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

    File: Process.Unix.cpp
    File: Process.Linux.cpp
    Date: 2021-6-12
    Author: Reece
***/
#include <RuntimeInternal.hpp>
#include "Processes.hpp"
#include "Process.Unix.hpp"

#include <unistd.h>
#include <fcntl.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <sys/wait.h>

//#include <Source/Threading/Primitives/Semaphore.Unix.hpp>

namespace Aurora::Processes
{
    struct ProcessImpl;

    static AuThreadPrimitives::RWLockUnique_t gRWLock;
    static AuHashMap<pid_t, ProcessImpl *> gPidLookupMap; 

    ProcessImpl::ProcessImpl(const StartupParmaters &params) : startup_(params)
    {
        AuIOFS::NormalizePath(this->startup_.process, this->startup_.process);

        this->startup_.args.insert(startup_.args.begin(), startup_.process);

        for (const auto &arg : this->startup_.args)
        {
            this->cargs_.push_back(arg.c_str());
            this->debug_ += arg + " ";
        }

        this->cargs_.push_back(nullptr);
        if (this->debug_.size())
        {
            this->debug_.resize(this->debug_.size() - 1);
        }
    }

    ProcessImpl::~ProcessImpl()
    {
        if (this->type_ == ESpawnType::eSpawnChildProcessWorker)
        {
            TryKill();
            Terminate();
        }

       {
            AU_LOCK_GUARD(gRWLock->AsWritable());

            if (this->alive_)
            {
                if (this->type_ == ESpawnType::eSpawnThreadLeader)
                {
                    ::kill(this->pidt_, SIGCONT);
                }
            }

            AuTryRemove(gPidLookupMap, this->pidt_);
        }

        ShutdownPipes();
    }

    AuUInt ProcessImpl::GetProcessId()
    {
        return this->pidt_;
    }

    void ProcessImpl::ByeLol(AuSInt code)
    {
        this->exitCode_ = code;

        if (this->finished_)
        {
            this->finished_->Set();
        }
    }

    void ProcessImpl::ShutdownPipes()
    {
        if (auto fd = AuExchange(pipeStdErr_[0], {})) close(fd);
        if (auto fd = AuExchange(pipeStdErr_[1], {})) close(fd);
        if (auto fd = AuExchange(pipeStdOut_[0], {})) close(fd);
        if (auto fd = AuExchange(pipeStdOut_[1], {})) close(fd);
        if (auto fd = AuExchange(pipeStdIn_[0],  {})) close(fd);
        if (auto fd = AuExchange(pipeStdIn_[1],  {})) close(fd);
    }

    bool ProcessImpl::TryKill()
    {
        AU_LOCK_GUARD(gRWLock->AsReadable());
        
        if (this->alive_)
        {
            return ::kill(this->pidt_, SIGTERM) == 0;
        }

        return true;
    }

    bool ProcessImpl::Terminate()
    {
        AU_LOCK_GUARD(gRWLock->AsReadable());

        if (this->alive_)
        {
            return ::kill(this->pidt_, SIGKILL) == 0;
        }
        
        return true;
    }

    AuSPtr<Aurora::Threading::IWaitable> ProcessImpl::AsWaitable()
    {
        return this->finished_;
    }

    AuSInt ProcessImpl::GetExitCode()
    {
        return this->exitCode_;
    }

    bool ProcessImpl::Read(EStandardHandle stream, const AuMemoryViewStreamWrite &destination, bool nonblock)
    {
        auto handle = stream == EStandardHandle::eStdError ? this->pipeStdErr_[0] : this->pipeStdOut_[0];
        if (handle < 0)
        {
            return false;
        }

        auto control = fcntl(handle, F_GETFL);
        auto ref = control;

        if (nonblock)
        {
            control |= O_NONBLOCK;
        }
        else
        {
            control &= ~O_NONBLOCK;
        }

        if (ref != control)
        {
            fcntl(handle, F_SETFL, control);
        }

        auto tmp = read(handle, destination.ptr, destination.length);
        if (tmp < 0)
        {
            return false;
        }

        destination.outVariable = tmp;
        return true;
    }

    bool ProcessImpl::Write(const AuMemoryViewStreamRead &source)
    {
        auto handle = this->pipeStdIn_[1];
        if (!handle)
        {
            return false;
        }

        return write(handle, source.ptr, source.length) == source.length;
    }

    bool ProcessImpl::Init()
    {
        if (this->startup_.fwdOut)
        {
            if (!pipe(this->pipeStdOut_))
            {
                return false;
            }
        }

        if (this->startup_.fwdErr)
        {
            if (!pipe(this->pipeStdErr_))
            {
                return false;
            }
        }

        if (this->startup_.fwdIn)
        {
            if (!pipe(this->pipeStdIn_))
            {
                return false;
            }
        }

        this->finished_ = AuThreadPrimitives::EventShared(false, false, true);
        return bool(this->finished_);
    }

    bool ProcessImpl::Start()
    {
        this->exitCode_ = 0x10110100;

        if (this->type_ == ESpawnType::eSpawnOvermap)
        {
            execv(this->startup_.process.c_str(), (char *const *)this->cargs_.data()); // https://pubs.opengroup.org/onlinepubs/9699919799/functions/exec.html
            SysPushErrorGen("execv didn't overwrite the process map, given {} ({})", this->startup_.process, this->debug_);
            return false;
        }

        pid_t pid;
        {
            //Threading::Primitives::Semaphore semaphore;
            pid = fork();
            if (pid == 0)
            {
                    
                if (this->startup_.fwdIn)
                {
                    dup2(pipeStdIn_[0], STDIN_FILENO);
                    close(AuExchange(pipeStdIn_[0], 0));
                }
                    
                if (this->startup_.fwdErr)
                {
                    dup2(pipeStdErr_[1], STDERR_FILENO);
                    close(AuExchange(pipeStdErr_[1], 0));
                }
                    
                if (this->startup_.fwdOut)
                {
                    dup2(pipeStdOut_[1], STDOUT_FILENO);
                    close(AuExchange(pipeStdOut_[1], 0));
                }

                if (this->type_ != ESpawnType::eSpawnChildProcessWorker)
                {
                    setsid();
                }

                {
                    AU_LOCK_GUARD(gSpinLock->AsWritable());
                    AuTryInsert(gPidLookupMap, getpid(), this);
                }

                this->alive_ = true;

                //semaphore.Unlock();

                execv(this->startup_.process.c_str(), (char * const *)this->cargs_.data()); // https://pubs.opengroup.org/onlinepubs/9699919799/functions/exec.html
                
                SysPushErrorGen("execv didn't overwrite the process map, given {} ({})", this->startup_.process, this->debug_);
                return false;
            }
            else if (pid < 0)
            {
                return false;
            }
            else
            {
                this->pidt_ = pid;
                //semaphore.Lock();
            }
        }

        return true;
    }
    
    AUKN_SYM IProcess *SpawnNew(const StartupParmaters &params)
    {
        auto ret = _new ProcessImpl(params);

        if (!ret)
        {
            return {};
        }

        if (!ret->Init())
        {
            delete ret;
            return {};
        }

        return ret;
    }

    AUKN_SYM void SpawnRelease(IProcess *process)
    {
        AuSafeDelete<ProcessImpl *>(process);
    }

    static void HandleChildTermiantion(pid_t pid, int code)
    {
        AU_LOCK_GUARD(gRWLock->AsReadable());

        auto handler = gPidLookupMap.find(pid);
        if (handler == gPidLookupMap.end()) return;

        {
            auto process = *handler;
            process.second->ByeLol(code);
        }
    }

    static void SigChldHandler(int)
    {
        int code;
        pid_t pid;

        while (true)
        {
            pid = wait3(&code, WNOHANG, nullptr);

            if ((pid == 0) || 
                (pid == -1))
            {
                break;
            }
            
            HandleChildTermiantion(pid, code);
        }
    }

    void InitUnix()
    {
        signal(SIGCHLD, SigChldHandler);
        gRWLock = AuThreadPrimitives::RWLockUnique();
    }

    void DeinitUnix()
    {
        gRWLock.reset();
    }
}