import {
    createDecipheriv,
    createCipheriv,
    createHash,
    createHmac,
    randomBytes,
} from 'node:crypto';

export type EncryptedStoreSecret = {
    ciphertext: Buffer;
    nonce: Buffer;
    fingerprint: string;
};

/**
 * 密钥只在此边界短暂以明文存在。数据库保存 AES-GCM 密文和随机 nonce，
 * fingerprint 是不可逆 HMAC，仅用于安全地识别同一份密钥。
 */
export function encryptStoreSecret(
    plaintext: string,
    keyMaterial: string,
): EncryptedStoreSecret {
    const key = createHash('sha256').update(keyMaterial).digest();
    const nonce = randomBytes(12);
    const cipher = createCipheriv('aes-256-gcm', key, nonce);
    const ciphertext = Buffer.concat([
        cipher.update(plaintext, 'utf8'),
        cipher.final(),
        cipher.getAuthTag(),
    ]);
    return {
        ciphertext,
        nonce,
        fingerprint: createHmac('sha256', key)
            .update(plaintext)
            .digest('base64url'),
    };
}

/** 仅供受信任的后台 Worker 使用；调用方不得记录返回值。 */
export function decryptStoreSecret(
    ciphertextWithTag: Buffer,
    nonce: Buffer,
    keyMaterial: string,
): string {
    const authenticationTagLength = 16;
    if (ciphertextWithTag.length <= authenticationTagLength) {
        throw new Error('Invalid encrypted store secret');
    }
    const key = createHash('sha256').update(keyMaterial).digest();
    const ciphertext = ciphertextWithTag.subarray(0, -authenticationTagLength);
    const tag = ciphertextWithTag.subarray(-authenticationTagLength);
    const decipher = createDecipheriv('aes-256-gcm', key, nonce);
    decipher.setAuthTag(tag);
    return Buffer.concat([
        decipher.update(ciphertext),
        decipher.final(),
    ]).toString('utf8');
}