// pv--监听 url变动

import { innertEvent, on } from './utils'

class Pv {
  private path: string
  private currentPageUrl: string 
  constructor() {
    this.path = this.getPath();
    this.currentPageUrl = document.referrer;
    this.recordPv();
    this.sendPv();
  }

  sendPv() {
    innertEvent.trigger('pv', {
      referrer: this.currentPageUrl
    });
    this.currentPageUrl = location.href;
  }

  recordPv() {
    if(!history.pushState || !window.addEventListener) return;
    // hash监听
    window.addEventListener('hashchange', () => {
      this.handleHashState();
    });
    // history监听
    on(history, 'pushState', () => {
      this.pushStateOverride();
    } );
    on(history, 'replaceState', () => {
      this.replaceStateOverride();
    } );
    // history.pushState()或history.replaceState()不会触发popstate事件，需要监听
    window.addEventListener('popstate', () => {
      this.handlePopState();
    });
  }

  // hash变动
  handleHashState() {
    this.handleUrlChange(false);
  }

  // history变动
  pushStateOverride() {
    this.handleUrlChange(true);
  }

  replaceStateOverride() {
    this.handleUrlChange(true);
  }

  handlePopState() {
    this.handleUrlChange(true);
  }

  getPath(): string {
    return location.pathname + location.search;
  }

  shouldTrackUrlChange(newPath: string, oldPath: string): boolean {
    return !!(newPath && oldPath);
  }

  // url变动
  handleUrlChange(historyDidUpdate: boolean) {
    setTimeout(() => {
      // history变动
      if (historyDidUpdate) {
        const oldPath = this.path;
        const newPath = this.getPath();
        if(oldPath != newPath && this.shouldTrackUrlChange(newPath, oldPath)) {
          this.path = newPath;
          this.sendPv();
        }
      } else {
        // 否则是hash变动
        this.sendPv();
      }
    }, 0);
  }  
}

export default Pv