import CryptoJS from 'crypto-js';

/**
 * Backenddan kelgan shifrlangan tokenni ochish
 */
export const decryptToken = (encryptedBase64: string) => {
    try {
        // 1. Base64 dan WordArray ga
        const encryptedData = CryptoJS.enc.Base64.parse(encryptedBase64);

        // 2. IV (dastlabki 16 bayt)
        const iv = CryptoJS.lib.WordArray.create(encryptedData.words.slice(0, 4));

        // 3. Ciphertext (qolgan qism)
        const ciphertext = CryptoJS.lib.WordArray.create(
            encryptedData.words.slice(4),
            encryptedData.sigBytes - 16
        );

        // 4. Maxfiy kalit
        const key = CryptoJS.enc.Utf8.parse("12345678901234567890123456789012");

        // 5. CipherParams yaratish
        const cipherParams = CryptoJS.lib.CipherParams.create({
            ciphertext,
            key,
            iv
        });

        // 6. Dekodlash
        const decrypted = CryptoJS.AES.decrypt(cipherParams, key, {
            iv,
            mode: CryptoJS.mode.CBC,
            padding: CryptoJS.pad.Pkcs7
        });

        return decrypted.toString(CryptoJS.enc.Utf8);
    } catch (error) {
        return null;
    }
};