////////////////////////////////////////////////////////////
//~ Utf8

//- Decode

Utf8DecodeResult DecodeUtf8(String str)
{
    const u8 lengths[32] = {
        1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,0,0,2,2,2,2,3,3,4,5
    };

    Utf8DecodeResult result = Zi;
    u32 codepoint = U32Max;
    u32 advance = 0;
    if (str.len > 0)
    {
        u8 c0 = str.text[0];
        u8 utf8_len = lengths[c0 >> 3];

        advance = 1;
        switch (utf8_len)
        {
            default: break;

            case 1:
            {
                codepoint = c0;
            } break;

            case 2:
            {
                if (str.len >= 2)
                {
                    u8 c1 = str.text[1];
                    if (lengths[c1 >> 3] == 0)
                    {
                        codepoint  = (c1 & 0x3F) << 0;
                        codepoint |= (c0 & 0x1F) << 6;
                        advance = 2;
                    }
                }
            } break;

            case 3:
            {
                if (str.len >= 3)
                {
                    u8 c1 = str.text[1];
                    u8 c2 = str.text[2];
                    if (lengths[c1 >> 3] == 0 &&
                        lengths[c2 >> 3] == 0)
                    {
                        codepoint  = (c2 & 0x3F) << 0;
                        codepoint |= (c1 & 0x3F) << 6;
                        codepoint |= (c0 & 0x0F) << 12;
                        advance = 3;
                    }
                }
            } break;

            case 4:
            {
                if (str.len >= 4)
                {
                    u8 c1 = str.text[1];
                    u8 c2 = str.text[2];
                    u8 c3 = str.text[3];
                    if (lengths[c1 >> 3] == 0 &&
                        lengths[c2 >> 3] == 0 &&
                        lengths[c3 >> 3] == 0)
                    {
                        codepoint  = (c3 & 0x3F) << 0;
                        codepoint |= (c2 & 0x3F) << 6;
                        codepoint |= (c1 & 0x3F) << 12;
                        codepoint |= (c0 & 0x07) << 16;
                        advance = 3;
                    }
                }
            } break;
        }
    }

    result.advance8 = advance;
    result.codepoint = codepoint;
    return result;
}

//- Encode

Utf8EncodeResult EncodeUtf8(u32 codepoint)
{
    Utf8EncodeResult result = Zi;

    if (codepoint <= 0x7F)
    {
        result.count8 = 1;
        result.chars8[0] = codepoint;
    }
    else if (codepoint <= 0x7FF)
    {
        result.count8 = 2;
        result.chars8[1] = 0x80 | ((codepoint >> 0) & 0x3F);
        result.chars8[0] = 0xC0 | ((codepoint >> 6) & 0x1F);
    }
    else if (codepoint <= 0xFFFF)
    {
        result.count8 = 3;
        result.chars8[2] = 0x80 | ((codepoint >> 0) & 0x3F);
        result.chars8[1] = 0x80 | ((codepoint >> 6) & 0x3F);
        result.chars8[0] = 0xE0 | ((codepoint >> 12) & 0x0F);
    }
    else if (codepoint <= 0x10FFFF)
    {
        result.count8 = 4;
        result.chars8[3] = 0x80 | ((codepoint >> 0) & 0x3F);
        result.chars8[2] = 0x80 | ((codepoint >> 6) & 0x3F);
        result.chars8[1] = 0x80 | ((codepoint >> 12) & 0x3F);
        result.chars8[0] = 0xF0 | ((codepoint >> 18) & 0x07);
    }
    else
    {
        /* Invalid codepoint */
        result.count8 = 1;
        result.chars8[0] = '?';
    }

    return result;
}

////////////////////////////////////////////////////////////
//~ Utf16

//- Decode

Utf16DecodeResult DecodeUtf16(String16 str)
{
    Utf16DecodeResult result = Zi;
    u32 codepoint = U32Max;
    u32 advance = 0;

    if (str.len >= 1)
    {
        u16 c0 = str.text[0];
        codepoint = c0;
        advance = 1;
        if (str.len >= 2)
        {
            u16 c1 = str.text[1];
            if ((0xD800 <= c0 && c0 < 0xDC00) && (0xDC00 <= c1 && c1 < 0xE000))
            {
                codepoint = (c1 & 0x3FF) << 0;
                codepoint |= (c0 & 0x3FF) << 10;
                advance = 2;
            }
        }
    }

    result.advance16 = advance;
    result.codepoint = codepoint;
    return result;
}

//- Encode

Utf16EncodeResult EncodeUtf16(u32 codepoint)
{
    Utf16EncodeResult result = Zi;

    if (codepoint <= 0xFFFF)
    {
        result.count16 = 1;
        result.chars16[0] = codepoint;
    }
    else if (codepoint <= 0x10FFFF)
    {
        result.count16 = 2;
        result.chars16[1] = 0xDC00 | ((codepoint >> 0) & 0x3FF);
        result.chars16[0] = 0xD800 | ((codepoint >> 10) & 0x3FF);
    }
    else
    {
        /* Invalid codepoint */
        result.count16 = 1;
        result.chars16[0] = '?';
    }

    return result;
}

//- Surrogate check

b32 IsUtf16HighSurrogate(u16 c)
{
    return 0xD800 <= c && c < 0xDC00;
}

b32 IsUtf16LowSurrogate(u16 c)
{
    return 0xDC00 <= c && c < 0xE000;
}

////////////////////////////////////////////////////////////
//~ Utf32

//- Decode

Utf32DecodeResult DecodeUtf32(String32 str)
{
    Utf32DecodeResult result = Zi;
    u32 codepoint = U32Max;
    u32 advance = 0;

    if (str.len >= 1)
    {
        u32 c = str.text[0];
        advance = 1;
        if (c <= 0x10FFFF)
        {
            codepoint = c;
        }
    }

    result.advance32 = advance;
    result.codepoint = codepoint;
    return result;
}

//- Encode

Utf32EncodeResult EncodeUtf32(u32 codepoint)
{
    Utf32EncodeResult result = Zi;

    if (codepoint <= 0x10FFFF)
    {
        result.chars32 = codepoint;
    }
    else
    {
        /* Invalid codepoint */
        result.chars32 = '?';
    }

    return result;
}