"use strict";

Cu.import("resource://gre/modules/Services.jsm");

XPCOMUtils.defineLazyModuleGetter(this, "Preferences",
                                  "resource://gre/modules/Preferences.jsm");

// WeakMap[Extension -> Theme]
let themeMap = new WeakMap();

/** Class representing a theme. */
class Theme {
  /**
   * Creates a theme instance.
   */
  constructor() {
    // A dictionary of light weight theme styles.
    this.lwtStyles = {};
  }

  /**
   * Loads a theme by reading the properties from the extension's manifest.
   * This method will override any currently applied theme.
   *
   * @param {Object} details Theme part of the manifest. Supported
   *   properties can be found in the schema under ThemeType.
   */
  load(details) {
    if (details.colors) {
      this.loadColors(details.colors);
    }

    if (details.images) {
      this.loadImages(details.images);
    }

    // Lightweight themes require all properties to be defined.
    if (this.lwtStyles.headerURL &&
        this.lwtStyles.accentcolor &&
        this.lwtStyles.textcolor) {
      Services.obs.notifyObservers(null,
        "lightweight-theme-styling-update",
        JSON.stringify(this.lwtStyles));
    }
  }

  /**
   * Helper method for loading colors found in the extension's manifest.
   *
   * @param {Object} colors Dictionary mapping color properties to values.
   */
  loadColors(colors) {
    let {accentcolor, textcolor} = colors;

    if (accentcolor) {
      this.lwtStyles.accentcolor = accentcolor;
    }

    if (textcolor) {
      this.lwtStyles.textcolor = textcolor;
    }
  }

  /**
   * Helper method for loading images found in the extension's manifest.
   *
   * @param {Object} images Dictionary mapping image properties to values.
   */
  loadImages(images) {
    let {headerURL} = images;

    if (headerURL) {
      this.lwtStyles.headerURL = headerURL;
    }
  }

  /**
   * Unloads the currently applied theme.
   */
  unload() {
    Services.obs.notifyObservers(null,
      "lightweight-theme-styling-update",
      null);
  }
}

/* eslint-disable mozilla/balanced-listeners */
extensions.on("manifest_theme", (type, directive, extension, manifest) => {
  if (!Preferences.get("extensions.webextensions.themes.enabled")) {
    // Return early if themes are disabled.
    return;
  }

  let theme = new Theme();
  theme.load(manifest.theme);
  themeMap.set(extension, theme);
});

extensions.on("shutdown", (type, extension) => {
  let theme = themeMap.get(extension);

  // We won't have a theme if theme's aren't enabled.
  if (!theme) {
    return;
  }

  theme.unload();
});
/* eslint-enable mozilla/balanced-listeners */

extensions.registerSchemaAPI("theme", "addon_parent", context => {
  let {extension} = context;
  return {
    theme: {
      update(details) {
        let theme = themeMap.get(extension);

        // We won't have a theme if theme's aren't enabled.
        if (!theme) {
          return;
        }

        theme.load(details);
      },
    },
  };
});