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/*
 * Variant.java
 *
 * Created on September 27, 2007, 3:12 PM
 *
 */

package javax.ws.rs.core;

import java.io.StringWriter;
import java.util.List;
import java.util.Locale;
import javax.ws.rs.ext.RuntimeDelegate;

/**
 * Abstraction for a resource representation variant. 
 */
public class Variant {
    
    private Locale language;
    private MediaType mediaType;
    private String encoding;
    
    /**
     * Create a new instance of Variant
     * @param mediaType the media type of the variant - may be null
     * @param language the language of the variant - may be null
     * @param encoding the content encoding of the variant - may be null
     * @throws java.lang.IllegalArgumentException if all three parameters are
     * null
     */
    public Variant(MediaType mediaType, Locale language, String encoding) {
        if (mediaType==null && language==null && encoding==null)
            throw new IllegalArgumentException("mediaType, language, encoding all null");
        this.encoding = encoding;
        this.language = language;
        this.mediaType = mediaType;
    }
    
    /**
     * Get the language of the variant
     * @return the language or null if none set
     */
    public Locale getLanguage() {
        return language;
    }

    /**
     * Get the media type of the variant
     * @return the media type or null if none set
     */
    public MediaType getMediaType() {
        return mediaType;
    }

    /**
     * Get the encoding of the variant
     * @return the encoding or null if none set
     */
    public String getEncoding() {
        return encoding;
    }
    
    /**
     * Create a {@link VariantListBuilder} initialized with a set of supported
     * media types.
     * @param mediaTypes the available mediaTypes. If specific charsets
     * are supported they should be included as parameters of the respective
     * media type.
     * @return the initailized builder
     * @throws java.lang.IllegalArgumentException if mediaTypes is null or
     * contains no elements.
     */
    public static VariantListBuilder mediaTypes(MediaType... mediaTypes) {
        VariantListBuilder b = VariantListBuilder.newInstance();
        b.mediaTypes(mediaTypes);
        return b;
    }
    
    /**
     * Create a {@link VariantListBuilder} initialized with a set of supported
     * languages.
     * @param languages the available languages.
     * @return the initailized builder
     * @throws java.lang.IllegalArgumentException if languages is null or
     * contains no elements.
     */
    public static VariantListBuilder languages(Locale... languages) {
        VariantListBuilder b = VariantListBuilder.newInstance();
        b.languages(languages);
        return b;
    }
    
    /**
     * Create a {@link VariantListBuilder} initialized with a set of supported
     * encodings.
     * @param encodings the available encodings.
     * @return the initailized builder
     * @throws java.lang.IllegalArgumentException if encodings is null or
     * contains no elements.
     */
    public static VariantListBuilder encodings(String... encodings) {
        VariantListBuilder b = VariantListBuilder.newInstance();
        b.encodings(encodings);
        return b;
    }

    /**
     * Generate hash code from variant properties.
     * @return the hash code
     */
    @Override
    public int hashCode() {
        int hash = 7;
        hash = 29 * hash + (this.language != null ? this.language.hashCode() : 0);
        hash = 29 * hash + (this.mediaType != null ? this.mediaType.hashCode() : 0);
        hash = 29 * hash + (this.encoding != null ? this.encoding.hashCode() : 0);
        return hash;
    }

    /**
     * Compares obj to this variant to see if they are the same 
     * considering all property values.
     * @param obj the object to compare to
     * @return true if the two variants are the same, false otherwise.
     */
    @Override
    public boolean equals(Object obj) {
        if (obj == null) {
            return false;
        }
        if (getClass() != obj.getClass()) {
            return false;
        }
        final Variant other = (Variant) obj;
        if (this.language != other.language && (this.language == null || !this.language.equals(other.language))) {
            return false;
        }
        if (this.mediaType != other.mediaType && (this.mediaType == null || !this.mediaType.equals(other.mediaType))) {
            return false;
        }
        if (this.encoding != other.encoding && (this.encoding == null || !this.encoding.equals(other.encoding))) {
            return false;
        }
        return true;
    }

    @Override
    public String toString() {
        StringWriter w = new StringWriter();
        w.append("Variant[mediaType=");
        w.append(mediaType==null ? "null" : mediaType.toString());
        w.append(", language=");
        w.append(language==null ? "null" : language.toString());
        w.append(", encoding=");
        w.append(encoding==null ? "null" : encoding);
        w.append("]");
        return w.toString();
    }
    
    /**
     * A builder for a list of representation variants. 
     */
    public static abstract class VariantListBuilder {
        
        /**
         * Protected constructor, use the static <code>newInstance</code>
         * method to obtain an instance.
         */
        protected VariantListBuilder() {}
        
        /**
         * Create a new builder instance.
         * @return a new Builder
         */
        public static VariantListBuilder newInstance() {
            VariantListBuilder b = RuntimeDelegate.getInstance().createVariantListBuilder();
            return b;
        }
                
        /**
         * Build a list of representation variants from the current state of
         * the builder. After this method is called the builder is reset to
         * an empty state.
         * @return a list of representation variants
         */
        public abstract List<Variant> build();
        
        /**
         * Add the current combination of metadata to the list of supported variants,
         * after this method is called the current combination of metadata is emptied.
         * If more than one value is supplied for one or more of the variant properties
         * then a variant will be generated for each possible combination. E.g.
         * in the following <code>list</code> would have four members:
         * <p><pre>List<Variant> list = VariantListBuilder.newInstance().languages("en","fr")
         *   .encodings("zip", "identity").add().build()</pre>
         * 
         * @return the updated builder
         * @throws java.lang.IllegalStateException if there is not at least one
         * mediaType, language or encoding set for the current variant.
         */
        public abstract VariantListBuilder add();
        
        /**
         * Set the language[s] for this variant.
         * @param languages the available languages
         * @return the updated builder
         */
        public abstract VariantListBuilder languages(Locale... languages);
        
        /**
         * Set the encoding[s] for this variant.
         * @param encodings the available encodings
         * @return the updated builder
         */
        public abstract VariantListBuilder encodings(String... encodings);
        
        /**
         * Set the media type[s] for this variant.
         * @param mediaTypes the available mediaTypes. If specific charsets
         * are supported they should be included as parameters of the respective
         * media type.
         * @return the updated builder
         */
        public abstract VariantListBuilder mediaTypes(MediaType... mediaTypes);
    }
}