// Include the top-level Vertica SDK file
#include "Vertica.h"
// Using the Vertica namespace means we don't have to prefix all
// class references with Vertica::
using namespace Vertica;
/* 
 * ScalarFunction implementation for a UDSF that adds 
 * two numbers together. 
 */
class Add2Ints : public ScalarFunction
 {
    public:
   /*
    * This function does all of the actual processing for the UDF.
    * In this case, it simply reads two integer values and returns
    * their sum.
    *
    * The inputs are retrieved via arg_reader
    * The outputs are returned via arg_writer
    */
    virtual void processBlock(ServerInterface &srvInterface,
                            BlockReader &arg_reader,
                            BlockWriter &res_writer)
    {
    // While we have input to process
        do {
            // Read the two integer input parameters by calling the
            // BlockReader.getIntRef class function
            const vint a = arg_reader.getIntRef(0);
            const vint b = arg_reader.getIntRef(1);
            // Call BlockWriter.setInt to store the output value, which is the
            //  two input values added together
            res_writer.setInt(a+b);
            // Finish writing the row, and advance to the next output row
            res_writer.next();
            // Continue looping until there are no more input rows
        } while (arg_reader.next());
  }
};

/*
 * This class provides metadata about the ScalarFunction class, and
 * also instantiates a member of that class when needed.
 */
class Add2IntsFactory : public ScalarFunctionFactory
{
	// return an instance of Add2Ints to perform the actual addition.
	virtual ScalarFunction *createScalarFunction(ServerInterface &interface)
	{
		// Calls the vt_createFuncObj to create the new Add2Ints class instance.
		return vt_createFuncObj(interface.allocator, Add2Ints);
	}
	// This function returns the description of the input and outputs of the
	// Add2Ints class's processBlock function.  It stores this information in
	// two ColumnTypes objects, one for the input parameters, and one for
	// the return value.
	virtual void getPrototype(ServerInterface &interface,
	ColumnTypes &argTypes,
	ColumnTypes &returnType)
	{
		// Takes two ints as inputs, so add ints to the argTypes object
		argTypes.addInt();
		argTypes.addInt();
		// returns a single int, so add a single int to the returnType object.
		// Note that ScalarFunctions *always* return a single value.
		returnType.addInt();
	}
};

RegisterFactory(Add2IntsFactory);