/*
	This program is used to apply an fcmd file (output of pdiff)
	fcmd-exec [ -pN ] fcmd-file
	-pN works like the -pN patch option. It remove the leading
	the N directories from the path
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>

static void usage()
{
	fprintf (stderr,
		"fcmd-exec [ -pN ] file\n"
		"\tApply the commands found in file\n"
		"fcmd-exec [ -pN ] -\n"
		"\tApply the commands read from standard input\n"
		"\n"
		"\t-pN works like the patch command. It removes\n"
		"\tthe leading directory components before applying\n"
		"\tthe command\n");
}
static const char *fcmd_skip (int n, const char *file)
{
	while (n > 0){
		const char *pt = strchr(file,'/');
		if (pt == NULL){
			break;
		}
		while (*pt == '/') pt++;
		file = pt;
		n--;
	}
	return file;
}

static int fcmd_unlink (const char *relfile)
{
	int ret = unlink (relfile);
	if (ret == -1){
		if (errno == EEXIST){
			ret = 0;
		}else{
			fprintf (stderr,"Can't remove %s (%s)\n"
				,relfile,strerror(errno));
		}
	}
	return ret;
}




static int fcmd_process(int parg, FILE *fin)
{
	int ret = 0;
	char buf[2000];
	int noline=0;
	while (ret == 0 && fgets(buf,sizeof(buf)-1,fin)!=NULL){
		noline++;
		if (buf[0] != '#' && buf[0] != '\n'){
			char verb[2000],file[2000],rest[2000];
			if (sscanf(buf,"%s %s %s",verb,file,rest)>=2){
				if (strcmp(verb,"UNLINK")==0){
					const char *relfile = fcmd_skip(parg,file);
					printf ("unlink %s\n",relfile);
					ret = fcmd_unlink (relfile);
				}else if (strcmp(verb,"LINK")==0){
					const char *relfile = fcmd_skip(parg,file);
					ret = fcmd_unlink (relfile);
					ret = symlink (rest,relfile);
					if (ret == -1){
						fprintf (stderr,"Can't symlink %s (%s)\n"
							,relfile,strerror(errno));
					}
				}else{
					fprintf (stderr,"Invalid command %s, line %d\n"
						,verb,noline);
					ret = -1;
				}
			}else{
				fprintf (stderr,"Invalid command %s, line %d\n"
					,buf,noline);
				ret = -1;
			}
		}
	}
	return ret;
}

int main (int argc, char *argv[])
{
	int ret = -1;
	int parg = 0;
	int i;
	for (i=1; i<argc; i++){
		if (strncmp(argv[i],"-p",2)==0){
			parg = atoi(argv[i]+2);
		}else{
			break;
		}
	}
	if (i != argc - 1){
		usage();
	}else if (strcmp(argv[i],"-")==0){
		ret = fcmd_process(parg, stdin);
	}else{
		FILE *fin = fopen (argv[i],"r");
		if (fin == NULL){
			fprintf (stderr,"Can't open file %s (%s)\n",argv[i]
				,strerror(errno));
		}else{
			ret = fcmd_process(parg,fin);
			fclose (fin);
		}
	}
	return ret;
}