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

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

namespace Aurora::Memory
{
    static const auto kBufferPageSize  = 512;
    //static const auto kBufferBasePower = 8;
    static const auto kBufferInitialPower = 9;// -kBufferBasePower; // 4-bit integer

    /***
     * A bytebuffer object represents a linear, partially-linear resizable, buffer **or** a ring buffer. 
     *
     * Use cases for a ring buffer include wrapping streams for a use case in which the consumer may
     * expect arbitrary stream seeks of an otherwise limited consume-once stream
     * 
     *  IE;
     *  -> Peeking a header in a datagram, or tcp stream; where instead of freeing the datagram or double
     *       buffering the network stack when required, a ring buffer is used to prevent reallocation on each frame
     *  -> Peeking, or seeking back after, compression read. A compression api could be fed on-Sdemand or ad hoc,
     *       writing to its write head pointer, while never running out of space so long as the decompressed ring 
    *        read head continues moving
     *
     * Small, linear, write/read-once [de]serialization use cases may elect to allocate a buffer and 
     *  follow the linear fast paths; perhaps even enabling flagExpandable for hopefully-smarter-than-stdvec-scaling 
     * 
     * Ring buffers scale from the write head, to the read head, potentially going-around in the process
     *
     * Linear flagExpandable buffers scale from [0, length]; reallocating at end of buffer if flagExpandable is enabled
     *  if expanding is enabled, 
     *     realloc(max(size + offset, (offset / kBufferPageSize + 1) * kBufferPageSize))
     *
     * Deprecates INetworkStream, fixes allocation issues around compression backends
     * Superseeds abuse of AuList<AuUInt8> for binary blobs, alongside Memory::Array
     */
    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;
        // - implicit padding
        AuUInt8 scaleSize;// : 4; screw it.... we should just take 6 * (4/8) up to 32/64, we wont go up a slab allocation bucket, whatever you want to call it
        ///////////////////////////////////////////////////////////////////////
        
        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;
            buffer.base           = {};
            buffer.length         = {};
            buffer.allocSize      = {};
            buffer.writePtr       = {};
            buffer.readPtr        = {};
            buffer.flagCircular   = {};
            buffer.flagExpandable = {};
            buffer.scaleSize      = {};
        }
        
        ByteBuffer(const ByteBuffer &buffer, bool preservePointers = true)
        {
            this->base      = FAlloc<AuUInt8 *>(buffer.length);
            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);
            this->flagCircular = buffer.flagCircular;
            this->flagExpandable = buffer.flagExpandable;
            this->scaleSize = buffer.scaleSize;
        }

        ByteBuffer(const void *in, AuUInt length, bool circular = false, bool expandable = false) : flagCircular(circular), flagExpandable(expandable), flagReadError(0), flagWriteError(0)
        {
            this->base      = FAlloc<AuUInt8 *>(length);
            if (!this->base)
            {
                Reset();
                return;
            }
            this->length    = length;
            this->allocSize = length;
            this->readPtr   = this->base;
            this->writePtr  = this->readPtr + this->length;
            AuMemcpy(this->base, in, this->length);
            this->scaleSize = kBufferInitialPower;
        }
        
        ByteBuffer(const AuList<AuUInt8> &vector, bool circular = false, bool expandable = false) : flagCircular(circular), flagExpandable(expandable), flagReadError(0), flagWriteError(0)
        {
            this->base      = FAlloc<AuUInt8 *>(vector.size());
            if (!this->base)
            {
                Reset();
                return;
            }
            this->length    = vector.size();
            this->allocSize = vector.size();
            this->readPtr   = this->base;
            this->writePtr  = this->readPtr + this->length;
            AuMemcpy(this->base, vector.data(), this->length);
            this->scaleSize = kBufferInitialPower;
        }
        
        ByteBuffer(AuUInt length, bool circular = false, bool expandable = false) : flagCircular(circular), flagExpandable(expandable), flagReadError(0), flagWriteError(0)
        {
            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;
            this->scaleSize = kBufferInitialPower;
        }

        template<typename T>
        ByteBuffer(T *base, T *end, bool circular = false, bool expandable = false) : flagCircular(circular), flagExpandable(expandable), flagReadError(0), flagWriteError(0)
        {
            auto length = static_cast<AuUInt>(end - base) * sizeof(T);
            this->base = ZAlloc<AuUInt8 *>(length);
            if (!this->base)
            {
                Reset();
                return;
            }
            this->length = length;
            this->allocSize = length;
            this->readPtr = this->base;
            this->writePtr = this->base;
            this->scaleSize = kBufferInitialPower;
            AuMemcpy(this->base, base, length);
        }
        
        ByteBuffer() : flagCircular(0), flagExpandable(true), flagReadError(0), flagWriteError(0)
        {
            this->base      = {};
            this->length    = {};
            this->allocSize = {};
            this->readPtr   = {};
            this->writePtr  = {};
            this->scaleSize = kBufferInitialPower;
        }

        ~ByteBuffer()
        {
            if (this->base)
            {
                Free(this->base);
            }
        }

        inline void ResetPositions()
        {
            this->flagReadError  = 0;
            this->flagWriteError = 0;
            this->readPtr        = base;
            this->writePtr       = base;
        }
        
        // Iterator
        inline auline AuUInt8 * data() const;
        inline auline AuUInt    size() const;
        inline auline AuUInt8 * begin() const;
        inline auline AuUInt8 * end() const;
        inline auline bool      empty() const;
        inline void clear();
        inline void resize(AuUInt size);
        inline void reserve(AuUInt size);
        
        // Utils To alternative types 
        inline auline AuList<AuUInt8> ToVector() const;

        inline AuUInt32 GetAllocationPower() const;
        inline operator AuList<AuUInt8>() const;
        inline operator MemoryViewRead()  const;

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

        // Move assignment
        inline ByteBuffer &operator =(ByteBuffer &&);

        // &byteArray[n]
        inline AuUInt8 &operator [](AuUInt idx);
        
        // if (byteArray) -> if (byteArray->IsValid())
        inline operator bool() const;

        inline AuList<AuUInt8> RemainingBytesToVector(bool endAtWrite = true) const;

        
        // 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);
        inline auline AuUInt RemainingBytes(bool endAtWrite = true);

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

        
        inline AuOptional<AuUInt8 *> WriterTryGetWriteHeadFor(AuUInt32 nBytes);

        // Memory operations

        inline auline bool Allocate(AuUInt length, bool fast = true);
        inline auline bool SetBuffer(const void *in, AuUInt length);
        inline auline bool SetBuffer(const AuList<AuUInt8> &buffer);

        inline auline void GC();
        inline void Reset();
        inline void Reserve(AuUInt length);
        inline auline bool IsEmpty() const;
        inline auline bool HasStreamError() const;
        inline auline bool IsValid() const;

        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);

        // Typed read/write
        template<typename T>
        T Read();

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

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

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

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