// Copyright 2012 Google Inc. All Rights Reserved.
//
// 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.collide.client.document.linedimensions;

import com.google.collide.client.util.Elements;
import com.google.collide.client.util.dom.FontDimensionsCalculator;
import com.google.collide.client.util.dom.FontDimensionsCalculator.FontDimensions;
import com.google.collide.shared.util.StringUtils;

import elemental.css.CSSStyleDeclaration;
import elemental.html.Element;

/**
 * A {@link MeasurementProvider} which utilizes the DOM to measure a string.
 */
class BrowserMeasurementProvider implements MeasurementProvider {

  /**
   * The minimum number of characters we require to measure.
   * #getRenderedStringWidth(String) will use this to duplicate the string when
   * measuring short strings.
   */
  /*
   * this is not completely arbitrary, too low of a number and WebKit
   * mis-calculates the width due to rounding errors and minor variations in
   * zoom level character widths. As a reference, 10.0 was too small.
   */
  private static final double MINIMUM_TEXT_LENGTH = 30.0;

  private final FontDimensions fontDimensions;
  private final Element element;

  public BrowserMeasurementProvider(FontDimensionsCalculator calculator) {
    fontDimensions = calculator.getFontDimensions();

    element = Elements.createSpanElement(calculator.getFontClassName());
    element.getStyle().setVisibility(CSSStyleDeclaration.Visibility.HIDDEN);
    element.getStyle().setPosition(CSSStyleDeclaration.Position.ABSOLUTE);
    Elements.getBody().appendChild(element);
  }

  @Override
  public double getCharacterWidth() {
    return fontDimensions.getCharacterWidth();
  }

  @Override
  public double measureStringWidth(String text) {
    LineDimensionsUtils.markTimeline(getClass(), "Starting measurement of text");
    int instances = (int) Math.ceil(MINIMUM_TEXT_LENGTH / text.length());
    /*
     * We add a hardspace since this prevents bi-directional combining marks
     * from screwing with our measurement (these spaces must be removed from our
     * result at the end).
     */
    element.setTextContent(StringUtils.repeatString(text + "\u00A0", instances));
    double width = (element.getBoundingClientRect().getWidth() - (getCharacterWidth() * instances))
        / instances;
    LineDimensionsUtils.markTimeline(getClass(), "End measurement of text");
    return width;
  }
}