/*******************************************************************************
 * K&R 5-7
 *
 * Line sorting program using pointers
 *
 * program: linesort
 *  
 *  Using a local char array instead of alloc()
 *
 *  date: 14 November 2024
 *
 * ~yetimach
 ******************************************************************************/

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

#define LOCALBUFSIZE 50000 
#define MAXLEN 1000
#define MAXLINES 50

char *lineptr[MAXLINES];

void my_swap(char *v[], int i, int j){
    char *temp;
    temp = v[i];
    v[i] = v[j];
    v[j] = temp;
}

void my_qsort(char *v[], int left, int right){
    int i, last;
    if (left >= right)
        return;
    my_swap(v, left, (left + right)/2);
    last = left;
    for (i = left+1; i <= right; i++)
        if (strcmp(v[i], v[left]) < 0)
            my_swap(v, ++last, i);
    my_swap(v, left, last);
    my_qsort(v, left, last-1);
    my_qsort(v, last+1, right);
}

void writelines(char *lptr[], int nlines){
    while (nlines-- > 0)
        printf("%s\n", *lptr++);
}

int my_getline(char *s, int max){
    int c, i;
    for (i = 0; i < max-1 && (c = getchar()) != '\n' && c != EOF; *s++ = c, i++)
        ;
    *s = '\0'; 
    if (i >= max-1)
        return -1;
    else
        return i;
}

int readlines(char *lptr[], char lb[], int maxlines){
    int len, nlines, i;
    static int lbl = 0; /* local buffer length */
    char *p, line[MAXLEN];
    nlines = 0;
    while ((len = my_getline(line, MAXLEN)) > 0)
        if (nlines >= maxlines || lbl >= LOCALBUFSIZE-1)
            return -1;
        else {
            line[len] = '\0'; 
            p = &lb[lbl];
            lptr[nlines++] = p;
            i = 0;
            while ((lb[lbl++] = line[i++])) /* strcat doesn't seem to do quite*/
                 ;                          /* what I want... but this works  */
        }
    return nlines;
}

int main()
{
    static char localbuf[LOCALBUFSIZE];
    int nlines;
    if ((nlines = readlines(lineptr, localbuf, MAXLINES)) >= 0){
        my_qsort(lineptr, 0, nlines-1);
        writelines(lineptr, nlines);
    } else {
        printf("error: input too big to sort\n");
        return 1;
    }
    return 0;
}