#include <err.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

void showtodo(void);
void addtodo(void);
void deltodo(int);
int mygetline(char[], int, FILE*);

static char *todofile = "/home/mujo/.todo";

/* read a line into s, return line length */
/* not using getline(3) for learning purposes */
int
mygetline(char s[], int lim, FILE *file)
{
	int c, i;

	for (i = 0; i < lim - 1 && (c = getc(file)) != EOF \
	    && c != '\n'; ++i) {
		s[i] = c;
	}
	if (c == '\n') {
		s[i] = '\n';
		++i;
	}
	s[i] = '\0';
	return i;
}

/* read from todo file and write to stdout */
void
showtodo()
{
	FILE *file;
	int len, i;
	char line[BUFSIZ];

	if ((file = fopen(todofile, "r")) == NULL)
		err(1, "fopen");
	for (i = 1; (len = mygetline(line, BUFSIZ, file)) > 0; ++i)
		printf("%d: %s", i, line);
	fclose(file);
}

/* read from stdin and write to todo file */
void
addtodo()
{
	FILE *file;
	int c;

	if ((file = fopen(todofile, "a")) == NULL)
		err(1, "fopen");
	while ((c = getc(stdin)) != '\n')
		putc(c, file);
	putc('\n', file);
	fclose(file);
}

/* remove line, numbered ln, from todo file */
void
deltodo(int lnum)
{
	FILE *file, *tmp;
	int c, lcur;

	lcur = 1;
	if ((file = fopen(todofile, "r")) == NULL)
		err(1, "fopen");
	if ((tmp = tmpfile()) == NULL)
		err(1, "tmpfile");
	while ((c = getc(file)) != EOF) {
		if (lcur != lnum)
			putc(c, tmp);
		if (c == '\n')
			++lcur;
	}
	rewind(tmp);
	fclose(file);
	/* reopen todo file for writing to truncate */
	if ((file = fopen(todofile, "w")) == NULL)
		err(1, "fopen");
	while ((c = getc(tmp)) != EOF)
		putc(c, file);
	fclose(file);
	fclose(tmp);
}

int
main(int argc, char *argv[])
{
	int ch;
	int ln;
	const char *errstr;

	if (argc == 1)
		showtodo();
	while ((ch = getopt(argc, argv, "sad:")) != -1) {
		switch(ch) {
		case 's':
			showtodo();
			break;
		case 'a':
			addtodo();
			break;
		case 'd':
			ln = strtonum(optarg, 1, INT_MAX, &errstr);
			if (errstr != NULL)
				err(1, "line num is %s: %s", errstr, optarg);
			deltodo(ln);
			break;
		default:
			errx(1, "-<s|a|d> show|add|del");
		}
	}
	return 0;
}