/**
 * Use this to connect authentication providers that support OIDC.
 *
 * ```ts {5-8}
 * import { OidcProvider } from "@openauthjs/openauth/provider/oidc"
 *
 * export default issuer({
 *   providers: {
 *     oauth2: OidcProvider({
 *       clientId: "1234567890",
 *       issuer: "https://auth.myserver.com"
 *     })
 *   }
 * })
 * ```
 *
 *
 * @packageDocumentation
 */

import { JWTPayload } from 'hono/utils/jwt/types';
import { createLocalJWKSet, JSONWebKeySet, jwtVerify } from 'jose';

import { WellKnown } from '../client.js';
import { OauthError } from '../error.js';
import { getRelativeUrl, lazy } from '../util.js';
import { Provider } from './provider.js';

export interface OidcConfig {
	/**
	 * @internal
	 */
	type?: string;
	/**
	 * The client ID.
	 *
	 * This is just a string to identify your app.
	 *
	 * @example
	 * ```ts
	 * {
	 *   clientID: "my-client"
	 * }
	 * ```
	 */
	clientID: string;
	/**
	 * The URL of your authorization server.
	 *
	 * @example
	 * ```ts
	 * {
	 *   issuer: "https://auth.myserver.com"
	 * }
	 * ```
	 */
	issuer: string;
	/**
	 * A list of OIDC scopes that you want to request.
	 *
	 * @example
	 * ```ts
	 * {
	 *   scopes: ["openid", "profile", "email"]
	 * }
	 * ```
	 */
	scopes?: string[];
	/**
	 * Any additional parameters that you want to pass to the authorization endpoint.
	 * @example
	 * ```ts
	 * {
	 *   query: {
	 *     prompt: "consent"
	 *   }
	 * }
	 * ```
	 */
	query?: Record<string, string>;
}

/**
 * @internal
 */
export type OidcWrappedConfig = Omit<OidcConfig, 'issuer' | 'name'>;

interface ProviderState {
	state: string;
	nonce: string;
	redirect: string;
}

/**
 * @internal
 */
export interface IdTokenResponse {
	idToken: string;
	claims: Record<string, any>;
	raw: Record<string, any>;
}

export function OidcProvider(config: OidcConfig): Provider<{ id: JWTPayload; clientID: string }> {
	const query = config.query || {};
	const scopes = config.scopes || [];

	const wk = lazy(() =>
		fetch(config.issuer + '/.well-known/openid-configuration').then(async (r) => {
			if (!r.ok) throw new Error(await r.text());
			return r.json() as Promise<WellKnown>;
		})
	);

	const jwks = lazy(() =>
		wk()
			.then((r) => r.jwks_uri)
			.then(async (uri) => {
				const r = await fetch(uri);
				if (!r.ok) throw new Error(await r.text());
				return createLocalJWKSet((await r.json()) as JSONWebKeySet);
			})
	);

	return {
		type: config.type || 'oidc',
		init(routes, ctx) {
			routes.get('/authorize', async (c) => {
				const provider: ProviderState = {
					state: crypto.randomUUID(),
					nonce: crypto.randomUUID(),
					redirect: getRelativeUrl(c, './callback')
				};
				await ctx.set(c, 'provider', 60 * 10, provider);
				const authorization = new URL(await wk().then((r) => r.authorization_endpoint));
				authorization.searchParams.set('client_id', config.clientID);
				authorization.searchParams.set('response_type', 'id_token');
				authorization.searchParams.set('response_mode', 'form_post');
				authorization.searchParams.set('state', provider.state);
				authorization.searchParams.set('nonce', provider.nonce);
				authorization.searchParams.set('redirect_uri', provider.redirect);
				authorization.searchParams.set('scope', ['openid', ...scopes].join(' '));
				for (const [key, value] of Object.entries(query)) {
					authorization.searchParams.set(key, value);
				}
				return c.redirect(authorization.toString());
			});

			routes.post('/callback', async (c) => {
				const provider = await ctx.get<ProviderState>(c, 'provider');
				if (!provider) return c.redirect(getRelativeUrl(c, './authorize'));
				const body = await c.req.formData();
				const error = body.get('error');
				if (error)
					throw new OauthError(
						error.toString() as any,
						body.get('error_description')?.toString() || ''
					);
				const idToken = body.get('id_token');
				if (!idToken) throw new OauthError('invalid_request', 'Missing id_token');
				const result = await jwtVerify(idToken.toString(), await jwks(), {
					audience: config.clientID
				});
				if (result.payload.nonce !== provider.nonce) {
					throw new OauthError('invalid_request', 'Invalid nonce');
				}
				return ctx.success(c, {
					id: result.payload,
					clientID: config.clientID
				});
			});
		}
	};
}