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

    File: ByteBuffer.hpp
    Date: 2021-8-5
    Author: Reece
***/
#pragma once

#include <Aurora/Locale/ECodePage.hpp>

namespace Aurora::Memory
{
    enum class EStringType
    {
        eStringTerminated,
        eStringByte,
        eStringWord,
        eStringDword, 
        eStringQword
    };

    // TODO: rework scaling
    static const auto kBufferPageSize  = 512;
    static const auto kBufferInitialPower = 9;

    /***
     * A bytebuffer object represents a:
     *  *  optionally resizable buffer;
     *  *  -n infinite read/writer stream pair, in ring buffer mode;
     *  *  synonym for fulfill-once AuList<AuUInt8> & output parameters;
     *  *  stream of arbitrary serialization/deserialization, seekable read/writes;
     *  *  ...tuple of <buffer base, read head, write head> and some flags;
     *  *  ...method by which one can serialize data in-place via SharedByteBuffer
     * 
     * EG (2022): 
     * -> AuProtocol ProtocolPiece buffers
     * -> AuCompression internal buffer
     * -> A sockets' output stream / buffer for user-read/write and overlapped submission
     * -> ...
     *
     * Deprecates INetworkStream, fixes allocation issues around compression backends
     * Superseeds abuse of AuList<AuUInt8> for binary blobs alongside other fixed u8 arrays
     */
    struct ByteBuffer
    {
        ///////////////////////////////////////////////////////////////////////
        // Stable ByteBuffer ABI Header; length and read/write head pointers //
        ///////////////////////////////////////////////////////////////////////
        
        /// Internal capacity to mitigate trivial reallocs
        AuUInt allocSize;
        
        /// Abstract size
        AuUInt length;

        /// Buffer pointer
        AuUInt8 *base {};
        /// Stream pointer
        AuUInt8 *readPtr {};
        /// Stream pointer
        AuUInt8 *writePtr {};
        
        ///////////////////////////////////////////////////////////////////////
        //  Stable ByteBuffer ABI Header; u32 flags                          //
        ///////////////////////////////////////////////////////////////////////
        /// Is ring buffer?
        AuUInt8 flagCircular   : 1 {};

        /// Should resize linear buffer to accommodate additional writes
        AuUInt8 flagExpandable : 1 {};
        
        AuUInt8 flagReadError  : 1 {};
        AuUInt8 flagWriteError : 1 {};
        AuUInt8 flagNoFree : 1 {};
        AuUInt8 flagNoRealloc: 1 {};
        AuUInt8 flagAlwaysExpandable : 1 {};
        // TODO: flag: allow circular overrun to allow for 100% access of the buffer from either read head
        // - implicit padding
        AuUInt8 scaleSize {};// 
        AuUInt8 alignment {};
        ///////////////////////////////////////////////////////////////////////
        
        /**
         * @brief Move constructor
         * @param buffer 
        */
        inline ByteBuffer(ByteBuffer &&buffer)
        {
            this->base                  = buffer.base;
            this->length                = buffer.length;
            this->allocSize             = buffer.length;
            this->writePtr              = this->base + (buffer.writePtr - buffer.base);
            this->readPtr               = this->base + (buffer.readPtr - buffer.base);
            this->flagCircular          = buffer.flagCircular;
            this->flagExpandable        = buffer.flagExpandable;
            this->scaleSize             = buffer.scaleSize;
            this->flagReadError         = buffer.flagReadError;
            this->flagWriteError        = buffer.flagWriteError;
            this->alignment             = buffer.alignment;
            buffer.base                 = {};
            buffer.length               = {};
            buffer.allocSize            = {};
            buffer.writePtr             = {};
            buffer.readPtr              = {};
            buffer.flagCircular         = {};
            buffer.flagExpandable       = {};
            buffer.flagAlwaysExpandable = {};
            buffer.scaleSize            = {};
            buffer.alignment            = {};
        }
        
        /**
         * @brief Copy with possible preserve pointers
         * @param buffer 
         * @param preservePointers 
        */
        inline ByteBuffer(const ByteBuffer &buffer, bool preservePointers = true)
        {
            if (buffer.length)
            {
                if (buffer.alignment)
                {
                    this->base      = ZAlloc<AuUInt8 *>(buffer.length, buffer.alignment);
                }
                else
                {
                    this->base      = ZAlloc<AuUInt8 *>(buffer.length);
                }
            }
            this->scaleSize = buffer.scaleSize;
            this->flagCircular = buffer.flagCircular;
            this->flagExpandable = buffer.flagExpandable;
            this->flagAlwaysExpandable = buffer.flagAlwaysExpandable;
            if (!this->base)
            {
                Reset();
                return;
            }
            this->length    = buffer.length;
            this->allocSize = buffer.length;
            if (preservePointers)
            {
                this->writePtr = this->base + (buffer.writePtr - buffer.base);
                this->readPtr  = this->base + (buffer.readPtr - buffer.base);
            }
            else
            {
                this->writePtr = this->base;
                this->readPtr  = this->base;
            }
            AuMemcpy(this->base, buffer.base, this->length);
        }

        /**
         * @brief Copy pointer range into a new ring or byte buffer
         * @param in 
         * @param length 
         * @param circular 
         * @param expandable 
        */
        inline ByteBuffer(const void *in, AuUInt length, bool circular = false, bool expandable = false) : flagCircular(circular), flagExpandable(expandable), flagReadError(0), flagWriteError(0)
        {
            this->scaleSize = kBufferInitialPower;
            this->base      = length ? ZAlloc<AuUInt8 *>(length) : nullptr;
            if (!this->base)
            {
                Reset();
                return;
            }
            if (!in)
            {
                Reset();
                return;
            }
            this->length    = length;
            this->allocSize = length;
            this->readPtr   = this->base;
            this->writePtr  = this->readPtr + this->length;
            AuMemcpy(this->base, in, this->length);
        }
        
        inline ByteBuffer(const AuList<AuUInt8> &vector, bool circular = false, bool expandable = false) : flagCircular(circular), flagExpandable(expandable), flagReadError(0), flagWriteError(0)
        {
            this->scaleSize = kBufferInitialPower;
            this->base      = vector.size() ? ZAlloc<AuUInt8 *>(vector.size()) : nullptr;
            if (!this->base)
            {
                Reset();
                return;
            }
            this->length    = vector.size();
            this->allocSize = this->length;
            this->readPtr   = this->base;
            this->writePtr  = this->readPtr + this->length;
            AuMemcpy(this->base, vector.data(), this->length);
        }
        
        inline ByteBuffer(AuUInt length, bool circular = false, bool expandable = false) : flagCircular(circular), flagExpandable(expandable), flagReadError(0), flagWriteError(0)
        {
            this->scaleSize = kBufferInitialPower;
            if (!length)
            {
                Reset();
                return;
            }
            this->base      = ZAlloc<AuUInt8 *>(length);
            if (!this->base)
            {
                Reset();
                return;
            }
            this->length    = length;
            this->allocSize = length;
            this->readPtr   = this->base;
            this->writePtr  = this->base;
        }
        
        inline ByteBuffer(AuUInt length, AuUInt alignment, bool circular = false, bool expandable = false) : flagCircular(circular), flagExpandable(expandable), flagReadError(0), flagWriteError(0)
        {
            if (!length)
            {
                Reset();
                return;
            }
            this->scaleSize = kBufferInitialPower;
            this->base      = ZAlloc<AuUInt8 *>(length, alignment);
            this->alignment = alignment;
            if (!this->base)
            {
                Reset();
                return;
            }
            this->length    = length;
            this->allocSize = length;
            this->readPtr   = this->base;
            this->writePtr  = this->base;
        }

        template<typename T>
        ByteBuffer(T *base, T *end, bool circular = false, bool expandable = false) : flagCircular(circular), flagExpandable(expandable), flagReadError(0), flagWriteError(0)
        {
            if (!base)
            {
                Reset();
                return;
            }
            if (!end)
            {
                Reset();
                return;
            }
            auto length = static_cast<AuUInt>(end - base) * sizeof(T);
            this->base =  length ? ZAlloc<AuUInt8 *>(length) : nullptr;
            this->scaleSize = kBufferInitialPower;
            if (!this->base)
            {
                Reset();
                return;
            }
            this->length    = length;
            this->allocSize = length;
            this->readPtr   = this->base;
            this->writePtr  = this->base + length;
            AuMemcpy(this->base, base, length);
        }
        
        /**
         * @brief Default constructor, allocates an auto-expanding linear bytebuffer
        */
        inline ByteBuffer() : flagCircular(0), flagExpandable(true), flagReadError(0), flagWriteError(0)
        {
            this->base      = {};
            this->length    = {};
            this->allocSize = {};
            this->readPtr   = {};
            this->writePtr  = {};
            this->scaleSize = kBufferInitialPower;
        }

        inline ~ByteBuffer()
        {
            if (this->base && !this->flagNoFree)
            {
                Free(this->base);
            }
        }

        inline void ResetPositions()
        {
            this->flagReadError  = 0;
            this->flagWriteError = 0;
            this->readPtr        = base;
            this->writePtr       = base;
        }
        
        // utils: Iterator

        /**
         * @brief base of the bytebuffer
         * @return 
        */
        inline auline AuUInt8 * data() const;

        /**
         * @brief size of the byte array as requested by the caller (actual allocation may differ, ::allocSize)
         * @return 
        */
        inline auline AuUInt    size() const;

        /**
         * @brief linear read begin
         * @warning writers should use ::GetLinearWriteable(uDesiredLength) or ::GetOrAllocateLinearWriteable(...)
         * @return 
        */
        inline auline const AuUInt8 * begin();
        inline auline const AuUInt8 * cbegin() const;
        
        /**
         * @brief linear read end
         * @warning writers should use ::GetLinearWriteable(uDesiredLength) or ::GetOrAllocateLinearWriteable(...)
         * @return 
        */
        inline auline const AuUInt8 * end();
        inline auline const AuUInt8 * cend() const;

        inline auline bool      empty() const;
        
        inline void clear();
        inline void resize(AuUInt size);
        inline void reserve(AuUInt size);
        
        // utils: Utils to alternative types 
        inline auline AuList<AuUInt8> ToVector() const;

        inline AuUInt32 GetAllocationPower() const;
        inline operator MemoryViewRead() const;
        inline operator MemoryViewWrite();

        // utils: Internal buffer comparison
        inline bool operator ==(const AuList<AuUInt8> &) const;
        inline bool operator ==(const MemoryViewRead &) const;
        inline bool operator ==(const ByteBuffer &) const;

        // utils: Move assignment
        inline ByteBuffer &operator =(ByteBuffer &&);
        inline ByteBuffer &operator =(const ByteBuffer &buffer);

        // utils: &byteArray[n]

        /**
         * @brief read u8 reference relative to the base
         * @warning not const safe
         * @param idx 
         * @return 
        */
        inline AuUInt8 &operator [](AuUInt idx) const;
        
        // utils: if (byteArray) -> if (byteArray->IsValid())
        inline operator bool() const;

        inline AuList<AuUInt8> RemainingBytesToVector(bool endAtWrite = true) const;
        // ... utils are mostly const functions that provide language intrinsics, access, and container-like compatibility
        // ByteBuffer specific utils can be found under Utilities
        
        // Seek / Position
        inline auline bool ReaderTryGoForward(AuUInt32 offset);
        inline auline bool ReaderTryGoBack(AuUInt32 offset);
               
        inline auline bool WriterTryGoForward(AuUInt32 offset);

        inline auline AuUInt RemainingWrite(bool endAtRead = true) const;
        inline auline AuUInt RemainingBytes(bool endAtWrite = true) const;

        inline auline bool Skip(AuUInt count);
        inline auline AuUInt GetReadOffset() const;
        inline auline AuUInt GetWriteOffset() const;

        inline auline void ResetReadPointer();
        
        inline auline MemoryViewRead GetNextLinearRead();
        inline auline MemoryViewWrite GetNextLinearWrite();

        inline auline bool CanWrite(AuUInt length);
        inline auline bool CanRead(AuUInt length);

        /**
         * @brief Returns a linear amount of memory for exactly length of linear bytes
         * @param length
         * @return
        */
        inline auline MemoryViewRead GetLinearReadableForExactly(AuUInt length)
        {
            return GetLinearReadable(length);
        }

        inline auline MemoryViewWrite GetLinearWriteableForExactly(AuUInt length)
        {
            return GetLinearWriteable(length);
        }

        /**
         * @brief Returns a linear amount of memory of at least length
         * @param length
         * @return
        */
        inline auline MemoryViewRead GetLinearReadableForAtleast(AuUInt length);

        inline auline MemoryViewWrite GetLinearWriteableForAtleast(AuUInt length);

        /**
         * @brief Returns a linear amount of memory capped to length
         * @param length 
         * @return 
        */
        inline auline MemoryViewRead GetLinearReadableForNoMore(AuUInt length);

        inline auline MemoryViewWrite GetLinearWriteableForNoMore(AuUInt length);

        /// legacy: ForExactly variant
        inline auline MemoryViewRead GetLinearReadable(AuUInt length);

        /// legacy: ForExactly variant
        inline auline MemoryViewWrite GetLinearWriteable(AuUInt length);

        /**
         * @brief 
         *     Expected use-case:
         *         Consider the prototype: void MyFunction(AuByteBuffer &output);
         *     
         *         Where the valid expected uses fall in line with the following truth table:
         *         
         *         * PASS
         *           AuByteBuffer defaultBuffer;
         *           MyFunction(defaultBuffer);
         *           if (defaultBuffer) {}
         * 
         *         * FAIL
         *           AuByteBuffer defaultBuffer;
         *           defaultBuffer.WriteTagged<AuUInt32>(32)
         *           MyFunction(defaultBuffer);
         *           if (defaultBuffer) {}
         * 
         *         * FAIL
         *           AuByteBuffer defaultBuffer;
         *           MyFunction(defaultBuffer);
         *           MyFunction(defaultBuffer); // !!!
         * 
         *         * PASS
         *           AuByteBuffer writeStream(512);
         *           writeStream.WriteTagged<AuUInt32>(32)
         *           MyFunction(defaultBuffer);
         *           if (defaultBuffer) {}
         * 
         * @param length 
         * @return 
        */
        inline auline MemoryViewWrite GetOrAllocateLinearWriteable(AuUInt length);

        // Memory operations

        inline auline bool Allocate(AuUInt length);
        inline auline bool Allocate(AuUInt length, AuUInt alignment);
        inline auline bool SetBuffer(MemoryViewRead readView, bool bMoveWriteHeadForReaders = true);

        /**
         * @brief Releases excess memory (comparable to shrink to fit in the c++ stl)
         * @return 
        */
        inline auline void GC();

        /**
         * @brief Releases all resources and resets the bytebuffer without an allocation
        */
        inline void Reset();

        /**
         * @brief Expands the underlying buffer allocation to at least length.
         *        Does nothing on failure. Programs can try to allocate in real time
         *        and handle the write error flag condition from there. To pull the
         *        real buffer size, see member field allocSize.
         * @param length 
        */
        inline void Reserve(AuUInt length);

        /**
         * @brief Is allocated or dummy object?
         * @return 
        */
        inline auline bool IsEmpty() const;

        /**
         * @brief Is an error flag set?
         * @return 
        */
        inline auline bool HasStreamError() const;
        
        /**
         * @brief Returns true so long as
         *        1) an error has not occured or,
         *        1) the relevant error flag was reset; and
         *        2) there is a valid underlying buffer
         * 
         * @return 
        */
        inline auline bool IsValid() const;

        /**
         * @brief Allocate at least length bytes, without adjusting the relative read/write head offsets
         * @param length 
         * @return 
        */
        inline auline bool Resize(AuUInt length);

        // Basic Read Write

        inline auline AuUInt Write(const void *buffer, AuUInt requestLength);
        inline auline AuUInt Read(void *out, AuUInt requestedLength, bool peek = false);

        inline auline AuUInt Write(const MemoryViewRead &read)
        {
            return Write(read.ptr, read.length);
        }

        inline auline AuUInt Read(const MemoryViewWrite &write)
        {
            return Read(write.ptr, write.length);
        }

        // String API

        inline bool WriteString(std::string_view string, EStringType type = EStringType::eStringDword, Locale::ECodePage codepage = Locale::ECodePage::eUTF8);
        inline bool ReadString(AuString &string, EStringType type = EStringType::eStringDword, Locale::ECodePage codepage = Locale::ECodePage::eUTF8);

        // Copy, concat, etc 
        inline AuUInt WriteFromEx(ByteBuffer &buffer,
                                  AuUInt uLength);
        inline bool WriteFrom(ByteBuffer &buffer);

        // Utilities
        inline bool Trim(AuUInt tail);
        inline bool Pad(AuUInt16 aPowOf2, AuUInt8 magicCharacter = '\x00');
        inline bool Fill(AuUInt length, AuUInt8 magicCharacter = '\x00');

        // Templated read/write for **PODs**
        // (yes, there's some support for non-primitive classes this early into the abstraction.)
        // (AuString and some other containers may work, but really, we need a typed bytebuffer.)
        template<typename T>
        T Read();

        // Panics if flagReadError is true by the end of deserialization
        template<typename T>
        T ReadChecked();

        template<typename T>
        bool Write(const T &in);

        template<typename T>
        bool Write(T &in);

        template<typename T>
        bool Read(T &out);

        template<typename T>
        bool WriteTagged(const T &in);

        template<typename T>
        bool WriteTagged(T &in);

        template<typename T>
        bool ReadTagged(T &out);

        template<typename T>
        T ReadTagged();
        //

        inline AuUInt calcDifferenceBetweenHeadsUnsigned(AuUInt8 *pHeadPointer, AuUInt8 *pSubtrahend)
        {
            if (pHeadPointer > pSubtrahend)
            {
                return pHeadPointer - pSubtrahend;
            }
            else
            {
                return (pSubtrahend - this->base) + ((this->base + this->length) - pHeadPointer);
            }
        }

        inline AuSInt calcDifferenceBetweenHeadsSigned(AuUInt8 *pHeadPointer, AuUInt8 *pSubtrahend)
        {
            if (pHeadPointer > pSubtrahend)
            {
                return pHeadPointer - pSubtrahend;
            }
            else
            {
                return -(pSubtrahend - this->base);
            }
        }
    };

    struct SharedByteBuffer : ByteBuffer
    {
        AuSPtr<void> memory;

        inline SharedByteBuffer(AuSPtr<MemoryViewWrite> pWriteView) : ByteBuffer()
        {
            this->allocSize  = 0;
            this->base       = (AuUInt8 *)pWriteView->ptr;
            this->length     = pWriteView->length;
            this->readPtr    = this->base;
            this->writePtr   = this->base + this->length;
            this->flagNoFree = true;
            this->memory     = pWriteView;
        }

        inline SharedByteBuffer(AuSPtr<void> pRAIIParentOwner, MemoryViewWrite view) : ByteBuffer()
        {
            this->allocSize  = 0;
            this->base       = (AuUInt8 *)view.ptr;
            this->length     = view.length;
            this->readPtr    = this->base;
            this->writePtr   = this->base + this->length;
            this->flagNoFree = true;
            this->memory     = pRAIIParentOwner;
        }
    };

    struct SharableByteBuffer : ByteBuffer,
        AuEnableSharedFromThis<SharableByteBuffer>
    {
        SharableByteBuffer() : ByteBuffer()
        {

        }

        SharableByteBuffer(AuUInt uLength, bool circular = false, bool expandable = false) : ByteBuffer(uLength, circular, expandable)
        {

        }

        SharableByteBuffer(AuUInt uLength, AuUInt uAlignment, bool circular = false, bool expandable = false) : ByteBuffer(uLength, uAlignment, circular, expandable)
        {

        }

    private:
        MemoryViewRead readView;
        MemoryViewWrite writeView;

    public:
        inline AuSPtr<MemoryViewWrite> ToSharedWriteView()
        {
            this->writeView = *this;
            return { this->SharedFromThis(), &this->writeView };
        }

        inline AuSPtr<MemoryViewRead> ToSharedReadView()
        {
            this->readView = *this;
            return { this->SharedFromThis(), &this->readView };
        }

        inline operator AuSPtr<MemoryViewWrite>()
        {
            return this->ToSharedWriteView();
        }

        inline operator AuSPtr<MemoryViewRead>()
        {
            return this->ToSharedReadView();
        }
    };


    static ByteBuffer NewResizableBuffer(AuUInt32 length = 0)
    {
        return ByteBuffer(length, false, true);
    }

    static ByteBuffer NewRingBuffer(AuUInt32 length = 1024 * 5)
    {
        return ByteBuffer(length, true, false);
    }

    static AuSPtr<SharableByteBuffer> NewSharableResizableBuffer(AuUInt32 length = 0)
    {
        auto pThat = AuMakeShared<SharableByteBuffer>(length, false, true);
        if (!(pThat && *pThat))
        {
            return {};
        }
        return pThat;
    }

    static AuSPtr<SharableByteBuffer> NewSharableBuffer(AuUInt32 length = 0)
    {
        auto pThat = AuMakeShared<SharableByteBuffer>(length);
        if (!(pThat && *pThat))
        {
            return {};
        }
        return pThat;
    }
}