// ==UserScript==
// @name           Fluent Reveal Tabs
// @version        1.1.3
// @author         aminomancer
// @homepage       https://github.com/aminomancer/uc.css.js
// @description    Adds a visual effect to tabs similar to the spotlight gradient effect on Windows 10's start menu tiles. When hovering a tab, a subtle radial gradient is applied under the mouse. Inspired by this [proof of concept](https://www.reddit.com/r/FirefoxCSS/comments/ng5lnt/proof_of_concept_legacy_edge_like_interaction/) by black7375.
// @downloadURL    https://cdn.jsdelivr.net/gh/aminomancer/uc.css.js@master/JS/fluentRevealTabs.uc.js
// @updateURL      https://cdn.jsdelivr.net/gh/aminomancer/uc.css.js@master/JS/fluentRevealTabs.uc.js
// @license        This Source Code Form is subject to the terms of the Creative Commons Attribution-NonCommercial-ShareAlike International License, v. 4.0. If a copy of the CC BY-NC-SA 4.0 was not distributed with this file, You can obtain one at http://creativecommons.org/licenses/by-nc-sa/4.0/ or send a letter to Creative Commons, PO Box 1866, Mountain View, CA 94042, USA.
// ==/UserScript==

(function () {
  class FluentRevealEffect {
    // user configuration
    static options = {
      // whether to show the effect if the tab is selected. this doesn't look
      // good with my theme so I set it to false.
      showOnSelectedTab: false,

      // whether to show the effect on pinned tabs. likewise, doesn't look good
      // with my theme but may work with yours.
      showOnPinnedTab: false,

      // the color of the gradient. default is sort of a faint baby blue.
      // you may prefer just white, e.g. hsla(0, 0%, 100%, 0.05)
      lightColor: "hsla(224, 100%, 80%, 0.05)",

      // how wide the radial gradient is. 50px looks best with my theme, but
      // default proton tabs are larger so you may want to try 60 or even 70.
      gradientSize: 50,

      // whether to show an additional light burst when clicking a tab. I don't
      // recommend this since it doesn't play nicely with dragging & dropping if
      // you release while your mouse is outside the tab box. I can probably fix
      // this issue but I don't think it's a great fit for tabs anyway.
      clickEffect: false,
    };

    /**
     * sleep for n ms
     * @param {integer} ms (how long to wait)
     * @returns a promise resolved after the passed number of milliseconds
     */
    static sleep(ms) {
      return new Promise(resolve => setTimeout(resolve, ms));
    }

    // instantiate the handler for a given window
    constructor() {
      this._options = FluentRevealEffect.options;
      gBrowser.tabContainer.addEventListener("TabOpen", e =>
        this.applyEffect(e.target.querySelector(".tab-content"), true)
      );
      gBrowser.tabs.forEach(tab =>
        this.applyEffect(tab.querySelector(".tab-content"), true)
      );
    }

    /**
     * main event handler. handles all the mouse behavior.
     * @param {object} e (event)
     */
    handleEvent(e) {
      // grab the colors and behavior from the event. this allows us to apply
      // different colors/behavior to different elements and makes the script
      // more adaptable for future expansion or user extension.
      let { gradientSize, lightColor, clickEffect } =
        e.currentTarget.fluentRevealState;
      // calculate gradient display coordinates based on mouse and element coords.
      let x = e.pageX - this.getOffset(e.currentTarget).left - window.scrollX;
      let y = e.pageY - this.getOffset(e.currentTarget).top - window.scrollY;
      // the effect is actually applied to the element by setting its
      // background-color value to this.
      let cssLightEffect = `radial-gradient(circle ${gradientSize}px at ${x}px ${y}px, ${lightColor}, rgba(255,255,255,0)), radial-gradient(circle ${70}px at ${x}px ${y}px, rgba(255,255,255,0), ${lightColor}, rgba(255,255,255,0), rgba(255,255,255,0))`;

      switch (e.type) {
        case "mousemove":
          // if the element is a tab, check if it's selected or pinned and check
          // if the user options hide the effect on selected or pinned tabs.
          // determines if we should avoid showing the effect on the element at
          // the current time.
          if (this.shouldClear(e.currentTarget)) {
            return this.clearEffect(e.currentTarget);
          }
          // mousemove events still trigger while the element is clicked. so if
          // the click effect is enabled and the element is pressed, we want to
          // apply a different effect than we normally would.
          this.drawEffect(
            e.currentTarget,
            x,
            y,
            lightColor,
            gradientSize,
            clickEffect && e.currentTarget.fluentRevealState.is_pressed
              ? cssLightEffect
              : null
          );
          break;

        case "mouseleave":
          // mouse left the element so remove the background-image property.
          this.clearEffect(e.currentTarget);
          break;

        case "mousedown":
          // again, check if it's selected or pinned
          if (this.shouldClear(e.currentTarget)) {
            return this.clearEffect(e.currentTarget);
          }
          e.currentTarget.fluentRevealState.is_pressed = true;
          this.drawEffect(
            e.currentTarget,
            x,
            y,
            lightColor,
            gradientSize,
            cssLightEffect
          );
          break;

        case "mouseup":
          if (this.shouldClear(e.currentTarget)) {
            return this.clearEffect(e.currentTarget);
          }
          e.currentTarget.fluentRevealState.is_pressed = false;
          this.drawEffect(e.currentTarget, x, y, lightColor, gradientSize);
          break;
      }
    }

    /**
     * Reveal Effect
     * https://github.com/d2phap/fluent-reveal-effect
     *
     * MIT License
     * Copyright (c) 2018 Duong Dieu Phap
     *
     * Permission is hereby granted, free of charge, to any person obtaining a copy
     * of this software and associated documentation files (the "Software"), to deal
     * in the Software without restriction, including without limitation the rights
     * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
     * copies of the Software, and to permit persons to whom the Software is
     * furnished to do so, subject to the following conditions:
     *
     * The above copyright notice and this permission notice shall be included in all
     * copies or substantial portions of the Software.
     *
     * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
     * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
     * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
     * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
     * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
     * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
     * SOFTWARE.
     */

    /**
     * main entry point for applying all the script behavior to an element.
     * @param {object} element (a DOM node to apply the effect to)
     * @param {boolean} isTab (pass true if applying to a child of a tab)
     * @param {object} options (an object containing options similar to the
     *                         static options at the top of the script)
     */
    applyEffect(element, isTab = false, options = this._options) {
      // you may pass an options object when calling this method, but the
      // options object passed does not necessarily contain ALL the properties
      // of the static options object at the top of the script. if you pass just
      // {gradientSize, lightColor} then clickEffect would be undefined rather
      // than true or false. undefined is falsy so it's parsed like false. but
      // if the default (static) clickEffect option was set to true, then it
      // should default to true when you don't pass it, not default to false. so
      // we need to set each of these values equal to 1) the option in the
      // passed options object if it exists, or 2) the option in the static
      // options object. if we just said let {clickEffect, gradientSize,
      // lightColor} = options; then any values not passed in the options object
      // would default to false. instead we're gonna set each one individually.
      // I haven't run into this issue before so please let me know if there's a
      // faster/shorter way of doing this.
      let { clickEffect } =
        options.clickEffect === undefined ? this._options : options;
      let { gradientSize } =
        options.gradientSize === undefined ? this._options : options;
      let { lightColor } =
        options.lightColor === undefined ? this._options : options;

      // cache the values on the element itself. this is how we can support different
      // options for different elements, something the library doesn't support.
      element.fluentRevealState = {
        clickEffect,
        lightColor,
        gradientSize,
        isTab,
        is_pressed: false,
      };

      // make sure we don't add duplicate event listeners if applyEffect() is
      // somehow called more than once on the same element. this shouldn't
      // normally happen since the script itself only ever invokes the method
      // when a tab is created. but if you want to mess around with the script,
      // apply it to additional elements, this is a good safeguard against
      // listeners piling up.
      if (!element.getAttribute("fluent-reveal-hover")) {
        element.setAttribute("fluent-reveal-hover", true);
        element.addEventListener("mousemove", this);
        element.addEventListener("mouseleave", this);
      }

      // only set up the click effect if the option is enabled and the element
      // doesn't already have a click effect.
      if (clickEffect && !element.getAttribute("fluent-reveal-click")) {
        element.setAttribute("fluent-reveal-click", true);
        element.addEventListener("mousedown", this);
        element.addEventListener("mouseup", this);
      }
    }

    /**
     * completely remove the script behavior from a given element. isn't actually
     * used by the script, but it's here if you ever need it for some reason. usage:
     * fluentRevealFx.revertElement(gBrowser.selectedTab.querySelector(".tab-content"))
     * @param {object} element (a DOM node)
     */
    revertElement(element) {
      // this isn't really necessary but just for the sake of completeness...
      try {
        // try to delete the property
        delete element.fluentRevealState;
      } catch (e) {
        // if it's undeletable (e.g. the element was sealed) then at least negate it.
        element.fluentRevealState = null;
      }

      if (element.getAttribute("fluent-reveal-hover")) {
        element.removeAttribute("fluent-reveal-hover");
        element.removeEventListener("mousemove", this);
        element.removeEventListener("mouseleave", this);
      }

      if (element.getAttribute("fluent-reveal-click")) {
        element.removeAttribute("fluent-reveal-click");
        element.removeEventListener("mousedown", this);
        element.removeEventListener("mouseup", this);
      }
    }

    /**
     * invoked when the mouse leaves an element, or when effects would otherwise
     * be applied to a selected/pinned tab if user options prevent it.
     * @param {object} element (a DOM node)
     */
    clearEffect(element) {
      element.fluentRevealState.is_pressed = false;
      // the original library memoized the element's computed background-image on
      // applyEffect(), and set the inline style's background-image back to the
      // memoized background-image when clearing the effect. this would work fine
      // if you have total control of the DOM, such as if you were using the
      // library for a website you control. but since we're hacking a browser, we
      // can't be using inline styles willy-nilly. if we left an inline style
      // every time we cleared the effect, it would override firefox's internal
      // CSS rules. it would basically mean the background-image of the element
      // could only ever be defined by the script. that wouldn't be a problem for
      // the script as-is, because we only apply the effect to elements that
      // shouldn't ever have a background-image defined by CSS in the first
      // place. so instead of doing that we just remove the inline
      // background-image property altogether, so the element can go back to
      // displaying whatever background-image CSS tells it to.
      element.style.removeProperty("background-image");
    }

    /**
     * test whether the effect should be removed/forgone on a given element
     * because the element is a selected or pinned tab.
     * @param {object} element (a DOM node)
     * @returns {boolean} (true if effect should not be shown)
     */
    shouldClear(element) {
      // if it's not a tab then it never needs to be skipped
      if (!element.fluentRevealState.isTab) return false;
      // the effect isn't actually applied to the tab itself but to
      // .tab-content, so traverse up to the actual tab element which holds
      // properties like selected, pinned.
      let tab = element.tab || element.closest("tab");
      return (
        (!this._options.showOnSelectedTab && tab.selected) ||
        (!this._options.showOnPinnedTab && tab.pinned)
      );
    }

    /**
     * used to calculate the x and y coordinates used in drawing the gradient
     * @param {object} element (a DOM node)
     * @returns {object} (an object containing top and left coordinates)
     */
    getOffset(element) {
      return {
        top: element.getBoundingClientRect().top,
        left: element.getBoundingClientRect().left,
      };
    }

    /**
     * finally draw the specified effect on a given element, that is, give the
     * element an inline background-image property
     * @param {object} element (a DOM node)
     * @param {integer} x (x coordinate for gradient center)
     * @param {integer} y (y coordinate for gradient center)
     * @param {string} lightColor (any color value accepted by CSS, e.g. "#FFF",
     *                            "rgba(125, 125, 125, 0.5)", or
     *                            "hsla(50, 0%, 100%, 0.2)")
     * @param {integer} gradientSize (how many pixels wide the gradient should be)
     * @param {string} cssLightEffect (technically, any background-image value accepted by
     *                                CSS, but should be a radial-gradient() function,
     *                                surrounded by quotes)
     */
    drawEffect(element, x, y, lightColor, gradientSize, cssLightEffect = null) {
      if (!element) return;
      element.style.backgroundImage =
        cssLightEffect ??
        `radial-gradient(circle ${gradientSize}px at ${x}px ${y}px, ${lightColor}, rgba(255,255,255,0))`;
    }
  }

  function init() {
    // instantiate the class on a global property to share the methods with
    // other scripts if desired.
    window.fluentRevealFx = new FluentRevealEffect();
  }

  if (gBrowserInit.delayedStartupFinished) {
    init();
  } else {
    let delayedListener = (subject, topic) => {
      if (topic == "browser-delayed-startup-finished" && subject == window) {
        Services.obs.removeObserver(delayedListener, topic);
        init();
      }
    };
    Services.obs.addObserver(
      delayedListener,
      "browser-delayed-startup-finished"
    );
  }
})();