.. _exercise:

Exercise
########

You know everything now about writting zcfg matadata files and get short pieces 
of code in ``service.c`` or ``ogr_service_provider.py`` depending if you choosen 
C or Python programming language respectively.

The goal of this exercise is to implement the following multiple geometries services :

  - Intersection
  - Union
  - Difference
  - SymDifference

C version
*********

Your are now invited to edit the source.c file you have created during this workshop 
to add the multiple geometries, using the following OGR C-API functions :

  - `OGR_G_Intersection <http://www.gdal.org/ogr/ogr__api_8h.html#5a271b5c7b72994120e7a6bbc7e7e5cb>`__ (OGRGeometryH, OGRGeometryH)
  - `OGR_G_Union <http://www.gdal.org/ogr/ogr__api_8h.html#5a271b5c7b72994120e7a6bbc7e7e5cb>`__ (OGRGeometryH, OGRGeometryH)
  - `OGR_G_Difference <http://www.gdal.org/ogr/ogr__api_8h.html#497977bec6ecd9dade7a9694f776be64>`__ (OGRGeometryH, OGRGeometryH)
  - `OGR_G_SymmetricDifference <http://www.gdal.org/ogr/ogr__api_8h.html#d6dacf495617a230c6f19950bc415f17>`__ (OGRGeometryH, OGRGeometryH)

You can use the ``Boundary.zcfg`` file as example, rename the InputPolygon input 
to ``InputEntity1`` and add a similar input named ``IntputEntity2``. You are 
invited to update other values in the ZOO Metadata File to set the proper 
metadata informations.

Python Version
**************

Your are invited to edit the ``ogr_ws_service_provider.py`` file you created 
during this workshop to add the multiple geometries using the following 
``osgeo.ogr`` Geometry methods applied on the first Geometry instance :

  - Intersection(Geometry)
  - Union(Geometry)
  - Difference(Geometry)
  - SymmetricDifference(Geometry)

You can once again use the ``Boundary.zcfg`` file as example, rename the ``InputPolygon`` 
input to ``InputEntity1`` and add a similar input named ``IntputEntity2``. You are 
invited to update other values in the ZOO metadata file to set the proper metadata 
informations.

Testing your services
*********************

Once the multiple geometries Services are deployed on your local environment, 
please reload the ``zoo-ogr.html`` file created during the previous section 
from your browser and test your brand new ZOO Services.