/***
    Copyright (C) 2024 J Reece Wilson (a/k/a "Reece"). All rights reserved.

    File: auUTF8Iterator.ipp
    Date: 2024-08-31
    Author: Reece
    Notes: UTF8 iterator
***/
#pragma once

inline constexpr AuUTF8Iterator::AuUTF8Iterator()
{

}

inline constexpr AuUTF8Iterator::AuUTF8Iterator(const AuUTF8Iterator &copy) :
    baseView(copy.baseView),
    pCurrent(copy.pCurrent)
{

}

inline constexpr AuUTF8Iterator::AuUTF8Iterator(AuUTF8Iterator &&copy) :
    baseView(copy.baseView),
    pCurrent(copy.pCurrent)
{

}

inline constexpr AuUTF8Iterator &AuUTF8Iterator::operator =(const AuUTF8Iterator &copy)
{
    this->baseView = copy.baseView;
    this->baseView = copy.pCurrent;
    return *this;
}

inline constexpr AuUTF8Iterator &AuUTF8Iterator::operator =(AuUTF8Iterator &&move)
{
    this->baseView = move.baseView;
    this->pCurrent = move.pCurrent;
    return *this;
}

inline AuUTF8Iterator::AuUTF8Iterator(const char *pStart)
{
    this->baseView = pStart;
    this->pCurrent = pStart;
}

inline AuUTF8Iterator::AuUTF8Iterator(const AuROString &in, AuUInt uOffset)
{
    this->baseView = in;
    this->pCurrent = in.Begin();

    if (uOffset != AuROString::npos)
    {
        auto out = AuCodepointsGetByteOffset(in, uOffset);
        if (out != AuROString::npos)
        {
            this->pCurrent += out;
        }
        else
        {
            this->pCurrent = in.End();
        }
    }
}

AuUTF8Iterator AuUTF8Iterator::FromStringView(AuROString in, AuUInt uOffset)
{
    return AuUTF8Iterator(in, uOffset);
}

inline constexpr const char *AuUTF8Iterator::base() const
{
    return this->pCurrent;
}

inline constexpr const char *AuUTF8Iterator::Base() const
{
    return this->pCurrent;
}

inline constexpr AuUTF8Iterator AuUTF8Iterator::end() const
{
    AuUTF8Iterator ret;
    ret.baseView = this->baseView;
    ret.pCurrent = this->baseView.End();
    return ret;
}

inline constexpr AuUTF8Iterator AuUTF8Iterator::End() const
{
    AuUTF8Iterator ret;
    ret.baseView = this->baseView;
    ret.pCurrent = this->baseView.End();
    return ret;
}

inline constexpr AuOptional<AuUInt32> AuUTF8Iterator::operator*() const
{
    auto pBegin  = this->baseView.Begin();
    auto uDiff   = this->pCurrent - pBegin;
    auto uLength = this->baseView.Length();

    if (uLength == uDiff)
    {
        return {};
    }

    auto pNext   = pBegin + uDiff;
    auto uNext   = uLength - uDiff;

    return AuCodepointsDecodeOne(AuROString(pNext, uNext));
}

inline constexpr AuUTF8Iterator::pointer AuUTF8Iterator::operator->() const
{
    return this->base();
}

inline constexpr AuUTF8Iterator &AuUTF8Iterator::operator++()
{
    auto pBegin  = this->baseView.Begin();
    auto uDiff   = this->pCurrent - pBegin;
    auto uLength = this->baseView.Length();

    if (uLength == uDiff)
    {
        return *this;
    }

    auto pNext   = pBegin + uDiff;
    auto uNext   = uLength - uDiff;

    if (auto uCount = AuCodepointsNextLength(AuROString(pNext, uNext)))
    {
        this->pCurrent += uCount;
    }
    else
    {
        *this = this->End();
    }

    return *this;
}

inline constexpr AuUTF8Iterator AuUTF8Iterator::operator++(int)
{
    AuUTF8Iterator ret = *this;
    ++ret;
    return ret;
}

inline constexpr AuUTF8Iterator &AuUTF8Iterator::operator--()
{
    auto pBegin  = this->baseView.Begin();
    auto uDiff   = this->pCurrent - pBegin;
    auto uLength = this->baseView.Length();

    if (uLength == uDiff)
    {
        return *this;
    }
        
    {
        auto uOffset = AuCodepointsFindPreviousValidByteOffsetFromByteOffset(this->baseView, uDiff);
        if (uOffset != AuString::npos)
        {
            this->pCurrent = pBegin + uOffset;
        }
        else
        {
            this->pCurrent = pBegin;
            return *this;
        }
    }

    return *this;
}

inline constexpr AuUTF8Iterator AuUTF8Iterator::operator--(int)
{
    AuUTF8Iterator ret = *this;
    --ret;
    return ret;
}

inline constexpr AuUTF8Iterator AuUTF8Iterator::operator+(const difference_type offset) const
{
    AuUTF8Iterator copy = *this;
    copy += offset;
    return copy;
}
    
inline constexpr AuUTF8Iterator &AuUTF8Iterator::operator+=(const difference_type offset)
{
    auto pBegin  = this->baseView.Begin();
    auto uDiff   = this->pCurrent - pBegin;
    auto uLength = this->baseView.Length();

    if (uLength == uDiff ||
        offset == 0)
    {
        return *this;
    }

    if (offset < 0)
    {
        (*this)-= 0 - offset;
        return *this;
    }

    auto pNext   = pBegin + uDiff;
    auto uNext   = uLength - uDiff;

    for (AU_ITERATE_N(i, AuUInt(offset)))
    {
        if (auto uCount = AuCodepointsNextLength(AuROString(pNext, uNext)))
        {
            pNext += uCount;
            uNext -= uCount;
            this->pCurrent += uCount;
        }
        else
        {
            *this = this->End();
            return *this;
        }
    }

    return *this;
}

inline constexpr AuUTF8Iterator AuUTF8Iterator::operator-(const difference_type offset) const
{
    AuUTF8Iterator copy = *this;
    copy -= offset;
    return copy;
}

inline constexpr AuUTF8Iterator &AuUTF8Iterator::operator-=(const difference_type offset)
{
    auto pBegin  = this->baseView.Begin();
    auto uDiff   = this->pCurrent - pBegin;
    auto uLength = this->baseView.Length();

    if (uLength == uDiff ||
        offset == 0)
    {
        return *this;
    }

    if (offset < 0)
    {
        (*this)+= 0 - offset;
        return *this;
    }

    for (AU_ITERATE_N(i, AuUInt(offset)))
    {
        auto uOffset = AuCodepointsFindPreviousValidByteOffsetFromByteOffset(this->baseView, uDiff);
        if (uOffset != AuString::npos)
        {
            this->pCurrent = pBegin + uOffset;
            uDiff          = uOffset;
        }
        else
        {
            this->pCurrent = pBegin;
            return *this;
        }
    }

    return *this;
}
    
inline constexpr AuOptional<AuUInt32> AuUTF8Iterator::operator[](const difference_type offset) const
{
    auto ret = *this;
    ret += offset;
    return *ret;
}