init.luau

--!strict
local function from16(decimal)
    return string.format("%X", decimal)  -- 대문자 16진수
end


function from2(num: number): string
    if num == 0 then return '0' end
    local result = '';
    while true do
        if num < 1.1 then
            break
        end
        result = `{num % 2}{result}`;
        num = math.floor(num / 2);
    end
    return result
end

export type UTF16Impl = {
    __index: UTF16Impl,
    codepoint: (str: string) -> (number),
    encode: (str: string) -> (string),
    decode: (str: string) -> (string),
}

local utf16 = {} :: UTF16Impl
utf16.__index = utf16

function utf16.codepoint(str)
    return utf8.codepoint(str);
end

function utf16.decode(str) 
    return utf8.char(tonumber(str, 16) :: number);
end

function utf16.encode(str)
    local codePoint = utf8.codepoint(str);
    local str16 = from16(codePoint);
    local result = '';

    if tonumber(str16, 16) <= 0xFFFF then 
        result = str16;
        for i=1, 4 - #str16 do
            result = `0{result}`;
        end
    else
        local str2 = from2(codePoint);
        for i=1, 20 - #str2 do
            str2 = `0{str2}`;
        end
        result = from16(tonumber(`110110{str2:sub(1, 10)}110111{str2:sub(11)}`, 2) :: number);
    end

    return result;
end

return utf16