LanguageTag.java

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package com.sun.jersey.core.header;

import com.sun.jersey.core.header.reader.HttpHeaderReader;
import java.text.ParseException;
import java.util.Locale;

/**
 * A language tag.
 * 
 * @author Paul.Sandoz@Sun.Com
 */
public class LanguageTag {
    
    protected String tag;
    
    protected String primaryTag;
    
    protected String subTags;
    
    protected LanguageTag() {    
    }

    public static LanguageTag valueOf(String s) throws IllegalArgumentException {
        LanguageTag lt = new LanguageTag();

        try {
            lt.parse(s);
        } catch (ParseException pe) {
            throw new IllegalArgumentException(pe);
        }

        return lt;
    }
    
    public LanguageTag(String primaryTag, String subTags) {
        if (subTags != null && subTags.length() > 0)
            this.tag = primaryTag + "-" + subTags;
        else 
            this.tag = primaryTag;
        
        this.primaryTag = primaryTag;
        
        this.subTags = subTags;
    }
    
    public LanguageTag(String header) throws ParseException {
        this(HttpHeaderReader.newInstance(header));
    }
    
    public LanguageTag(HttpHeaderReader reader) throws ParseException {
        // Skip any white space
        reader.hasNext();
        
        tag = reader.nextToken();
        
        if (reader.hasNext())
            throw new ParseException("Invalid Language tag", reader.getIndex());
        
        parse(tag);
    }
    
    public final boolean isCompatible(Locale tag) {
        if (this.tag.equals("*"))
            return true;

        if (subTags == null) {
            return primaryTag.equalsIgnoreCase(tag.getLanguage());
        } else {
            return primaryTag.equalsIgnoreCase(tag.getLanguage()) &&
                    subTags.equalsIgnoreCase(tag.getCountry());
        }
    }

    public final Locale getAsLocale() {
        return (subTags == null)
                ? new Locale(primaryTag)
                : new Locale(primaryTag, subTags);
    }

    protected final void parse(String languageTag) throws ParseException {
        if (!isValid(languageTag)) {
            throw new ParseException("String, " + languageTag + ", is not a valid language tag", 0);
        }
        
        int index = languageTag.indexOf('-');
        if (index == -1) {
            primaryTag = languageTag;
            subTags = null;
        } else {
            primaryTag = languageTag.substring(0, index);
            subTags = languageTag.substring(index + 1, languageTag.length());
        }        
    }
    
    private boolean isValid(String tag) {
        int alphaCount = 0;
        for (int i = 0; i < tag.length(); i++) {
            final char c = tag.charAt(i);
            if (c == '-') {
                if (alphaCount == 0)
                    return false;
                alphaCount = 0;
            } else if (('A' <= c && c <= 'Z') || ('a' <= c && c <= 'z')) {
                alphaCount++;
                if (alphaCount > 8)
                    return false;
            } else {
                return false;
            }
        }
        return (alphaCount != 0);
    }

    public final String getTag() {
        return tag;
    }

    public final String getPrimaryTag() {
        return primaryTag;
    }

    public final String getSubTags() {
        return subTags;
    }

    @Override
    public boolean equals(Object object) {
        if(object instanceof LanguageTag) {
            LanguageTag lt = (LanguageTag)object;

            if(this.tag != null)
                if(!this.tag.equals(lt.getTag()))
                    return false;
            else
                if(lt.getTag() != null)
                    return false;

            if(this.primaryTag != null)
                if(!this.primaryTag.equals(lt.getPrimaryTag()))
                    return false;
            else
                if(lt.getPrimaryTag() != null)
                    return false;

            if(this.subTags != null)
                if(!this.subTags.equals(lt.getSubTags()))
                    return false;
            else
                if(lt.getSubTags() != null)
                    return false;

            return true;
        } else {
            return false;
        }
    }

    @Override
    public int hashCode() {
        return  (tag == null ? 0 : tag.hashCode()) +
                (primaryTag == null ? 0 : primaryTag.hashCode()) +
                (subTags == null ? 0 : primaryTag.hashCode());
    }

    @Override
    public String toString() {
        return primaryTag + (subTags == null ? "" : subTags);
    }
}