import type { v1 } from '@standard-schema/spec';
/**
 * Use the OpenAuth client kick off your OAuth flows, exchange tokens, refresh tokens,
 * and verify tokens.
 *
 * First, create a client.
 *
 * ```ts title="client.ts"
 * import { createClient } from "@openauthjs/openauth/client"
 *
 * const client = createClient({
 *   clientID: "my-client",
 *   issuer: "https://auth.myserver.com"
 * })
 * ```
 *
 * Kick off the OAuth flow by calling `authorize`.
 *
 * ```ts
 * const redirect_uri = "https://myserver.com/callback"
 *
 * const { url } = await client.authorize(
 *   redirect_uri,
 *   "code"
 * )
 * ```
 *
 * When the user completes the flow, `exchange` the code for tokens.
 *
 * ```ts
 * const tokens = await client.exchange(query.get("code"), redirect_uri)
 * ```
 *
 * And `verify` the tokens.
 *
 * ```ts
 * const verified = await client.verify(subjects, tokens.access)
 * ```
 *
 * @packageDocumentation
 */
import { createLocalJWKSet, errors, JSONWebKeySet, jwtVerify, decodeJwt } from 'jose';

import {
	InvalidAccessTokenError,
	InvalidAuthorizationCodeError,
	InvalidRefreshTokenError,
	InvalidSubjectError
} from './error.js';
import { generatePKCE } from './pkce.js';
import { SubjectSchema } from './subject.js';

/**
 * The well-known information for an OAuth 2.0 authorization server.
 * @internal
 */
export interface WellKnown {
	/**
	 * The URI to the JWKS endpoint.
	 */
	jwks_uri: string;
	/**
	 * The URI to the token endpoint.
	 */
	token_endpoint: string;
	/**
	 * The URI to the authorization endpoint.
	 */
	authorization_endpoint: string;
}

/**
 * The tokens returned by the auth server.
 */
export interface Tokens {
	/**
	 * The access token.
	 */
	access: string;
	/**
	 * The refresh token.
	 */
	refresh: string;

	/**
	 * The number of seconds until the access token expires.
	 */
	expiresIn: number;
}

interface ResponseLike {
	json(): Promise<unknown>;
	ok: Response['ok'];
}
type FetchLike = (...args: any[]) => Promise<ResponseLike>;

/**
 * The challenge that you can use to verify the code.
 */
export type Challenge = {
	/**
	 * The state that was sent to the redirect URI.
	 */
	state: string;
	/**
	 * The verifier that was sent to the redirect URI.
	 */
	verifier?: string;
};

/**
 * Configure the client.
 */
export interface ClientInput {
	/**
	 * The client ID. This is just a string to identify your app.
	 *
	 * If you have a web app and a mobile app, you want to use different client IDs both.
	 *
	 * @example
	 * ```ts
	 * {
	 *   clientID: "my-client"
	 * }
	 * ```
	 */
	clientID: string;
	/**
	 * The URL of your OpenAuth server.
	 *
	 * @example
	 * ```ts
	 * {
	 *   issuer: "https://auth.myserver.com"
	 * }
	 * ```
	 */
	issuer?: string;
	/**
	 * Optionally, override the internally used fetch function.
	 *
	 * This is useful if you are using a polyfilled fetch function in your application and you
	 * want the client to use it too.
	 */
	fetch?: FetchLike;
}

export interface AuthorizeOptions {
	/**
	 * Enable the PKCE flow. This is for SPA apps.
	 *
	 * ```ts
	 * {
	 *   pkce: true
	 * }
	 * ```
	 *
	 * @default false
	 */
	pkce?: boolean;
	/**
	 * The provider you want to use for the OAuth flow.
	 *
	 * ```ts
	 * {
	 *   provider: "google"
	 * }
	 * ```
	 *
	 * If no provider is specified, the user is directed to a page where they can select from the
	 * list of configured providers.
	 *
	 * If there's only one provider configured, the user will be redirected to that.
	 */
	provider?: string;
}

export interface AuthorizeResult {
	/**
	 * The challenge that you can use to verify the code. This is for the PKCE flow for SPA apps.
	 *
	 * This is an object that you _stringify_ and store it in session storage.
	 *
	 * ```ts
	 * sessionStorage.setItem("challenge", JSON.stringify(challenge))
	 * ```
	 */
	challenge: Challenge;
	/**
	 * The URL to redirect the user to. This starts the OAuth flow.
	 *
	 * For example, for SPA apps.
	 *
	 * ```ts
	 * location.href = url
	 * ```
	 */
	url: string;
}

/**
 * Returned when the exchange is successful.
 */
export interface ExchangeSuccess {
	/**
	 * This is always `false` when the exchange is successful.
	 */
	err: false;
	/**
	 * The access and refresh tokens.
	 */
	tokens: Tokens;
}

/**
 * Returned when the exchange fails.
 */
export interface ExchangeError {
	/**
	 * The type of error that occurred. You can handle this by checking the type.
	 *
	 * @example
	 * ```ts
	 * import { InvalidAuthorizationCodeError } from "@openauthjs/openauth/error"
	 *
	 * console.log(err instanceof InvalidAuthorizationCodeError)
	 *```
	 */
	err: InvalidAuthorizationCodeError;
}

export interface RefreshOptions {
	/**
	 * Optionally, pass in the access token.
	 */
	access?: string;
}

/**
 * Returned when the refresh is successful.
 */
export interface RefreshSuccess {
	/**
	 * This is always `false` when the refresh is successful.
	 */
	err: false;
	/**
	 * Returns the refreshed tokens only if they've been refreshed.
	 *
	 * If they are still valid, this will be `undefined`.
	 */
	tokens?: Tokens;
}

/**
 * Returned when the refresh fails.
 */
export interface RefreshError {
	/**
	 * The type of error that occurred. You can handle this by checking the type.
	 *
	 * @example
	 * ```ts
	 * import { InvalidRefreshTokenError } from "@openauthjs/openauth/error"
	 *
	 * console.log(err instanceof InvalidRefreshTokenError)
	 *```
	 */
	err: InvalidRefreshTokenError | InvalidAccessTokenError;
}

export interface VerifyOptions {
	/**
	 * Optionally, pass in the refresh token.
	 *
	 * If passed in, this will automatically refresh the access token if it has expired.
	 */
	refresh?: string;
	/**
	 * @internal
	 */
	issuer?: string;
	/**
	 * @internal
	 */
	audience?: string;
	/**
	 * Optionally, override the internally used fetch function.
	 *
	 * This is useful if you are using a polyfilled fetch function in your application and you
	 * want the client to use it too.
	 */
	fetch?: FetchLike;
}

export interface VerifyResult<T extends SubjectSchema> {
	/**
	 * This is always `undefined` when the verify is successful.
	 */
	err?: undefined;
	/**
	 * Returns the refreshed tokens only if they’ve been refreshed.
	 *
	 * If they are still valid, this will be undefined.
	 */
	tokens?: Tokens;
	/**
	 * @internal
	 */
	aud: string;
	/**
	 * The decoded subjects from the access token.
	 *
	 * Has the same shape as the subjects you defined when creating the issuer.
	 */
	subject: {
		[type in keyof T]: { type: type; properties: v1.InferOutput<T[type]> };
	}[keyof T];
}

/**
 * Returned when the verify call fails.
 */
export interface VerifyError {
	/**
	 * The type of error that occurred. You can handle this by checking the type.
	 *
	 * @example
	 * ```ts
	 * import { InvalidRefreshTokenError } from "@openauthjs/openauth/error"
	 *
	 * console.log(err instanceof InvalidRefreshTokenError)
	 *```
	 */
	err: InvalidRefreshTokenError | InvalidAccessTokenError;
}

/**
 * An instance of the OpenAuth client contains the following methods.
 */
export interface Client {
	/**
	 * Start the autorization flow. For example, in SSR sites.
	 *
	 * ```ts
	 * const { url } = await client.authorize(<redirect_uri>, "code")
	 * ```
	 *
	 * This takes a redirect URI and the type of flow you want to use. The redirect URI is the
	 * location where the user will be redirected to after the flow is complete.
	 *
	 * Supports both the _code_ and _token_ flows. We recommend using the _code_ flow as it's more
	 * secure.
	 *
	 * :::tip
	 * This returns a URL to redirect the user to. This starts the OAuth flow.
	 * :::
	 *
	 * This returns a URL to the auth server. You can redirect the user to the URL to start the
	 * OAuth flow.
	 *
	 * For SPA apps, we recommend using the PKCE flow.
	 *
	 * ```ts {4}
	 * const { challenge, url } = await client.authorize(
	 *   <redirect_uri>,
	 *   "code",
	 *   { pkce: true }
	 * )
	 * ```
	 *
	 * This returns a redirect URL and a challenge that you need to use later to verify the code.
	 */
	authorize(
		redirectURI: string,
		response: 'code' | 'token',
		opts?: AuthorizeOptions
	): Promise<AuthorizeResult>;
	/**
	 * Exchange the code for access and refresh tokens.
	 *
	 * ```ts
	 * const exchanged = await client.exchange(<code>, <redirect_uri>)
	 * ```
	 *
	 * You call this after the user has been redirected back to your app after the OAuth flow.
	 *
	 * :::tip
	 * For SSR sites, the code is returned in the query parameter.
	 * :::
	 *
	 * So the code comes from the query parameter in the redirect URI. The redirect URI here is
	 * the one that you passed in to the `authorize` call when starting the flow.
	 *
	 * :::tip
	 * For SPA sites, the code is returned through the URL hash.
	 * :::
	 *
	 * If you used the PKCE flow for an SPA app, the code is returned as a part of the redirect URL
	 * hash.
	 *
	 * ```ts {4}
	 * const exchanged = await client.exchange(
	 *   <code>,
	 *   <redirect_uri>,
	 *   <challenge.verifier>
	 * )
	 * ```
	 *
	 * You also need to pass in the previously stored challenge verifier.
	 *
	 * This method returns the access and refresh tokens. Or if it fails, it returns an error that
	 * you can handle depending on the error.
	 *
	 * ```ts
	 * import { InvalidAuthorizationCodeError } from "@openauthjs/openauth/error"
	 *
	 * if (exchanged.err) {
	 *   if (exchanged.err instanceof InvalidAuthorizationCodeError) {
	 *     // handle invalid code error
	 *   }
	 *   else {
	 *     // handle other errors
	 *   }
	 * }
	 *
	 * const { access, refresh } = exchanged.tokens
	 * ```
	 */
	exchange(
		code: string,
		redirectURI: string,
		verifier?: string
	): Promise<ExchangeSuccess | ExchangeError>;
	/**
	 * Refreshes the tokens if they have expired. This is used in an SPA app to maintain the
	 * session, without logging the user out.
	 *
	 * ```ts
	 * const next = await client.refresh(<refresh_token>)
	 * ```
	 *
	 * Can optionally take the access token as well. If passed in, this will skip the refresh
	 * if the access token is still valid.
	 *
	 * ```ts
	 * const next = await client.refresh(<refresh_token>, { access: <access_token> })
	 * ```
	 *
	 * This returns the refreshed tokens only if they've been refreshed.
	 *
	 * ```ts
	 * if (!next.err) {
	 *   // tokens are still valid
	 * }
	 * if (next.tokens) {
	 *   const { access, refresh } = next.tokens
	 * }
	 * ```
	 *
	 * Or if it fails, it returns an error that you can handle depending on the error.
	 *
	 * ```ts
	 * import { InvalidRefreshTokenError } from "@openauthjs/openauth/error"
	 *
	 * if (next.err) {
	 *   if (next.err instanceof InvalidRefreshTokenError) {
	 *     // handle invalid refresh token error
	 *   }
	 *   else {
	 *     // handle other errors
	 *   }
	 * }
	 * ```
	 */
	refresh(refresh: string, opts?: RefreshOptions): Promise<RefreshSuccess | RefreshError>;
	/**
	 * Verify the token in the incoming request.
	 *
	 * This is typically used for SSR sites where the token is stored in an HTTP only cookie. And
	 * is passed to the server on every request.
	 *
	 * ```ts
	 * const verified = await client.verify(<subjects>, <token>)
	 * ```
	 *
	 * This takes the subjects that you had previously defined when creating the issuer.
	 *
	 * :::tip
	 * If the refresh token is passed in, it'll automatically refresh the access token.
	 * :::
	 *
	 * This can optionally take the refresh token as well. If passed in, it'll automatically
	 * refresh the access token if it has expired.
	 *
	 * ```ts
	 * const verified = await client.verify(<subjects>, <token>, { refresh: <refresh_token> })
	 * ```
	 *
	 * This returns the decoded subjects from the access token. And the tokens if they've been
	 * refreshed.
	 *
	 * ```ts
	 * // based on the subjects you defined earlier
	 * console.log(verified.subject.properties.userID)
	 *
	 * if (verified.tokens) {
	 *   const { access, refresh } = verified.tokens
	 * }
	 * ```
	 *
	 * Or if it fails, it returns an error that you can handle depending on the error.
	 *
	 * ```ts
	 * import { InvalidRefreshTokenError } from "@openauthjs/openauth/error"
	 *
	 * if (verified.err) {
	 *   if (verified.err instanceof InvalidRefreshTokenError) {
	 *     // handle invalid refresh token error
	 *   }
	 *   else {
	 *     // handle other errors
	 *   }
	 * }
	 * ```
	 */
	verify<T extends SubjectSchema>(
		subjects: T,
		token: string,
		options?: VerifyOptions
	): Promise<VerifyResult<T> | VerifyError>;
}

/**
 * Create an OpenAuth client.
 *
 * @param input - Configure the client.
 */
export function createClient(input: ClientInput): Client {
	const jwksCache = new Map<string, ReturnType<typeof createLocalJWKSet>>();
	const issuerCache = new Map<string, WellKnown>();
	const issuer = input.issuer || process.env.OPENAUTH_ISSUER;
	if (!issuer) throw new Error('No issuer');
	const f = input.fetch ?? fetch;

	async function getIssuer() {
		const cached = issuerCache.get(issuer!);
		if (cached) return cached;
		const wellKnown = (await (f || fetch)(`${issuer}/.well-known/oauth-authorization-server`).then(
			(r) => r.json()
		)) as WellKnown;
		issuerCache.set(issuer!, wellKnown);
		return wellKnown;
	}

	async function getJWKS() {
		const wk = await getIssuer();
		const cached = jwksCache.get(issuer!);
		if (cached) return cached;
		const keyset = (await (f || fetch)(wk.jwks_uri).then((r) => r.json())) as JSONWebKeySet;
		const result = createLocalJWKSet(keyset);
		jwksCache.set(issuer!, result);
		return result;
	}

	const result = {
		async authorize(redirectURI: string, response: 'code' | 'token', opts?: AuthorizeOptions) {
			const result = new URL(issuer + '/authorize');
			const challenge: Challenge = {
				state: crypto.randomUUID()
			};
			result.searchParams.set('client_id', input.clientID);
			result.searchParams.set('redirect_uri', redirectURI);
			result.searchParams.set('response_type', response);
			result.searchParams.set('state', challenge.state);
			if (opts?.provider) result.searchParams.set('provider', opts.provider);
			if (opts?.pkce && response === 'code') {
				const pkce = await generatePKCE();
				result.searchParams.set('code_challenge_method', 'S256');
				result.searchParams.set('code_challenge', pkce.challenge);
				challenge.verifier = pkce.verifier;
			}
			return {
				challenge,
				url: result.toString()
			};
		},
		/**
		 * @deprecated use `authorize` instead, it will do pkce by default unless disabled with `opts.pkce = false`
		 */
		async pkce(
			redirectURI: string,
			opts?: {
				provider?: string;
			}
		) {
			const result = new URL(issuer + '/authorize');
			if (opts?.provider) result.searchParams.set('provider', opts.provider);
			result.searchParams.set('client_id', input.clientID);
			result.searchParams.set('redirect_uri', redirectURI);
			result.searchParams.set('response_type', 'code');
			const pkce = await generatePKCE();
			result.searchParams.set('code_challenge_method', 'S256');
			result.searchParams.set('code_challenge', pkce.challenge);
			return [pkce.verifier, result.toString()];
		},
		async exchange(
			code: string,
			redirectURI: string,
			verifier?: string
		): Promise<ExchangeSuccess | ExchangeError> {
			const tokens = await f(issuer + '/token', {
				method: 'POST',
				headers: {
					'Content-Type': 'application/x-www-form-urlencoded'
				},
				body: new URLSearchParams({
					code,
					redirect_uri: redirectURI,
					grant_type: 'authorization_code',
					client_id: input.clientID,
					code_verifier: verifier || ''
				}).toString()
			});
			const json = (await tokens.json()) as any;
			if (!tokens.ok) {
				return {
					err: new InvalidAuthorizationCodeError()
				};
			}
			return {
				err: false,
				tokens: {
					access: json.access_token as string,
					refresh: json.refresh_token as string,
					expiresIn: json.expires_in as number
				}
			};
		},
		async refresh(refresh: string, opts?: RefreshOptions): Promise<RefreshSuccess | RefreshError> {
			if (opts && opts.access) {
				const decoded = decodeJwt(opts.access);
				if (!decoded) {
					return {
						err: new InvalidAccessTokenError()
					};
				}
				// allow 30s window for expiration
				if ((decoded.exp || 0) > Date.now() / 1000 + 30) {
					return {
						err: false
					};
				}
			}
			const tokens = await f(issuer + '/token', {
				method: 'POST',
				headers: {
					'Content-Type': 'application/x-www-form-urlencoded'
				},
				body: new URLSearchParams({
					grant_type: 'refresh_token',
					refresh_token: refresh
				}).toString()
			});
			const json = (await tokens.json()) as any;
			if (!tokens.ok) {
				return {
					err: new InvalidRefreshTokenError()
				};
			}
			return {
				err: false,
				tokens: {
					access: json.access_token as string,
					refresh: json.refresh_token as string,
					expiresIn: json.expires_in as number
				}
			};
		},
		async verify<T extends SubjectSchema>(
			subjects: T,
			token: string,
			options?: VerifyOptions
		): Promise<VerifyResult<T> | VerifyError> {
			const jwks = await getJWKS();
			try {
				const result = await jwtVerify<{
					mode: 'access';
					type: keyof T;
					properties: v1.InferInput<T[keyof T]>;
				}>(token, jwks, {
					issuer
				});
				const validated = await subjects[result.payload.type]['~standard'].validate(
					result.payload.properties
				);
				if (!validated.issues && result.payload.mode === 'access') {
					return {
						aud: result.payload.aud as string,
						subject: {
							type: result.payload.type,
							properties: validated.value
						} as any
					};
				}
				return {
					err: new InvalidSubjectError()
				};
			} catch (e) {
				if (e instanceof errors.JWTExpired && options?.refresh) {
					const refreshed = await this.refresh(options.refresh);
					if (refreshed.err) return refreshed;
					const verified = await result.verify(subjects, refreshed.tokens!.access, {
						refresh: refreshed.tokens!.refresh,
						issuer,
						fetch: options?.fetch
					});
					if (verified.err) return verified;
					verified.tokens = refreshed.tokens;
					return verified;
				}
				return {
					err: new InvalidAccessTokenError()
				};
			}
		}
	};
	return result;
}