#include "PDE.h"

using namespace std;

/*
 * Constructor for the PDE class. You should:
 *   - calculate dx from a, b and N.
 *   - allocate memory for x.
 *   - set sensible default values for ts, t, build and rebuild.
 *   - fill x with the gridpoints.
 */
PDE::PDE(int N, double dt, double a, double b, double theta) :
  N(N), dt(dt), a(a), b(b), theta(theta), u(N+1), 
  lhs(N+1), rhs(N+1), le(N+1), li(N+1) 
{
  // You need to fill in this method.
  
}

/*
 * Destructor for the PDE class.
 * You should delete any memory you allocated in the constructor.
 */
PDE::~PDE() {
  // You need to fill in this method.
  
}

/*
 * Timestepper for the PDE class. You should:
 * 
 * - Build the timestepping matrices by calling construct() if they need to be
 *   constructed (as determined by the rebuild and built flags).
 * - Calculate the current time, and solve the equation:
 *    
 *      lhs*u^{n+1} = rhs*u^n
 *
 *   Remember to impose boundary conditions once you have calculate rhs*u^n.
 */
void PDE::timestep() {
  // You need to fill in this method.
  
}

/**
 * Construct the left-hand side and right-hand side tri-diagonal matrices
 * this->lhs and this->rhs which are used to solve the discretised system. To
 * do this, you will need to use this->le and this->li, which are the explicit
 * and implicit discretised differential operators respectively.
 */
void PDE::construct() {
  // You need to fill in this method.

}

/**
 * Prints out the solution field.
 */
void PDE::print() {
  // This method is complete.
  int i;
  for (i = 0; i <= N; i++) {
    cout << setw(10) << x[i] << setw(15) << u[i] << endl;
  }
}

/**
 * This function allows you to output the solution field (at any time) to any
 * stream. For example; if one has:
 *
 * PDE obj = new PDE();
 * ofstream outfile("outfile.txt");
 * cout << obj;
 * outfile << obj;
 *
 * Note that the first line will obviously not compile since PDE is an
 * abstract base class.
 */
ostream &operator<<(ostream &stream, PDE &obj) {
  // This method is complete.
  int i;

  for (i = 0; i <= obj.N; i++)
    stream << setw(10) << obj.x[i] << setw(15) << obj.u[i] << endl;

  return stream;
}

/*
 * Return the i-th grid point (i.e. a + i*dx).
 */
double PDE::xv(int i) const {
  // You need to fill in this method.
  
}

/*
 * Returns a copy of the solution field u.
 */
const Field PDE::getU() const {
  // You need to fill in this method.
  
}