/* fix - combine file and diff listing Author: Erik Baalbergen */

/* Notes:
   * files old and old.fix are equal after the following commands
	  diff old new > difflist
	  fix old difflist > old.fix
   * the diff output is assumed to be produced by my diff program.
   * the difflist has the following form:
	  difflist ::= chunk*
	  chunk ::= append | delete | change ;
	  append ::= n1 'a' n2 [',' n3]? '\n' ['> ' line '\n'](n3 - n2 + 1)
	  delete ::= n1 [',' n2]? 'd' n3 '\n' ['< ' line '\n'](n2 - n1 + 1)
	  change ::= n1 [',' n2]? 'c' n3 [',' n4]? '\n'
		     ['< ' line '\n'](n2 - n1 + 1)
		     '---\n'
		     ['> ' line '\n'](n4 - n3 + 1)
	  where
	  - n[1234] is an unsigned integer
	  - "[pat](expr)" means "(expr) occurences of pat"
	  - "[pat]?" means "either pat or nothing"
   * the information in the diff listing is checked against the file to which
     it is applied; an error is printed if there is a conflict
*/

#include <stdio.h>

extern char *fgets();
extern FILE *fopen();
#define LINELEN        1024

char *prog = 0;

char *
getline(fp, b)
       FILE *fp;
       char *b;
{
       if (fgets(b, LINELEN, fp) == NULL)
	       fatal("unexpected eof");
       return b;
}

#define copy(str) printf("%s", str)

main(argc, argv)
       char **argv;
{
       char cmd, *fl, *fd, obuf[LINELEN], nbuf[LINELEN];
       int o1, o2, n1, n2, here;
       FILE *fpf, *fpd;

       prog = argv[0];
       if (argc != 3)
	       fatal("use: %s original-file diff-list-file", prog);
       if ((fpf = fopen(argv[1], "r")) == NULL)
	       fatal("can't read %s", argv[1]);
       if ((fpd = fopen(argv[2], "r")) == NULL)
	       fatal("can't read %s", argv[2]);
       here = 0;
       while (getcommand(fpd, &o1, &o2, &cmd, &n1, &n2)) {
	       while (here < o1 - 1) {
		       here++;
		       copy(getline(fpf, obuf));
	       }
	       switch (cmd) {
	       case 'c':
	       case 'd':
		       if (cmd == 'd' && n1 != n2)
			       fatal("delete count conflict");
		       while (o1 <= o2) {
			       fl = getline(fpf, obuf);
			       here++;
			       fd = getline(fpd, nbuf);
			       if (strncmp(fd, "< ", 2))
				       fatal("illegal delete line");
			       if (strcmp(fl, fd + 2))
				       fatal("delete line conflict");
			       o1++;
		       }
		       if (cmd == 'd')
			       break;
		       if (strcmp(getline(fpd, nbuf), "---\n"))
			       fatal("illegal separator in chunk");
		       /*FALLTHROUGH*/
	       case 'a':
		       if (cmd == 'a') {
			       if (o1 != o2)
				       fatal("append count conflict");
			       copy(getline(fpf, obuf));
			       here++;
		       }
		       while (n1 <= n2) {
			       if (strncmp(getline(fpd, nbuf), "> ", 2))
				       fatal("illegal append line");
			       copy(nbuf + 2);
			       n1++;
		       }
		       break;
	       }
       }
       while (fgets(obuf, LINELEN, fpf) != NULL)
	       copy(obuf);
       exit(0);
}

isdigit(c)
       char c;
{
       return c >= '0' && c <= '9';
}

char *
range(s, p1, p2)
       char *s;
       int *p1, *p2;
{
       register int v1 = 0, v2;

       while (isdigit(*s))
	       v1 = 10 * v1 + *s++ - '0';
       v2 = v1;
       if (*s == ',') {
	       s++;
	       v2 = 0;
	       while (isdigit(*s))
		       v2 = 10 * v2 + *s++ - '0';
       }
       if (v1 == 0 || v2 == 0 || v1 > v2)
	       fatal("illegal range");
       *p1 = v1;
       *p2 = v2;
       return s;
}

getcommand(fp, o1, o2, pcmd, n1, n2)
       FILE *fp;
       int *o1, *o2, *n1, *n2;
       char *pcmd;
{
       char buf[LINELEN];
       register char *s;
       char cmd;

       if ((s = fgets(buf, LINELEN, fp)) == NULL)
	       return 0;
       s = range(s, o1, o2);
       if ((cmd = *s++) != 'a' && cmd != 'c' && cmd != 'd')
	       fatal("illegal command");
       s = range(s, n1, n2);
       if (*s != '\n' && s[1] != '\0')
	       fatal("extra characters at end of command: %s", s);
       *pcmd = cmd;
       return 1;
}

fatal(s, a)
       char *s, *a;
{
       fprintf(stderr, "%s: fatal: ", prog);
       fprintf(stderr, s, a);
       fprintf(stderr, "\n");
       exit(1);
}