/***
    Copyright (C) 2022 J Reece Wilson (a/k/a "Reece"). All rights reserved.

    File: IOAdapterAsyncStream.cpp
    Date: 2022-6-6
    Author: Reece
***/
#include <Source/RuntimeInternal.hpp>
#include <Aurora/IO/IOExperimental.hpp>
#include "IOAdapterAsyncStream.hpp"
#include "IOWaitableIOLoopSource.hpp"

namespace Aurora::IO
{
    struct AsyncStreamAdapater;

    struct AsyncStreamReader : IAsyncStreamReader
    {
        AsyncStreamAdapater *parent;

        EStreamError IsOpen() override;
        EStreamError Read(const Memory::MemoryViewStreamWrite &parameters) override;
        void Close() override;

        EStreamError BeginRead(const AuSPtr<Memory::MemoryViewWrite> &internalView) override;
        EStreamError Dequeue(AuUInt reqLength, Memory::MemoryViewWrite &out) override;
    };
  
    struct AsyncStreamMemory : AuMemoryViewWrite
    {
        AsyncStreamMemory(const AuMemoryViewWrite &ref);
        AsyncStreamMemory(const AuSPtr<AuMemoryViewWrite> &ref);
        AsyncStreamMemory(AuUInt length);
        ~AsyncStreamMemory();

        bool IsValid();
        AuSPtr<AuMemoryViewWrite> pin;
        AuUInt streamIndex {};
        // todo shared
    };

    struct AsyncStreamWriter : IStreamWriter
    {
        ~AsyncStreamWriter();
        AsyncStreamAdapater *parent;

        EStreamError IsOpen() override;
        EStreamError Write(const Memory::MemoryViewStreamRead &parameters) override;
        void Close() override;
        void Flush() override;

        void Preframe();
        void Frame();

        AuList<AuSPtr<AsyncStreamMemory>> writesPending;
        bool HasWorkItems();
        bool used {};
    };

    struct AsyncStreamAdapater : IAsyncStreamAdapater, AuEnableSharedFromThis<AsyncStreamAdapater>
    {
        AsyncStreamAdapater();

        AuSPtr<AsyncStreamMemory> AllocateNextPageCached(AuUInt length);

        virtual AuSPtr<IAsyncStreamReader> ToStreamReader() override;
        virtual AuSPtr<IStreamWriter> ToStreamWriter() override;

        virtual AuSPtr<IIOWaitableItem> ToWaitable() override;

        virtual bool Reset() override;

        bool Init(const AuSPtr<IAsyncTransaction> &transaction, bool isStream);

        AuSPtr<AsyncStreamMemory> lastAllocation;
        AuSPtr<IAsyncTransaction> transaction;

        bool   SetFlushOnWrite(bool value) override;

        void   ReserveBuffer(AuUInt length) override;

        AuUInt GetReadOffset();
        AuUInt SetReadOffset(AuUInt offset);

        AuUInt GetWriteOffset();
        AuUInt SetWriteOffset(AuUInt offset);

        bool asyncActive {};
        AuUInt readOffset {};
        AuUInt writeOffset {};
        bool isStream {};

        bool flushOnWrite {true};

        AuOptionalEx<EStreamError> errorCode;
        int locked {};

        AsyncStreamReader reader;
        AsyncStreamWriter writer;
        IOWatachableIOLoopSource source;
    };


    AsyncStreamMemory::AsyncStreamMemory(const AuMemoryViewWrite &ref) :
        AuMemoryViewWrite(ref.ptr, ref.length)
    {

    }
    
    AsyncStreamMemory::AsyncStreamMemory(const AuSPtr<AuMemoryViewWrite> &ref) :
        AuMemoryViewWrite(ref->ptr, ref->length),
        pin(ref)
    {

    }

    AsyncStreamMemory::AsyncStreamMemory(AuUInt length) : AuMemoryViewWrite(AuMemory::ZAlloc<AuUInt8*>(length), length)
    {

    }

    AsyncStreamMemory::~AsyncStreamMemory()
    {
        if (this->ptr)
        {
            AuMemory::Free(this->ptr);
            this->ptr = nullptr;
        }
    }

    bool AsyncStreamMemory::IsValid()
    {
        return bool(this->ptr);
    }

    bool   AsyncStreamAdapater::SetFlushOnWrite(bool value)
    {
        return AuExchange(this->flushOnWrite, value);
    }

    AuUInt AsyncStreamAdapater::GetReadOffset()
    {
        return this->readOffset;
    }

    AuUInt AsyncStreamAdapater::SetReadOffset(AuUInt offset)
    {
        if (this->locked == 1)
        {
            this->writer.Preframe();
        }
        return AuExchange(this->readOffset, offset);
    }

    AuUInt AsyncStreamAdapater::GetWriteOffset()
    {
        if (this->locked == 1)
        {
            this->writer.Preframe();
        }
        return this->writeOffset;
    }

    AuUInt AsyncStreamAdapater::SetWriteOffset(AuUInt offset)
    {
        return AuExchange(this->writeOffset, offset);
    }

    bool AsyncStreamAdapater::Init(const AuSPtr<IAsyncTransaction> &transaction, bool isStream)
    {
        this->transaction = transaction;
        this->lastAllocation.reset();
        this->asyncActive = false;
        this->reader.parent = this;
        this->writer.parent = this;
        return true;
    }

    AsyncStreamAdapater::AsyncStreamAdapater() : source({})
    {

    }

    AuSPtr<AsyncStreamMemory> AsyncStreamAdapater::AllocateNextPageCached(AuUInt length)
    {
        if (this->lastAllocation)
        {
            if (this->lastAllocation->length >= length)
            {
                return this->lastAllocation;
            }
        }

        auto newMem = AuMakeShared<AsyncStreamMemory>(length);
        if (!newMem)
        {
            SysPushErrorMem();
            return {};
        }

        if (!newMem->IsValid())
        {
            SysPushErrorMem();
            return {};
        }
        
        return this->lastAllocation = newMem;
    }

    EStreamError AsyncStreamReader::IsOpen()
    {
        return this->parent->errorCode.HasValue() ? 
               this->parent->errorCode.value() : 
               EStreamError::eErrorNone;
    }

    EStreamError AsyncStreamReader::BeginRead(const AuSPtr<Memory::MemoryViewWrite> &internalView)
    {
        if (parent->lastAllocation)
        {
            auto length = parent->transaction->GetLastPacketLength();
            if (length &&
                parent->lastAllocation->streamIndex != length)
            {
                AuDebugBreak();
                return EStreamError::eErrorStreamInterrupted;
            }

            parent->lastAllocation.reset();
        }

        if (parent->asyncActive && !parent->transaction->Complete())
        {
            AuDebugBreak();
            return EStreamError::eErrorStreamInterrupted;
        }

        // Async success or blank state
        parent->transaction->Reset();
        parent->asyncActive = true;

        parent->lastAllocation = AuMakeShared<AsyncStreamMemory>(internalView);
        if (!parent->lastAllocation)
        {
            AuDebugBreak();
            return EStreamError::eErrorStreamInterrupted;
        }

        parent->lastAllocation->streamIndex = 0;

        if (!parent->transaction->StartRead(parent->isStream ? 0 : parent->readOffset, parent->lastAllocation))
        {
            parent->asyncActive = false;
            SysPushErrorNested("Couldn't start async aio read");
            return EStreamError::eErrorStreamInterrupted;
        }

        return EStreamError::eErrorNone;
    }

    EStreamError AsyncStreamReader::Dequeue(AuUInt reqLength, Memory::MemoryViewWrite &out)
    {
        out = {};

        // Transaction error
        if (parent->transaction->Failed())
        {
            parent->asyncActive = false;
            parent->transaction->Reset();
            return EStreamError::eErrorStreamInterrupted;
        }

        // Async error
        if (parent->errorCode.HasValue())
        {
            auto code = parent->isStream ?
                parent->errorCode.Value() :
                AuExchange(parent->errorCode, {}).Value();

            if (code != EStreamError::eErrorNone)
            {
                parent->asyncActive = false;
                parent->transaction->Reset();
                return code;
            }
        }

        auto length = parent->transaction->GetLastPacketLength();
        if (!length)
        {
            parent->asyncActive = false;
            parent->transaction->Reset();
            return EStreamError::eErrorNone;
        }

        auto streamIndex = parent->lastAllocation->streamIndex;
        if (streamIndex == length)
        {
            return EStreamError::eErrorNone;
        }

        auto toRead = AuMin<AuUInt>(parent->lastAllocation->length, length - streamIndex);
        auto bRequestedLen = bool(reqLength);

        out.ptr    = this->parent->lastAllocation->ToPointer() + streamIndex;
        out.length = reqLength ? AuMin(toRead, reqLength) : toRead;

        if (bRequestedLen)
        {
            streamIndex += out.length;
            parent->lastAllocation->streamIndex = streamIndex;
            
            if (!parent->isStream)
            {
                parent->readOffset += out.length;
            }

            if (parent->lastAllocation->streamIndex == length)
            {
                parent->asyncActive = false;
                parent->transaction->Reset();
            }
        }

        return EStreamError::eErrorNone;
    }

    EStreamError AsyncStreamReader::Read(const Memory::MemoryViewStreamWrite &parameters)
    {
        if (!parameters.length)
        {
            SysPushErrorArg();
            return EStreamError::eErrorEndOfStream;
        }

        // Read from the last tranaction, if not fully consumed
        if (parent->lastAllocation)
        {
            auto length = parent->transaction->GetLastPacketLength();
            if (length &&
                parent->lastAllocation->streamIndex != length)
            {
                auto toRead = AuMin<AuUInt>(parameters.length, length - parent->lastAllocation->streamIndex);
                if (toRead)
                {
                    if (parameters.ptr)
                    {
                        AuMemcpy(parameters.ptr, parent->lastAllocation->Begin<AuUInt8>() + parent->lastAllocation->streamIndex, toRead);

                        if (parent->isStream)
                        {
                            parent->lastAllocation->streamIndex += toRead;
                        }
                        else
                        {
                            parent->lastAllocation->streamIndex += length;
                            parent->readOffset += length;
                        }
                    }
                }

                if (parent->isStream)
                {
                    parent->lastAllocation->streamIndex += length;
                }

                parameters.outVariable = toRead;
                return EStreamError::eErrorNone;
            }

            if (parent->transaction && parent->transaction->Failed())
            {
                SysPushErrorIO("AIO transaction read failed: {}", parent->transaction->GetOSErrorCode());
                parent->errorCode = EStreamError::eErrorStreamInterrupted;
                parent->lastAllocation.reset();
            }
        }

        // Async error
        if (parent->errorCode.HasValue())
        {
            auto code = parent->isStream ?
                        parent->errorCode.Value() :
                        AuExchange(parent->errorCode, {}).Value();

            if (code != EStreamError::eErrorNone)
            {
                return code;
            }
        }

        // Async awaiting response
        if (parent->asyncActive && !parent->transaction->Complete())
        {
            parameters.outVariable = 0;
            return EStreamError::eErrorNone;
        }

        // Async success or blank state
        parent->transaction->Reset();
        parent->asyncActive = true;

        parent->lastAllocation = parent->AllocateNextPageCached(parameters.length);
        parent->lastAllocation->streamIndex = 0;

        if (!parent->transaction->StartRead(parent->isStream ? 0 : parent->readOffset, parent->lastAllocation))
        {
            parent->asyncActive = false;
            SysPushErrorNested("Couldn't start async aio read");
            return EStreamError::eErrorStreamInterrupted;
        }

        return EStreamError::eErrorNone;
    }

    void AsyncStreamReader::Close()
    {

    }
    
    AsyncStreamWriter::~AsyncStreamWriter()
    {
        if (used)
        {
            Flush();
        }
    }

    EStreamError AsyncStreamWriter::IsOpen()
    {
        return this->parent->errorCode.HasValue() ? 
               this->parent->errorCode.value() : 
               EStreamError::eErrorNone;
    }

    EStreamError AsyncStreamWriter::Write(const Memory::MemoryViewStreamRead &parameters)
    {
        used = true;

        if (!parameters.ptr)
        {
            return EStreamError::eErrorStreamInterrupted;
        }

        Preframe();

        if (parent->errorCode.HasValue())
        {
            auto code = parent->isStream ?
                        parent->errorCode.Value() :
                        AuExchange(parent->errorCode, {}).Value();

            if (code != EStreamError::eErrorNone)
            {
                return code;
            }
        }

        auto newMem = AuMakeShared<AsyncStreamMemory>(parameters.length);
        if (!newMem)
        {
            SysPushErrorMem();
            return EStreamError::eErrorStreamInterrupted;
        }

        if (!newMem->IsValid())
        {
            SysPushErrorMem();
            return EStreamError::eErrorStreamInterrupted;
        }

        AuMemcpy(newMem->ptr, parameters.ptr, parameters.length);
        parameters.outVariable = parameters.length;

        if (!AuTryInsert(this->writesPending, newMem))
        {
            SysPushErrorMem();
            return EStreamError::eErrorStreamInterrupted;
        }

        if (this->parent->flushOnWrite)
        {
            Frame();
        }

        return EStreamError::eErrorNone;
    }

    void AsyncStreamWriter::Flush()
    {
        Preframe();
        Frame();
    }

    void AsyncStreamWriter::Close()
    {
        Flush();
    }

    void AsyncStreamWriter::Preframe()
    {
        if (parent->transaction->Complete())
        {
            if (parent->transaction->Failed())
            {
                SysPushErrorIO("AIO transaction write failed: {}", parent->transaction->GetOSErrorCode());
                parent->errorCode = EStreamError::eErrorStreamInterrupted;
                parent->lastAllocation.reset();
            }
            else
            {
                 parent->transaction->GetLastPacketLength();
            }

            parent->transaction->Reset();
        }
    }

    void AsyncStreamWriter::Frame()
    {
        AuSPtr<AsyncStreamMemory> buffer;

        if (this->writesPending.size() == 1)
        {
            buffer = AuMove(this->writesPending[0]);
        }
        else
        {
            AuUInt length {};

            for (auto &a : this->writesPending)
            {
                length += a->length;
            }

            buffer = this->parent->AllocateNextPageCached(length);
            if (!buffer)
            {
                return;
            }

            AuUInt index {};

            for (auto &a : this->writesPending)
            {
                if (a->length + index > buffer->length)
                {
                    SysPanic("");
                }

                AuMemcpy(buffer->Begin<AuUInt8>() + index, a->ptr, a->length);
                index += a->length;
            }

            //....
        }

        // Async success or blank state
        parent->transaction->Reset();
        parent->asyncActive = true;

        struct WriteMem : AuMemoryViewRead
        {
            AuSPtr<AsyncStreamMemory> write;
        };

        auto annoying = AuMakeShared<WriteMem>();
        if (!annoying)
        {
            SysPushErrorMem();
            return;
        }

        annoying->write = buffer;
        annoying->ptr = buffer->ptr;
        annoying->length = buffer->length;

        parent->lastAllocation = buffer;
        parent->lastAllocation->streamIndex = 0;

        if (!parent->transaction->StartWrite(parent->isStream ? 0 : parent->writeOffset, annoying))
        {
            parent->asyncActive = false;
            SysPushErrorNested("Couldn't start async aio write");
            return;
        }

        this->writesPending.clear();
    }

    bool AsyncStreamWriter::HasWorkItems()
    {
        return this->writesPending.size();
    }

    AuSPtr<IAsyncStreamReader> AsyncStreamAdapater::ToStreamReader()
    {
        if (this->locked != 0 && this->locked != 2)
        {
            return {};
        }

        this->locked = 2;

        return AuSPtr<IAsyncStreamReader>(AuSharedFromThis(), &this->reader);
    }

    AuSPtr<IStreamWriter> AsyncStreamAdapater::ToStreamWriter()
    {
        if (this->locked != 0 && this->locked != 1)
        {
            return {};
        }

        this->locked = 1;

        return AuSPtr<IStreamWriter>(AuSharedFromThis(), &this->writer);
    }

    AuSPtr<IIOWaitableItem> AsyncStreamAdapater::ToWaitable()
    {
        this->source.SetLoopSource(this->transaction->NewLoopSource());
        return AuSPtr<IIOWaitableItem>(AuSharedFromThis(), &this->source);
    }

    void AsyncStreamAdapater::ReserveBuffer(AuUInt length)
    {
        if (!this->lastAllocation || !this->asyncActive)
        {
            this->lastAllocation = this->AllocateNextPageCached(length);
        }
    }

    bool AsyncStreamAdapater::Reset()
    {
        if (this->locked == 1)
        {
            if (this->writer.HasWorkItems())
            {
                return false;
            }

            this->writer.Flush();
        }

        if (this->asyncActive)
        {
            if (!this->transaction->Complete())
            {
                return false;
            }
        }
        
        this->locked = 0;
        this->transaction->Reset();
        this->writeOffset = 0;
        this->readOffset = 0;
        return true;
    }

    AUKN_SYM AuSPtr<IAsyncStreamAdapater> NewAsyncStreamAdapter(const AuSPtr<IAsyncTransaction> &transaction, bool isStream)
    {
        if (!transaction)
        {
            SysPushErrorArg();
            return {};
        }

        auto adapter = AuMakeShared<AsyncStreamAdapater>();
        if (!adapter)
        {
            return {};
        }

        if (!adapter->Init(transaction, isStream))
        {
            return {};
        }

        return adapter;
    }
}