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/*

 * Copyright 2010 Google Inc.

 *

 * 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 com.google.gwt.user.cellview.client;

import com.google.gwt.core.client.GWT;

import com.google.gwt.event.dom.client.ClickEvent;

import com.google.gwt.event.dom.client.ClickHandler;

import com.google.gwt.i18n.client.NumberFormat;

import com.google.gwt.resources.client.ClientBundle;

import com.google.gwt.resources.client.CssResource;

import com.google.gwt.resources.client.ImageResource;

import com.google.gwt.resources.client.ImageResource.ImageOptions;

import com.google.gwt.uibinder.client.UiConstructor;

import com.google.gwt.user.client.ui.HTML;

import com.google.gwt.user.client.ui.HasVerticalAlignment;

import com.google.gwt.user.client.ui.HorizontalPanel;

import com.google.gwt.user.client.ui.Image;

import com.google.gwt.view.client.HasRows;

import com.google.gwt.view.client.Range;

/**

 * A pager for controlling a {@link HasRows} that only supports simple page

 * navigation.

 *

 * <p>

 * <h3>Example</h3>

 * {@example com.google.gwt.examples.cellview.SimplePagerExample}

 * </p>

 */

public class GssSimplePager extends AbstractPager {

  /**

   * A ClientBundle that provides images for this widget.

   */

  public static interface Resources extends ClientBundle {

    /**

     * The image used to skip ahead multiple pages.

     */

    @ImageOptions(flipRtl = true)

    ImageResource simplePagerFastForward();

    /**

     * The disabled "fast forward" image.

     */

    @ImageOptions(flipRtl = true)

    ImageResource simplePagerFastForwardDisabled();

    /**

     * The image used to go to the first page.

     */

    @ImageOptions(flipRtl = true)

    ImageResource simplePagerFirstPage();

    /**

     * The disabled first page image.

     */

    @ImageOptions(flipRtl = true)

    ImageResource simplePagerFirstPageDisabled();

    /**

     * The image used to go to the last page.

     */

    @ImageOptions(flipRtl = true)

    ImageResource simplePagerLastPage();

    /**

     * The disabled last page image.

     */

    @ImageOptions(flipRtl = true)

    ImageResource simplePagerLastPageDisabled();

    /**

     * The image used to go to the next page.

     */

    @ImageOptions(flipRtl = true)

    ImageResource simplePagerNextPage();

    /**

     * The disabled next page image.

     */

    @ImageOptions(flipRtl = true)

    ImageResource simplePagerNextPageDisabled();

    /**

     * The image used to go to the previous page.

     */

    @ImageOptions(flipRtl = true)

    ImageResource simplePagerPreviousPage();

    /**

     * The disabled previous page image.

     */

    @ImageOptions(flipRtl = true)

    ImageResource simplePagerPreviousPageDisabled();

    /**

     * The styles used in this widget.

     */

    @Source("SimplePager.css")

    Style simplePagerStyle();

  }

  /**

   * Styles used by this widget.

   */

  public static interface Style extends CssResource {

    /**

     * Applied to buttons.

     */

    String button();

    /**

     * Applied to disabled buttons.

     */

    String disabledButton();

    /**

     * Applied to the details text.

     */

    String pageDetails();

  }

  /**

   * The location of the text relative to the paging buttons.

   */

  public static enum TextLocation {

    CENTER, LEFT, RIGHT;

  }

  private static int DEFAULT_FAST_FORWARD_ROWS = 1000;

  private static Resources DEFAULT_RESOURCES;

  private static Resources getDefaultResources() {

    if (DEFAULT_RESOURCES == null) {

      DEFAULT_RESOURCES = GWT.create(Resources.class);

    }

    return DEFAULT_RESOURCES;

  }

  private final Image fastForward;

  private final int fastForwardRows;

  private final Image firstPage;

  /**

   * We use an {@link HTML} so we can embed the loading image.

   */

  private final HTML label = new HTML();

  private final Image lastPage;

  /**

   * Set to true when the next and last buttons are disabled.

   */

  private boolean nextDisabled;

  private final Image nextPage;

  /**

   * Set to true when the prev and first buttons are disabled.

   */

  private boolean prevDisabled;

  private final Image prevPage;

  /**

   * The {@link Resources} used by this widget.

   */

  private final Resources resources;

  /**

   * The {@link Style} used by this widget.

   */

  private final Style style;

  /**

   * Construct a {@link GssSimplePager} with the default text location.

   */

  public GssSimplePager() {

    this(TextLocation.CENTER);

  }

  /**

   * Construct a {@link GssSimplePager} with the specified text location.

   *

   * @param location the location of the text relative to the buttons

   */

  @UiConstructor

  // Hack for Google I/O demo

  public GssSimplePager(TextLocation location) {

    this(location, getDefaultResources(), false, DEFAULT_FAST_FORWARD_ROWS,

        true);

  }

  /**

   * Construct a {@link GssSimplePager} with the specified resources.

   *

   * @param location the location of the text relative to the buttons

   * @param resources the {@link Resources} to use

   * @param showFastForwardButton if true, show a fast-forward button that

   *          advances by a larger increment than a single page

   * @param fastForwardRows the number of rows to jump when fast forwarding

   * @param showLastPageButton if true, show a button to go the the last page

   */

  public GssSimplePager(TextLocation location, Resources resources,

      boolean showFastForwardButton, final int fastForwardRows,

      boolean showLastPageButton) {

    this.resources = resources;

    this.fastForwardRows = fastForwardRows;

    this.style = resources.simplePagerStyle();

    this.style.ensureInjected();

    // Create the buttons.

    firstPage = new Image(resources.simplePagerFirstPage());

    firstPage.addClickHandler(new ClickHandler() {

      public void onClick(ClickEvent event) {

        firstPage();

      }

    });

    nextPage = new Image(resources.simplePagerNextPage());

    nextPage.addClickHandler(new ClickHandler() {

      public void onClick(ClickEvent event) {

        nextPage();

      }

    });

    prevPage = new Image(resources.simplePagerPreviousPage());

    prevPage.addClickHandler(new ClickHandler() {

      public void onClick(ClickEvent event) {

        previousPage();

      }

    });

    if (showLastPageButton) {

      lastPage = new Image(resources.simplePagerLastPage());

      lastPage.addClickHandler(new ClickHandler() {

        public void onClick(ClickEvent event) {

          lastPage();

        }

      });

    } else {

      lastPage = null;

    }

    if (showFastForwardButton) {

      fastForward = new Image(resources.simplePagerFastForward());

      fastForward.addClickHandler(new ClickHandler() {

        public void onClick(ClickEvent event) {

          setPage(getPage() + getFastForwardPages());

        }

      });

    } else {

      fastForward = null;

    }

    // Construct the widget.

    HorizontalPanel layout = new HorizontalPanel();

    layout.setVerticalAlignment(HasVerticalAlignment.ALIGN_MIDDLE);

    initWidget(layout);

    if (location == TextLocation.RIGHT) {

      layout.add(label);

    }

    layout.add(firstPage);

    layout.add(prevPage);

    if (location == TextLocation.CENTER) {

      layout.add(label);

    }

    layout.add(nextPage);

    if (showFastForwardButton) {

      layout.add(fastForward);

    }

    if (showLastPageButton) {

      layout.add(lastPage);

    }

    if (location == TextLocation.LEFT) {

      layout.add(label);

    }

    // Add style names to the cells.

    firstPage.getElement().getParentElement().addClassName(style.button());

    prevPage.getElement().getParentElement().addClassName(style.button());

    label.getElement().getParentElement().addClassName(style.pageDetails());

    nextPage.getElement().getParentElement().addClassName(style.button());

    if (showFastForwardButton) {

      fastForward.getElement().getParentElement().addClassName(style.button());

    }

    if (showLastPageButton) {

      lastPage.getElement().getParentElement().addClassName(style.button());

    }

    // Disable the buttons by default.

    setDisplay(null);

  }

  @Override

  public void firstPage() {

    super.firstPage();

  }

  @Override

  public int getPage() {

    return super.getPage();

  }

  @Override

  public int getPageCount() {

    return super.getPageCount();

  }

  @Override

  public boolean hasNextPage() {

    return super.hasNextPage();

  }

  @Override

  public boolean hasNextPages(int pages) {

    return super.hasNextPages(pages);

  }

  @Override

  public boolean hasPage(int index) {

    return super.hasPage(index);

  }

  @Override

  public boolean hasPreviousPage() {

    return super.hasPreviousPage();

  }

  @Override

  public boolean hasPreviousPages(int pages) {

    return super.hasPreviousPages(pages);

  }

  @Override

  public void lastPage() {

    super.lastPage();

  }

  @Override

  public void lastPageStart() {

    super.lastPageStart();

  }

  @Override

  public void nextPage() {

    super.nextPage();

  }

  @Override

  public void previousPage() {

    super.previousPage();

  }

  @Override

  public void setDisplay(HasRows display) {

    // Enable or disable all buttons.

    boolean disableButtons = (display == null);

    setFastForwardDisabled(disableButtons);

    setNextPageButtonsDisabled(disableButtons);

    setPrevPageButtonsDisabled(disableButtons);

    super.setDisplay(display);

  }

  @Override

  public void setPage(int index) {

    super.setPage(index);

  }

  @Override

  public void setPageSize(int pageSize) {

    super.setPageSize(pageSize);

  }

  @Override

  public void setPageStart(int index) {

    super.setPageStart(index);

  }

  /**

   * Let the page know that the table is loading. Call this method to clear all

   * data from the table and hide the current range when new data is being

   * loaded into the table.

   */

  public void startLoading() {

    getDisplay().setRowCount(0, true);

    label.setHTML("");

  }

  /**

   * Get the text to display in the pager that reflects the state of the pager.

   *

   * @return the text

   */

  protected String createText() {

    // Default text is 1 based.

    NumberFormat formatter = NumberFormat.getFormat("#,###");

    HasRows display = getDisplay();

    Range range = display.getVisibleRange();

    int pageStart = range.getStart() + 1;

    int pageSize = range.getLength();

    int dataSize = display.getRowCount();

    int endIndex = Math.min(dataSize, pageStart + pageSize - 1);

    endIndex = Math.max(pageStart, endIndex);

    boolean exact = display.isRowCountExact();

    return formatter.format(pageStart) + "-" + formatter.format(endIndex)

        + (exact ? " of " : " of over ") + formatter.format(dataSize);

  }

  @Override

  protected void onRangeOrRowCountChanged() {

    HasRows display = getDisplay();

    label.setText(createText());

    // Update the prev and first buttons.

    setPrevPageButtonsDisabled(!hasPreviousPage());

    // Update the next and last buttons.

    if (isRangeLimited() || !display.isRowCountExact()) {

      setNextPageButtonsDisabled(!hasNextPage());

      setFastForwardDisabled(!hasNextPages(getFastForwardPages()));

    }

  }

  /**

   * Check if the next button is disabled. Visible for testing.

   */

  boolean isNextButtonDisabled() {

    return nextDisabled;

  }

  /**

   * Check if the previous button is disabled. Visible for testing.

   */

  boolean isPreviousButtonDisabled() {

    return prevDisabled;

  }

  /**

   * Get the number of pages to fast forward based on the current page size.

   *

   * @return the number of pages to fast forward

   */

  private int getFastForwardPages() {

    int pageSize = getPageSize();

    return pageSize > 0 ? fastForwardRows / pageSize : 0;

  }

  /**

   * Enable or disable the fast forward button.

   *

   * @param disabled true to disable, false to enable

   */

  private void setFastForwardDisabled(boolean disabled) {

    if (fastForward == null) {

      return;

    }

    if (disabled) {

      fastForward.setResource(resources.simplePagerFastForwardDisabled());

      fastForward.getElement().getParentElement().addClassName(

          style.disabledButton());

    } else {

      fastForward.setResource(resources.simplePagerFastForward());

      fastForward.getElement().getParentElement().removeClassName(

          style.disabledButton());

    }

  }

  /**

   * Enable or disable the next page buttons.

   *

   * @param disabled true to disable, false to enable

   */

  private void setNextPageButtonsDisabled(boolean disabled) {

    if (disabled == nextDisabled) {

      return;

    }

    nextDisabled = disabled;

    if (disabled) {

      nextPage.setResource(resources.simplePagerNextPageDisabled());

      nextPage.getElement().getParentElement().addClassName(

          style.disabledButton());

      if (lastPage != null) {

        lastPage.setResource(resources.simplePagerLastPageDisabled());

        lastPage.getElement().getParentElement().addClassName(

            style.disabledButton());

      }

    } else {

      nextPage.setResource(resources.simplePagerNextPage());

      nextPage.getElement().getParentElement().removeClassName(

          style.disabledButton());

      if (lastPage != null) {

        lastPage.setResource(resources.simplePagerLastPage());

        lastPage.getElement().getParentElement().removeClassName(

            style.disabledButton());

      }

    }

  }

  /**

   * Enable or disable the previous page buttons.

   *

   * @param disabled true to disable, false to enable

   */

  private void setPrevPageButtonsDisabled(boolean disabled) {

    if (disabled == prevDisabled) {

      return;

    }

    prevDisabled = disabled;

    if (disabled) {

      firstPage.setResource(resources.simplePagerFirstPageDisabled());

      firstPage.getElement().getParentElement().addClassName(

          style.disabledButton());

      prevPage.setResource(resources.simplePagerPreviousPageDisabled());

      prevPage.getElement().getParentElement().addClassName(

          style.disabledButton());

    } else {

      firstPage.setResource(resources.simplePagerFirstPage());

      firstPage.getElement().getParentElement().removeClassName(

          style.disabledButton());

      prevPage.setResource(resources.simplePagerPreviousPage());

      prevPage.getElement().getParentElement().removeClassName(

          style.disabledButton());

    }

  }

}