import { getAuth } from './auth';

export interface RequestScopeTicket {
  accountKey: string;
  pageGeneration: number;
  lane: string;
  laneGeneration: number;
}

export interface PageRequestScope {
  activate: () => void;
  begin: (lane: string) => RequestScopeTicket;
  invalidate: () => void;
  isCurrent: (ticket: RequestScopeTicket) => boolean;
}

const tokenFingerprint = (token: string) => {
  let hash = 2166136261;
  for (let index = 0; index < token.length; index += 1) {
    hash ^= token.charCodeAt(index);
    hash = Math.imul(hash, 16777619);
  }
  return (hash >>> 0).toString(16).padStart(8, '0');
};

export const currentAccountKey = () => {
  const auth = getAuth();
  return `${auth.phone}|${auth.clientId}|${tokenFingerprint(auth.token)}`;
};

export const createPageRequestScope = (): PageRequestScope => {
  let active = false;
  let accountKey = '';
  let pageGeneration = 0;
  const laneGenerations = new Map<string, number>();

  const activate = () => {
    active = true;
    accountKey = currentAccountKey();
    pageGeneration += 1;
    laneGenerations.clear();
  };

  const begin = (lane: string): RequestScopeTicket => {
    const nextAccountKey = currentAccountKey();
    if (active && nextAccountKey !== accountKey) {
      accountKey = nextAccountKey;
      pageGeneration += 1;
      laneGenerations.clear();
    }
    const laneGeneration = (laneGenerations.get(lane) || 0) + 1;
    laneGenerations.set(lane, laneGeneration);
    return { accountKey, pageGeneration, lane, laneGeneration };
  };

  return {
    activate,
    begin,
    invalidate: () => {
      active = false;
      pageGeneration += 1;
      laneGenerations.clear();
    },
    isCurrent: (ticket) => active
      && ticket.pageGeneration === pageGeneration
      && ticket.accountKey === accountKey
      && ticket.accountKey === currentAccountKey()
      && ticket.laneGeneration === laneGenerations.get(ticket.lane)
  };
};