#include <string.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include "gnumeric.h"

gboolean acquire_lock(const char* filename)
{
	char *lockfile;
	gboolean retval = FALSE;
	int fd;

	g_return_val_if_fail(filename != NULL, FALSE);
	g_return_val_if_fail(strlen(filename) != 0, FALSE);
	if( is_locked(filename) == TRUE ) {
		return FALSE;
	}

	lockfile = g_malloc(strlen(filename) + 5);
	strcpy(lockfile, filename);
	strcat(lockfile, ".lck");

	if ((fd = open(lockfile, O_WRONLY|O_CREAT|O_EXCL, S_IREAD|S_IWRITE)) >= 0) {
		/* Lock succeeded */
		char *lockstr;
		char hostname[256];
		int stringsize; // size of locking string
		long pid;
		    
		/* Create the locking string, format is 
		 * hostname:pid 
		 * FBK 15-9-2002: cleanup memory allocation and pid use
		 */
		gethostname(hostname, 255);
		pid = (long) getpid();
		stringsize = strlen(hostname) + ( 4 * sizeof (long) ) +1; 
		lockstr = g_malloc(stringsize);
		
		snprintf(lockstr, stringsize, "%s:%ld", hostname, pid);
		printf("DEBUG: Locking %s with %s\n", lockfile, lockstr);
		write(fd, lockstr, strlen(lockstr));
		close(fd);
		g_free(lockstr);

		retval = TRUE;
	} 
	g_free(lockfile);

	return retval;
}

gboolean relinquish_lock(const char* filename)
{
	char *lockfile;
	gboolean retval = FALSE;
	int fd;

	g_return_val_if_fail(filename != NULL, FALSE);
	g_return_val_if_fail(strlen(filename) != 0, FALSE);

	lockfile = g_malloc(strlen(filename) + 5);
	strcpy(lockfile, filename);
	strcat(lockfile, ".lck");

	if ((fd = open(lockfile, O_RDONLY)) >= 0) {
		char lockstr[300] = "\0";
		int pid = 0;
		if (read(fd, lockstr, 300) >= 0) {
			char *hostname1;
			char *pidstr;
			int index;
			char hostname2[256] = "\0";
			gethostname(hostname2, 255);
			index = strchr(lockstr, ':') - lockstr;
			if (index > 0) {
				lockstr[index] = '\0';
				hostname1 = lockstr;
				pidstr = lockstr + index + 1;
				pid = atoi(pidstr);
			}
			printf("hostname = %s, pid = %d\n", hostname1, pid);
			if ((getpid() == pid) && 
			    (strcmp(hostname2, hostname1) == 0)) {
				printf("DEBUG: Relinquishing lock to %s!\n", filename);
				close(fd);
				/* Unlink the lockfile */
				unlink(lockfile);
				retval = TRUE;
			} else {
				/* Not ours to relinquish */
				printf("DEBUG: Lock file %s is not ours!\n", lockfile);
				close(fd);
			}
		} else {
			printf("DEBUG: error during read (%d)\n", errno);
			close(fd);
		}
	} else {
		printf("DEBUG: Lock file %s doesn't exist!\n", lockfile);
	}
	g_free(lockfile);

	return retval;
}

gboolean is_locked(const char* filename)
{
	char *lockfile;
	gboolean retval = FALSE;
	int ret;
      struct stat st;
	g_return_val_if_fail(filename != NULL, FALSE);
	g_return_val_if_fail(strlen(filename) != 0, FALSE);

	lockfile = g_malloc(strlen(filename) + 5);
	strcpy(lockfile, filename);
	strcat(lockfile, ".lck");
      
	if ((ret = stat(lockfile, &st)) >= 0) {

		retval = TRUE;
	}
	return retval;
}