// Copyright (C) 2013 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package net.codemirror.lib;

import com.google.gerrit.client.rpc.CallbackGroup;
import com.google.gwt.core.client.Callback;
import com.google.gwt.core.client.ScriptInjector;
import com.google.gwt.dom.client.ScriptElement;
import com.google.gwt.dom.client.StyleInjector;
import com.google.gwt.resources.client.ExternalTextResource;
import com.google.gwt.resources.client.ResourceCallback;
import com.google.gwt.resources.client.ResourceException;
import com.google.gwt.resources.client.TextResource;
import com.google.gwt.safehtml.shared.SafeUri;
import com.google.gwt.user.client.rpc.AsyncCallback;

public class Loader {
  private static native boolean isLibLoaded() /*-{ return $wnd.hasOwnProperty('CodeMirror'); }-*/;

  static void initLibrary(AsyncCallback<Void> cb) {
    if (isLibLoaded()) {
      cb.onSuccess(null);
      return;
    }

    CallbackGroup group = new CallbackGroup();
    injectCss(Lib.I.css(), group.<Void>addEmpty());
    injectScript(
        Lib.I.js().getSafeUri(),
        group.add(
            new AsyncCallback<Void>() {
              @Override
              public void onSuccess(Void result) {
                Vim.initKeyMap();
              }

              @Override
              public void onFailure(Throwable caught) {}
            }));
    group.addListener(cb);
    group.done();
  }

  private static void injectCss(ExternalTextResource css, AsyncCallback<Void> cb) {
    try {
      css.getText(
          new ResourceCallback<TextResource>() {
            @Override
            public void onSuccess(TextResource resource) {
              StyleInjector.inject(resource.getText());
              Lib.I.style().ensureInjected();
              cb.onSuccess(null);
            }

            @Override
            public void onError(ResourceException e) {
              cb.onFailure(e);
            }
          });
    } catch (ResourceException e) {
      cb.onFailure(e);
    }
  }

  public static void injectScript(SafeUri js, AsyncCallback<Void> callback) {
    final ScriptElement[] script = new ScriptElement[1];
    script[0] =
        ScriptInjector.fromUrl(js.asString())
            .setWindow(ScriptInjector.TOP_WINDOW)
            .setCallback(
                new Callback<Void, Exception>() {
                  @Override
                  public void onSuccess(Void result) {
                    script[0].removeFromParent();
                    callback.onSuccess(result);
                  }

                  @Override
                  public void onFailure(Exception reason) {
                    callback.onFailure(reason);
                  }
                })
            .inject()
            .cast();
  }

  private Loader() {}
}