import * as kbpgp from "kbpgp";
import promisify from "es6-promisify";

const ECC_SIZES = ["256", "384"];
const RSA_SIZES = ["1024", "2048", "4096"];
const KEY_SIZES = RSA_SIZES.concat(ECC_SIZES);
const KEY_TYPES = ["RSA", "ECC"];

/**
 * PGP operations.
 *
 * @author tlwr [toby@toby.codes]
 * @copyright Crown Copyright 2016
 * @license Apache-2.0
 *
 * @namespace
 */
const PGP = {
    KEY_SIZES: KEY_SIZES,

    /**
     * Validate PGP Key Size
     * @param {string} keySize
     * @returns {Integer}
     */
    validateKeySize(keySize, keyType) {
        if (KEY_SIZES.indexOf(keySize) < 0) {
            throw `Invalid key size ${keySize}, must be in ${JSON.stringify(KEY_SIZES)}`;
        }

        if (keyType === "ecc") {
            if (ECC_SIZES.indexOf(keySize) >= 0) {
                return parseInt(keySize, 10);
            } else {
                throw `Invalid key size ${keySize}, must be in ${JSON.stringify(ECC_SIZES)} for ECC`;
            }
        } else {
            if (RSA_SIZES.indexOf(keySize) >= 0) {
                return parseInt(keySize, 10);
            } else {
                throw `Invalid key size ${keySize}, must be in ${JSON.stringify(RSA_SIZES)} for RSA`;
            }
        }
    },

    /**
     * Get size of subkey
     * @param {Integer} keySize
     * @returns {Integer}
     */
    getSubkeySize(keySize) {
        return {
            1024: 1024,
            2048: 1024,
            4096: 2048,
            256:   256,
            384:   256,
        }[keySize];
    },


    KEY_TYPES: KEY_TYPES,

    /**
     * Validate PGP Key Type
     * @param {string} keyType
     * @returns {string}
     */
    validateKeyType(keyType) {
        if (KEY_TYPES.indexOf(keyType) >= 0) return keyType.toLowerCase();
        throw `Invalid key type ${keyType}, must be in ${JSON.stringify(KEY_TYPES)}`;
    },

    /**
     * Generate PGP Key Pair operation.
     *
     * @author tlwr [toby@toby.codes]
     * @param {string} input
     * @param {Object[]} args
     * @returns {string}
     */
    runGenerateKeyPair(input, args) {
        let keyType  = args[0],
            keySize  = args[1],
            password = args[2],
            name     = args[3],
            email    = args[4];

        keyType = PGP.validateKeyType(keyType);
        keySize = PGP.validateKeySize(keySize, keyType);

        let userIdentifier = "";
        if (name) userIdentifier += name;
        if (email) userIdentifier += ` <${email}>`;

        let flags = kbpgp.const.openpgp.certify_keys;
        flags = flags | kbpgp.const.openpgp.sign_data;
        flags = flags | kbpgp.const.openpgp.auth;
        flags = flags | kbpgp.const.openpgp.encrypt_comm;
        flags = flags | kbpgp.const.openpgp.encrypt_storage;

        let keyGenerationOptions = {
            userid: userIdentifier,
            ecc: keyType === "ecc",
            primary: {
                nbits: keySize,
                flags: flags,
                expire_in: 0 // eslint-disable-line camelcase
            },
            subkeys: [{
                nbits: PGP.getSubkeySize(keySize),
                flags: kbpgp.const.openpgp.sign_data,
                expire_in: 86400 * 365 * 8 // eslint-disable-line camelcase
            }, {
                nbits: PGP.getSubkeySize(keySize),
                flags: kbpgp.const.openpgp.encrypt_comm | kbpgp.const.openpgp.encrypt_storage,
                expire_in: 86400 * 365 * 2 // eslint-disable-line camelcase
            }],
        };
        return new Promise(async (resolve, reject) => {
            try {
                const unsignedKey = await promisify(kbpgp.KeyManager.generate)(keyGenerationOptions);
                await promisify(unsignedKey.sign, unsignedKey)({});
                let signedKey = unsignedKey;
                let privateKeyExportOptions = {};
                if (password) privateKeyExportOptions.passphrase = password;
                const privateKey = await promisify(signedKey.export_pgp_private, signedKey)(privateKeyExportOptions);
                const publicKey = await promisify(signedKey.export_pgp_public, signedKey)({});
                resolve(privateKey + "\n" + publicKey);
            } catch (err) {
                reject(`Error from kbpgp whilst generating key pair: ${err}`);
            }
        });
    }
};

export default PGP;