#include "hecl/SteamFinder.hpp"
#include "hecl/hecl.hpp"
#ifdef WIN32
#include <winreg.h>
#define PATH_SEP L'\\'
#else
#define PATH_SEP '/'
#endif

namespace hecl
{

/* Used to extract alternate steam install directories from libraryfolders.vdf */
static const std::regex regSteamPath(R"(^\s+\"[0-9]+\"\s+\"(.*)\")",
                                     std::regex::ECMAScript|std::regex::optimize);

hecl::SystemString FindCommonSteamApp(const hecl::SystemChar* name)
{
    hecl::SystemString steamInstallDir;
    hecl::Sstat theStat;

#ifdef WIN32
    HKEY hkey;
    hecl::SystemChar _steamInstallDir[MAX_PATH] = {0};
    if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, _S("Software\\Valve\\Steam"),
                     0, KEY_QUERY_VALUE, &hkey) != ERROR_SUCCESS)
    {
        if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, _S("Software\\Valve\\Steam"),
                         0, KEY_QUERY_VALUE | KEY_WOW64_32KEY, &hkey) != ERROR_SUCCESS)
            return {};
    }

    DWORD size = MAX_PATH;
    if (RegQueryValueEx(hkey, _S("InstallPath"), nullptr, nullptr,
                        (LPBYTE)_steamInstallDir, &size) == ERROR_SUCCESS)
        steamInstallDir = _steamInstallDir;
    RegCloseKey(hkey);

    if (steamInstallDir.empty())
        return {};

#elif defined(__APPLE__)
    steamInstallDir = getenv("HOME");
    steamInstallDir += "/Library/Application Support/Steam";
    if (hecl::Stat(steamInstallDir.c_str(), &theStat) || !S_ISDIR(theStat.st_mode))
        return {};

#else
    steamInstallDir = getenv("HOME");
    steamInstallDir += "/.local/share/Steam";
    if (hecl::Stat(steamInstallDir.c_str(), &theStat) || !S_ISDIR(theStat.st_mode))
    {
        steamInstallDir = getenv("HOME");
        steamInstallDir += "/.steam/steam";
        if (hecl::Stat(steamInstallDir.c_str(), &theStat) || !S_ISDIR(theStat.st_mode))
            return {};
    }

#endif

    hecl::SystemString appPath = hecl::SystemString(_S("common")) + PATH_SEP + name;

    /* Try main steam install directory first */
    hecl::SystemString steamAppsMain = steamInstallDir + PATH_SEP + _S("steamapps");
    hecl::SystemString mainAppPath = steamAppsMain + PATH_SEP + appPath;
    if (!hecl::Stat(mainAppPath.c_str(), &theStat) && S_ISDIR(theStat.st_mode))
        return mainAppPath;

    /* Iterate alternate steam install dirs */
    hecl::SystemString libraryFoldersVdfPath = steamAppsMain + PATH_SEP + _S("libraryfolders.vdf");
    FILE* fp = hecl::Fopen(libraryFoldersVdfPath.c_str(), _S("r"));
    if (!fp)
        return {};
    hecl::FSeek(fp, 0, SEEK_END);
    int64_t fileLen = hecl::FTell(fp);
    if (fileLen <= 0)
    {
        fclose(fp);
        return {};
    }
    hecl::FSeek(fp, 0, SEEK_SET);
    std::string fileBuf;
    fileBuf.resize(fileLen);
    if (fread(&fileBuf[0], 1, fileLen, fp) != fileLen)
    {
        fclose(fp);
        return {};
    }
    fclose(fp);

    std::smatch dirMatch;
    auto begin = fileBuf.cbegin();
    auto end = fileBuf.cend();
    while (std::regex_search(begin, end, dirMatch, regSteamPath))
    {
        std::string match = dirMatch[1].str();
        hecl::SystemStringView otherInstallDir(match);
        hecl::SystemString otherAppPath = otherInstallDir.sys_str() + PATH_SEP +
            _S("steamapps") + PATH_SEP + appPath;
        if (!hecl::Stat(otherAppPath.c_str(), &theStat) && S_ISDIR(theStat.st_mode))
            return otherAppPath;
        begin = dirMatch.suffix().first;
    }

    return {};
}

}