ionic-framework/packages/vue-router/src/locationHistory.ts

import { RouteInfo } from './types';

export const createLocationHistory = () => {
  const locationHistory: RouteInfo[] = [];
  const tabsHistory: { [k: string]: RouteInfo[] } = {};

  const add = (routeInfo: RouteInfo) => {
    switch (routeInfo.routerAction) {
      case "replace":
        replaceRoute(routeInfo);
        break;
      case "pop":
        pop(routeInfo);
        break;
      default:
        addRoute(routeInfo);
        break;
    }

    if (routeInfo.routerDirection === 'root') {
      clearHistory();
      addRoute(routeInfo);
    }
  }

  const update = (routeInfo: RouteInfo) => {
    const locationIndex = locationHistory.findIndex(x => x.id === routeInfo.id);
    if (locationIndex > -1) {
      locationHistory.splice(locationIndex, 1, routeInfo);
    }
    const tabArray = tabsHistory[routeInfo.tab || ''];
    if (tabArray) {
      const tabIndex = tabArray.findIndex(x => x.id === routeInfo.id);
      if (tabIndex > -1) {
        tabArray.splice(tabIndex, 1, routeInfo);
      } else {
        tabArray.push(routeInfo);
      }
    } else if (routeInfo.tab) {
      tabsHistory[routeInfo.tab] = [routeInfo];
    }
  }

  const replaceRoute = (routeInfo: RouteInfo) => {
    const routeInfos = getTabsHistory(routeInfo.tab);
    routeInfos && routeInfos.pop();
    locationHistory.pop();
    addRoute(routeInfo);
  }

  const pop = (routeInfo: RouteInfo) => {
    const tabHistory = getTabsHistory(routeInfo.tab);
    let ri;
    if (tabHistory) {
      // Pop all routes until we are back
      ri = tabHistory[tabHistory.length - 1];
      while (ri && ri.id !== routeInfo.id) {
        tabHistory.pop();
        ri = tabHistory[tabHistory.length - 1];
      }
      // Replace with updated route
      tabHistory.pop();
      tabHistory.push(routeInfo);
    }

    ri = locationHistory[locationHistory.length - 1];
    while (ri && ri.id !== routeInfo.id) {
      locationHistory.pop();
      ri = locationHistory[locationHistory.length - 1];
    }
    // Replace with updated route
    locationHistory.pop();
    locationHistory.push(routeInfo);
  }

  const addRoute = (routeInfo: RouteInfo) => {
    const tabHistory = getTabsHistory(routeInfo.tab);
    if (tabHistory) {
      // If the latest routeInfo is the same (going back and forth between tabs), replace it
      if (tabHistory[tabHistory.length - 1] && tabHistory[tabHistory.length - 1].id === routeInfo.id) {
        tabHistory.pop();
      }
      tabHistory.push(routeInfo);
    }
    locationHistory.push(routeInfo);
  }

  const clearHistory = () => {
    locationHistory.length = 0;
    Object.keys(tabsHistory).forEach(key => {
      tabsHistory[key] = [];
    });
  }
  const getTabsHistory = (tab: string): RouteInfo[] => {
    let history;
    if (tab) {
      history = tabsHistory[tab];
      if (!history) {
        history = tabsHistory[tab] = [];
      }
    }

    return history;
  }

  const size = () => locationHistory.length;

  const updateByHistoryPosition = (routeInfo: RouteInfo, updateEntries: boolean) => {
    const existingRouteIndex = locationHistory.findIndex(r => r.position === routeInfo.position);
    if (existingRouteIndex === -1) return;

    locationHistory[existingRouteIndex].pathname = routeInfo.pathname;

    if (updateEntries) {
      locationHistory[existingRouteIndex].pushedByRoute = routeInfo.pushedByRoute;
    }
  }

  /**
   * Finds and returns the location history item
   * given the state of browser's history API.
   * This is useful when jumping around in browser
   * history using router.go.
   */
  const current = (initialHistory: number, currentHistory: number) => {
    /**
     * initialHistory does not always start at 0 if users navigated
     * to app from another website, so doing this math lets us
     * find the correct index in our locationHistory array.
     */
    const index = currentHistory - initialHistory;
    return locationHistory[index] || last();
  }
  const previous = () => locationHistory[locationHistory.length - 2] || last();
  const last = () => locationHistory[locationHistory.length - 1];

  /**
   * With the introduction of router.go support, we no longer remove
   * items from locationHistory as they may be needed again in the future.
   * As a result, we need to look at the current position in location history
   * to see if users can navigate back n pages. Previously we were checking
   * the length of locationHistory, but that only worked since we were pruning
   * the array.
   */
  const canGoBack = (deep: number = 1, initialHistory: number, currentHistory: number) => {
    return currentHistory - deep >= initialHistory;
  }

  const getFirstRouteInfoForTab = (tab: string): RouteInfo | undefined => {
    const tabHistory = getTabsHistory(tab);
    if (tabHistory) {
      return tabHistory[0];
    }
    return undefined;
  }

  const getCurrentRouteInfoForTab = (tab: string): RouteInfo | undefined => {
    const tabHistory = getTabsHistory(tab);
    if (tabHistory) {
      return tabHistory[tabHistory.length - 1];
    }
    return undefined;
  }

  /**
   * Finds and returns the previous view based upon
   * what originally pushed it (pushedByRoute).
   * When `delta` < -1 then we should just index into
   * to array because the previous view that we want is not
   * necessarily the view that pushed our current view.
   * Additionally, when jumping around in history, we
   * do not modify the locationHistory stack so we would
   * not update pushedByRoute anyways.
   */
  const findLastLocation = (routeInfo: RouteInfo, delta: number = -1): RouteInfo | undefined => {
    const routeInfos = getTabsHistory(routeInfo.tab);
    if (routeInfos) {
      if (delta < -1) {
        return routeInfos[routeInfos.length - 1 + delta];
      } else {
        for (let i = routeInfos.length - 2; i >= 0; i--) {
          const ri = routeInfos[i];
          if (ri) {
            if (ri.pathname === routeInfo.pushedByRoute) {
              return ri;
            }
          }
        }
      }
    }
    if (delta < -1) {
      return locationHistory[locationHistory.length - 1 + delta];
    } else {
      for (let i = locationHistory.length - 2; i >= 0; i--) {
        const ri = locationHistory[i];
        if (ri) {
          if (ri.pathname === routeInfo.pushedByRoute) {
            return ri;
          }
        }
      }
    }
    return undefined;
  }

  return {
    current,
    updateByHistoryPosition,
    size,
    last,
    previous,
    add,
    canGoBack,
    update,
    getFirstRouteInfoForTab,
    getCurrentRouteInfoForTab,
    findLastLocation
  }
}