package com.ctc.wstx.io;

import java.io.IOException;
import java.net.URL;

import com.ctc.wstx.util.URLUtil;

Helper class that is used to defer construction of URL to help with cases where real URL is not actually needed, and incoming System Id may not even resolve properly. 

Note that class is meant to be accessed from a single thread, and
is not designed as multi-thread safe. Specifically it is not to be
used for caching or as a key, but strictly as System Id for processing
of a single XML document.
Since:
4.4/**
 * Helper class that is used to defer construction of {@link URL}
 * to help with cases where real URL is not actually needed, and
 * incoming System Id may not even resolve properly.
 *<p>
 * Note that class is meant to be accessed from a single thread, and
 * is not designed as multi-thread safe. Specifically it is not to be
 * used for caching or as a key, but strictly as System Id for processing
 * of a single XML document.
 * 
 * @since 4.4
 */
public class SystemId
{
    protected URL mURL;

    protected String mSystemId;

    protected SystemId(String systemId, URL url) {
        if (systemId == null && url == null) {
            throw new IllegalArgumentException("Can not pass null for both systemId and url");
        }
        mSystemId = systemId;
        mURL = url;
    }
	
    public static SystemId construct(String systemId) {
        return (systemId == null) ? null : new SystemId(systemId, null);
    }

    public static SystemId construct(URL url) {
        return (url == null) ? null : new SystemId(null, url);
    }

    public static SystemId construct(String systemId, URL url) {
        if (systemId == null && url == null) {
            return null;
        }
        return new SystemId(systemId, url);
    }

    public URL asURL() throws IOException {
        if (mURL == null) {
            mURL = URLUtil.urlFromSystemId(mSystemId);
        }
        return mURL;
    }

    public boolean hasResolvedURL() {
        return (mURL != null);
    }
	
    @Override
    public String toString() {
	    if (mSystemId == null) {
	        mSystemId = mURL.toExternalForm();
	    }
	    return mSystemId;
    }
}