/*
 * Copyright 2023, Andrew Lindesay <apl@lindesay.co.nz>.
 * All rights reserved. Distributed under the terms of the MIT License.
 */


#include "JwtTokenHelper.h"

#include "DataIOUtils.h"
#include "Json.h"
#include "JsonMessageWriter.h"

#include <ctype.h>


/*static*/ bool
JwtTokenHelper::IsValid(const BString& value)
{
        int countDots = 0;

        for (int i = 0; i < value.Length(); i++) {
                char ch = value[i];

                if ('.' == ch)
                        countDots++;
                else {
                        if (!_IsBase64(ch))
                                return false;
                }
        }

        return 2 == countDots;
}


/*! A JWT token is split into three parts separated by a '.' character. The
    middle section is a base-64 encoded string and within the string is JSON
    structured data. The JSON data contains key-value pairs which carry data
    about the token. This method will take a JWT token, will find the middle
    section and will parse the claims into the supplied 'message' parameter.
*/

/*static*/ status_t
JwtTokenHelper::ParseClaims(const BString& token, BMessage& message)
{
        int firstDot = token.FindFirst('.');

        if (firstDot == B_ERROR)
                return B_BAD_VALUE;

        // find the end of the first section by looking for the next dot.

        int secondDot = token.FindFirst('.', firstDot + 1);

        if (secondDot == B_ERROR)
                return B_BAD_VALUE;

        BMemoryIO memoryIo(&(token.String())[firstDot + 1], (secondDot - firstDot) - 1);
        Base64DecodingDataIO base64DecodingIo(&memoryIo, '-', '_');
        BJsonMessageWriter writer(message);
        BJson::Parse(&base64DecodingIo, &writer);

        return writer.ErrorStatus();
}


/*! Note this is base64 "url" standard that disallows "/" and "+" and instead
    uses "-" and "_".
*/

/*static*/ bool
JwtTokenHelper::_IsBase64(char ch)
{
        return isalnum(ch)
                || '=' == ch
                || '-' == ch
                || '_' == ch;
}