/*
 * Copyright 2017-2017 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"). You may not use this file except in compliance with
 * the License. A copy of the License is located at
 *
 *     http://aws.amazon.com/apache2.0/
 *
 * or in the "license" file accompanying this file. This file is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
 * CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions
 * and limitations under the License.
 */


import { parse } from 'url';  // Used for OAuth parsing of Cognito Hosted UI
import { launchUri } from './urlOpener';
import * as oAuthStorage from './oauthStorage';

import {
  OAuthOpts,
  isCognitoHostedOpts,
  CognitoHostedUIIdentityProvider
} from '../types/Auth';

import {
  ConsoleLogger as Logger,
  Hub
} from '@aws-amplify/core';

const SHA256 = require("crypto-js/sha256");
const Base64 = require("crypto-js/enc-base64");

const AMPLIFY_SYMBOL = ((typeof Symbol !== 'undefined' && typeof Symbol.for === 'function') ?
    Symbol.for('amplify_default') : '@@amplify_default') as Symbol;

const dispatchAuthEvent = (event:string, data:any, message:string) => {
  Hub.dispatch('auth', { event, data, message }, 'Auth', AMPLIFY_SYMBOL);
};

const logger = new Logger('OAuth');

export default class OAuth {

  private _urlOpener;
  private _config;
  private _cognitoClientId;
  private _scopes;

  constructor({
    config,
    cognitoClientId,
    scopes = []
  }: {
    scopes: string[],
    config: OAuthOpts,
    cognitoClientId: string
  }) {
    this._urlOpener = config.urlOpener || launchUri;
    this._config = config;
    this._cognitoClientId = cognitoClientId;
    this._scopes = scopes;
  }

  public oauthSignIn(
    responseType = 'code',
    domain: string,
    redirectSignIn: string,
    clientId: string,
    provider: CognitoHostedUIIdentityProvider | string = CognitoHostedUIIdentityProvider.Cognito) {

    const state = this._generateState(32);
    oAuthStorage.setState(state);

    const pkce_key = this._generateRandom(128);
    oAuthStorage.setPKCE(pkce_key);
    
    const code_challenge = this._generateChallenge(pkce_key);
    const code_challenge_method = 'S256';

    const queryString = Object.entries({
      redirect_uri: redirectSignIn,
      response_type: responseType, 
      client_id: clientId,
      identity_provider: provider,
      scopes: this._scopes,
      state,
      ...(responseType === 'code'?{code_challenge}:{}),
      ...(responseType === 'code'?{code_challenge_method}:{})
    }).map(([k,v]) => `${encodeURIComponent(k)}=${encodeURIComponent(v)}`).join('&');

    const URL = `https://${domain}/oauth2/authorize?${queryString}`;
    logger.debug(`Redirecting to ${URL}`);
    this._urlOpener(URL, redirectSignIn);
  }

  private async _handleCodeFlow(currentUrl: string) {
    /* Convert URL into an object with parameters as keys
    { redirect_uri: 'http://localhost:3000/', response_type: 'code', ...} */
    const { code } = (parse(currentUrl).query || '')
      .split('&')
      .map((pairings) => pairings.split('='))
      .reduce((accum, [k, v]) => ({ ...accum, [k]: v }), { code: undefined });

    if (!code) { return; }

    
    const oAuthTokenEndpoint = 'https://' + this._config.domain + '/oauth2/token';
      
    dispatchAuthEvent(
      'codeFlow',
      {},
      `Retrieving tokens from ${oAuthTokenEndpoint}`
    );

    const client_id = isCognitoHostedOpts(this._config)
      ? this._cognitoClientId
      : this._config.clientID;

    const redirect_uri = isCognitoHostedOpts(this._config)
      ? this._config.redirectSignIn
      : this._config.redirectUri;

    const code_verifier = oAuthStorage.getPKCE();

    const oAuthTokenBody = {
      grant_type: 'authorization_code',
      code,
      client_id,
      redirect_uri,
      ...(code_verifier ? { code_verifier } : {})
    };

    logger.debug(`Calling token endpoint: ${oAuthTokenEndpoint} with`, oAuthTokenBody);

    const body = Object.entries(oAuthTokenBody)
      .map(([k, v]) =>`${encodeURIComponent(k)}=${encodeURIComponent(v)}`)
      .join('&');

    const { access_token, refresh_token, id_token, error } = await (await fetch(oAuthTokenEndpoint, {
        method: 'POST',
        headers: {
          'Content-Type': 'application/x-www-form-urlencoded'
        },
        body: typeof URLSearchParams !== 'undefined' ? new URLSearchParams(body) : body
      }) as any).json();

      if (error) {
        throw new Error(error);
      }

      return {
        accessToken: access_token,
        refreshToken: refresh_token,
        idToken: id_token
      };
  }

  private async _handleImplicitFlow(currentUrl: string) {

    const { id_token, access_token } = parse(currentUrl).hash
      .substr(1) // Remove # from returned code
      .split('&')
      .map((pairings) => pairings.split('='))
      .reduce((accum, [k, v]) => ({ ...accum, [k]: v }), {
        id_token: undefined, access_token: undefined
      });

    dispatchAuthEvent(
      'implicitFlow',
      {},
      `Got tokens from ${currentUrl}`
    );
    logger.debug(`Retrieving implicit tokens from ${currentUrl} with`);

    return {
      accessToken: access_token,
      idToken: id_token,
      refreshToken: null
    };
  }

  public async handleAuthResponse(currentUrl?: string) {
    const urlParams = currentUrl ? {
      ...(parse(currentUrl).hash || '#').substr(1)
        .split('&')
        .map(entry => entry.split('='))
        .reduce((acc, [k, v]) => (acc[k] = v, acc), {}),
      ...(parse(currentUrl).query || '')
        .split('&')
        .map(entry => entry.split('='))
        .reduce((acc, [k, v]) => (acc[k] = v, acc), {})
    } as any : {};
    const { error, error_description } = urlParams;

    if (error) {
      throw new Error(error_description);
    }

    this._validateState(urlParams);

    logger.debug(`Starting ${this._config.responseType} flow with ${currentUrl}`);
    if (this._config.responseType === 'code') {
      return this._handleCodeFlow(currentUrl);
    } else {
      return this._handleImplicitFlow(currentUrl);
    }
  }

  private _validateState(urlParams: any) {
    if (!urlParams) { return; }

    const savedState = oAuthStorage.getState();
    const { state: returnedState } = urlParams;

    // This is because savedState only exists if the flow was initiated by Amplify
    if (savedState && savedState !== returnedState) {
      throw new Error('Invalid state in OAuth flow');
    }
  }

  public async signOut() {
    let oAuthLogoutEndpoint = 'https://' + this._config.domain + '/logout?';

    const client_id = isCognitoHostedOpts(this._config)
      ? this._cognitoClientId
      : this._config.oauth.clientID;

    const signout_uri = isCognitoHostedOpts(this._config)
      ? this._config.redirectSignOut
      : this._config.returnTo;

    oAuthLogoutEndpoint += Object.entries({
      client_id,
      logout_uri: encodeURIComponent(signout_uri)
    }).map(([k, v]) => `${k}=${v}`).join('&');

    dispatchAuthEvent(
      'oAuthSignOut',
      {oAuth: 'signOut'},
      `Signing out from ${oAuthLogoutEndpoint}`
    );
    logger.debug(`Signing out from ${oAuthLogoutEndpoint}`);
    
    this._urlOpener(oAuthLogoutEndpoint);
  }

  private _generateState(length: number) {
    let result = '';
    let i = length;
    const chars = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
    for (; i > 0; --i) result += chars[Math.round(Math.random() * (chars.length - 1))];
    return result;
  }

  private _generateChallenge(code:string) {
    return this._base64URL(SHA256(code));
  }

  private _base64URL(string) {
    return string.toString(Base64).replace(/=/g, '').replace(/\+/g, '-').replace(/\//g, '_');
  }

  private _generateRandom(size: number) {
    const CHARSET = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-._~';
    const buffer = new Uint8Array(size);
    if (typeof window !== 'undefined' && !!(window.crypto)) {
      window.crypto.getRandomValues(buffer);
    } else {
      for (let i = 0; i < size; i += 1) {
        buffer[i] = (Math.random() * CHARSET.length) | 0;
      }
    }
    return this._bufferToString(buffer);
  }

  private _bufferToString(buffer: Uint8Array) {
    const CHARSET = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
    const state = [];
    for (let i = 0; i < buffer.byteLength; i += 1) {
      const index = buffer[i] % CHARSET.length;
      state.push(CHARSET[index]);
    }
    return state.join('');
  }
}