/***
    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)
    {
        return mkdir(path.c_str(), 0775) == 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.exists          = 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)
    {
        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->existsFile)
            {
                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->existsDirectory)
            {
                continue;
            }

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

        return true;
    }
    
    AUKN_SYM bool WriteFile(const AuString &path, const Memory::MemoryViewRead &blob)
    {
        auto file = OpenWriteUnique(path);
        SysCheckReturn(file, false);

        AuUInt written = blob.length;
        if (!file->Write(Memory::MemoryViewStreamRead(blob, written)))
        {
            SysPushErrorMem();
            return false;
        }
         
        if (written != blob.length)
        {  
            SysPushErrorIO();
            return false;
        }

        return true;
    }    

    AUKN_SYM bool ReadFile(const AuString &path, AuByteBuffer &buffer)
    {
        AuUInt read;

        auto file = OpenReadUnique(path, EFileAdvisoryLockLevel::eNoSafety);
        SysCheckReturn(file, false);
        
        auto len  = file->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 (len == 0)
        {
            if (AuStartsWith(path, "/proc/") ||
                AuStartsWith(path, "/sys/") ||
                AuStartsWith(path, "/dev/"))
            {
                len = 4096 * 10;
            }
            else
            {
                buffer.clear();
                return true;
            }
        }

        if (!AuTryResize(buffer, len))
        {
            SysPushErrorMem();
            return false;
        }

        if (!file->Read(Memory::MemoryViewStreamWrite {buffer.begin(), buffer.end(), read})) 
        {
            SysPushErrorIO();
            return false; 
        }
        
        // NOTE: File devices love to lie
        //       Do not entertain an arbitrarily large page length provided by non-regular fds

        return AuTryResize(buffer, read);
    }

    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)
    {
        return UnixExists(NormalizePathRet(path), false);
    }

    AUKN_SYM bool DirExists(const AuString &path)
    {
        return UnixExists(NormalizePathRet(path), true);
    }
    
    AUKN_SYM bool DirMk(const AuString &path)
    {
        return CreateDirectories(NormalizePathRet(path), false);
    }

    AUKN_SYM bool Remove(const AuString &path)
    {
        return remove(NormalizePathRet(path).c_str()) != -1;
    }

    AUKN_SYM bool Relink(const AuString &src, const AuString &dest)
    {
        return rename(NormalizePathRet(src).c_str(), NormalizePathRet(dest).c_str()) != -1;
    }

#if defined(AURORA_IS_LINUX_DERIVED)

    AUKN_SYM bool Copy(const AuString &src, const AuString &dest)
    {
        auto normalizedSrcPath  = NormalizePathRet(src);
        auto normalizedDestPath = NormalizePathRet(dest);

        int input, output;

        if ((input = open(normalizedSrcPath.c_str(), O_RDONLY)) == -1)
        {
            return false;
        }

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

        if ((output = creat(normalizedDestPath.c_str(), fileinfo.st_mode)) == -1)
        {
            close(input);
            return false;
        }

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

        close(input);
        close(output);
        return result;    
    }
    
#elif defined(AURORA_IS_BSD_DERIVED)

    AUKN_SYM bool Copy(const AuString &src, const AuString &dest)
    {
        auto normalizedSrcPath  = NormalizePathRet(src);
        auto normalizedDestPath = NormalizePathRet(dest);

        int input, output;

        if ((input = open(normalizedSrcPath.c_str(), O_RDONLY)) == -1)
        {
            return false;
        }

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

        if ((output = creat(normalizedDestPath.c_str(), fileinfo.st_mode)) == -1)
        {
            close(input);
            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 = {};
        auto path = NormalizePathRet(pathRel);

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

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

        stat.existsFile           = S_ISREG(s.st_mode);
        stat.existsDirectory      = S_ISDIR(s.st_mode);
        stat.existsSystemResource = S_ISSOCK(s.st_mode);
        stat.exists               = stat.existsFile || stat.existsDirectory || stat.existsSystemResource;

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

        stat.size = s.st_size;

        stat.created  = Time::CTimeToMS(s.st_ctime);
        stat.modified = Time::CTimeToMS(s.st_mtime);
        stat.accessed = Time::CTimeToMS(s.st_atime);

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

        return true;
    }
}
#endif