/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

"use strict";

/**
 * Colors for themes taken from:
 * https://developer.mozilla.org/en-US/docs/Tools/DevToolsColors
 */

const { Ci, Cu } = require("chrome");
const { NetUtil } = Cu.import("resource://gre/modules/NetUtil.jsm", {});
loader.lazyRequireGetter(this, "Services");
loader.lazyImporter(this, "gDevTools", "resource://devtools/client/framework/gDevTools.jsm");

const VARIABLES_URI = "chrome://devtools/skin/variables.css";
const THEME_SELECTOR_STRINGS = {
  light: ":root.theme-light {",
  dark: ":root.theme-dark {"
}

let variableFileContents;

/**
 * Returns a string of the file found at URI
 */
function readURI (uri) {
  let stream = NetUtil.newChannel({
    uri: NetUtil.newURI(uri, "UTF-8"),
    loadUsingSystemPrincipal: true}
  ).open();

  let count = stream.available();
  let data = NetUtil.readInputStreamToString(stream, count, { charset: "UTF-8" });
  stream.close();
  return data;
}

/**
 * Takes a theme name and returns the contents of its variable rule block.
 * The first time this runs fetches the variables CSS file and caches it.
 */
function getThemeFile (name) {
  if (!variableFileContents) {
    variableFileContents = readURI(VARIABLES_URI);
  }

  // If there's no theme expected for this name, use `light` as default.
  let selector = THEME_SELECTOR_STRINGS[name] ||
                 THEME_SELECTOR_STRINGS["light"];

  // This is a pretty naive way to find the contents between:
  // selector {
  //   name: val;
  // }
  // There is test coverage for this feature (browser_theme.js)
  // so if an } is introduced in the variables file it will catch that.
  let theme = variableFileContents;
  theme = theme.substring(theme.indexOf(selector));
  theme = theme.substring(0, theme.indexOf("}"));

  return theme;
}

/**
 * Returns the string value of the current theme,
 * like "dark" or "light".
 */
const getTheme = exports.getTheme = () => Services.prefs.getCharPref("devtools.theme");

/**
 * Returns a color indicated by `type` (like "toolbar-background", or "highlight-red"),
 * with the ability to specify a theme, or use whatever the current theme is
 * if left unset. If theme not found, falls back to "light" theme. Returns null
 * if the type cannot be found for the theme given.
 */
const getColor = exports.getColor = (type, theme) => {
  let themeName = theme || getTheme();
  let themeFile = getThemeFile(themeName);
  let match = themeFile.match(new RegExp("--theme-" + type + ": (.*);"));

  // Return the appropriate variable in the theme, or otherwise, null.
  return match ? match[1] : null;
};

/**
 * Mimics selecting the theme selector in the toolbox;
 * sets the preference and emits an event on gDevTools to trigger
 * the themeing.
 */
const setTheme = exports.setTheme = (newTheme) => {
  let oldTheme = getTheme();

  Services.prefs.setCharPref("devtools.theme", newTheme);
  gDevTools.emit("pref-changed", {
    pref: "devtools.theme",
    newValue: newTheme,
    oldValue: oldTheme
  });
};