/*
 * Copyright 2021 Inrupt Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to use,
 * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
 * Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
 * PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

/**
 * @hidden
 */
import { EventEmitter } from "events";
import {
  ILoginInputOptions,
  ISessionInfo,
  IStorage,
  ResourceServerSession,
} from "@inrupt/solid-client-authn-core";
import { v4 } from "uuid";
import ClientAuthentication from "./ClientAuthentication";
import { getClientAuthenticationWithDependencies } from "./dependencies";

export interface ISessionOptions {
  /**
   * A private storage, unreachable to other scripts on the page. Typically in-memory.
   */
  secureStorage: IStorage;
  /**
   * A storage where non-sensitive information may be stored, potentially longer-lived than the secure storage.
   */
  insecureStorage: IStorage;
  /**
   * Details about the current session
   */
  sessionInfo: ISessionInfo;
  /**
   * An instance of the library core. Typically obtained using `getClientAuthenticationWithDependencies`.
   */
  clientAuthentication: ClientAuthentication;
}

/**
 * A {@link Session} object represents a user's session on an application. The session holds state, as it stores information enabling acces to private resources after login for instance.
 */
export class Session extends EventEmitter {
  /**
   * Information regarding the current session.
   */
  public readonly info: ISessionInfo;

  private clientAuthentication: ClientAuthentication;

  private tokenRequestInProgress = false;

  /**
   * Session object constructor. Typically called as follows:
   *
   * ```typescript
   * const session = new Session();
   * ```
   * @param sessionOptions The options enabling the correct instantiation of
   * the session. Either both storages or clientAuthentication are required. For
   * more information, see {@link ISessionOptions}.
   * @param sessionId A magic string uniquely identifying the session.
   *
   */
  constructor(
    sessionOptions: Partial<ISessionOptions> = {},
    sessionId?: string
  ) {
    super();

    if (sessionOptions.clientAuthentication) {
      this.clientAuthentication = sessionOptions.clientAuthentication;
    } else if (sessionOptions.secureStorage && sessionOptions.insecureStorage) {
      this.clientAuthentication = getClientAuthenticationWithDependencies({
        secureStorage: sessionOptions.secureStorage,
        insecureStorage: sessionOptions.insecureStorage,
      });
    } else {
      this.clientAuthentication = getClientAuthenticationWithDependencies({});
    }

    if (sessionOptions.sessionInfo) {
      this.info = {
        sessionId: sessionOptions.sessionInfo.sessionId,
        isLoggedIn: false,
        webId: sessionOptions.sessionInfo.webId,
      };
    } else {
      this.info = {
        sessionId: sessionId ?? v4(),
        isLoggedIn: false,
      };
    }
  }

  /**
   * Triggers the login process. Note that this method will redirect the user away from your app.
   *
   * @param options Parameter to customize the login behaviour. In particular, two options are mandatory: `options.oidcIssuer`, the user's identity provider, and `options.redirectUrl`, the URL to which the user will be redirected after logging in their identity provider.
   * @returns This method should redirect the user away from the app: it does not return anything. The login process is completed by {@linkcode handleIncomingRedirect}.
   */
  // Define these functions as properties so that they don't get accidentally re-bound.
  // Isn't Javascript fun?
  login = async (options: ILoginInputOptions): Promise<void> => {
    await this.clientAuthentication.login(this.info.sessionId, {
      ...options,
    });
  };

  /**
   * Fetches data using available login information. If the user is not logged in, this will behave as a regular `fetch`. The signature of this method is identical to the [canonical `fetch`](https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API).
   *
   * @param url The URL from which data should be fetched.
   * @param init Optional parameters customizing the request, by specifying an HTTP method, headers, a body, etc. Follows the [WHATWG Fetch Standard](https://fetch.spec.whatwg.org/).
   */
  fetch = async (url: RequestInfo, init?: RequestInit): Promise<Response> => {
    return this.clientAuthentication.fetch(url, init);
  };

  /**
   * Logs the user out of the application. This does not log the user out of their Solid identity provider, and should not redirect the user away.
   */
  logout = async (): Promise<void> => {
    await this.clientAuthentication.logout(this.info.sessionId);
    this.info.isLoggedIn = false;
    this.emit("logout");
  };

  /**
   * Completes the login process by processing the information provided by the Solid identity provider through redirect.
   *
   * @param url The URL of the page handling the redirect, including the query parameters — these contain the information to process the login.
   */
  handleIncomingRedirect = async (
    url: string
  ): Promise<ISessionInfo | undefined> => {
    if (this.info.isLoggedIn) {
      return this.info;
    }
    if (this.tokenRequestInProgress) {
      return undefined;
    }

    // Unfortunately, regular sessions are lost when the user refreshes the page or opens a new tab.
    // While we're figuring out the API for a longer-term solution, as a temporary workaround some
    // *resource* servers set a cookie that keeps the user logged in after authenticated requests,
    // and expose the fact that they set it on a special endpoint.
    // After login, we store that fact in LocalStorage. This means that we can now look for that
    // data, and if present, indicate that the user is already logged in.
    // Note that there are a lot of edge cases that won't work well with this approach, so it willl
    // be removed in due time.
    const storedSessionCookieReference = window.localStorage.getItem(
      "tmp-resource-server-session-info"
    );
    if (typeof storedSessionCookieReference === "string") {
      // TOOD: Re-use the type used when writing this data:
      // https://github.com/inrupt/solid-client-authn-js/pull/920/files#diff-659ac87dfd3711f4cfcea3c7bf6970980f4740fd59df45f04c7977bffaa23e98R118
      // To keep temporary code together
      // eslint-disable-next-line no-inner-declarations
      function isValidSessionCookieReference(
        reference: Record<string, unknown>
      ): reference is ResourceServerSession {
        const resourceServers = Object.keys(
          (reference as ResourceServerSession).sessions ?? {}
        );
        return (
          typeof (reference as ResourceServerSession).webId === "string" &&
          resourceServers.length > 0 &&
          typeof (reference as ResourceServerSession).sessions[
            resourceServers[0]
          ].expiration === "number"
        );
      }
      const reference = JSON.parse(storedSessionCookieReference);
      if (isValidSessionCookieReference(reference)) {
        const resourceServers = Object.keys(reference.sessions);
        const webIdOrigin = new URL(reference.webId).hostname;
        const ownResourceServer = resourceServers.find((resourceServer) => {
          return new URL(resourceServer).hostname === webIdOrigin;
        });
        // Usually the user's WebID is also a Resource server for them,
        // so we pick the expiration time for that. If it doesn't exist,
        // we just pick the first (and probably only) one:
        const relevantServer = ownResourceServer ?? resourceServers[0];
        // If the cookie is valid for fewer than five minutes,
        // pretend it's not valid anymore already, to avoid small misalignments
        // resulting in invalid states:
        if (
          reference.sessions[relevantServer].expiration - Date.now() >
          5 * 60 * 1000
        ) {
          this.info.isLoggedIn = true;
          this.info.webId = reference.webId;
          return this.info;
        }
      }
    }
    // end of temporary workaround.

    this.tokenRequestInProgress = true;
    const sessionInfo = await this.clientAuthentication.handleIncomingRedirect(
      url
    );
    if (sessionInfo) {
      this.info.isLoggedIn = sessionInfo.isLoggedIn;
      this.info.webId = sessionInfo.webId;
      this.info.sessionId = sessionInfo.sessionId;
      if (sessionInfo.isLoggedIn) {
        // The login event can only be triggered **after** the user has been
        // redirected from the IdP with access and ID tokens.
        this.emit("login");
      }
    }
    this.tokenRequestInProgress = false;
    return sessionInfo;
  };

  /**
   * Register a callback function to be called when a user completes login.
   *
   * The callback is called when {@link handleIncomingRedirect} completes successfully.
   *
   * @param callback The function called when a user completes login.
   */
  onLogin(callback: () => unknown): void {
    this.on("login", callback);
  }

  /**
   * Register a callback function to be called when a user logs out:
   *
   * @param callback The function called when a user completes logout.
   */
  onLogout(callback: () => unknown): void {
    this.on("logout", callback);
  }
}