import * as qs from 'querystring';

import type { ClientOAuth2, ClientOAuth2Options } from './ClientOAuth2';
import type { ClientOAuth2Token, ClientOAuth2TokenData } from './ClientOAuth2Token';
import { DEFAULT_HEADERS, DEFAULT_URL_BASE } from './constants';
import { auth, expects, getAuthError, getRequestOptions } from './utils';

interface CodeFlowBody {
	code: string | string[];
	grant_type: 'authorization_code';
	redirect_uri?: string;
	client_id?: string;
}

/**
 * Support authorization code OAuth 2.0 grant.
 *
 * Reference: http://tools.ietf.org/html/rfc6749#section-4.1
 */
export class CodeFlow {
	constructor(private client: ClientOAuth2) {}

	/**
	 * Generate the uri for doing the first redirect.
	 */
	getUri(opts?: Partial<ClientOAuth2Options>): string {
		const options: ClientOAuth2Options = { ...this.client.options, ...opts };

		// Check the required parameters are set.
		expects(options, 'clientId', 'authorizationUri');

		const url = new URL(options.authorizationUri);

		const queryParams = {
			...options.query,
			client_id: options.clientId,
			redirect_uri: options.redirectUri,
			response_type: 'code',
			state: options.state,
			...(options.scopes ? { scope: options.scopes.join(options.scopesSeparator ?? ' ') } : {}),
		};

		for (const [key, value] of Object.entries(queryParams)) {
			if (value !== null && value !== undefined) {
				url.searchParams.append(key, value);
			}
		}

		return url.toString();
	}

	/**
	 * Get the code token from the redirected uri and make another request for
	 * the user access token.
	 */
	async getToken(
		urlString: string,
		opts?: Partial<ClientOAuth2Options>,
	): Promise<ClientOAuth2Token> {
		const options: ClientOAuth2Options = { ...this.client.options, ...opts };
		expects(options, 'clientId', 'accessTokenUri');

		const url = new URL(urlString, DEFAULT_URL_BASE);
		if (
			typeof options.redirectUri === 'string' &&
			typeof url.pathname === 'string' &&
			url.pathname !== new URL(options.redirectUri, DEFAULT_URL_BASE).pathname
		) {
			throw new TypeError('Redirected path should match configured path, but got: ' + url.pathname);
		}

		if (!url.search?.substring(1)) {
			throw new TypeError(`Unable to process uri: ${urlString}`);
		}

		const data =
			typeof url.search === 'string' ? qs.parse(url.search.substring(1)) : url.search || {};

		// eslint-disable-next-line @typescript-eslint/ban-ts-comment
		// @ts-ignore
		const error = getAuthError(data);
		if (error) throw error;

		if (options.state && data.state !== options.state) {
			// eslint-disable-next-line @typescript-eslint/restrict-template-expressions
			throw new TypeError(`Invalid state: ${data.state}`);
		}

		// Check whether the response code is set.
		if (!data.code) {
			throw new TypeError('Missing code, unable to request token');
		}

		const headers = { ...DEFAULT_HEADERS };
		const body: CodeFlowBody = {
			code: data.code,
			grant_type: 'authorization_code',
			redirect_uri: options.redirectUri,
		};

		// `client_id`: REQUIRED, if the client is not authenticating with the
		// authorization server as described in Section 3.2.1.
		// Reference: https://tools.ietf.org/html/rfc6749#section-3.2.1
		if (options.clientSecret) {
			headers.Authorization = auth(options.clientId, options.clientSecret);
		} else {
			body.client_id = options.clientId;
		}

		const requestOptions = getRequestOptions(
			{
				url: options.accessTokenUri,
				method: 'POST',
				headers,
				body,
			},
			options,
		);

		const responseData = await this.client.request<ClientOAuth2TokenData>(requestOptions);
		return this.client.createToken(responseData);
	}
}