Auth.ts

import axios from "axios";
import type { GetUserTokenOptions, UserTokenContext } from "../Interface";

/**
 * Browser compaitable function to encode base64 string.
 */
const encodeBase64 = typeof Buffer === "undefined" ? btoa : buffer => Buffer.from(buffer).toString("base64");

/**
 * A manager to perform actions regarding the authorization to the web api.
 */
export class AuthManager {
	/**
	 * A manager to perform actions regarding the authorization to the web api.
	 *
	 * @param token Your spotify web api token.
	 * @example const auth = new AuthManager('token');
	 */
	public constructor(public token: string) {
	}

	/**
	 * Returns an api token from your spotify application client id and client secret!
	 *
	 * @param clientID Your spotify app's client id.
	 * @param clientSecret Your spotify app's client secret.
	 * @example await auth.getApiToken('id', 'secret');
	 */
	public async getApiToken(clientID: string, clientSecret: string): Promise<string> {
		const { data } = await axios({
			method: "POST",
			url: "https://accounts.spotify.com/api/token",
			params: {
				grant_type: "client_credentials",
				token: this.token,
				client_id: clientID,
				client_secret: clientSecret,
			},
			headers: {
				"Content-Type": "application/x-www-form-urlencoded",
			},
			data: {},
		});

		return data.access_token;
	}

	/**
	 * Returns a acces token of a spotify user through the authorization process.
	 *
	 * @param options Options required to get spotify user token!
	 * @example
	 * await auth.getUserToken({
	 *    clientID: 'id',
	 *    clientSecret: 'secret',
	 *    code: 'code', // If attempting to get user token through authorization
	 *    refreshToken: 'token', // If attempting to refresh token!
	 *    redirectURL: 'url' // Needs to be the same what you have enetered while authorizing the token!
	 * })
	 */
	public async getUserToken(options: GetUserTokenOptions): Promise<UserTokenContext> {
		if (!options.refreshToken && !options.code)
			throw new TypeError(
				"The 'refresh token' and the 'authorization code' supplied to generate a user token is invalid.",
			);

		const grant_type = options.refreshToken && !options.code ? "refresh_token" : "authorization_code";

		const { data } = await axios({
			method: "post",
			url: "https://accounts.spotify.com/api/token",
			params: {
				grant_type,
				code: options.code,
				refresh_token: options.refreshToken,
				redirect_uri: options.redirectURL,
			},
			headers: {
				"Content-Type": "application/x-www-form-urlencoded",
				Authorization: `Basic ${encodeBase64(options.clientID + ":" + options.clientSecret)}`,
			},
			data: {},
		});

		return {
			accessToken: data.access_token,
			tokenType: data.token_type,
			scope: data.scope,
			refreshToken: data.refresh_token,
			expiresIn: data.expires_in,
		};
	}
}