import { HalfCryptoKeyPair } from "encryption/types";

export interface RSAKeyEncryptorI {
    encryptKey(key: CryptoKey): Promise<ArrayBuffer>;
    decryptKey(
        encryptedKey: ArrayBuffer,
        decryptedKeyAlgorithm: AesKeyAlgorithm
    ): Promise<CryptoKey>;
}

export function RSAKeyEncryptor(
    keyPair: CryptoKeyPair | HalfCryptoKeyPair
): RSAKeyEncryptorI {
    const { publicKey, privateKey } = keyPair as CryptoKeyPair;

    const exportFormat = "jwk";
    const algorithm = RSAKeyEncryptor.getDefaultAlgorithm();

    return {
        async encryptKey(key: CryptoKey): Promise<ArrayBuffer> {
            if (!publicKey) {
                throw new Error(
                    "Cannot encrypt key as publicKey has not been supplied."
                );
            }
            return await crypto.subtle.wrapKey(
                exportFormat,
                key,
                publicKey,
                algorithm
            );
        },
        async decryptKey(
            encryptedKey: ArrayBuffer,
            decryptedKeyAlgorithm: AesKeyAlgorithm
        ): Promise<CryptoKey> {
            if (!privateKey) {
                throw new Error(
                    "Cannot decrypt key as publicKey has not been supplied."
                );
            }
            return await crypto.subtle.unwrapKey(
                exportFormat,
                encryptedKey,
                privateKey,
                algorithm,
                decryptedKeyAlgorithm,
                true,
                ["encrypt", "decrypt"]
            );
        }
    };
}

RSAKeyEncryptor.getDefaultAlgorithm = function(): RsaHashedKeyGenParams {
    return Object.freeze({
        name: "RSA-OAEP",
        modulusLength: 2048,
        // From MDN: Unless you have a good reason to use something else, specify 65537 here ([0x01, 0x00, 0x01]).
        publicExponent: new Uint8Array([0x01, 0x00, 0x01]),
        hash: "SHA-512"
    });
};

RSAKeyEncryptor.generateKeyPair = async function(): Promise<CryptoKeyPair> {
    return (await crypto.subtle.generateKey(
        RSAKeyEncryptor.getDefaultAlgorithm(),
        // We need to be able to save this key to the user document, so it needs to be extractable
        true,
        ["wrapKey", "unwrapKey"]
    )) as CryptoKeyPair;
};