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package org.apache.cayenne.exp.parser;

import java.io.PrintWriter;
import java.util.Map;

import org.apache.cayenne.DataObject;
import org.apache.cayenne.ObjectId;
import org.apache.cayenne.exp.Expression;
import org.apache.cayenne.map.Entity;

/**
 * Path expression traversing DB relationships and attributes.
 * 
 * @since 1.1
 * @author Andrei Adamchik
 */
public class ASTDbPath extends ASTPath {
    ASTDbPath(int id) {
        super(id);
    }

    public ASTDbPath() {
        super(ExpressionParserTreeConstants.JJTDBPATH);
    }

    public ASTDbPath(Object value) {
        super(ExpressionParserTreeConstants.JJTDBPATH);
        setPath(value);
    }

    protected Object evaluateNode(Object o) throws Exception {
        // TODO: implement resolving DB_PATH for DataObjects

        if (o instanceof Entity) {
            return evaluateEntityNode((Entity) o);
        }

        Map map = toMap(o);
        return (map != null) ? map.get(path) : null;
    }

    protected Map toMap(Object o) {
        if (o instanceof Map) {
            return (Map) o;
        }
        else if (o instanceof ObjectId) {
            return ((ObjectId) o).getIdSnapshot();
        }
        else if (o instanceof DataObject) {
            DataObject dataObject = (DataObject) o;

            // TODO: returns ObjectId snapshot for now.. should probably
            // retrieve full snapshot...
            ObjectId oid = dataObject.getObjectId();
            return (oid != null) ? oid.getIdSnapshot() : null;
        }
        else {
            return null;
        }
    }

    /**
     * Creates a copy of this expression node, without copying children.
     */
    public Expression shallowCopy() {
        ASTDbPath copy = new ASTDbPath(id);
        copy.path = path;
        return copy;
    }

    public void encodeAsString(PrintWriter pw) {
        pw.print("db:");
        pw.print(path);
    }

    public int getType() {
        return Expression.DB_PATH;
    }
}