//
//  FileSystemUtil.cpp
//
//  Low-level filesystem functions.
//

#define _FILE_OFFSET_BITS 64

#include "utils/FileSystemUtil.h"

#include <sys/stat.h>
#include <string.h>

#ifdef WIN32
// Because windows...
#include <direct.h>
#include <Windows.h>
#define getcwd _getcwd
#define mkdir(x,y) _mkdir(x)
#define snprintf _snprintf
#define stat64 _stat64
#define unlink _unlink
#define S_ISREG(x) (((x) & S_IFMT) == S_IFREG)
#define S_ISDIR(x) (((x) & S_IFMT) == S_IFDIR)
#else
#include <dirent.h>
#include <unistd.h>
#endif

// Try to get the install prefix as defined when CMake was run.
// The installPrefix directory is the value set for CMAKE_INSTALL_DIRECTORY during build.
// The datarootdir directory is the value set for CMAKE_INSTALL_DATAROOTDIR during build.
// If not defined, the default prefix path '/usr/local' and the default datarootdir
// directory 'share' will be used, i.e. combining to '/usr/local/share'.
#ifdef __unix__
#ifdef ES_INSTALL_PREFIX
std::string installPrefix = ES_INSTALL_PREFIX;
#else
std::string installPrefix = "/usr/local";
#endif
#ifdef ES_DATAROOTDIR
std::string dataRootDir = ES_DATAROOTDIR;
#else
std::string dataRootDir = "share";
#endif
#endif

namespace Utils
{
    namespace FileSystem
    {
        static std::string homePath = "";
        static std::string exePath = "";

        #if defined(_WIN32)
        static std::string convertFromWideString(const std::wstring wstring)
        {
            int numBytes = WideCharToMultiByte(CP_UTF8, 0, wstring.c_str(),
                    (int)wstring.length(), nullptr, 0, nullptr, nullptr);
            std::string string;

            string.resize(numBytes);
            WideCharToMultiByte(CP_UTF8, 0, wstring.c_str(), (int)wstring.length(),
                    (char*)string.c_str(), numBytes, nullptr, nullptr);

            return std::string(string);
        }
        #endif

        stringList getDirContent(const std::string& _path, const bool _recursive)
        {
            std::string path = getGenericPath(_path);
            stringList contentList;

            // Only parse the directory, if it's a directory.
            if (isDirectory(path)) {

                #if defined(_WIN32)
                WIN32_FIND_DATAW findData;
                std::string wildcard = path + "/*";
                HANDLE hFind = FindFirstFileW(std::wstring(wildcard.begin(),
                        wildcard.end()).c_str(), &findData);

                if (hFind != INVALID_HANDLE_VALUE) {
                    // Loop over all files in the directory.
                    do {
                        std::string name = convertFromWideString(findData.cFileName);
                        // Ignore "." and ".."
                        if ((name != ".") && (name != "..")) {
                            std::string fullName(getGenericPath(path + "/" + name));
                            contentList.push_back(fullName);

                            if (_recursive && isDirectory(fullName))
                                contentList.merge(getDirContent(fullName, true));
                        }
                    }
                    while (FindNextFileW(hFind, &findData));
                    FindClose(hFind);
                }
                #else
                DIR* dir = opendir(path.c_str());

                if (dir != NULL) {
                    struct dirent* entry;
                    // Loop over all files in the directory.
                    while ((entry = readdir(dir)) != NULL) {
                        std::string name(entry->d_name);

                        // Ignore "." and ".."
                        if ((name != ".") && (name != "..")) {
                            std::string fullName(getGenericPath(path + "/" + name));
                            contentList.push_back(fullName);

                            if (_recursive && isDirectory(fullName))
                                contentList.merge(getDirContent(fullName, true));
                        }
                    }
                    closedir(dir);
                }
                #endif
            }
            contentList.sort();
            return contentList;
        }

        stringList getPathList(const std::string& _path)
        {
            stringList pathList;
            std::string path = getGenericPath(_path);
            size_t start = 0;
            size_t end = 0;

            // Split at '/'
            while ((end = path.find("/", start)) != std::string::npos) {
                if (end != start)
                    pathList.push_back(std::string(path, start, end - start));
                start = end + 1;
            }
            // Add last folder / file to pathList.
            if (start != path.size())
                pathList.push_back(std::string(path, start, path.size() - start));

            return pathList;
        }

        void setHomePath(const std::string& _path)
        {
            homePath = getGenericPath(_path);
        }

        std::string getHomePath()
        {
            // Only construct the homepath once.
            if (homePath.length())
                return homePath;

            // Check for HOME environment variable.
            if (!homePath.length()) {
                std::string envHome = getenv("HOME");
                if (envHome.length())
                    homePath = getGenericPath(envHome);
            }

            #if defined(_WIN32)
            // On Windows we need to check HOMEDRIVE and HOMEPATH.
            if (!homePath.length()) {
                std::string envHomeDrive = getenv("HOMEDRIVE");
                std::string envHomePath  = getenv("HOMEPATH");
                if (envHomeDrive.length() && envHomePath.length())
                    homePath = getGenericPath(envHomeDrive + "/" + envHomePath);
            }
            #endif // _WIN32

            // No homepath found, fall back to current working directory.
            if (!homePath.length())
                homePath = getCWDPath();

            return homePath;
        }

        std::string getCWDPath()
        {
            char temp[512];

            // Return current working directory.
            return (getcwd(temp, 512) ? getGenericPath(temp) : "");
        }

        void setExePath(const std::string& _path)
        {
            constexpr int path_max = 32767;
            #if defined(_WIN32)
            std::wstring result(path_max, 0);
            if (GetModuleFileNameW(nullptr, &result[0], path_max) != 0)
                exePath = convertFromWideString(result);
            #else
            std::string result(path_max, 0);
            if (readlink("/proc/self/exe", &result[0], path_max) != -1)
                exePath = result;
            #endif
            exePath = getCanonicalPath(exePath);

            // Fallback to argv[0] if everything else fails.
            if (exePath.empty())
                exePath = getCanonicalPath(_path);
            if (isRegularFile(exePath))
                exePath = getParent(exePath);
        }

        std::string getExePath()
        {
            return exePath;
        }

        std::string getInstallPrefixPath()
        {
            // There seems to be a bug in CMake that when deleting the CMakeCache.txt
            // file and running cmake, the ES_DATAROOTDIR is not populated, i.e. this fails:
            // add_definitions(-DES_DATAROOTDIR="${CMAKE_INSTALL_DATAROOTDIR}")
            // Re-running cmake a second time populates it correctly. But ES_INSTALL_PREFIX
            // is always populated correctly on my machine which is very strange.
            // Anyway, as an extra precaution, let's set datarootdir to 'share' if it's blank,
            // as that's what most people would want anyway. When this bug has been fixed in
            // CMake this code can be removed.
            // Just in case, let's set installPrefix to '/usr/local' if blank as well as a
            // fallback precaution as maybe some make environments won't handle this
            // correctly either.
            if (!installPrefix.length())
                installPrefix = "/usr/local";
            if (!dataRootDir.length())
                dataRootDir = "share";
            return installPrefix + "/" + dataRootDir;
        }

        std::string getPreferredPath(const std::string& _path)
        {
            std::string path = _path;
            size_t offset = std::string::npos;
            #if defined(_WIN32)
            // Convert '/' to '\\'
            while ((offset = path.find('/')) != std::string::npos)
                path.replace(offset, 1, "\\");
            #endif
            return path;
        }

        std::string getGenericPath(const std::string& _path)
        {
            std::string path = _path;
            size_t offset = std::string::npos;

            // Remove "\\\\?\\"
            if ((path.find("\\\\?\\")) == 0)
                path.erase(0, 4);

            // Convert '\\' to '/'
            while ((offset = path.find('\\')) != std::string::npos)
                path.replace(offset, 1 ,"/");

            // Remove double '/'
            while ((offset = path.find("//")) != std::string::npos)
                path.erase(offset, 1);

            // Remove trailing '/' when the path is more than a simple '/'
            while (path.length() > 1 && ((offset = path.find_last_of('/')) == (path.length() - 1)))
                path.erase(offset, 1);

            return path;
        }

        std::string getEscapedPath(const std::string& _path)
        {
            std::string path = getGenericPath(_path);

            #if defined(_WIN32)
            // Windows escapes stuff by just putting everything in quotes.
            return '"' + getPreferredPath(path) + '"';
            #else
            // Insert a backslash before most characters that would mess up a bash path.
            const char* invalidChars = "\\ '\"!$^&*(){}[]?;<>";
            const char* invalidChar = invalidChars;

            while (*invalidChar) {
                size_t start = 0;
                size_t offset = 0;

                while ((offset = path.find(*invalidChar, start)) != std::string::npos) {
                    start = offset + 1;

                    if ((offset == 0) || (path[offset - 1] != '\\')) {
                        path.insert(offset, 1, '\\');
                        ++start;
                    }
                }
                ++invalidChar;
            }
            return path;
            #endif
        }

        std::string getCanonicalPath(const std::string& _path)
        {
            // Hack for builtin resources.
            if ((_path[0] == ':') && (_path[1] == '/'))
                return _path;

            std::string path = exists(_path) ? getAbsolutePath(_path) : getGenericPath(_path);

            // Cleanup path.
            bool scan = true;
            while (scan) {
                stringList pathList = getPathList(path);

                path.clear();
                scan = false;

                for (stringList::const_iterator it = pathList.cbegin();
                        it != pathList.cend(); ++it) {
                    // Ignore empty.
                    if ((*it).empty())
                        continue;

                    // Remove "/./"
                    if ((*it) == ".")
                        continue;

                    // Resolve "/../"
                    if ((*it) == "..") {
                        path = getParent(path);
                        continue;
                    }

                    #if defined(_WIN32)
                    // Append folder to path.
                    path += (path.size() == 0) ? (*it) : ("/" + (*it));
                    #else
                    // Append folder to path.
                    path += ("/" + (*it));
                    #endif

                    // Resolve symlink.
                    if (isSymlink(path)) {
                        std::string resolved = resolveSymlink(path);

                        if (resolved.empty())
                            return "";

                        if (isAbsolute(resolved))
                            path = resolved;
                        else
                            path = getParent(path) + "/" + resolved;

                        for (++it; it != pathList.cend(); ++it)
                            path += (path.size() == 0) ? (*it) : ("/" + (*it));

                        scan = true;
                        break;
                    }
                }
            }
            return path;
        }

        std::string getAbsolutePath(const std::string& _path, const std::string& _base)
        {
            std::string path = getGenericPath(_path);
            std::string base = isAbsolute(_base) ? getGenericPath(_base) : getAbsolutePath(_base);

            // Return absolute path.
            return isAbsolute(path) ? path : getGenericPath(base + "/" + path);

        }

        std::string getParent(const std::string& _path)
        {
            std::string path = getGenericPath(_path);
            size_t offset = std::string::npos;

            // Find last '/' and erase it.
            if ((offset = path.find_last_of('/')) != std::string::npos)
                return path.erase(offset);

            // No parent found.
            return path;
        }

        std::string getFileName(const std::string& _path)
        {
            std::string path = getGenericPath(_path);
            size_t offset = std::string::npos;

            // Find last '/' and return the filename.
            if ((offset = path.find_last_of('/')) != std::string::npos)
                return ((path[offset + 1] == 0) ? "." : std::string(path, offset + 1));

            // No '/' found, entire path is a filename.
            return path;
        }

        std::string getStem(const std::string& _path)
        {
            std::string fileName = getFileName(_path);
            size_t offset = std::string::npos;

            // Empty fileName.
            if (fileName == ".")
                return fileName;

            // Find last '.' and erase the extension.
            if ((offset = fileName.find_last_of('.')) != std::string::npos)
                return fileName.erase(offset);

            // No '.' found, filename has no extension.
            return fileName;
        }

        std::string getExtension(const std::string& _path)
        {
            std::string fileName = getFileName(_path);
            size_t offset = std::string::npos;

            // Empty fileName.
            if (fileName == ".")
                return fileName;

            // Find last '.' and return the extension.
            if ((offset = fileName.find_last_of('.')) != std::string::npos)
                return std::string(fileName, offset);

            // No '.' found, filename has no extension.
            return ".";
        }

        std::string resolveRelativePath(const std::string& _path,
                const std::string& _relativeTo, const bool _allowHome)
        {
            std::string path = getGenericPath(_path);
            std::string relativeTo = isDirectory(_relativeTo) ?
                    getGenericPath(_relativeTo) : getParent(_relativeTo);

            // Nothing to resolve.
            if (!path.length())
                return path;

            // Replace '.' with relativeTo.
            if ((path[0] == '.') && (path[1] == '/'))
                return (relativeTo + &(path[1]));

            // Replace '~' with homePath.
            if (_allowHome && (path[0] == '~') && (path[1] == '/'))
                return (getHomePath() + &(path[1]));

            // Nothing to resolve.
            return path;
        }

        std::string createRelativePath(const std::string& _path,
                const std::string& _relativeTo, const bool _allowHome)
        {
            bool contains = false;
            std::string path = removeCommonPath(_path, _relativeTo, contains);

            if (contains)
                return ("./" + path);

            if (_allowHome) {
                path = removeCommonPath(_path, getHomePath(), contains);

                if (contains)
                    return ("~/" + path);
            }
            return path;
        }

        std::string removeCommonPath(const std::string& _path,
                const std::string& _common, bool& _contains)
        {
            std::string path   = getGenericPath(_path);
            std::string common = isDirectory(_common) ?
                    getGenericPath(_common) : getParent(_common);

            // Check if path contains common.
            if (path.find(common) == 0) {
                _contains = true;
                return path.substr(common.length() + 1);
            }

            // It didn't.
            _contains = false;
            return path;
        }

        std::string resolveSymlink(const std::string& _path)
        {
            std::string path = getGenericPath(_path);
            std::string resolved;

            #if defined(_WIN32)
            HANDLE hFile = CreateFile(path.c_str(), FILE_READ_ATTRIBUTES, FILE_SHARE_READ,
                    0, OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, 0);

            if (hFile != INVALID_HANDLE_VALUE) {
                resolved.resize(GetFinalPathNameByHandle(hFile, nullptr, 0,
                        FILE_NAME_NORMALIZED) + 1);
                if (GetFinalPathNameByHandle(hFile, (LPSTR)resolved.data(),
                        (DWORD)resolved.size(), FILE_NAME_NORMALIZED) > 0) {
                    resolved.resize(resolved.size() - 1);
                    resolved = getGenericPath(resolved);
                }
                CloseHandle(hFile);
            }
            #else
            struct stat info;

            // Check if lstat succeeded.
            if (lstat(path.c_str(), &info) == 0) {
                resolved.resize(info.st_size);
                if (readlink(path.c_str(), (char*)resolved.data(), resolved.size()) > 0)
                    resolved = getGenericPath(resolved);
            }
            #endif
            return resolved;
        }

        bool removeFile(const std::string& _path)
        {
            std::string path = getGenericPath(_path);

            // Don't remove if it doesn't exists.
            if (!exists(path))
                return true;

            // Try to remove file.
            return (unlink(path.c_str()) == 0);
        }

        bool createDirectory(const std::string& _path)
        {
            std::string path = getGenericPath(_path);

            // Don't create if it already exists.
            if (exists(path))
                return true;

            // Try to create directory.
            if (mkdir(path.c_str(), 0755) == 0)
                return true;

            // Failed to create directory, try to create the parent.
            std::string parent = getParent(path);

            // Only try to create parent if it's not identical to path.
            if (parent != path)
                createDirectory(parent);

            // Try to create directory again now that the parent should exist.
            return (mkdir(path.c_str(), 0755) == 0);
        }

        bool exists(const std::string& _path)
        {
            std::string path = getGenericPath(_path);
            struct stat64 info;

            return (stat64(path.c_str(), &info) == 0);
        }

        bool isAbsolute(const std::string& _path)
        {
            std::string path = getGenericPath(_path);

            #if defined(_WIN32)
            return ((path.size() > 1) && (path[1] == ':'));
            #else
            return ((path.size() > 0) && (path[0] == '/'));
            #endif
        }

        bool isRegularFile(const std::string& _path)
        {
            std::string path = getGenericPath(_path);
            struct stat64 info;

            if (stat64(path.c_str(), &info) != 0)
                return false;

            // Check for S_IFREG attribute.
            return (S_ISREG(info.st_mode));
        }

        bool isDirectory(const std::string& _path)
        {
            std::string path = getGenericPath(_path);
            struct stat info;

            if (stat(path.c_str(), &info) != 0)
                return false;

            // Check for S_IFDIR attribute.
            return (S_ISDIR(info.st_mode));
        }

        bool isSymlink(const std::string& _path)
        {
            std::string path = getGenericPath(_path);

            #if defined(_WIN32)
            // Check for symlink attribute.
            const DWORD Attributes = GetFileAttributes(path.c_str());
            if ((Attributes != INVALID_FILE_ATTRIBUTES) &&
                    (Attributes & FILE_ATTRIBUTE_REPARSE_POINT))
                return true;
            #else
            struct stat info;

            if (lstat(path.c_str(), &info) != 0)
                return false;

            // Check for S_IFLNK attribute.
            return (S_ISLNK(info.st_mode));
            #endif

            // Not a symlink.
            return false;
        }

        bool isHidden(const std::string& _path)
        {
            std::string path = getGenericPath(_path);

            #if defined(_WIN32)
            // Check for hidden attribute.
            const DWORD Attributes = GetFileAttributes(path.c_str());
            if ((Attributes != INVALID_FILE_ATTRIBUTES) && (Attributes & FILE_ATTRIBUTE_HIDDEN))
                return true;
            #endif // _WIN32

            // Filenames starting with . are hidden in Linux, but
            // we do this check for windows as well.
            if (getFileName(path)[0] == '.')
                return true;

            return false;
        }

    } // FileSystem::
} // Utils::