#include "simulation.h"
#include <cstring>

namespace simulation
{
    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)
        {
            int offset = x + y * grid->x_max + z * (grid->y_max * grid->x_max);
            return offset;
        }
        return -1;
    }

    void step(
        double millisecondsSinceLastStep,
        SimulationGrid* grid)
    {
        for (unsigned char x = 0; x < grid->x_max; x++)
        {
            for (unsigned char y = 0; y < grid->y_max; y++)
            {
                for (unsigned char z = 0; z < grid->z_max; z++)
                {
                    int offset = getCellOffset(x, y, z, grid);
                    unsigned int material = grid->in[offset];
                    switch (material)
                    {
                    case WATER:
                        {
                            int downOffset = getCellOffset(x, y - 1, z, grid);
                            // Flow down if cell is empty
                            if (downOffset >= 0 && grid->out[downOffset] == 0)
                            {
                                grid->out[downOffset] = material;
                                grid->out[offset] = VACUUM;
                            } else
                            {
                                // Stay in the same location
                                grid->out[offset] = material;
                            }
                            break;
                        }
                    case MERCURY:
                        {
                            break;
                        }
                    default:
                        {
                            grid->out[offset] = material;
                        }
                    }
                }
            }
        }
    }

    void prepareForNextStep(SimulationGrid* grid)
    {
        // Flip the buffers
        unsigned int* inCells = grid->in;
        grid->in = grid->out;
        grid->out = inCells;
        // Clear out buffer
        size_t bufferSizeInBytes = sizeof(unsigned int) * grid->x_max * grid->y_max * grid->z_max;
        std::memset(grid->out, VACUUM, bufferSizeInBytes);
    }
}