// ==UserScript==
// @name YouTube Playback speed adjust
// @version 0.9
// @namespace userjs.osm
// @match *://www.youtube.com/*
// @grant none
// ==/UserScript==

"use strict";


class PlaySpeed {
  // Dom accessors
  get dom_video() {
    return document.querySelector("video");
  };
  
  get dom_container() {
    return document.getElementById("movie_player");
  };

  // Constructor
  constructor() {
    let self = this;

    this.overlay = null;
    this.rate = this.saved_rate;

    this.domevent = window.addEventListener("DOMContentLoaded", () => {
      let videos = document.getElementsByTagName("video");

      if (videos[0])
        videos[0].addEventListener("playing", () => {
          // Refresh
          self.set_rate(self.rate);
        });
    });
    
    // Handle keypresses
    this.keyevent = window.addEventListener("keydown", e => {
      // [ :: Decrease speed
      // ] :: Increase speed
      // Shift- :: Smaller steps
      // Alt-   :: Coarser steps
      if (e.keyCode === 219) // [
        self.set_rate(self.rate - self.modifier_step(e));
      else if (e.keyCode === 221) // ]
        self.set_rate(self.rate + self.modifier_step(e));
      // \       :: Restore speed
      // Shift-\ :: Save speed
      // Alt-\   :: Set speed to 1
      else if (e.keyCode === 220) { // \
        if (e.altKey)
          self.set_rate(1);
        else if (e.shiftKey)
          self.save();
        else
          self.restore();
      }
    });
  };

  // Get step size from modifier keys
  modifier_step(e) {
    if (e.shiftKey == e.altKey)
      return 0.1;
    if (e.shiftKey)
      return 0.01;
    else if (e.altKey)
      return 1;
  };

  // Speed overlay
  do_overlay(rate) {
    let div = this.dom_container;
    let ol = this.overlay;

    if (div) {
      let need_overlay = Math.abs(rate - 1) > 0.001;

      if (!need_overlay) {
        if (ol) {
          div.removeChild(ol);
          ol = this.overlay = null;
        }

        return;
      }

      if (!ol) {
        ol = this.overlay = document.createElement("div");
        ol.style.position = "absolute";
        ol.style.top = 0;
        ol.style.left = 0;
        ol.style.zIndex = 10;
        div.appendChild(ol);
      }

      ol.textContent = rate.toPrecision(3);
    }
  };

  // set rates
  set_rate(rate) {
    this.dom_video.playbackRate = rate;
    this.do_overlay(rate);
    this.rate = rate;
  };

  // Restore from localstorage
  get lst_key() {
    return "yt_playspeed_adjust";
  };

  get saved_rate() {
    let saved = window.localStorage.getItem(this.lst_key);
    
    if (saved)
      return parseFloat(saved);
    else
      return 1;
  }
  
  restore() {
    this.set_rate(this.saved_rate);
  }
    
  save() {
    window.localStorage.setItem(this.lst_key, this.rate.toPrecision(5));
  }
};


const yt_playspeed = new PlaySpeed();