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

    File: ConsoleStd.cpp
    Date: 2021-6-8
    Author: Reece
***/
#include <Source/RuntimeInternal.hpp>
#include "ConsoleStd.hpp"
#include "Source/Locale/Locale.hpp"

#if defined(AURORA_IS_MODERNNT_DERIVED) || defined(AURORA_IS_POSIX_DERIVED) 

    #if defined(AURORA_IS_MODERNNT_DERIVED)
        // nothing yet
    #elif defined(AURORA_IS_POSIX_DERIVED)
        #define IO_POSIX_STREAMS

        #include <stdio.h>
        #include <sys/select.h>
        #include <unistd.h>
    #endif 

    // compile time preprocessor definition to strip std stream based IO
    #if !(defined(AURORA_DISABLE_STD_CONSOLE))
        #define ENABLE_STD_CONSOLE
    #endif
#endif

namespace Aurora::Console::ConsoleStd
{
#if defined(ENABLE_STD_CONSOLE) 

#if defined(AURORA_IS_MODERNNT_DERIVED)
    #define DEFAULT_HANDLE_VAL INVALID_HANDLE_VALUE
    using StreamHandle_t = HANDLE;
   
    static StreamHandle_t     gWin32Thread = INVALID_HANDLE_VALUE;
#elif defined(IO_POSIX_STREAMS)
    #define DEFAULT_HANDLE_VAL 0xFFFFFFFF
    using StreamHandle_t = int;
#endif
    #define IS_STREAM_HANDLE_VALID(h) (h != DEFAULT_HANDLE_VAL)

    static bool AsyncReadAnyOrReadStreamBlock();

    static const AuMach        kLineBufferMax = 2048;
    static AuUInt8             gLineEncodedBuffer[kLineBufferMax];
    static AuUInt              gEncodedIndex = 0;
    static AuString            gLineBuffer(kLineBufferMax, 0);
    static AuUInt              gLineIndex = 0;
    static StreamHandle_t      gTerminateConsole;
    static StreamHandle_t      gInputStream = DEFAULT_HANDLE_VAL;
    static StreamHandle_t      gOutputStream = DEFAULT_HANDLE_VAL;
    
    static AuThreadPrimitives::SpinLock gRingLock;

    
    #if defined(AURORA_IS_MODERNNT_DERIVED)
    static DWORD WINAPI StdInWin32Thread(void*)
    {
        HANDLE a[2] = {gInputStream, gTerminateConsole};

        while (true)
        {
            WaitForMultipleObjectsEx(2, a, false, 25, 0);

            if (WaitForSingleObject(gTerminateConsole, 0) == WAIT_OBJECT_0)
            {
                break;
            }

            AsyncReadAnyOrReadStreamBlock();
        }

        return 1;
    }
    #endif

    static void StartLogger()
    {
        if (gRuntimeConfig.console.enableStdPassthrough && gRuntimeConfig.console.enableStdOut)
        {
            return;
        }

        Console::Hooks::AddFunctionalHook([](const Aurora::Console::ConsoleMessage &string) -> void
        {
        #if (defined(DEBUG) || defined(STAGING)) && defined(AURORA_IS_MODERNNT_DERIVED)
            auto debugLine = string.ToSimplified() + "\r\n";
            OutputDebugStringW(Locale::ConvertFromUTF8(debugLine).c_str());
        #endif 

            if (!gRuntimeConfig.console.enableStdOut)
            {
                return;
            }

            auto writeLine = string.ToConsole();

        #if defined(AURORA_IS_MODERNNT_DERIVED)
            writeLine += '\r';
        #endif 
            writeLine += '\n';

        #if defined(IO_POSIX_STREAMS)
            if (Locale::GetInternalCodePage() == Locale::ECodePage::eUTF8)
            {
                WriteStdOut(writeLine.data(), writeLine.size());
            }
            else
            {
                AuString slow;
                slow.resize(writeLine.size() * 4);
                auto len = Locale::Encoding::EncodeUTF8(writeLine, Aurora::Memory::MemoryViewWrite {slow.data(), slow.size()}, Locale::ECodePage::eSysUnk);
                if (len.first != 0)
                {
                    WriteStdOut(slow.data(), len.second);
                }
                else
                {
                    // better write this than nothing
                    WriteStdOut(writeLine.data(), writeLine.size());
                }
            }

        #elif defined(AURORA_IS_MODERNNT_DERIVED)
            WriteStdOut(writeLine.data(), writeLine.size());
        #endif

        });
    }

    void Start()
    {
        static bool gConsoleStarted = false;
        if (std::exchange(gConsoleStarted, true)) return;

    #if defined(AURORA_IS_MODERNNT_DERIVED)

        DWORD dwMode;
        bool ok;
        // Obtain a win32 file HANDLE of STDIN
        auto fileHandle = CreateFileA("CONIN$",
                                      GENERIC_READ | GENERIC_WRITE,
                                      FILE_SHARE_READ,
                                      NULL,
                                      OPEN_EXISTING,
                                      FILE_ATTRIBUTE_NORMAL,
                                      NULL);
        
        SysAssert(fileHandle != INVALID_HANDLE_VALUE, "Couldn't open CONIN");
        gInputStream = fileHandle;

        // Obtain a win32 file HANDLE of STDOUT
        fileHandle = CreateFileA("CONOUT$",
                                 GENERIC_READ | GENERIC_WRITE,
                                 FILE_SHARE_READ | FILE_SHARE_WRITE,
                                 NULL,
                                 OPEN_EXISTING,
                                 FILE_ATTRIBUTE_NORMAL,
                                 NULL);

        SysAssert(fileHandle != INVALID_HANDLE_VALUE, "Couldn't open CONOUT");
        gOutputStream = fileHandle;
    
        // Get current console flags
        if (GetConsoleMode(gOutputStream, &dwMode))
        {
            if (gRuntimeConfig.console.enableStdPassthrough ^ gRuntimeConfig.console.enableStdOut)
            {
                // Enable escape processing; enable colored output
                dwMode |= ENABLE_PROCESSED_OUTPUT | ENABLE_VIRTUAL_TERMINAL_PROCESSING;
                ok = SetConsoleMode(gOutputStream, dwMode);
                SysAssert(ok, "Couldn't set console mode");

                // Set the output stream to use UTF-8
                ok = SetConsoleOutputCP(CP_UTF8);
                SysAssert(ok, "Couldn't maintain UTF-8 stdout stream");
            }
        }

        // Set binary mode if redirecting stdin to user
        if (gRuntimeConfig.console.enableStdPassthrough && gRuntimeConfig.console.enableStdOut)
        {
            SetConsoleMode(gOutputStream, 0);
        }
        
        if (gRuntimeConfig.console.enableStdPassthrough ^ gRuntimeConfig.console.enableStdIn)
        {
            ok = SetConsoleCP(CP_UTF8);
        #if 0
            SysAssert(ok, "Couldn't maintain UTF-8 stdin stream");
        #endif

        } 
        
        if (gRuntimeConfig.console.enableStdPassthrough && gRuntimeConfig.console.enableStdIn)
        {
            if (!GetConsoleMode(gInputStream, &dwMode))
            {
                ok = SetConsoleMode(gInputStream, dwMode & ~(ENABLE_PROCESSED_INPUT | ENABLE_LINE_INPUT));
                SysAssert(ok, "Couldn't maintain binary stdin stream");
            }
        }
        else
        {
            gTerminateConsole = CreateEvent(nullptr, true, false, nullptr);
            gWin32Thread      = CreateThread(nullptr, 0, StdInWin32Thread, nullptr, 0, nullptr);
        }

    #elif defined(AURORA_IS_POSIX_DERIVED)
    
        gInputStream  = STDIN_FILENO;
        gOutputStream = STDOUT_FILENO;

    #endif 

        SysAssert(gInputStream, "Couldn't allocate input stream handler");
        SysAssert(gOutputStream, "Couldn't allocate output stream handler");

        StartLogger();
    }

    void Init()
    {

    #if defined(AURORA_PLATFORM_WIN32)

        if (GetConsoleWindow() == NULL)
        {
            if (!gRuntimeConfig.console.enableConsole)
            {
                return;
            }

            if (!gRuntimeConfig.console.forceConsoleWindow)
            {
                return;
            }

            auto ok = AllocConsole();
            SysAssert(ok, "Request of a Win32 console yielded nada, forceConsole wasn't respected");
        }
        else
        {
            // Under windows, applications linked with the console subsystem flag should have output no matter what disableAll/forceConsoleWindow says
            // The amount of effort it takes to link as console app for a conhost window far exceeds whatever 'forceConsoleWindow' is defined as
            // One does not simply switch over to conapp for the fun of it. We can't or at least shouldn't destroy or hide conhost with hacks 
            // Assuming stdconsole is wanted - DO NOT RETURN - LINK AS A WINDOWED APP IF YOU DO NOT WANT A CONSOLE WINDOW
        } 
    
    #elif defined(AURORA_IS_POSIX_DERIVED)
        
        // no always means no under UNIX targets
        // we *know* stdin/out will be available under these standards
        if (gRuntimeConfig.console.disableAllConsoles)
        {
            return;
        }
        
    #endif
    
        Start();
    }

    AuUInt32 WriteStdOut(const void *data, AuUInt32 length)
    {
        if (!IS_STREAM_HANDLE_VALID(gOutputStream))
        {
            return 0;
        }

    #if defined(IO_POSIX_STREAMS)
        AuInt32 written = write(gOutputStream, data, length);
        if (written < 0)
        {
            return 0;
        }
    #elif defined(AURORA_IS_MODERNNT_DERIVED)
        DWORD written;
        if (!WriteFile(gOutputStream, data, length, &written, NULL))
        {
            return 0;
        }
    #endif

        return written;
    }
    
    static bool InputStreamAvailable()
    {
    #if defined(IO_POSIX_STREAMS)
        timeval tv {};
        fd_set fds {};
        FD_ZERO(&fds);
        FD_SET(gInputStream, &fds);
        select(gInputStream + 1, &fds, NULL, NULL, &tv);
        return (FD_ISSET(0, &fds));
    #elif defined(AURORA_IS_MODERNNT_DERIVED)
        // Inline non-blocking is not legal on windows. 
        // One can force it with the overlapped flag, seemingly valid since win8, but defined as illegal since the 90s 
        return false; 
    #else
        return false;
    #endif
    }

    AuUInt32 ReadStdIn(void *data, AuUInt32 length)
    {
        Pump();

        gRingLock.Lock();
        auto readable = std::min(AuUInt32(length), AuUInt32(gEncodedIndex));

        std::memcpy(data, gLineEncodedBuffer, readable);

        const auto remainingBytes = gEncodedIndex - readable;
        if (remainingBytes)
        {
            std::memmove(gLineEncodedBuffer, &gLineEncodedBuffer[readable], remainingBytes);
        }

        gEncodedIndex = remainingBytes;
        gRingLock.Unlock();
        return readable;
    }

    static void ProcessLines()
    {
        AuMach index = 0, startIdx = 0;

        if (gLineIndex == 0)
        {
            return;
        }

        auto end = gLineBuffer.data() + gLineIndex;

        while (true)
        {
            auto a = std::find(gLineBuffer.data() + startIdx, end, '\n');
            if (a == end) break;
            index = a - gLineBuffer.data();

            auto line = gLineBuffer.substr(startIdx, index - startIdx);
            startIdx  = index + 1;

            if (line[line.size() - 1] == '\r')
            {
                line.pop_back();
            }

            if (line.size())
            {
                Console::DispatchRawLine(line);
            }
        }

        if (index != 0)
        {
            const auto remainingBytes = gLineIndex - startIdx;
            if (remainingBytes)
            {
                std::memmove(gLineBuffer.data(), &gLineBuffer.data()[startIdx], remainingBytes);
                gLineIndex -= startIdx;
            }
        }
    }

    static void ProcessLinesSysCP()
    {
    #if defined(AURORA_IS_MODERNNT_DERIVED)
        static Locale::Encoding::TextStreamEncoder stream(Locale::ECodePage::eUTF8);
    #else
        static Locale::Encoding::TextStreamEncoder stream(Locale::GetInternalCodePage());
    #endif

        AU_LOCK_GUARD(&gRingLock);

        auto ret = stream.DecodeUTF8(gLineEncodedBuffer, gEncodedIndex, gLineBuffer.data() + gLineIndex, gLineBuffer.size() - gLineIndex);

        // increment backline buffer
        {
            const auto remainingBytes = gEncodedIndex - ret.first;
            if (remainingBytes)
            {
                std::memmove(gLineEncodedBuffer, &gLineEncodedBuffer[ret.first], remainingBytes);
            }

            gEncodedIndex = remainingBytes;
        }

        // increment frontline buffer
        {
            gLineIndex += ret.second;
        }

        ProcessLines();
    }

    static AuUInt32 SyncReadConsole()
    {
        void *data  = &gLineEncodedBuffer[gEncodedIndex];
        auto length = kLineBufferMax - gEncodedIndex;

        if (!IS_STREAM_HANDLE_VALID(gInputStream))
        {
            return 0;
        }

        if (length == 0)
        {
            return 0;
        }

    #if defined(AURORA_IS_MODERNNT_DERIVED)

        DWORD read = length;
        if (!ReadFile(gInputStream, data, read, &read, NULL))
        {
            return 0;
        }
        
        gRingLock.Lock();
        gEncodedIndex += read;
        gRingLock.Unlock();

        return read;

    #elif defined(IO_POSIX_STREAMS)
        
        auto bread = ::read(gInputStream, data, length);
        if (bread < 0)
        { 
            return 0;
        }
        
        gRingLock.Lock();
        gEncodedIndex += bread;
        gRingLock.Unlock();

        return bread;

    #else

        return 0;

    #endif
    }

    static bool AsyncReadAnyOrReadStreamBlock()
    {
        if (!SyncReadConsole())
        {
            return false;
        }
        
        if (gRuntimeConfig.console.enableStdPassthrough && gRuntimeConfig.console.enableStdIn)
        {
            return true;
        }
     
        ProcessLinesSysCP();
        return true;
    }

    void Pump()
    {
        if (!gRuntimeConfig.console.enableStdPassthrough && !gRuntimeConfig.console.enableStdIn)
        {
            return;
        }

        if (!IS_STREAM_HANDLE_VALID(gInputStream))
        {
            return;
        }

        if (!InputStreamAvailable())
        {
            return;
        }
        
        AsyncReadAnyOrReadStreamBlock();
    }

    void Exit()
    {
        if (IS_STREAM_HANDLE_VALID(gTerminateConsole))
        {
        #if defined(AURORA_IS_MODERNNT_DERIVED)
            SetEvent(gTerminateConsole);
        #endif
        }

    #if defined(AURORA_IS_MODERNNT_DERIVED)

        if (IS_STREAM_HANDLE_VALID(gWin32Thread))
        {
            CancelSynchronousIo(gWin32Thread);
            if (WaitForSingleObject(gWin32Thread, 200) != WAIT_OBJECT_0)
            {
                TerminateThread(gWin32Thread, 0);
            }
        }

        AuWin32CloseHandle(gWin32Thread);
        AuWin32CloseHandle(gTerminateConsole);
        
        // Note: CloseHandle in the middle of a ReadFile blocks
        AuWin32CloseHandle(gInputStream);
        AuWin32CloseHandle(gOutputStream);

    #endif
        
    }

#else
    
    void Pump()
    {
    }
    
    void Init()
    {
    }

    void Exit()
    {
    }
    
    void Start()
    {
    }
#endif
}