// PROGRAM koch
// improved output 8/9/95 by computing aspect ratio
// generate triadic Koch curve using recursion

#include "TrueBASIC.h"
#include "csgraphics.h"

int main();
void initial(double *x1, double *y1, double *x2, double *y2, int *n);
void draw(double x1, double y1, double x2, double y2, int n);

int main()
{
    int k = 0, n;
    double x1, x2, y1, y2;

    GWopen(0);

    initial(&x1, &y1, &x2, &y2, &n);
    // draw Koch curve for different number of iterations
    do
    {
        k = 0;
        draw(x1, y1, x2, y2, n);
        while(!TBkeyinput());
        k = TBgetkey();                     // pause until any key is hit
        ++n;                                // number of stages of generation
        GWclear(-1);
    } while(k != 's');

    GWquit();
    return 0;
}

void initial(double *x1, double *y1, double *x2, double *y2, int *n)
{
    float xwin, ywin;

    (*n) = 0;                               // number of iterations
    (*x1) = 1;                              // coordinates at left end of line
    (*y1) = 5;                              // arbitrary units
    (*x2) = 10;                             // coordinates at right end of line
    (*y2) = 5;
    compute_aspect_ratio(8.0f, &xwin, &ywin);
    GWindow(0.0f, 0.0f, xwin, ywin);
    GWsetpen(BLUE, -1, -1, -1);
}

void draw(double x1, double y1, double x2, double y2, int n)
{
    double dx, dy, x1n, x2n, xmid, y1n, y2n, ymid;

    if(n > 0)
    {
        dx = (x2 - x1)/3;
        dy = (y2 - y1)/3;
        x1n = x1 + dx;
        y1n = y1 + dy;
        x2n = x1 + 2*dx;
        y2n = y1 + 2*dy;
        // rotate line segment (dx,dy) by 60 degs and add to (x1n,y1n)
        xmid = 0.5*dx - 0.866*dy + x1n;
        ymid = 0.5*dy + 0.866*dx + y1n;
        draw(x1, y1, x1n, y1n, n-1);
        draw(x1n, y1n, xmid, ymid, n-1);
        draw(xmid, ymid, x2n, y2n, n-1);
        draw(x2n, y2n, x2, y2, n-1);
    }
    else
        GWline((float)(x1), (float)(y1), (float)(x2), (float)(y2));
}