Remove requirement for documents to be in GeoJSON

[jkerr5]

The provider implementation assumes the documents are in GeoJSON right now. It should work against documents in any format and rely on the TDE template to map elements to columns in the rows.

Related to #6, the geometry is not transformed so the geometry that is fetched must be in GeoJSON to return correctly.

[jkerr5]

• Right now, we assume the data coming back from the optic document join is GeoJSON
• We have to return GeoJSON to Koop so if we support other formats in documents, we have to have logic to convert to GeoJSON
• For documents with just points
  • It seems like it would be better to have the points in the row index and convert those to GeoJSON
  • What if there is more than one point per document? Multi-point features could end up with a row per point which wouldn’t necessarily be wrong but it seems inefficient. The good thing is that that can be abstracted using the templates
  • Technically, a document could have points throughout and at multiple paths. We need to have the list of XPaths to use to select all the points out of the document and return them as a GeoJSON multi-point feature
• For documents with regions, the regions need to be cts regions so we can easily convert to GeoJSON
• The feature layer descriptor tells us what type of features are in the layer - “geometryType"
  • A layer can only be one “feature class” so they all have to be the same type - Is this true? What about esriGeometryAny or esriGeometryBag? Can a feature layer have these set as the geometry type?
  • Koop only seems to support Point, Polygon and Polyline: https://github.com/koopjs/FeatureServer/blob/0b9f9c89221953b2764086b6a72b4a4dce70b730/src/utils.js#L26

[jkerr5]

For polygons, it is straight forward: use the xpath that's in the layer descriptor to select the cts:regions and then use toGeosjon() to convert to geojson https://docs.marklogic.com/geojson.toGeojson

For points, there are a bunch of point formats we support There are 5 types of point indexes

• Element
• Element Child Pair
• Element Pair
• Attribute Pair
• Path

We need some sort of "handler" for each type.

Also, we currently have the point indexes that we use hard-coded:

    const pointPaths = [
      '//geometry[type = "MultiPoint"]//array-node("coordinates")',
      '//geometry[type = "Point"]//array-node("coordinates")'
    ];

To support something other than GeoJSON, we would need these to be configurable as well.

Last, to complete this, we also need to change so the path for the region index is not hard-coded as well:

    const regionPaths = [
      cts.geospatialRegionPathReference('/envelope/ctsRegion')
    ];

[jkerr5]

@jmamanpara I created a wiki page https://github.com/koopjs/koop-provider-marklogic/wiki/Layer-Descriptor-Geometry-Section to show the different types of geometry properties that could be in a layer descriptor. It's still a work in progress but hopefully it gives you something to start with.