package org.etk.core.rest.impl.header;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;

import javax.ws.rs.Consumes;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;


public final class MediaTypeHelper {

  /**
   * Constructor. 
   */
  private MediaTypeHelper() {
  }
  
  /**
   * Compare two mimetypes. The main rule for sorting media types is :
   * <p>
   * <li>n / m</li>
   * <li>n / *</li>
   * <li>* / *</li>
   * <p>
   * Method that explicitly list of media types is sorted before a method that
   * list * / *.
   */
  public static final Comparator<MediaType> MEDIA_TYPE_COMPARATOR = new Comparator<MediaType>() {
  
    /**
     * {@inheritDoc}
     */
    public int compare(MediaType o1, MediaType o2) {
      if (o1.getType().equals(MediaType.MEDIA_TYPE_WILDCARD)
          && !o2.getType().equals(MediaType.MEDIA_TYPE_WILDCARD)) {
        return 1;
      }
  
      if (!o1.getType().equals(MediaType.MEDIA_TYPE_WILDCARD)
          && o2.getType().equals(MediaType.MEDIA_TYPE_WILDCARD)) {
        return -1;
      }
  
      if (o1.getSubtype().equals(MediaType.MEDIA_TYPE_WILDCARD)
          && !o2.getSubtype().equals(MediaType.MEDIA_TYPE_WILDCARD)) {
        return 1;
      }
  
      if (!o1.getSubtype().equals(MediaType.MEDIA_TYPE_WILDCARD)
          && o2.getSubtype().equals(MediaType.MEDIA_TYPE_WILDCARD)) {
        return -1;
      }
  
      return 0;
    }
    
  };
  
  /**
   * Default media type. It minds any content type.
   */
  public static final String                DEFAULT               = "*/*";

  /**
   * Default media type. It minds any content type.
   */
  public static final MediaType             DEFAULT_TYPE          = new MediaType("*", "*");

  /**
   * List which contains default media type.
   */
  public static final List<MediaType>       DEFAULT_TYPE_LIST     = Collections.singletonList(DEFAULT_TYPE);

  /**
   * WADL media type.
   */
  public static final String                WADL                  = "application/vnd.sun.wadl+xml";

  /**
   * WADL media type.
   */
  public static final MediaType             WADL_TYPE             = new MediaType("application",
                                                                                  "vnd.sun.wadl+xml");
  
  /**
   * Create a list of media type for given Consumes annotation. If parameter
   * mime is null then list with single element
   * {@link MediaTypeHelper#DEFAULT_TYPE} will be returned.
   * 
   * @param mime the Consumes annotation.
   * @return ordered list of media types.
   */
  public static List<MediaType> createConsumesList(Consumes mime) {
    if (mime == null) {
      return DEFAULT_TYPE_LIST; 
    }
    
    return createMediaTypesList(mime.value());
  }
  
  /**
   * Create a list of media type for given Produces annotation. If parameter
   * mime is null then list with single element
   * {@link MediaTypeHelper#DEFAULT_TYPE} will be returned.
   * 
   * @param mime the Produces annotation.
   * @return ordered list of media types.
   */
  public static List<MediaType> createProducesList(Produces mime) {
    if (mime == null) {
      return DEFAULT_TYPE_LIST; 
    }
    
    return createMediaTypesList(mime.value());
  }

  /**
   * Useful for checking does method able to consume certain media type.
   * 
   * @param consumes list of consumed media types
   * @param contentType should be checked
   * @return true contentType is compatible to one of consumes, false otherwise
   */
  public static boolean isConsume(List<MediaType> consumes, MediaType contentType) {
    for (MediaType c : consumes) {
      if (contentType.isCompatible(c))
        return true; 
    }
    
    return false;
  }

  /**
   * Create a list of media type from string array.
   * 
   * @param mimes source string array
   * @return ordered list of media types
   */
  private static List<MediaType> createMediaTypesList(String[] mimes) {
    List<MediaType> l = new ArrayList<MediaType>(mimes.length);
    for (String m : mimes)
      l.add(MediaType.valueOf(m));

    Collections.sort(l, MEDIA_TYPE_COMPARATOR);
    return l;
  }

  /**
   * Looking for accept media type with the best quality. Accept list of media
   * type must be sorted by quality value.
   * 
   * @param accept See {@link AcceptMediaType}, {@link QualityValue}
   * @param produces list of produces media type, See {@link Produces}
   * @return quality value of best found compatible accept media type or 0.0 if
   *         media types are not compatible
   */
  @SuppressWarnings("unchecked")
  public static float processQuality(List<MediaType> accept, List<MediaType> produces) {
    // NOTE accept contains list of AcceptMediaType instead
    // MediaType, see ContainerRequest#getAcceptableMediaTypes
    Iterator i = accept.iterator();
    while (i.hasNext()) {
      AcceptMediaType a = (AcceptMediaType) i.next();
      if ("*".equals(a.getType())) // accept everything, not need continue
        return a.getQvalue();
      for (MediaType p : produces) {
        if (p.isCompatible(a))
          return a.getQvalue();
      }
    }
    
    return 0.0F; // 0 quality not acceptable
  }

}