/*

 -----------------------------------------------------------------------------

 This source file is part of OGRE

 (Object-oriented Graphics Rendering Engine)

 For the latest info, see http://www.ogre3d.org/

 Copyright (c) 2000-2014 Torus Knot Software Ltd

 Permission is hereby granted, free of charge, to any person obtaining a copy

 of this software and associated documentation files (the "Software"), to deal

 in the Software without restriction, including without limitation the rights

 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

 copies of the Software, and to permit persons to whom the Software is

 furnished to do so, subject to the following conditions:

 The above copyright notice and this permission notice shall be included in

 all copies or substantial portions of the Software.

 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

 THE SOFTWARE.

 -----------------------------------------------------------------------------

 */

#include "OgreFileSystemLayer.h"

#include <errno.h>

#include <unistd.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <pwd.h>

#include <dlfcn.h>

namespace Ogre

{

    namespace {

        /** Get actual file pointed to by symlink */

        const Ogre::String resolveSymlink(const Ogre::String& symlink)

        {

            ssize_t bufsize = 256;

            char* resolved = 0;

            do

            {

                char* buf = OGRE_ALLOC_T(char, bufsize, Ogre::MEMCATEGORY_GENERAL);

                ssize_t retval = readlink(symlink.c_str(), buf, bufsize);

                if (retval == -1)

                {

                    OGRE_FREE(buf, Ogre::MEMCATEGORY_GENERAL);

                    break;

                }

                if (retval < bufsize)

                {

                    // operation was successful.

                    // readlink does not guarantee to 0-terminate, so do this manually

                    buf[retval] = '\0';

                    resolved = buf;

                }

                else

                {

                    // buffer was too small, grow buffer and try again

                    OGRE_FREE(buf, Ogre::MEMCATEGORY_GENERAL);

                    bufsize <<= 1;

                }

            } while (!resolved);

            if (resolved)

            {

                Ogre::String result (resolved);

                OGRE_FREE(resolved, Ogre::MEMCATEGORY_GENERAL);

                return result;

            }

            else

                return "";

        }

    }

    String FileSystemLayer::resolveBundlePath(String path)

    {

        // With Ubuntu snaps absolute paths are relative to the snap package.

        char* env_SNAP = getenv("SNAP");

        if (env_SNAP && !path.empty() && path[0] == '/' && // only adjust absolute dirs

            !StringUtil::startsWith(path, "/snap")) // not a snap path already

            path = env_SNAP + path;

        return path;

    }

    //---------------------------------------------------------------------

    void FileSystemLayer::getConfigPaths()

    {

        // try to determine the application's path:

        // recent systems should provide the executable path via the /proc system

        Ogre::String appPath = resolveSymlink("/proc/self/exe");

        if (appPath.empty())

        {

            // if /proc/self/exe isn't available, try it via the program's pid

            pid_t pid = getpid();

            char proc[64];

            int retval = snprintf(proc, sizeof(proc), "/proc/%llu/exe", (unsigned long long) pid);

            if (retval > 0 && retval < (long)sizeof(proc))

                appPath = resolveSymlink(proc);

        }

        if (!appPath.empty())

        {

            // we need to strip the executable name from the path

            Ogre::String::size_type pos = appPath.rfind('/');

            if (pos != Ogre::String::npos)

                appPath.erase(pos);

            // use application path as first config search path

            mConfigPaths.push_back(appPath + '/');

        }

        Dl_info info;

        if (dladdr((const void*)resolveSymlink, &info))

        {

            String base(info.dli_fname);

            // need to strip the module filename from the path

            String::size_type pos = base.rfind('/');

            if (pos != String::npos)

                base.erase(pos);

            String dirname = StringUtil::format("OGRE-%d.%d/", OGRE_VERSION_MAJOR, OGRE_VERSION_MINOR);

            // search inside ../share/OGRE-X.Y

            mConfigPaths.push_back(StringUtil::normalizeFilePath(base + "/../share/"+dirname, false));

            // then look relative to PIP structure

            mConfigPaths.push_back(StringUtil::normalizeFilePath(base+"/../../../../share/"+dirname));

        }

        // then try system wide /etc

        mConfigPaths.push_back("/etc/OGRE/");

    }

    //---------------------------------------------------------------------

    void FileSystemLayer::prepareUserHome(const Ogre::String& subdir)

    {

        char* xdg_cache = getenv("XDG_CACHE_HOME");

        if(xdg_cache) {

            mHomePath = xdg_cache;

            mHomePath.append("/");

        } else {

            struct passwd* pwd = getpwuid(getuid());

            if (pwd)

            {

                mHomePath = pwd->pw_dir;

            }

            else

            {

                // try the $HOME environment variable

                mHomePath = getenv("HOME");

            }

            if(!mHomePath.empty()) {

                mHomePath.append("/.cache/");

            }

        }

        if (!mHomePath.empty())

        {

            // create the given subdir

            mHomePath.append(subdir + '/');

            if (mkdir(mHomePath.c_str(), 0755) != 0 && errno != EEXIST)

            {

                // can't create dir

                mHomePath.clear();

            }

        }

        if (mHomePath.empty())

        {

            // couldn't create dir in home directory, fall back to cwd

            mHomePath = "./";

        }

    }

    //---------------------------------------------------------------------

    bool FileSystemLayer::fileExists(const Ogre::String& path)

    {

        return access(path.c_str(), R_OK) == 0;

    }

    //---------------------------------------------------------------------

    bool FileSystemLayer::createDirectory(const Ogre::String& path)

    {

        return !mkdir(path.c_str(), 0755) || errno == EEXIST;

    }

    //---------------------------------------------------------------------

    bool FileSystemLayer::removeDirectory(const Ogre::String& path)

    {

        return !rmdir(path.c_str()) || errno == ENOENT;

    }

    //---------------------------------------------------------------------

    bool FileSystemLayer::removeFile(const Ogre::String& path)

    {

        return !unlink(path.c_str()) || errno == ENOENT;

    }

    //---------------------------------------------------------------------

    bool FileSystemLayer::renameFile(const Ogre::String& oldname, const Ogre::String& newname)

    {

        return !rename(oldname.c_str(), newname.c_str());

    }

}