package org.python.core.adapter;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import org.python.core.PyObject;

/**
 * A PyObjectAdapter attempts to adapt a Java Object with three user fillable
 * groups of adapters: preClass, class and postClass.
 * 
 */
public class ExtensiblePyObjectAdapter implements PyObjectAdapter {

    /**
     * @return true if a preClass, postClass or class adapter can handle this
     */
    public boolean canAdapt(Object o) {
        return findAdapter(preClassAdapters, o) != null || classAdapters.containsKey(o.getClass())
                || findAdapter(postClassAdapters, o) != null;
    }

    /**
     * Attempts to adapt o using the preClass, class and postClass adapters.
     * 
     * First each of the preClass adapters is asked in the order of addition if
     * they can adapt o. If so, they adapt it. Otherwise, if o.getClass() is
     * equal to one of the classes from the added ClassAdapters, that class
     * adapter is used. Finally, each of the post class adapters are asked in
     * turn if they can adapt o. If so, that adapter handles it. If none can,
     * null is returned.
     */
    public PyObject adapt(Object o) {
        PyObjectAdapter adapter = findAdapter(preClassAdapters, o);
        if (adapter != null) {
            return adapter.adapt(o);
        }

        adapter = (PyObjectAdapter) classAdapters.get(o.getClass());
        if (adapter != null) {
            return adapter.adapt(o);
        }

        adapter = findAdapter(postClassAdapters, o);
        if (adapter != null) {
            return adapter.adapt(o);
        }
        return null;
    }

    /**
     * Adds an adapter to the list of adapters to be tried before the
     * ClassAdapters.
     */
    public void addPreClass(PyObjectAdapter adapter) {
        preClassAdapters.add(adapter);
    }

    /**
     * Adds a Class handling adapter that will adapt any objects of its Class if
     * that object hasn't already been handled by one of the pre class adapters.
     */
    public void add(ClassAdapter adapter) {
        classAdapters.put(adapter.getAdaptedClass(), adapter);
    }

    /**
     * Adds an adapter to the list of adapters to be tried after the
     * ClassAdapters.
     */
    public void addPostClass(PyObjectAdapter converter) {
        postClassAdapters.add(converter);
    }

    private static PyObjectAdapter findAdapter(List l, Object o) {
        for (Iterator iter = l.iterator(); iter.hasNext();) {
            PyObjectAdapter adapter = (PyObjectAdapter) iter.next();
            if (adapter.canAdapt(o)) {
                return adapter;
            }
        }
        return null;
    }

    private List preClassAdapters = new ArrayList();

    private List postClassAdapters = new ArrayList();

    private Map classAdapters = new HashMap();

}