// ==UserScript==
// @name        HTML5 Video Playback Speed Control Keyboard Shortcut
// @namespace   HTML5VideoPlaybackSpeedControlKeyboardShortcut
// @description Add keyboard shortcuts to control HTML5 video playback rate. Available keyboard shortcuts are: <CTRL+[> = Decreate playback rate, <CTRL+]> = Increase playback rate, <CTRL+\> = Set playback rate increment/decrement unit, <CTRL+'> = Set playback to specific rate, <CTRL+;> Reset playback rate to default (to 1.0). Default playback rate incement/decrement is configurable via script.
// @version     1.2.6
// @license     AGPLv3
// @author      jcunews
// @include     *://*.khanacademy.org/
// @grant       none
// ==/UserScript==

(function() {

    /*
  Notes:
  1. YouTube's video playback speed menu selection will not be affected.
  2. Web browser playback rates: Firefox = 0.25 to 5.0; Chrome = 0.1 to 16.0.
  */

    //=== CONFIGURATION BEGIN ===
    var runIv = true;
    var interval = setInterval(() => {
        if(runIv) {
            try {
                //Playback rate increment/decrement unit
                var rateUnit = 1.0;

                //Duration (in milliseconds) to display On Screen Display (OSD) when changing playback rate. Set to zero or less to disable.
                var osdTimeout = 3000;

                var default_speed = 1.0;

                var ele = document.querySelector("VIDEO"), rate, inp;

                ele.playbackRate = default_speed;

                //=== CONFIGURATION END ===

                var eleOSD, osdTimer;
                function showOSD(rate) {
                    if (eleOSD) {
                        eleOSD.textContent = rate + "X";
                    } else {
                        eleOSD = document.createElement("DIV");
                        eleOSD.style.cssText = "position:fixed;z-index:999999999;right:5px;bottom:5px;margin:0;padding:5px;width:auto;height:auto;font:bold 10pt/normal monospace;background:#444;color:#fff";
                        eleOSD.textContent = rate + "X";
                        document.body.appendChild(eleOSD);
                    }
                    clearTimeout(osdTimer);
                    osdTimer = setTimeout(function() {
                        eleOSD.remove();
                        eleOSD = null;
                    }, osdTimeout);
                }

                addEventListener("keydown", function(ev) {
                    var ele = document.querySelector("VIDEO"), rate, inp;
                    if (ele && ev.ctrlKey && !ev.shiftKey && !ev.altKey) {
                        rate = rate = ele.playbackRate;
                        switch (ev.key) {
                            case "[":
                                rate -= rateUnit;
                                if (rate < 0.1) rate = 0.1;
                                break;
                            case "]":
                                rate += rateUnit;
                                if (rate > 16) rate = 16;
                                break;
                            case "\\":
                                if ((inp = prompt("Enter playback rate increment/decrement unit.", rate)) === null) return;
                                if (isNaN(inp = parseFloat(inp.trim())) || (inp <= 0) || (inp >= 16)) {
                                    alert("Number must be greater than zero, and less than 16.");
                                    return;
                                }
                                rate = inp;
                                break;
                            case "'":
                                if ((inp = prompt("Enter playback rate.\n(1.0 = Normal)", rate)) === null) return;
                                if (isNaN(inp = parseFloat(inp.trim())) || (inp < 0.1) || (inp > 16)) {
                                    alert("Number must be between 0.1 to 16 (inclusive).");
                                    return;
                                }
                                rate = inp;
                                break;
                            case ";":
                                rate = 1;
                                break;
                            default:
                                return;
                        }
                        rate = parseFloat(rate.toFixed(2));
                        ele.playbackRate = rate;
                        if (osdTimeout > 0) showOSD(ele.playbackRate);
                    }
                });
                runIv = false;
            } catch(e) {
            }
        }
    });

})();