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There is a newer version: 0.7.0-M1

package brooklyn.util.xstream;

import java.util.Map;
import java.util.Map.Entry;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import brooklyn.util.collections.MutableMap;
import brooklyn.util.exceptions.Exceptions;
import brooklyn.util.flags.TypeCoercions;
import brooklyn.util.text.Identifiers;

import com.thoughtworks.xstream.converters.MarshallingContext;
import com.thoughtworks.xstream.converters.UnmarshallingContext;
import com.thoughtworks.xstream.io.ExtendedHierarchicalStreamWriterHelper;
import com.thoughtworks.xstream.io.HierarchicalStreamReader;
import com.thoughtworks.xstream.io.HierarchicalStreamWriter;
import com.thoughtworks.xstream.mapper.Mapper;

/** converter which simplifies representation of a map for string-based keys,
 * to value, or value 
 * @author alex
 *
 */
public class StringKeyMapConverter extends MapConverter {

    private static final Logger log = LoggerFactory.getLogger(StringKeyMapConverter.class);
    
    // full stop is technically allowed ... goes against "best practice" ... 
    // but simplifies property maps, and is used elsewhere in xstream's repn
    final static String VALID_XML_NODE_NAME_CHARS = Identifiers.JAVA_VALID_NONSTART_CHARS + ".";
    
    public StringKeyMapConverter(Mapper mapper) {
        super(mapper);
    }
    
    protected boolean isKeyValidForNodeName(String key) {
        // return false to always write as  type) {
        return TypeCoercions.isPrimitiveOrBoxer(type) || String.class.equals(type) || type.isEnum();
    }
    
    @Override
    protected void unmarshalEntry(HierarchicalStreamReader reader, UnmarshallingContext context, Map map) {
        String key = reader.getNodeName(); 
        if (key.equals(getEntryNodeName())) key = reader.getAttribute("key");
        if (key==null) {
            super.unmarshalEntry(reader, context, map);
        } else {
            unmarshalStringKey(reader, context, map, key);
        }
    }

    protected void unmarshalStringKey(HierarchicalStreamReader reader, UnmarshallingContext context, Map map, String key) {
        String type = reader.getAttribute("type");
        Object value;
        if (type==null && reader.hasMoreChildren()) {
            reader.moveDown();
            value = readItem(reader, context, map);
            reader.moveUp();
        } else {
            Class typeC = type!=null ? mapper().realClass(type) : String.class;
            try {
                value = TypeCoercions.coerce(reader.getValue(), typeC);
            } catch (Exception e) {
                log.warn("FAILED to coerce "+reader.getValue()+" to "+typeC+": "+e);
                throw Exceptions.propagate(e);
            }
        }
        map.put(key, value);
    }

}