Token Token::extract(const KeyValuePairs& response) {
    std::string token_key, token_secret;

    KeyValuePairs::const_iterator it = response.find(Defaults::TOKEN_KEY);
    if (it == response.end())
        throw MissingKeyError("Couldn't find oauth_token in response");
    token_key = it->second;

    it = response.find(Defaults::TOKENSECRET_KEY);
    if (it == response.end())
        throw MissingKeyError("Couldn't find oauth_token_secret in response");
    token_secret = it->second;

    return Token(token_key, token_secret);
}
// Helper for parameters in key-value pair lists that should only appear
// once. Either replaces an existing entry or adds a new entry.
static void ReplaceOrInsertKeyValuePair(KeyValuePairs& kvp, const std::string& key, const std::string& value) {
    assert(kvp.count(key) <= 1);
    KeyValuePairs::iterator it = kvp.find(key);
    if (it != kvp.end())
        it->second = value;
    else
        kvp.insert(KeyValuePairs::value_type(key, value));
}
std::string Client::buildOAuthParameterString(
    ParameterStringType string_type,
    const Http::RequestType eType,
    const std::string& rawUrl,
    const std::string& rawData,
    const bool includeOAuthVerifierPin)
{
    KeyValuePairs rawKeyValuePairs;
    std::string rawParams;
    std::string oauthSignature;
    std::string paramsSeperator;
    std::string pureUrl( rawUrl );

    std::string separator;
    bool do_urlencode;
    if (string_type == AuthorizationHeaderString) {
        separator = ",";
        do_urlencode = false;
    }
    else { /*if (string_type == QueryStringString)*/
        separator = "&";
        do_urlencode = true;
    }

    /* Clear header string initially */
    rawKeyValuePairs.clear();

    /* If URL itself contains ?key=value, then extract and put them in map */
    size_t nPos = rawUrl.find_first_of( "?" );
    if( std::string::npos != nPos )
    {
        /* Get only URL */
        pureUrl = rawUrl.substr( 0, nPos );

        /* Get only key=value data part */
        std::string dataPart = rawUrl.substr( nPos + 1 );
        rawKeyValuePairs = ParseKeyValuePairs(dataPart);
    }

    // We always request URL encoding on the first pass so that the
    // signature generation works properly. This *relies* on
    // buildOAuthTokenKeyValuePairs overwriting values when we do the second
    // pass to get the values in the form we actually want. The signature and
    // rawdata are the only things that change, but the signature is only used
    // in the second pass and the rawdata is already encoded, regardless of
    // request type.

    /* Build key-value pairs needed for OAuth request token, without signature */
    buildOAuthTokenKeyValuePairs( includeOAuthVerifierPin, rawData, std::string( "" ), rawKeyValuePairs, true, true );

    /* Get url encoded base64 signature using request type, url and parameters */
    getSignature( eType, pureUrl, rawKeyValuePairs, oauthSignature );

    /* Now, again build key-value pairs with signature this time */
    buildOAuthTokenKeyValuePairs( includeOAuthVerifierPin, std::string( "" ), oauthSignature, rawKeyValuePairs, do_urlencode, false );

    /* Get OAuth header in string format. If we're getting the Authorization
     * header, we need to filter out other parameters.
     */
    if (string_type == AuthorizationHeaderString) {
        KeyValuePairs oauthKeyValuePairs;
        std::vector<std::string> oauth_keys;
        oauth_keys.push_back(Defaults::CONSUMERKEY_KEY);
        oauth_keys.push_back(Defaults::NONCE_KEY);
        oauth_keys.push_back(Defaults::SIGNATURE_KEY);
        oauth_keys.push_back(Defaults::SIGNATUREMETHOD_KEY);
        oauth_keys.push_back(Defaults::TIMESTAMP_KEY);
        oauth_keys.push_back(Defaults::TOKEN_KEY);
        oauth_keys.push_back(Defaults::VERIFIER_KEY);
        oauth_keys.push_back(Defaults::VERSION_KEY);

        for(size_t i = 0; i < oauth_keys.size(); i++) {
            assert(rawKeyValuePairs.count(oauth_keys[i]) <= 1);
            KeyValuePairs::iterator oauth_key_it = rawKeyValuePairs.find(oauth_keys[i]);
            if (oauth_key_it != rawKeyValuePairs.end())
                ReplaceOrInsertKeyValuePair(oauthKeyValuePairs, oauth_keys[i], oauth_key_it->second);
        }
        getStringFromOAuthKeyValuePairs( oauthKeyValuePairs, rawParams, separator );
    }
    else if (string_type == QueryStringString) {
        getStringFromOAuthKeyValuePairs( rawKeyValuePairs, rawParams, separator );
    }

    /* Build authorization header */
    return rawParams;
}