/* ScummVM - Graphic Adventure Engine
 *
 * ScummVM is the legal property of its developers, whose names
 * are too numerous to list here. Please refer to the COPYRIGHT
 * file distributed with this source distribution.
 *
 * 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 2
 * 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, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * $URL$
 * $Id$
 */

#if defined(UNIX)

#include "backends/fs/abstract-fs.h"

#ifdef MACOSX
#include <sys/types.h>
#endif
#include <sys/param.h>
#include <sys/stat.h>
#include <dirent.h>
#include <stdio.h>
#include <unistd.h>

/**
 * Implementation of the ScummVM file system API based on POSIX.
 * 
 * Parts of this class are documented in the base interface class, AbstractFilesystemNode.
 */
class POSIXFilesystemNode : public AbstractFilesystemNode {
protected:
	String _displayName;
	String _path;
	bool _isDirectory;
	bool _isValid;

public:
	/**
	 * Creates a POSIXFilesystemNode with the root node as path.
	 */
	POSIXFilesystemNode();
	
	/**
	 * Creates a POSIXFilesystemNode for a given path.
	 * 
	 * @param path String with the path the new node should point to.
	 * @param verify true if the isValid and isDirectory flags should be verified during the construction.
	 */
	POSIXFilesystemNode(const String &path, bool verify);
	
	virtual bool exists() const { return access(_path.c_str(), F_OK) == 0; }
	virtual String getDisplayName() const { return _displayName; }
	virtual String getName() const { return _displayName; }
	virtual String getPath() const { return _path; }
	virtual bool isDirectory() const { return _isDirectory; }
	virtual bool isReadable() const { return access(_path.c_str(), R_OK) == 0; }
	virtual bool isWritable() const { return access(_path.c_str(), W_OK) == 0; }
	
	virtual AbstractFilesystemNode *getChild(const String &n) const;
	virtual bool getChildren(AbstractFSList &list, ListMode mode, bool hidden) const;
	virtual AbstractFilesystemNode *getParent() const;
	
private:
	/**
	 * Tests and sets the _isValid and _isDirectory flags, using the stat() function.
	 */
	virtual void setFlags();
};

/**
 * Returns the last component of a given path.
 * 
 * Examples:
 * 			/foo/bar.txt would return /bar.txt
 * 			/foo/bar/    would return /bar/
 *  
 * @param str String containing the path.
 * @return Pointer to the first char of the last component inside str.
 */
const char *lastPathComponent(const Common::String &str) {
	if(str.empty())
		return "";
	
	const char *start = str.c_str();
	const char *cur = start + str.size() - 2;

	while (cur >= start && *cur != '/') {
		--cur;
	}

	return cur + 1;
}

void POSIXFilesystemNode::setFlags() {
	struct stat st;
	
	_isValid = (0 == stat(_path.c_str(), &st));
	_isDirectory = _isValid ? S_ISDIR(st.st_mode) : false;
}

POSIXFilesystemNode::POSIXFilesystemNode() {
/*  The Browser code now saves the last browsed directory into the config file.
    Hence the need to start at the "current" directory is far less, and we can
    remove this hack for now. Still, there may be some need to obtain a ref
    to the "current" directory. See the TODO list for some thoughts on this.
    
    I am leaving this code in here for the time being, to be used as reference.

	// FIXME: It is evil & slow to always call getcwd here.
	// The intention behind this hack was/is to be more user friendly
	// in our save/load dialogs: Instead of starting at the FS root,
	// we start at the current directory. However, that's just a hack.
	// Proper solution would be to extend FilesystemNode by the concept
	// of 'current' or 'default' directory, and then modify the
	// save/load dialogs to explicitly use that as starting point.
	char buf[MAXPATHLEN];
	getcwd(buf, MAXPATHLEN);

	_path = buf;
	_displayName = lastPathComponent(_path);
	_path += '/';
*/
	// The root dir.
	_path = "/";
	_displayName = _path;
	_isValid = true;
	_isDirectory = true;
}

POSIXFilesystemNode::POSIXFilesystemNode(const String &p, bool verify) {
	assert(p.size() > 0);

	_path = p;
	_displayName = lastPathComponent(_path);

	if (verify) {
		setFlags();
	}
}

AbstractFilesystemNode *POSIXFilesystemNode::getChild(const String &n) const {
	// FIXME: Pretty lame implementation! We do no error checking to speak
	// of, do not check if this is a special node, etc.
	assert(_isDirectory);
	
	String newPath(_path);
	if (_path.lastChar() != '/')
		newPath += '/';
	newPath += n;
	
	return new POSIXFilesystemNode(newPath, true);
}

bool POSIXFilesystemNode::getChildren(AbstractFSList &myList, ListMode mode, bool hidden) const {
	assert(_isDirectory);
	
	DIR *dirp = opendir(_path.c_str());
	struct dirent *dp;

	if (dirp == NULL)
		return false;

	// loop over dir entries using readdir
	while ((dp = readdir(dirp)) != NULL) {
		// Skip 'invisible' files if necessary
		if (dp->d_name[0] == '.' && !hidden) {
			continue;
		}
		// Skip '.' and '..' to avoid cycles
		if ((dp->d_name[0] == '.' && dp->d_name[1] == 0) || (dp->d_name[0] == '.' && dp->d_name[1] == '.')) {
			continue;
		}

		String newPath(_path);
		if (newPath.lastChar() != '/')
			newPath += '/';
		newPath += dp->d_name;

		POSIXFilesystemNode entry(newPath, false);

#if defined(SYSTEM_NOT_SUPPORTING_D_TYPE)
		/* TODO: d_type is not part of POSIX, so it might not be supported
		 * on some of our targets. For those systems where it isn't supported,
		 * add this #elif case, which tries to use stat() instead.
		 * 
		 * The d_type method is used to avoid costly recurrent stat() calls in big
		 * directories.
		 */
		entry.setFlags();
#else
		if (dp->d_type == DT_UNKNOWN) {
			// Fall back to stat()
			entry.setFlags();
		} else {
			entry._isValid = (dp->d_type == DT_DIR) || (dp->d_type == DT_REG) || (dp->d_type == DT_LNK);
			if (dp->d_type == DT_LNK) {
				struct stat st;
				if (stat(entry._path.c_str(), &st) == 0)
					entry._isDirectory = S_ISDIR(st.st_mode);
				else
					entry._isDirectory = false;
			} else {
				entry._isDirectory = (dp->d_type == DT_DIR);
			}
		}
#endif

		// Skip files that are invalid for some reason (e.g. because we couldn't
		// properly stat them).
		if (!entry._isValid)
			continue;

		// Honor the chosen mode
		if ((mode == FilesystemNode::kListFilesOnly && entry._isDirectory) ||
			(mode == FilesystemNode::kListDirectoriesOnly && !entry._isDirectory))
			continue;

		if (entry._isDirectory)
			entry._path += "/";
			
		myList.push_back(new POSIXFilesystemNode(entry));
	}
	closedir(dirp);
	
	return true;
}

AbstractFilesystemNode *POSIXFilesystemNode::getParent() const {
	if (_path == "/")
		return 0;

	const char *start = _path.c_str();
	const char *end = lastPathComponent(_path);

	return new POSIXFilesystemNode(String(start, end - start), true);
}

#endif //#if defined(UNIX)