/*
 -----------------------------------------------------------------------------
 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>

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 "";
        }
    }
    //---------------------------------------------------------------------
    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);
        }
        else
        {
            // couldn't find actual executable path, assume current working dir
            appPath = ".";
        }

        // use application path as first config search path
        mConfigPaths.push_back(appPath + '/');
        // then search inside ../share/OGRE
        mConfigPaths.push_back(appPath + "/../share/OGRE/");
        // 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());
    }
}
