import { Config } from '../config';

export interface LoginSession {
  state: string
  redirectUrl: string
  verifier: string
}

export function generateRandomString() {
  var array = new Uint32Array(28);
  window.crypto.getRandomValues(array);
  return Array.from(array, dec => ('0' + dec.toString(16)).substr(-2)).join('');
}

export function sha256(plain): PromiseLike<any> {
  const encoder = new TextEncoder();
  const data = encoder.encode(plain);
  return window.crypto.subtle.digest('SHA-256', data);
}

export function pkceChallengeFromVerifier(v): PromiseLike<string> {
  return sha256(v)
    .then(hashed => base64urlencode(hashed));
}

export function base64urlencode(str) {
  return btoa(String.fromCharCode.apply(null, new Uint8Array(str)))
      .replace(/\+/g, '-').replace(/\//g, '_').replace(/=+$/, '');
}

export function createLoginSession(): Promise<LoginSession> {
  // Based on https://auth0.com/docs/api-auth/tutorials/authorization-code-grant-pkce
  const state = generateRandomString();
  const verifier = generateRandomString();

  return new Promise<LoginSession>((resolve, reject) => {
    try {
      pkceChallengeFromVerifier(verifier).then(challenge => {
        console.log('Code challenge is', challenge);
        
        let redirectUrl=`${Config.oauth2AuthorizeURL}`;
        redirectUrl += `?audience=${encodeURIComponent(Config.oauth2Audience)}`;
        redirectUrl += `&scope=${encodeURIComponent(Config.oauth2Scope)}`;
        redirectUrl += `&response_type=code`;
        redirectUrl += `&client_id=${encodeURIComponent(Config.oauth2ClientId)}`
        redirectUrl += `&code_challenge=${encodeURIComponent(challenge)}`;
        redirectUrl += `&code_challenge_method=S256`
        redirectUrl += `&redirect_uri=${encodeURIComponent(Config.oauth2RedirectURI)}`;
        redirectUrl += `&state=${encodeURIComponent(state)}`;

        return resolve({
          state,
          redirectUrl,
          verifier,
        });
      });
    } catch(err) {
      return reject(err);
    }
  });  
};

export interface AccessTokenRequest {
  data: FormData,
  url: string
}

export function createAccessTokenRequest(code: string, verifier: string): AccessTokenRequest {
  const data = new FormData();
  data.append('grant_type', 'authorization_code');
  data.append('client_id', Config.oauth2ClientId);
  data.append('code_verifier', verifier);
  data.append('code', code);
  data.append('redirect_uri', Config.oauth2RedirectURI);
  return {
    url: Config.oauth2TokenURL,
    data,
  };
};

export function getLogoutURL(rawIdToken: string): string {
  let logoutURL = Config.oauth2LogoutURL;
  logoutURL += `?post_logout_redirect_uri=${encodeURIComponent(Config.oauth2PostLogoutRedirectURI)}`;
  logoutURL += `&id_token_hint=${encodeURIComponent(rawIdToken)}`;
  return logoutURL;
}

export interface AccessGrant {
  access_token: string
  expires_in: number
  id_token: string
  refresh_token: string
  scope: string
  token_type: string
}

export function saveLoginSessionState(verifier: string, state: string) {
  window.localStorage.setItem('login_verifier', verifier);
  window.localStorage.setItem('login_state', state);
}

export function getSavedLoginSessionState(cleanup = true) {
  const loginSession = {
    verifier: window.localStorage.getItem('login_verifier'),
    state: window.localStorage.getItem('login_state')
  };
  if (cleanup) {
    window.localStorage.removeItem('login_verifier');
    window.localStorage.removeItem('login_state');
  }
  return loginSession;
}

export function saveAccessGrant(grant: AccessGrant) {
  window.localStorage.setItem('access_grant', JSON.stringify(grant));
}

export function getSavedAccessGrant(): AccessGrant {
  const raw = window.localStorage.getItem('access_grant');
  if (raw === "") return null;
  return JSON.parse(raw) as AccessGrant;
}

export function clearAccessGrant() {
  window.localStorage.removeItem('access_grant');
}