// assume that F2CAD_USE_CppAD is defined
# include <f2cad/f2cad.hpp>

namespace {
	
	static CppADvector< CppAD::AD<double> > X;
	static CppAD::ADFun<double> *F = 0;
}

namespace f2cad {

void Independent(integer n, doublereal *x)
{
	// check not two Independents in a row
	assert( X.size() == 0 );

	// make sure the set of independent variables not empty
	assert( n > 0 );

	// check for a previously defined function (nonzero pointer)
	if( F != 0 )
	{	delete F;
		F = 0;
	}

	// move data into structure expected by CppAD
	X.resize(n);
	integer j;
	for(j = 0; j < n; j++)
		X[j] = x[j];

	// declare independent variables
	CppAD::Independent(X);

	// make x equivalent to X
	for(j = 0; j < n; j++)
		x[j] = X[j];

	return;
}

void Dependent(integer m, doublereal *y)
{
	// check that directly follows call to Independent
	assert( X.size() > 0 );
	assert( F == 0 );

	// make sure the set of dependent variables not empty
	assert( m > 0 );

	// move data into structure expected by CppAD
	CppADvector< CppAD::AD<double> > Y(m);
	integer i;
	for(i = 0; i < m; i++)
		Y[i] = y[i];

	// construct the AD function object
	F = new CppAD::ADFun<double>(X, Y);

	// no longer need independent variable information
	X.resize(0);
}


// linked here from Partial<doublereal>(integer i, integer j)
double Partial(const doublereal &zero, integer i, integer j)
{
	// check that directly follows call to Dependent
	assert( X.size() == 0 );
	assert( F != 0 );

	// check dimension of arguments
	integer m = F->Range();
	integer n = F->Domain();
	assert( 0 <= i );
	assert( 0 <= j );
	assert( i < m );
	assert( j < n );
	assert( zero == doublereal(0) );

	// move data into structure expected by CppAD
	CppADvector<double> dx(n);
	integer k;
	for(k = 0; k < n; k++)
		dx[k] = 0.;
	dx[j] = 1.; 

	// Forward mode calculation
	CppADvector<double> dy(m);
	dy = F->Forward(1, dx);

	// return the result
	return dy[i];
}

double Value(const doublereal &z)
{	// convert in a way that works even if we are recording
	return CppAD::Value( Var2Par(z) ); 
}

doublereal Sign(const doublereal* x, const doublereal* y)
{	if( *y >= 0. )
		return abs(*x);
	return -abs(*x);
}

} // end f2cad namespace