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

    File: EncoderIConv.cpp
    Date: 2021-8-19
    Author: Reece
***/
#include <Source/RuntimeInternal.hpp>
#include "Encoding.hpp"
#include "EncoderIConv.hpp"

#if defined(AURORA_IS_POSIX_DERIVED)
    #include <iconv.h>
#endif

namespace Aurora::Locale::Encoding
{

#if defined(AURORA_IS_POSIX_DERIVED)
    static AuHashMap<ECodePage, iconv_t> gIconvCodePage2UTF;
    static AuHashMap<ECodePage, iconv_t> gIconvUTF2CodePage;
#endif

    static void SanitizeIConvCharset(AuString &str)
    {
        if (AuStartsWith(str, "MS-"))
        {
            str = "WINDOWS-" + str.substr(3);
            return;
        }
        
        str = AuToUpper(str);
        
        if (str == "SJIS")
        {
            str = "SHIFT_JIS";
            return;
        }
        
        if (AuStartsWith(str, "LATIN-") && str.size() == 7)
        {
            str[5] = str[6];
            str.pop_back();
            return;
        }
        
        // str is now **probably** something your unix platform iconv can understand
    }

    static const char *PageToString(ECodePage page, AuString &temp)
    {
        const char *base {};

        if (page == ECodePage::eSysUnk)
        {
            temp = GetInternalCodePageString();
            SanitizeIConvCharset(temp);
            base = temp.c_str();
        }
        else
        {
            switch (page)
            {
            default:
            case ECodePage::e18030:
                base = "GB18030";
                break;
            case ECodePage::eLatin1:
                base = "LATIN1";
                break;
            case ECodePage::eUTF7:
                base = "UTF7";
                break;
            case ECodePage::e2312:
                base = "GB2312";
                break;
            case ECodePage::eGBK: 
                base = "GBK";
                break;
            case ECodePage::eSJIS:
                base = "SHIFT_JIS";
                break;
            case ECodePage::eUTF16:
                base = "UTF16";
                break;
            }
        }

        return base;
    }

    AuStreamReadWrittenPair_t IConvWork(iconv_t handle, const void *in, AuUInt length, void *out, AuUInt32 outLen)
    {
#if defined(AURORA_IS_POSIX_DERIVED)

        auto originalLength = length;
        size_t canReadLength = length;
        size_t canWriteLength = outLen;

        char * inPtr = (char *)in;
        char * outPtr = (char *)out;

        AuByteBuffer buffer;
        if (!out)
        {
            buffer.resize(length);
            outPtr = (char *)buffer.base;
            canWriteLength = outLen = buffer.length;
        }
        
        AuUInt32 a {}, b{};
        while (iconv(handle, &inPtr, &canReadLength, &outPtr, &canWriteLength) == (size_t) -1)
        {

            a += length - canReadLength;
            b += outLen - canWriteLength;
            length = canReadLength;

            if (!out)
            {
                if (errno == E2BIG)
                {
                    buffer.resize(AuMax(originalLength, buffer.length) * 2);
                    outPtr = (char *)buffer.base;
                    canWriteLength = outLen = buffer.length;
                    continue;
                }
            }

            SysPushErrorGen();
            return {};
        }

        a += length - canReadLength;
        b += outLen - canWriteLength;

        return {a, b};

    #else

        return {};

    #endif
    }

    AuStreamReadWrittenPair_t IConvCPToUTF8(ECodePage page, const void *in, AuUInt length, void *utf8, AuUInt32 utf8Max)
    {
#if defined(AURORA_IS_POSIX_DERIVED)

        auto handleItr = gIconvCodePage2UTF.find(page);
        if (handleItr == gIconvCodePage2UTF.end())
        {
            return {};
        }
        auto handle = handleItr->second;

        return IConvWork(handle, in, length, utf8, utf8Max);

    #else

        return {};

    #endif
    }

    AuStreamReadWrittenPair_t IConvUTF8ToCp(ECodePage page, const void *utf8, AuUInt32 utf8Length, void *cp, AuUInt32 cpLen)
    {
#if defined(AURORA_IS_POSIX_DERIVED)

        auto handleItr = gIconvUTF2CodePage.find(page);
        if (handleItr == gIconvUTF2CodePage.end())
        {
            return {};
        }
        auto handle = handleItr->second;

        return IConvWork(handle, utf8, utf8Length, cp, cpLen);
        
    #else

        return {};

    #endif
    }

    static void AddPair(ECodePage page)
    {
    #if defined(AURORA_IS_POSIX_DERIVED)
        AuString temp;

        auto fromLocale = PageToString(page, temp);
        if (!fromLocale)
        {
            SysPushErrorUnimplemented();
            return;
        }

        auto toUTF = iconv_open("UTF8", fromLocale);
        if (toUTF == (iconv_t) -1)
        {
            SysPushErrorGen();
            return;
        }

        auto fromUTF = iconv_open(fromLocale, "UTF8");
        if (fromUTF == (iconv_t) -1)
        {
            SysPushErrorGen();
            return;
        }

        AuTryInsert(gIconvCodePage2UTF, page, toUTF);
        AuTryInsert(gIconvUTF2CodePage, page, fromUTF);

    #endif
    }

    void InitIConv()
    {
        AddPair(ECodePage::eSysUnk);
        AddPair(ECodePage::eLatin1);
        AddPair(ECodePage::eUTF7);
        AddPair(ECodePage::e2312);
        AddPair(ECodePage::eGBK);
        AddPair(ECodePage::eSJIS);
        AddPair(ECodePage::eUTF16);
        AddPair(ECodePage::e18030);
    }
}