/*
#ifdef 0
 * 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/.
#endif
 */

// One of the possible values for the mousewheel.* preferences.
// From nsEventStateManager.cpp.
const MOUSE_SCROLL_ZOOM = 3;

Cu.import('resource://gre/modules/ContentPrefInstance.jsm');

function getContentPrefs(aWindow) {
  let context = aWindow ? aWindow.QueryInterface(Ci.nsIInterfaceRequestor)
                                 .getInterface(Ci.nsIWebNavigation)
                                 .QueryInterface(Ci.nsILoadContext) : null;
  return new ContentPrefInstance(context);
}

/**
 * Controls the "full zoom" setting and its site-specific preferences.
 */
var FullZoom = {
  // Identifies the setting in the content prefs database.
  name: "browser.content.full-zoom",

  // The global value (if any) for the setting.  Lazily loaded from the service
  // when first requested, then updated by the pref change listener as it changes.
  // If there is no global value, then this should be undefined.
  get globalValue() {
    var globalValue = getContentPrefs(gBrowser.contentDocument.defaultView).getPref(null, this.name);
    if (typeof globalValue != "undefined")
      globalValue = this._ensureValid(globalValue);
    delete this.globalValue;
    return this.globalValue = globalValue;
  },

  // browser.zoom.siteSpecific preference cache
  _siteSpecificPref: undefined,

  // browser.zoom.updateBackgroundTabs preference cache
  updateBackgroundTabs: undefined,

  get siteSpecific() {
    return this._siteSpecificPref;
  },

  //**************************************************************************//
  // nsISupports

  QueryInterface: XPCOMUtils.generateQI([Ci.nsIDOMEventListener,
                                         Ci.nsIObserver,
                                         Ci.nsIContentPrefObserver,
                                         Ci.nsISupportsWeakReference,
                                         Ci.nsISupports]),

  //**************************************************************************//
  // Initialization & Destruction

  init: function FullZoom_init() {
    // Listen for scrollwheel events so we can save scrollwheel-based changes.
    window.addEventListener("DOMMouseScroll", this, false);

    // Register ourselves with the service so we know when our pref changes.
    getContentPrefs().addObserver(this.name, this);

    this._siteSpecificPref =
      gPrefService.getBoolPref("browser.zoom.siteSpecific");
    this.updateBackgroundTabs =
      gPrefService.getBoolPref("browser.zoom.updateBackgroundTabs");
    // Listen for changes to the browser.zoom branch so we can enable/disable
    // updating background tabs and per-site saving and restoring of zoom levels.
    gPrefService.addObserver("browser.zoom.", this, true);
  },

  destroy: function FullZoom_destroy() {
    gPrefService.removeObserver("browser.zoom.", this);
    getContentPrefs().removeObserver(this.name, this);
    window.removeEventListener("DOMMouseScroll", this, false);
  },


  //**************************************************************************//
  // Event Handlers

  // nsIDOMEventListener

  handleEvent: function FullZoom_handleEvent(event) {
    switch (event.type) {
      case "DOMMouseScroll":
        this._handleMouseScrolled(event);
        break;
    }
  },

  _handleMouseScrolled: function FullZoom__handleMouseScrolled(event) {
    // Construct the "mousewheel action" pref key corresponding to this event.
    // Based on nsEventStateManager::WheelPrefs::GetBasePrefName().
    var pref = "mousewheel.";

    var pressedModifierCount = event.shiftKey + event.ctrlKey + event.altKey +
                                 event.metaKey + event.getModifierState("OS");
    if (pressedModifierCount != 1) {
      pref += "default.";
    } else if (event.shiftKey) {
      pref += "with_shift.";
    } else if (event.ctrlKey) {
      pref += "with_control.";
    } else if (event.altKey) {
      pref += "with_alt.";
    } else if (event.metaKey) {
      pref += "with_meta.";
    } else {
      pref += "with_win.";
    }

    pref += "action";

    // Don't do anything if this isn't a "zoom" scroll event.
    var isZoomEvent = false;
    try {
      isZoomEvent = (gPrefService.getIntPref(pref) == MOUSE_SCROLL_ZOOM);
    } catch (e) {}
    if (!isZoomEvent)
      return;

    // XXX Lazily cache all the possible action prefs so we don't have to get
    // them anew from the pref service for every scroll event?  We'd have to
    // make sure to observe them so we can update the cache when they change.

    // We have to call _applySettingToPref in a timeout because we handle
    // the event before the event state manager has a chance to apply the zoom
    // during nsEventStateManager::PostHandleEvent.
    window.setTimeout(function (self) { self._applySettingToPref() }, 0, this);
  },

  // nsIObserver

  observe: function (aSubject, aTopic, aData) {
    switch (aTopic) {
      case "nsPref:changed":
        switch (aData) {
          case "browser.zoom.siteSpecific":
            this._siteSpecificPref =
              gPrefService.getBoolPref("browser.zoom.siteSpecific");
            break;
          case "browser.zoom.updateBackgroundTabs":
            this.updateBackgroundTabs =
              gPrefService.getBoolPref("browser.zoom.updateBackgroundTabs");
            break;
        }
        break;
    }
  },

  // nsIContentPrefObserver

  onContentPrefSet: function FullZoom_onContentPrefSet(aGroup, aName, aValue) {
    let contentPrefs = getContentPrefs(gBrowser.contentDocument.defaultView);
    if (aGroup == contentPrefs.grouper.group(gBrowser.currentURI))
      this._applyPrefToSetting(aValue);
    else if (aGroup == null) {
      this.globalValue = this._ensureValid(aValue);

      // If the current page doesn't have a site-specific preference,
      // then its zoom should be set to the new global preference now that
      // the global preference has changed.
      if (!contentPrefs.hasPref(gBrowser.currentURI, this.name))
        this._applyPrefToSetting();
    }
  },

  onContentPrefRemoved: function FullZoom_onContentPrefRemoved(aGroup, aName) {
    let contentPrefs = getContentPrefs(gBrowser.contentDocument.defaultView);
    if (aGroup == contentPrefs.grouper.group(gBrowser.currentURI))
      this._applyPrefToSetting();
    else if (aGroup == null) {
      this.globalValue = undefined;

      // If the current page doesn't have a site-specific preference,
      // then its zoom should be set to the default preference now that
      // the global preference has changed.
      if (!contentPrefs.hasPref(gBrowser.currentURI, this.name))
        this._applyPrefToSetting();
    }
  },

  // location change observer

  /**
   * Called when the location of a tab changes.
   * When that happens, we need to update the current zoom level if appropriate.
   *
   * @param aURI
   *        A URI object representing the new location.
   * @param aIsTabSwitch
   *        Whether this location change has happened because of a tab switch.
   * @param aBrowser
   *        (optional) browser object displaying the document
   */
  onLocationChange: function FullZoom_onLocationChange(aURI, aIsTabSwitch, aBrowser) {
    if (!aURI || (aIsTabSwitch && !this.siteSpecific))
      return;

    // Avoid the cps roundtrip and apply the default/global pref.
    if (aURI.spec == "about:blank") {
      this._applyPrefToSetting(undefined, aBrowser);
      return;
    }

    let browser = aBrowser || gBrowser.selectedBrowser;

    // Media documents should always start at 1, and are not affected by prefs.
    if (!aIsTabSwitch && browser.contentDocument.mozSyntheticDocument) {
      ZoomManager.setZoomForBrowser(browser, 1);
      return;
    }

    let contentPrefs = getContentPrefs(gBrowser.contentDocument.defaultView);
    if (contentPrefs.hasCachedPref(aURI, this.name)) {
      let zoomValue = contentPrefs.getPref(aURI, this.name);
      this._applyPrefToSetting(zoomValue, browser);
    } else {
      var self = this;
      contentPrefs.getPref(aURI, this.name, function (aResult) {
        // Check that we're still where we expect to be in case this took a while.
        // Null check currentURI, since the window may have been destroyed before
        // we were called.
        if (browser.currentURI && aURI.equals(browser.currentURI)) {
          self._applyPrefToSetting(aResult, browser);
        }
      });
    }
  },

  // update state of zoom type menu item

  updateMenu: function FullZoom_updateMenu() {
    var menuItem = document.getElementById("toggle_zoom");

    menuItem.setAttribute("checked", !ZoomManager.useFullZoom);
  },

  //**************************************************************************//
  // Setting & Pref Manipulation

  reduce: function FullZoom_reduce() {
    ZoomManager.reduce();
    this._applySettingToPref();
  },

  enlarge: function FullZoom_enlarge() {
    ZoomManager.enlarge();
    this._applySettingToPref();
  },

  reset: function FullZoom_reset() {
    if (typeof this.globalValue != "undefined")
      ZoomManager.zoom = this.globalValue;
    else
      ZoomManager.reset();

    this._removePref();
  },

  /**
   * Set the zoom level for the current tab.
   *
   * Per nsPresContext::setFullZoom, we can set the zoom to its current value
   * without significant impact on performance, as the setting is only applied
   * if it differs from the current setting.  In fact getting the zoom and then
   * checking ourselves if it differs costs more.
   * 
   * And perhaps we should always set the zoom even if it was more expensive,
   * since DocumentViewerImpl::SetTextZoom claims that child documents can have
   * a different text zoom (although it would be unusual), and it implies that
   * those child text zooms should get updated when the parent zoom gets set,
   * and perhaps the same is true for full zoom
   * (although DocumentViewerImpl::SetFullZoom doesn't mention it).
   *
   * So when we apply new zoom values to the browser, we simply set the zoom.
   * We don't check first to see if the new value is the same as the current
   * one.
   **/
  _applyPrefToSetting: function FullZoom__applyPrefToSetting(aValue, aBrowser) {
    if ((!this.siteSpecific) || gInPrintPreviewMode)
      return;

    var browser = aBrowser || (gBrowser && gBrowser.selectedBrowser);
    try {
      if (browser.contentDocument.mozSyntheticDocument)
        return;

      if (typeof aValue != "undefined")
        ZoomManager.setZoomForBrowser(browser, this._ensureValid(aValue));
      else if (typeof this.globalValue != "undefined")
        ZoomManager.setZoomForBrowser(browser, this.globalValue);
      else
        ZoomManager.setZoomForBrowser(browser, 1);
    }
    catch(ex) {}
  },

  _applySettingToPref: function FullZoom__applySettingToPref() {
    if (!this.siteSpecific || gInPrintPreviewMode ||
        content.document.mozSyntheticDocument)
      return;

    var zoomLevel = ZoomManager.zoom;
    getContentPrefs(gBrowser.contentDocument.defaultView).setPref(gBrowser.currentURI, this.name, zoomLevel);
  },

  _removePref: function FullZoom__removePref() {
    if (!(content.document.mozSyntheticDocument))
      getContentPrefs(gBrowser.contentDocument.defaultView).removePref(gBrowser.currentURI, this.name);
  },


  //**************************************************************************//
  // Utilities

  _ensureValid: function FullZoom__ensureValid(aValue) {
    if (isNaN(aValue))
      return 1;

    if (aValue < ZoomManager.MIN)
      return ZoomManager.MIN;

    if (aValue > ZoomManager.MAX)
      return ZoomManager.MAX;

    return aValue;
  }
};