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package org.mozc.android.inputmethod.japanese.view;

import com.google.common.base.Optional;

import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.LinearGradient;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.Shader;
import android.graphics.Shader.TileMode;

/**
 * Drawable to render a candidate background.
 *
 */
public class CandidateBackgroundDrawable extends BaseBackgroundDrawable {

  private final int topColor;
  private final int bottomColor;
  private final int highlightColor;
  private final int borderColor;

  private int left;
  private int top;
  private int right;
  private int bottom;

  /** Cached Paint instance to reuse for performance reason. */
  private final Paint paint = new Paint();
  private Optional<Shader> shader = Optional.absent();

  public CandidateBackgroundDrawable(
      int leftPadding, int topPadding, int rightPadding, int bottomPadding,
      int topColor, int bottomColor, int highlightColor, int borderColor) {
    super(leftPadding, topPadding, rightPadding, bottomPadding);
    this.topColor = topColor;
    this.bottomColor = bottomColor;
    this.highlightColor = highlightColor;
    this.borderColor = borderColor;
  }

  @Override
  public void draw(Canvas canvas) {
    if (isCanvasRectEmpty()) {
      return;
    }

    // Local variable cache for better performance.
    Paint paint = this.paint;
    int left = this.left;
    int top = this.top;
    int right = this.right;
    int bottom = this.bottom;

    // Render border color.
    if (Color.alpha(borderColor) != 0) {
      paint.reset();
      paint.setColor(borderColor);
      canvas.drawRect(left, top, right, bottom, paint);
    }

    // Render left/top highlight.
    if (Color.alpha(highlightColor) != 0) {
      paint.reset();
      paint.setColor(highlightColor);
      canvas.drawRect(left, top, Math.max(left, right - 1), Math.max(top, bottom - 1), paint);
    }

    // Render filling color.
    if (shader.isPresent()) {
      paint.reset();
      paint.setShader(shader.get());
      canvas.drawRect(left + 1, top + 1,
                      Math.max(left + 1, right - 1), Math.max(top + 1, bottom - 1), paint);
    }
  }

  @Override
  protected void onBoundsChange(Rect rect) {
    super.onBoundsChange(rect);

    Rect canvasRect = getCanvasRect();
    left = canvasRect.left;
    top = canvasRect.top;
    right = canvasRect.right;
    bottom = canvasRect.bottom;
    if (Color.alpha(topColor | bottomColor) != 0) {
      shader = Optional.<Shader>of(
          new LinearGradient(0, top, 0, bottom, topColor, bottomColor, TileMode.CLAMP));
    }
  }
}
