#include "Cmprtmnt.h"
#include "Current.h"
#include <math.h>

Compartment::Compartment( void )
{
	// set variables to default values
	// LATER: get these from some preferences thing somewhere
	Gm = Gi = 1;
	EGm = Gm * -0.070;
	negC = -1;
	V[0] = V[1] = 0;
}

void Compartment::Step( const real dt )
{
	// This is the routine which actually calculates the new value of V.
	
	//	Algorithm to update V in a compartment by Exponential Euler integration:
	//	1. compute A = EG + i->comp2->V * i->G + j->E * j->G  for all currents i and all ion channels j
	// 	2. compute B = G + i->G + j->G  for all currents i and all ion channels j
	//	3. compute D = exp(B*dt/negC)
	//	4. compute Vnew = V*D + A/B*(1-D)

	real A = EGm, B = Gm;
	for (CurrentNode *ln = itsCurrentList; ln; ln = ln->itsNext) {
		// note: this is a lot of dereferencing... can this be streamlined more?
		A += ln->itsCurrent->GetEG();
		B += ln->itsCurrent->G;
	}
	
	real D = exp( B*dt / negC );
	
	int curIdx = itsMaster->GetCurIdx();
	V[!curIdx] = V[curIdx]*D + (A/B)*(1-D);
}