/*
Copyright 2019 Matthew Graham <sl@airmail.cc>

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <https://www.gnu.org/licenses/>.
*/

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

int main(int argc, char *argv[])
{
	FILE *fp, *tfp;
	char *fbuf;
	char *buf;
	long fsize, tsize;
	char instext[10000];
	fread(instext, sizeof(instext), 1, stdin);
	for (int i=1; argv[i]; i++) {
		if (argc>1&&(fp=fopen(argv[i], "a+"))==NULL) {
			fprintf(stderr, "ins: unable to open %s\n", argv[i]);
			continue;
		}
		if ((tfp=fopen(".instemp~~~", "a+"))==NULL) {
			fprintf(stderr, "ins: unable to open temporary file\n");
			return 1;
		}
		fseek(fp, 0L, SEEK_END);
		fsize=ftell(fp);
		fbuf=malloc(fsize+1);
		rewind(fp);
		fread(fbuf, fsize, 1, fp);
		buf=malloc(sizeof(instext)+sizeof(fbuf)+2);
		strcpy(buf, instext);
		strcat(buf, fbuf);
		fputs(buf, tfp);
		rename(".instemp~~~", argv[i]);
		free(buf);
		free(fbuf);
		fclose(fp);
		fclose(tfp);
	}
	return 0;
}