import CryptoJS from 'crypto-js';

// The key from your C# Middleware
// In a real app, prefer storing this in process.env.REACT_APP_ENCRYPTION_KEY
// const KEY_BASE64 = "h9J4kL2mN5pQ8rS1tV3wX6yZ0aB7cD9eF1gH3jK5mN6=";
const KEY_BASE64 = "u4J7p9Qx2hF5vYtLz8Kq3mN1sG0bRwXyZcD6eH8jFQw=";
/**
 * Decrypts the specific format sent by the C# EncryptionMiddleware.
 * Format: Base64([IV (16 bytes)] + [Encrypted Data])
 * * @param {string} encryptedBase64Str - The raw response text from the API
 * @returns {any} - The parsed JSON object or string
 */
export const decryptResponse = (encryptedBase64Str) => {
    try {
        // 1. Parse the Key
        const key = CryptoJS.enc.Base64.parse(KEY_BASE64);

        // 2. Parse the incoming Base64 string to a WordArray
        const fullWordArray = CryptoJS.enc.Base64.parse(encryptedBase64Str);

        // 3. Convert to Hex to easily slice the IV (16 bytes = 32 hex chars)
        // This is safer than manipulating WordArray indices directly
        const fullHex = CryptoJS.enc.Hex.stringify(fullWordArray);

        // 4. Extract IV (First 16 bytes / 32 hex characters)
        const ivHex = fullHex.substring(0, 32);
        const iv = CryptoJS.enc.Hex.parse(ivHex);

        // 5. Extract Ciphertext (The rest of the string)
        const cipherTextHex = fullHex.substring(32);
        const cipherParams = CryptoJS.lib.CipherParams.create({
            ciphertext: CryptoJS.enc.Hex.parse(cipherTextHex)
        });

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

        // 7. Convert to UTF-8 String
        const decryptedString = decrypted.toString(CryptoJS.enc.Utf8);

        if (!decryptedString) {
            throw new Error("Decryption produced empty result (Wrong Key/IV?)");
        }

        // 8. Try to parse JSON, otherwise return plain string
        try {
            return JSON.parse(decryptedString);
        } catch {
            return decryptedString;
        }

    } catch (error) {
        console.error("Decryption Failed:", error);
        return null;
    }
};