package jalview.renderer.seqfeatures;

import jalview.api.FeatureRenderer;
import jalview.api.FeaturesDisplayedI;
import jalview.datamodel.SequenceI;
import jalview.viewmodel.seqfeatures.FeatureRendererModel;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.image.BufferedImage;

/**
 * A helper class to find feature colour using an associated FeatureRenderer
 * 
 * @author gmcarstairs
 *
 */
public class FeatureColourFinder
{
  /*
   * the class we delegate feature finding to
   */
  private FeatureRenderer featureRenderer;

  /*
   * a 1-pixel image on which features can be drawn, for the case where
   * transparency allows 'see-through' of multiple feature colours
   */
  private BufferedImage offscreenImage;

  /**
   * Constructor
   * 
   * @param fr
   */
  public FeatureColourFinder(FeatureRenderer fr)
  {
    featureRenderer = fr;
    offscreenImage = new BufferedImage(1, 1, BufferedImage.TYPE_INT_ARGB);
  }

  /**
   * Answers the feature colour to show for the given sequence and column
   * position. This delegates to the FeatureRenderer to find the colour, which
   * will depend on feature location, visibility, ordering, colour scheme, and
   * whether or not transparency is applied. For feature rendering with
   * transparency, this class provides a dummy 'offscreen' graphics context
   * where multiple feature colours can be overlaid and the combined colour read
   * back.
   * 
   * @param defaultColour
   * @param seq
   * @param column
   *          alignment column position (base zero)
   * @return
   */
  public Color findFeatureColour(Color defaultColour, SequenceI seq,
          int column)
  {
    if (!((FeatureRendererModel) featureRenderer).hasRenderOrder())
    {
      return defaultColour;
    }

    FeaturesDisplayedI displayed = featureRenderer.getFeaturesDisplayed();
    if (displayed == null || displayed.getVisibleFeatureCount() == 0)
    {
      return defaultColour; // nothing to see here folks
    }

    Graphics g = null;

    /*
     * if transparency applies, provide a notional 1x1 graphics context 
     * that has been primed with the default colour
     */
    if (featureRenderer.getTransparency() != 1f)
    {
      g = offscreenImage.getGraphics();
      if (defaultColour != null)
      {
        offscreenImage.setRGB(0, 0, defaultColour.getRGB());
      }
    }

    Color c = featureRenderer.findFeatureColour(seq, column, g);
    if (c == null)
    {
      return defaultColour;
    }

    if (g != null)
    {
      c = new Color(offscreenImage.getRGB(0, 0));
    }
    return c;
  }
}