#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define TABSTOP 8
#define WIDTH 80
// the RATIO can't be less than 1/2
#define RATIO 2.0/3.0
#define BREAKSTR "-"

int bstrlen = strlen(BREAKSTR);

void fold(int width, int maxind);
void flush_wbuff(int wbi, char wbuff[]);
int insert_break(char buff[], int wbi);
int is_blank(char c);
int mv_cur(int n, char c);

/* fold input, takes one optional argument for max line width (excl \n) */
int main(int argc, char *argv[])
{
    int w;

    if (argc < 2 || (w = atoi(argv[1])) < 2)
        fold(WIDTH, RATIO * WIDTH);
    else
        fold(w, RATIO * w);

    return 0;
}

/* folds input lines to length, where minw <= length <= 'width'
 * if a line has no blank spaces after 'minw' chars a BREAKSTR is inserted */
void fold(int width, int minw)
{
    int c, n = 0; // n=0 is start of line
    int wbi = 0; // word buffer index 
    char wbuff[width - minw]; // word buffer for words over minw 

    while ((c = getchar()) != EOF) {
        n = mv_cur(n, c);
        
        if (c == '\n' || (n >= width+1 && is_blank(c))) {
            // handle newlines
            flush_wbuff(wbi, wbuff);
            putchar('\n');
            n = wbi = 0;
            continue;
        }
        
        if (n <= minw) // always print chars before minw
            putchar(c);
        else if (n <= width) { 
            /* add word (optionaly leading blank) after minw to wbuff
             * empty buffer if new blank is found */
            if (is_blank(c)) {
                flush_wbuff(wbi, wbuff);
                wbi = 0;
            }
            wbuff[wbi] = c;
            ++wbi;
        } else { // one char over edge, c != ' '
            n = insert_break(wbuff, wbi) + 1;
            putchar(c);
            wbi = 0;
        }
    }
}

void flush_wbuff(int wbi, char wbuff[])
{
    printf("%.*s", wbi, wbuff);
}

/* print buff and insert line break where its most fitting, 
 * return new cursor position 
 * '\n' is inserted before the last word or 'BREAKSTR\n' is inserted */
int insert_break(char wbuff[], int wbi)
{
    int i;

    if (wbi == 0) {
        putchar('\n');
        return 0;
    }

    if (is_blank(wbuff[0])) {
        putchar('\n');
        for (i=1; i < wbi; ++i)
            putchar(wbuff[i]);
        return wbi - 1;
    }



    flush_wbuff(wbi-bstrlen, wbuff);
    printf("%s\n", BREAKSTR);
    for (i = wbi-bstrlen; i < wbi; ++i)
        putchar(wbuff[i]);
    return bstrlen;
}

/* return new cursor position */
int mv_cur(int n, char c)
{
    if (c == '\t')
        return n + (TABSTOP - n % TABSTOP);
    else if (c == '\b')
        return n;
    return n+1;
}

int is_blank(char c)
{
    return (c == ' ' || c == '\t');
}