGenerateTempFilename` function.
       "/vsimem/" can be used for in-memory temporary files.
 
+-  .. lco:: TITLE
+      :choices: <string>
+      :since: 3.9
+
+      Dataset title (should be relatively short)
+
+-  .. lco:: DESCRIPTION
+      :choices: <string>
+      :since: 3.9
+
+      Dataset description (intended for free form long text)
+
 Creation Issues
 ---------------
 
diff --git a/ogr/ogrsf_frmts/flatgeobuf/ogr_flatgeobuf.h b/ogr/ogrsf_frmts/flatgeobuf/ogr_flatgeobuf.h
index 1a8aacd7cdd5..6621cdcc394b 100644
--- a/ogr/ogrsf_frmts/flatgeobuf/ogr_flatgeobuf.h
+++ b/ogr/ogrsf_frmts/flatgeobuf/ogr_flatgeobuf.h
@@ -103,13 +103,15 @@ class OGRFlatGeobufLayer final : public OGRLayer,
     bool m_ignoreAttributeFilter = false;
 
     // creation
+    GDALDataset *m_poDS = nullptr;  // parent dataset to get metadata from it
     bool m_create = false;
     std::deque<FeatureItem> m_featureItems;  // feature item description used to
                                              // create spatial index
     bool m_bCreateSpatialIndexAtClose = true;
     bool m_bVerifyBuffers = true;
     VSILFILE *m_poFpWrite = nullptr;
-    uint64_t m_writeOffset = 0;  // current write offset
+    CPLStringList m_aosCreationOption{};  // layer creation options
+    uint64_t m_writeOffset = 0;           // current write offset
     uint64_t m_offsetAfterHeader =
         0;  // offset after dummy header writing (when creating a file without
             // spatial index)
@@ -142,11 +144,12 @@ class OGRFlatGeobufLayer final : public OGRLayer,
     OGRFlatGeobufLayer(const FlatGeobuf::Header *, GByte *headerBuf,
                        const char *pszFilename, VSILFILE *poFp,
                        uint64_t offset);
-    OGRFlatGeobufLayer(const char *pszLayerName, const char *pszFilename,
+    OGRFlatGeobufLayer(GDALDataset *poDS, const char *pszLayerName,
+                       const char *pszFilename,
                        const OGRSpatialReference *poSpatialRef,
                        OGRwkbGeometryType eGType,
                        bool bCreateSpatialIndexAtClose, VSILFILE *poFpWrite,
-                       std::string &osTempFile);
+                       std::string &osTempFile, CSLConstList papszOptions);
 
   protected:
     virtual int GetNextArrowArray(struct ArrowArrayStream *,
@@ -163,7 +166,7 @@ class OGRFlatGeobufLayer final : public OGRLayer,
     static OGRFlatGeobufLayer *Open(const char *pszFilename, VSILFILE *fp,
                                     bool bVerifyBuffers);
     static OGRFlatGeobufLayer *
-    Create(const char *pszLayerName, const char *pszFilename,
+    Create(GDALDataset *poDS, const char *pszLayerName, const char *pszFilename,
            const OGRSpatialReference *poSpatialRef, OGRwkbGeometryType eGType,
            bool bCreateSpatialIndexAtClose, char **papszOptions);
 
@@ -192,6 +195,11 @@ class OGRFlatGeobufLayer final : public OGRLayer,
         m_bVerifyBuffers = CPL_TO_BOOL(bFlag);
     }
 
+    GDALDataset *GetDataset() override
+    {
+        return m_poDS;
+    }
+
     const std::string &GetFilename() const override
     {
         return m_osFilename;
diff --git a/ogr/ogrsf_frmts/flatgeobuf/ogrflatgeobufdataset.cpp b/ogr/ogrsf_frmts/flatgeobuf/ogrflatgeobufdataset.cpp
index 65190a3c6617..39261755d63f 100644
--- a/ogr/ogrsf_frmts/flatgeobuf/ogrflatgeobufdataset.cpp
+++ b/ogr/ogrsf_frmts/flatgeobuf/ogrflatgeobufdataset.cpp
@@ -155,6 +155,9 @@ void RegisterOGRFlatGeobuf()
         "create a spatial index' default='YES'/>"
         "  <Option name='TEMPORARY_DIR' type='string' description='Directory "
         "where temporary file should be created'/>"
+        "  <Option name='TITLE' type='string' description='Layer title'/>"
+        "  <Option name='DESCRIPTION' type='string' "
+        "description='Layer description'/>"
         "</LayerCreationOptionList>");
     poDriver->SetMetadataItem(
         GDAL_DMD_OPENOPTIONLIST,
@@ -445,7 +448,7 @@ OGRLayer *OGRFlatGeobufDataset::ICreateLayer(
 
     auto poLayer =
         std::unique_ptr<OGRFlatGeobufLayer>(OGRFlatGeobufLayer::Create(
-            pszLayerName, osFilename, poSpatialRef, eGType,
+            this, pszLayerName, osFilename, poSpatialRef, eGType,
             bCreateSpatialIndexAtClose, papszOptions));
     if (poLayer == nullptr)
         return nullptr;
diff --git a/ogr/ogrsf_frmts/flatgeobuf/ogrflatgeobufeditablelayer.cpp b/ogr/ogrsf_frmts/flatgeobuf/ogrflatgeobufeditablelayer.cpp
index 0744b97c97c2..96f06456e4ef 100644
--- a/ogr/ogrsf_frmts/flatgeobuf/ogrflatgeobufeditablelayer.cpp
+++ b/ogr/ogrsf_frmts/flatgeobuf/ogrflatgeobufeditablelayer.cpp
@@ -89,8 +89,9 @@ OGRErr OGRFlatGeobufEditableLayerSynchronizer::EditableSyncToDisk(
     auto createIndex = m_poFlatGeobufLayer->GetIndexNodeSize() > 0;
 
     OGRFlatGeobufLayer *poFlatGeobufTmpLayer = OGRFlatGeobufLayer::Create(
-        osLayerName.c_str(), osTmpFilename.c_str(), spatialRef, gType,
-        createIndex, m_papszOpenOptions);
+        m_poFlatGeobufLayer->GetDataset(), osLayerName.c_str(),
+        osTmpFilename.c_str(), spatialRef, gType, createIndex,
+        m_papszOpenOptions);
     if (poFlatGeobufTmpLayer == nullptr)
         return OGRERR_FAILURE;
 
diff --git a/ogr/ogrsf_frmts/flatgeobuf/ogrflatgeobuflayer.cpp b/ogr/ogrsf_frmts/flatgeobuf/ogrflatgeobuflayer.cpp
index 9350e9b2bb63..438ee5bb6dfd 100644
--- a/ogr/ogrsf_frmts/flatgeobuf/ogrflatgeobuflayer.cpp
+++ b/ogr/ogrsf_frmts/flatgeobuf/ogrflatgeobuflayer.cpp
@@ -154,6 +154,31 @@ OGRFlatGeobufLayer::OGRFlatGeobufLayer(const Header *poHeader, GByte *headerBuf,
 
     m_eGType = getOGRwkbGeometryType();
 
+    if (const auto title = poHeader->title())
+        SetMetadataItem("TITLE", title->c_str());
+
+    if (const auto description = poHeader->description())
+        SetMetadataItem("DESCRIPTION", description->c_str());
+
+    if (const auto metadata = poHeader->metadata())
+    {
+        CPLJSONDocument oDoc;
+        CPLErrorHandlerPusher oQuietError(CPLQuietErrorHandler);
+        CPLErrorStateBackuper oErrorStateBackuper;
+        if (oDoc.LoadMemory(metadata->c_str()) &&
+            oDoc.GetRoot().GetType() == CPLJSONObject::Type::Object)
+        {
+            for (auto oItem : oDoc.GetRoot().GetChildren())
+            {
+                if (oItem.GetType() == CPLJSONObject::Type::String)
+                {
+                    SetMetadataItem(oItem.GetName().c_str(),
+                                    oItem.ToString().c_str());
+                }
+            }
+        }
+    }
+
     const char *pszName =
         m_poHeader->name() ? m_poHeader->name()->c_str() : "unknown";
     m_poFeatureDefn = new OGRFeatureDefn(pszName);
@@ -168,19 +193,16 @@ OGRFlatGeobufLayer::OGRFlatGeobufLayer(const Header *poHeader, GByte *headerBuf,
     m_poFeatureDefn->Reference();
 }
 
-OGRFlatGeobufLayer::OGRFlatGeobufLayer(const char *pszLayerName,
-                                       const char *pszFilename,
-                                       const OGRSpatialReference *poSpatialRef,
-                                       OGRwkbGeometryType eGType,
-                                       bool bCreateSpatialIndexAtClose,
-                                       VSILFILE *poFpWrite,
-                                       std::string &osTempFile)
-    : m_eGType(eGType),
+OGRFlatGeobufLayer::OGRFlatGeobufLayer(
+    GDALDataset *poDS, const char *pszLayerName, const char *pszFilename,
+    const OGRSpatialReference *poSpatialRef, OGRwkbGeometryType eGType,
+    bool bCreateSpatialIndexAtClose, VSILFILE *poFpWrite,
+    std::string &osTempFile, CSLConstList papszOptions)
+    : m_eGType(eGType), m_poDS(poDS), m_create(true),
       m_bCreateSpatialIndexAtClose(bCreateSpatialIndexAtClose),
-      m_poFpWrite(poFpWrite), m_osTempFile(osTempFile)
+      m_poFpWrite(poFpWrite), m_aosCreationOption(papszOptions),
+      m_osTempFile(osTempFile)
 {
-    m_create = true;
-
     if (pszLayerName)
         m_osLayerName = pszLayerName;
     if (pszFilename)
@@ -457,9 +479,61 @@ void OGRFlatGeobufLayer::writeHeader(VSILFILE *poFp, uint64_t featuresCount,
         CPLFree(pszWKT);
     }
 
+    std::string osTitle(m_aosCreationOption.FetchNameValueDef("TITLE", ""));
+    std::string osDescription(
+        m_aosCreationOption.FetchNameValueDef("DESCRIPTION", ""));
+    std::string osMetadata;
+    CPLJSONObject oMetadataJSONObj;
+    bool bEmptyMetadata = true;
+    for (GDALMajorObject *poContainer :
+         {static_cast<GDALMajorObject *>(this),
+          static_cast<GDALMajorObject *>(
+              m_poDS && m_poDS->GetLayerCount() == 1 ? m_poDS : nullptr)})
+    {
+        if (poContainer)
+        {
+            if (char **papszMD = poContainer->GetMetadata())
+            {
+                for (CSLConstList papszIter = papszMD; *papszIter; ++papszIter)
+                {
+                    char *pszKey = nullptr;
+                    const char *pszValue =
+                        CPLParseNameValue(*papszIter, &pszKey);
+                    if (pszKey && pszValue && !EQUAL(pszKey, OLMD_FID64))
+                    {
+                        if (EQUAL(pszKey, "TITLE"))
+                        {
+                            if (osTitle.empty())
+                                osTitle = pszValue;
+                        }
+                        else if (EQUAL(pszKey, "DESCRIPTION"))
+                        {
+                            if (osDescription.empty())
+                                osDescription = pszValue;
+                        }
+                        else
+                        {
+                            bEmptyMetadata = false;
+                            oMetadataJSONObj.Add(pszKey, pszValue);
+                        }
+                    }
+                    CPLFree(pszKey);
+                }
+            }
+        }
+    }
+    if (!bEmptyMetadata)
+    {
+        osMetadata =
+            oMetadataJSONObj.Format(CPLJSONObject::PrettyFormat::Plain);
+    }
+
     const auto header = CreateHeaderDirect(
         fbb, m_osLayerName.c_str(), extentVector, m_geometryType, m_hasZ,
-        m_hasM, m_hasT, m_hasTM, &columns, featuresCount, m_indexNodeSize, crs);
+        m_hasM, m_hasT, m_hasTM, &columns, featuresCount, m_indexNodeSize, crs,
+        osTitle.empty() ? nullptr : osTitle.c_str(),
+        osDescription.empty() ? nullptr : osDescription.c_str(),
+        osMetadata.empty() ? nullptr : osMetadata.c_str());
     fbb.FinishSizePrefixed(header);
     c = VSIFWriteL(fbb.GetBufferPointer(), 1, fbb.GetSize(), poFp);
     CPLDebugOnly("FlatGeobuf", "Wrote header (%lu bytes)",
@@ -2409,11 +2483,10 @@ VSILFILE *OGRFlatGeobufLayer::CreateOutputFile(const CPLString &osFilename,
     return poFpWrite;
 }
 
-OGRFlatGeobufLayer *
-OGRFlatGeobufLayer::Create(const char *pszLayerName, const char *pszFilename,
-                           const OGRSpatialReference *poSpatialRef,
-                           OGRwkbGeometryType eGType,
-                           bool bCreateSpatialIndexAtClose, char **papszOptions)
+OGRFlatGeobufLayer *OGRFlatGeobufLayer::Create(
+    GDALDataset *poDS, const char *pszLayerName, const char *pszFilename,
+    const OGRSpatialReference *poSpatialRef, OGRwkbGeometryType eGType,
+    bool bCreateSpatialIndexAtClose, char **papszOptions)
 {
     std::string osTempFile = GetTempFilePath(pszFilename, papszOptions);
     VSILFILE *poFpWrite =
@@ -2421,8 +2494,8 @@ OGRFlatGeobufLayer::Create(const char *pszLayerName, const char *pszFilename,
     if (poFpWrite == nullptr)
         return nullptr;
     OGRFlatGeobufLayer *layer = new OGRFlatGeobufLayer(
-        pszLayerName, pszFilename, poSpatialRef, eGType,
-        bCreateSpatialIndexAtClose, poFpWrite, osTempFile);
+        poDS, pszLayerName, pszFilename, poSpatialRef, eGType,
+        bCreateSpatialIndexAtClose, poFpWrite, osTempFile, papszOptions);
     return layer;
 }