RootTranslator.java

/**
 * 
 */
package org.openrosa.client.jr.core.reference;

import java.io.IOException;

import org.openrosa.client.java.io.DataInputStream;
import org.openrosa.client.java.io.DataOutputStream;
import org.openrosa.client.jr.core.util.externalizable.DeserializationException;
import org.openrosa.client.jr.core.util.externalizable.ExtUtil;
import org.openrosa.client.jr.core.util.externalizable.Externalizable;
import org.openrosa.client.jr.core.util.externalizable.PrototypeFactory;

/**
 * A Root Translator is a simple reference factory which doesn't
 * actually derive any specific references, but rather translates
 * references from one prefix to another. This is useful for roots
 * which don't describe any real raw accessor like "jr://media/",
 * which could access a file reference (jr://file/) on one platform,
 * but a resource reference (jr://resource/) on another.
 * 
 * Root Translators can be externalized and used as a dynamically 
 * configured object.
 * 
 * @author ctsims
 *
 */
public class RootTranslator implements ReferenceFactory, Externalizable {
	
	public String prefix;
	public String translatedPrefix;
	
	/**
	 * Serialization only!
	 */
	public RootTranslator() {
		
	}
	
	/**
	 * Creates a translator which will create references of the 
	 * type described by translatedPrefix whenever references of
	 * the type prefix are being derived.
	 *  
	 * @param prefix
	 * @param translatedPrefix
	 */
	public RootTranslator(String prefix, String translatedPrefix) {
		//TODO: Manage semantics of "ends with /" etc here?
		this.prefix = prefix;
		this.translatedPrefix = translatedPrefix;
	}

	/* (non-Javadoc)
	 * @see org.commcare.reference.Root#derive(java.lang.String)
	 */
	public Reference derive(String URI) throws InvalidReferenceException {
		return ReferenceManager._().DeriveReference(translatedPrefix + URI.substring(prefix.length()));
	}

	/* (non-Javadoc)
	 * @see org.commcare.reference.Root#derive(java.lang.String, java.lang.String)
	 */
	public Reference derive(String URI, String context) throws InvalidReferenceException {
		return ReferenceManager._().DeriveReference(URI, translatedPrefix + context.substring(prefix.length()));
	}

	/* (non-Javadoc)
	 * @see org.commcare.reference.Root#derives(java.lang.String)
	 */
	public boolean derives(String URI) {
		if(URI.startsWith(prefix)) {
			return true;
		} else{
			return false;
		}
	}

	public void readExternal(DataInputStream in, PrototypeFactory pf)
			throws IOException, DeserializationException {
		prefix = ExtUtil.readString(in);
		translatedPrefix = ExtUtil.readString(in);
	}

	public void writeExternal(DataOutputStream out) throws IOException {		
		ExtUtil.writeString(out, prefix);
		ExtUtil.writeString(out, translatedPrefix);
	}

}