/**
 * \file
 * Routines for handling path names.
 * 
 * Authors:
 * 	Gonzalo Paniagua Javier (gonzalo@novell.com)
 * 	Miguel de Icaza (miguel@novell.com)
 *
 * (C) 2006 Novell, Inc.  http://www.novell.com
 *
 */
#include <config.h>
#include <glib.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
/* This is only needed for the mono_path_canonicalize code, MAXSYMLINKS, could be moved */
#ifdef HAVE_SYS_PARAM_H
#include <sys/param.h>
#endif

#include "mono-path.h"

/* Embedded systems lack MAXSYMLINKS */
#ifndef MAXSYMLINKS
#define MAXSYMLINKS 3
#endif

/* Resolves '..' and '.' references in a path. If the path provided is relative,
 * it will be relative to the current directory */

/* For Native Client, the above is not true.  Since there is no getcwd we fill */
/* in the file being passed in relative to '.' and don't resolve it            */

/* There are a couple of tests for this method in mono/test/mono-path.cs */
gchar *
mono_path_canonicalize (const char *path)
{
	gchar *abspath, *pos, *lastpos, *dest;
	int backc;

	if (g_path_is_absolute (path)) {
		abspath = g_strdup (path);
	} else {
		gchar *tmpdir = g_get_current_dir ();
		abspath = g_build_filename (tmpdir, path, NULL);
		g_free (tmpdir);
	}

#ifdef HOST_WIN32
	g_strdelimit (abspath, "/", '\\');
#endif
	abspath = g_strreverse (abspath);

	backc = 0;
	dest = lastpos = abspath;
	pos = strchr (lastpos, G_DIR_SEPARATOR);

	while (pos != NULL) {
		int len = pos - lastpos;
		if (len == 1 && lastpos [0] == '.') {
			// nop
		} else if (len == 2 && lastpos [0] == '.' && lastpos [1] == '.') {
			backc++;
		} else if (len > 0) {
			if (backc > 0) {
				backc--;
			} else {
				if (dest != lastpos) 
					/* The two strings can overlap */
					memmove (dest, lastpos, len + 1);
				dest += len + 1;
			}
		}
		lastpos = pos + 1;
		pos = strchr (lastpos, G_DIR_SEPARATOR);
	}

#ifdef HOST_WIN32
	/* Avoid removing the first '\' for UNC paths. We must make sure that it's indeed an UNC path
	by checking if the \\ pair happens exactly at the end of the string.
	*/
	if (*(lastpos-1) == G_DIR_SEPARATOR && *(lastpos-2) == G_DIR_SEPARATOR && *lastpos == 0)
		lastpos = lastpos-1;
#endif
	
	if (dest != lastpos) strcpy (dest, lastpos);
	
	g_strreverse (abspath);

	/* We strip away all trailing dir separators. This is not correct for the root directory,
	 * since we'll return an empty string, so re-append a dir separator if there is none in the
	 * result */
	if (strchr (abspath, G_DIR_SEPARATOR) == NULL) {
		int len = strlen (abspath);
		abspath = (gchar *) g_realloc (abspath, len + 2);
		abspath [len] = G_DIR_SEPARATOR;
		abspath [len+1] = 0;
	}

	return abspath;
}

/*
 * This ensures that the path that we store points to the final file
 * not a path to a symlink.
 */
#if !defined(HOST_NO_SYMLINKS)
static gchar *
resolve_symlink (const char *path)
{
	char *p, *concat, *dir;
	char buffer [PATH_MAX+1];
	int n, iterations = 0;

	p = g_strdup (path);
	do {
		iterations++;
		n = readlink (p, buffer, sizeof (buffer)-1);
		if (n < 0){
			char *copy = p;
			p = mono_path_canonicalize (copy);
			g_free (copy);
			return p;
		}
		
		buffer [n] = 0;
		if (!g_path_is_absolute (buffer)) {
			dir = g_path_get_dirname (p);
			concat = g_build_filename (dir, buffer, NULL);
			g_free (dir);
		} else {
			concat = g_strdup (buffer);
		}
		g_free (p);
		p = mono_path_canonicalize (concat);
		g_free (concat);
	} while (iterations < MAXSYMLINKS);

	return p;
}
#endif

gchar *
mono_path_resolve_symlinks (const char *path)
{
#if defined(HOST_NO_SYMLINKS)
	return mono_path_canonicalize (path);
#else
	gchar **split = g_strsplit (path, G_DIR_SEPARATOR_S, -1);
	gchar *p = g_strdup ("");
	int i;

	for (i = 0; split [i] != NULL; i++) {
		gchar *tmp = NULL;

		// resolve_symlink of "" goes into canonicalize which resolves to cwd
		if (strcmp (split [i], "") != 0) {
			tmp = g_strdup_printf ("%s%s", p, split [i]);
			g_free (p);
			p = resolve_symlink (tmp);
			g_free (tmp);
		}

		if (split [i+1] != NULL) {
			tmp = g_strdup_printf ("%s%s", p, G_DIR_SEPARATOR_S);
			g_free (p);
			p = tmp;
		}
	}

	g_strfreev (split);
	return p;
#endif
}