#include "simulation.h"

namespace simulation
{
    unsigned int getCellOffset(
        unsigned char x,
        unsigned char y,
        unsigned char z,
        SimulationGrid* grid)
    {
        if (x < grid->x_max && y < grid->y_max && z < grid->z_max)
        {
            unsigned int offset = x + y * grid->x_max + z * (grid->y_max * grid->x_max);
            return offset;
        }
        return -1;
    }

    void step(
        double millisecondsSinceLastStep,
        SimulationGrid* input,
        SimulationGrid* output)
    {
        for (unsigned char x = 0; x < input->x_max; x++)
        {
            for (unsigned char y = 0; y < input->y_max; y++)
            {
                for (unsigned char z = 0; z < input->z_max; z++)
                {
                    unsigned int offset = getCellOffset(x, y, z, input);
                    unsigned int material = input->cells[offset];
                    switch (material)
                    {
                    case WATER:
                        if (y > 0)
                        {
                            unsigned int downOffset = getCellOffset(x, y - 1, z, input);
                            // Flow down if cell is empty
                            if (output->cells[downOffset] == 0)
                            {
                                output->cells[downOffset] = material;
                            }
                        }
                    default:
                        output->cells[offset] = material;
                    }
                }
            }
        }
    }
}