/***
    Copyright (C) 2021 J Reece Wilson (a/k/a "Reece"). All rights reserved.

    File: FS.Unix.cpp
    Date: 2021-6-12
    Author: Reece
***/
#include <Source/RuntimeInternal.hpp>
#include "FS.hpp"
#include "FS.Generic.hpp"
#include <Source/Time/Time.hpp>

#if !defined(_AURUNTIME_GENERICFS)

#include <sys/types.h>
#include <dirent.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>

#if defined(AURORA_IS_LINUX_DERIVED)
    #include <sys/sendfile.h>
#endif

namespace Aurora::IO::FS
{
    bool _MkDir(const AuString &path)
    {
        AuString subdir;

        if ((path.size() > 1) && 
            ((path[path.size() - 1] == '/') ||
             (path[path.size() - 1] == '\\')))
        {
            subdir = path.substr(0, path.size() - 1);
        }
        else
        {
            subdir = path;
        }

        GoUpToSeparator(subdir, subdir);

        mode_t mode { 0775 };

        struct stat s;
        if (::stat(subdir.c_str(), &s) != -1)
        {
            mode = s.st_mode;
        }

        return ::mkdir(path.c_str(), mode) == 0;
    }

    struct ReadDirStructure : IReadDir
    {
        DIR *pDIR {};
        struct dirent *pDE {};
        bool bFirstTick { true };
        bool bDead { false };
        StatEx stat;
        AuString sPath;
        bool bFast {};

        ~ReadDirStructure()
        {
            if (this->pDIR)
            {
                ::closedir(this->pDIR);
            }
        }

        virtual StatEx *Next() override
        {
            bool bTryAgain {};

            if (this->bDead)
            {
                return {};
            }

            do 
            {
                if (!(this->pDE = ::readdir(this->pDIR)))
                {
                    this->bDead = true;
                    return {};
                }

                if (this->pDE->d_name == AuString(".") ||
                    this->pDE->d_name == AuString(".."))
                {
                    bTryAgain = true;
                    continue;
                }
                
                stat.bExists          = true;

                stat.fileName        = this->pDE->d_name;

                if (stat.fileName.empty())
                {
                    bTryAgain = true;
                    continue;
                }

                stat.path            = NormalizePathRet(this->sPath + stat.fileName);

                if (this->bFast)
                {
                //    nvm wont work. still need the is type dir/file flags
                //    return &stat;
                }

                if (!StatFile(stat.path.c_str(), stat))
                {
                    bTryAgain = true;
                }

            }
            while (AuExchange(bTryAgain, false));

            return &stat;
        }
    };

    static AuSPtr<IReadDir> ReadDirEx(const AuString &string, bool bFast)
    {
        if (string.empty())
        {
            SysPushErrorArg("Cannot open an IO handle to the provided empty path");
            return {};
        }

        auto pObj = AuMakeShared<ReadDirStructure>();
        if (!pObj)
        {
            SysPushErrorMem();
            return {};
        }

        pObj->bFast = bFast;

        if (!AuIOFS::NormalizePath(pObj->sPath, string))
        {
            SysPushErrorMem();
            return {};
        }

        if (!AuTryInsert(pObj->sPath, '/'))
        {
            SysPushErrorMem();
            return {};
        }

        pObj->pDIR = ::opendir(pObj->sPath.c_str());
        if (!pObj->pDIR)
        {
            SysPushErrorIO();
            return {};
        }

        return pObj;
    }

    AUKN_SYM AuSPtr<IReadDir> ReadDir(const AuString &string)
    {
        return ReadDirEx(string, false);
    }

    AUKN_SYM bool FilesInDirectory(const AuString &string, AuList<AuString> &files)
    {
        auto itr = ReadDirEx(string, true);
        if (!itr)
        {
            return false;
        }

        // SECURITY(): if next fails, its indistinguishable from end of file list, and will return true. it kinda sucks
        while (auto stat = itr->Next())
        {
            if (!stat->bExistsFile)
            {
                continue;
            }

            if (!AuTryInsert(files, stat->fileName))
            {
                return false;
            }
        }

        return true;
    }

    AUKN_SYM bool DirsInDirectory(const AuString &string, AuList<AuString> &dirs)
    {
        auto itr = ReadDirEx(string, true);
        if (!itr)
        {
            return false;
        }

        // SECURITY(): if next fails, its indistinguishable from end of file list, and will return true. it kinda sucks
        while (auto stat = itr->Next())
        {
            if (!stat->bExistsDirectory)
            {
                continue;
            }

            if (!AuTryInsert(dirs, stat->fileName))
            {
                return false;
            }
        }

        return true;
    }

    AUKN_SYM bool ReadFile(const AuString &path, AuByteBuffer &buffer)
    {
        AuMemoryViewWrite writeView;

        if (path.empty())
        {
            SysPushErrorArg("Cannot open an IO handle to the provided empty path");
            return false;
        }

        bool bIsStupidFD = 
            AuStartsWith(path, "/proc/") ||
            AuStartsWith(path, "/sys/") ||
            AuStartsWith(path, "/dev/");

        auto pFile = OpenReadUnique(path, bIsStupidFD ? EFileAdvisoryLockLevel::eNoSafety : EFileAdvisoryLockLevel::eBlockWrite);
        SysCheckReturn(pFile, false);
        
        bool bIsZero  = buffer.readPtr == buffer.base;
        auto qwLength = pFile->GetLength();

        // NOTE: Linux filesystems are such a cluster fuck of unimplemented interfaces and half-assed drivers
        //       It's not unusual for these "files" to not support the required seek operations across NIX-like oses.
        if (qwLength == 0)
        {
            if (bIsStupidFD)
            {
                qwLength = 4096 * 10;
            }
            else
            {
                return true;
            }
        }

        writeView = buffer.GetOrAllocateLinearWriteable(qwLength);
        if (!writeView)
        {
            return {};
        }

        AuUInt uLength { qwLength };
        if (!pFile->Read(Memory::MemoryViewStreamWrite { writeView, uLength }))
        {
            SysPushErrorIO();
            return false; 
        }

        // NOTE: File devices love to lie
        //       Do not entertain an arbitrarily large page length provided by non-regular fds

        buffer.writePtr += uLength;
        if (bIsZero)
        {
            AuTryDownsize(buffer, uLength);
        }
        
        return true;
    }

    static bool UnixExists(const AuString &path, bool dir)
    {
        struct stat s;
        int err = ::stat(path.c_str(), &s);
        if (-1 == err)
        {
            SysAssert(ENOENT == errno, "General File IO Error, path {}", path);
            return false;
        }
        return dir ? S_ISDIR(s.st_mode) : S_ISREG(s.st_mode);
    }
    
    AUKN_SYM bool FileExists(const AuString &path)
    {
        if (path.empty())
        {
            SysPushErrorArg("Cannot open an IO handle to the provided empty path");
            return false;
        }

        auto pathExpanded = NormalizePathRet(path);
        if (pathExpanded.empty())
        {
            SysPushErrorMemory();
            return false;
        }

        return UnixExists(pathExpanded, false);
    }

    AUKN_SYM bool DirExists(const AuString &path)
    {
        if (path.empty())
        {
            SysPushErrorArg("Cannot open an IO handle to the provided empty path");
            return false;
        }

        auto pathExpanded = NormalizePathRet(path);
        if (pathExpanded.empty())
        {
            SysPushErrorMemory();
            return false;
        }

        return UnixExists(pathExpanded, true);
    }
    
    AUKN_SYM bool DirMk(const AuString &path)
    {
        if (path.empty())
        {
            SysPushErrorArg("Cannot open an IO handle to the provided empty path");
            return false;
        }

        auto pathExpanded = NormalizePathRet(path);
        if (pathExpanded.empty())
        {
            SysPushErrorMemory();
            return false;
        }

        return CreateDirectories(pathExpanded, false);
    }

    AUKN_SYM bool Remove(const AuString &path)
    {
        struct stat s;

        if (path.empty())
        {
            SysPushErrorArg("Cannot open an IO handle to the provided empty path");
            return false;
        }

        auto pathExpanded = NormalizePathRet(path);
        if (pathExpanded.empty())
        {
            SysPushErrorMemory();
            return false;
        }

        if (::stat(pathExpanded.c_str(), &s) == -1)
        {
            if (errno == ENOENT)
            {
                return true;
            }
        }
        else
        {
            if (S_ISDIR(s.st_mode))
            {
                if (::rmdir(pathExpanded.c_str()) == 0)
                {
                    return true;
                }
            }

            if (S_ISREG(s.st_mode))
            {
                if (::unlink(pathExpanded.c_str()) == 0)
                {
                    return true;
                }
            }
        }

        if (::remove(pathExpanded.c_str()) == 0)
        {
            return true;
        }

        return false;
    }

    AUKN_SYM bool Relink(const AuString &src, const AuString &dest)
    {
        if (src.empty() ||
            dest.empty())
        {
            SysPushErrorArg("Cannot open an IO handle to the provided empty path");
            return false;
        }

        auto pathSrcExpanded = NormalizePathRet(src);
        auto pathExpanded = NormalizePathRet(dest);

        if (pathSrcExpanded.empty() ||
            pathExpanded.empty())
        {
            SysPushErrorMemory();
            return false;
        }

        return ::rename(pathSrcExpanded.c_str(), pathExpanded.c_str()) != -1;
    }

#if defined(AURORA_IS_LINUX_DERIVED)

    AUKN_SYM bool Copy(const AuString &src, const AuString &dest)
    {
        if (src.empty() ||
            dest.empty())
        {
            SysPushErrorArg("Cannot open an IO handle to the provided empty path");
            return false;
        }

        auto pathSrcExpanded = NormalizePathRet(src);
        auto pathExpanded = NormalizePathRet(dest);
        
        if (pathSrcExpanded.empty() ||
            pathExpanded.empty())
        {
            SysPushErrorMemory();
            return false;
        }

        CreateDirectories(pathExpanded, true);

        int input, output;

        if ((input = ::open(pathSrcExpanded.c_str(), O_RDONLY | O_CLOEXEC)) == -1)
        {
            return false;
        }

        struct stat fileinfo = { 0 };
        if (::fstat(input, &fileinfo) != 0)
        {
            ::close(input);
            SysPushErrorIO("fstat failed");
            return false;
        }

        if ((output = ::creat(pathExpanded.c_str(), fileinfo.st_mode)) == -1)
        {
            ::close(input);
            SysPushErrorIO("creat failed");
            return false;
        }

        off_t bytesCopied = 0;
        auto result = ::sendfile(output, input, &bytesCopied, fileinfo.st_size) != -1;

        ::close(input);
        ::close(output);
        return bytesCopied == fileinfo.st_size;    
    }
    
#elif defined(AURORA_IS_BSD_DERIVED)

    AUKN_SYM bool Copy(const AuString &src, const AuString &dest)
    {
        if (src.empty() ||
            dest.empty())
        {
            SysPushErrorArg("Cannot open an IO handle to the provided empty path");
            return false;
        }

        auto pathSrcExpanded = NormalizePathRet(src);
        auto pathExpanded = NormalizePathRet(dest);
        
        if (pathSrcExpanded.empty() ||
            pathExpanded.empty())
        {
            SysPushErrorMemory();
            return false;
        }

        CreateDirectories(pathExpanded, true);

        int input, output;

        if ((input = ::open(pathSrcExpanded.c_str(), O_RDONLY | O_CLOEXEC)) == -1)
        {
            return false;
        }

        struct stat fileinfo = { 0 };
        if (::fstat(input, &fileinfo) != 0)
        {
            close(input)
            SysPushErrorIO("fstat failed");
            return false;
        }

        if ((output = ::creat(pathExpanded.c_str(), fileinfo.st_mode)) == -1)
        {
            close(input);
            SysPushErrorIO("creat failed");
            return false;
        }

        auto result = ::fcopyfile(input, output, 0, COPYFILE_ALL) == 0;
        
        ::close(input);
        ::close(output);
        return result;    
    }
    
#else
    
    AUKN_SYM bool Copy(const AuString &src, const AuString &dest)
    {
        // TODO: not that i care
        return false;
    }
    
#endif
    
    AUKN_SYM bool StatFile(const AuString &pathRel, Stat &stat)
    {
        stat = {};

        if (pathRel.empty())
        {
            SysPushErrorArg("Cannot open an IO handle to the provided empty path");
            return false;
        }

        auto path = NormalizePathRet(pathRel);
        if (path.empty())
        {
            SysPushErrorMemory();
            return false;
        }

        struct stat s;
        auto err = ::stat(path.c_str(), &s);

        if (err == -1)
        {
            if (ENOENT != errno)
            {
                SysPushErrorIO("Critical IO error while stating file (errno: {}, path: {})", errno, path);
            }
            return false;
        }

        stat.bExistsFile           = S_ISREG(s.st_mode);
        stat.bExistsDirectory      = S_ISDIR(s.st_mode);
        stat.bExistsSystemResource = S_ISSOCK(s.st_mode);
        stat.bExists               = stat.bExistsFile || stat.bExistsDirectory || stat.bExistsSystemResource;

        if (!stat.bExists)
        {
            SysPushErrorIO("Missing attribute type in stat mode {} (of path {})", s.st_mode, path);
            return false;
        }

        stat.uSize = s.st_size;


    #if defined(AURORA_IS_LINUX_DERIVED)
        stat.createdNs  = AuUInt64(s.st_ctim.tv_nsec) + AuMSToNS<AuUInt64>(Time::CTimeToMS(s.st_ctim.tv_sec));
        stat.modifiedNs = AuUInt64(s.st_mtim.tv_nsec) + AuMSToNS<AuUInt64>(Time::CTimeToMS(s.st_mtim.tv_sec));
        stat.accessedNs = AuUInt64(s.st_atim.tv_nsec) + AuMSToNS<AuUInt64>(Time::CTimeToMS(s.st_atim.tv_sec));
    #else
        stat.createdNs  = AuMSToNS<AuUInt64>(Time::CTimeToMS(s.st_ctime));
        stat.modifiedNs = AuMSToNS<AuUInt64>(Time::CTimeToMS(s.st_mtime));
        stat.accessedNs = AuMSToNS<AuUInt64>(Time::CTimeToMS(s.st_atime));
    #endif

        err = lstat(path.c_str(), &s);
        if (err != -1)
        {
            stat.bSymLink = S_ISLNK(s.st_mode);
        }

        return true;
    }
}
#endif