package bsh.engine;

import bsh.Interpreter;
import javax.script.ScriptContext;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

import static javax.script.ScriptContext.ENGINE_SCOPE;

// 	Adopted from http://ikayzo.org/svn/beanshell/BeanShell/engine/src/bsh/engine/ScriptContextEngineView.java
/**
 * This class implements an ENGINE_SCOPE centric Map view of the ScriptContext
 * for engine implementations.  This class can be used to simplify engine
 * implementations which have the capability to bind their namespaces to Maps
 * or other external interfaces.
 * <p/>
 * Get operations on this view delegate to the
 * ScriptContext inheriting get() method that automatically traverses the
 * binding scopes in order or precedence.  Put operations on this view always
 * store values in the ENGINE_SCOPE bindings.  Other operations such as
 * size() and contains() are implemented appropriately, but perhaps not as
 * efficiently as possible.
 */
public class ScriptContextEngineView implements Map<String, Object> {

	ScriptContext context;


	public ScriptContextEngineView(ScriptContext context) {
		this.context = context;
	}


	/**
	 * Returns the number of unique object bindings in all scopes.
	 * (duplicate, shadowed, bindings count as a single binging).
	 */
	public int size() {
		return totalKeySet().size();
	}


	/**
	 * Returns true if no bindings are present in any scope of the context.
	 */
	public boolean isEmpty() {
		return totalKeySet().size() == 0;
	}


	/**
	 * Returns true if the key name is bound in any scope in the context.
	 * The key must be a String.
	 *
	 * @param key key whose presence in this map is to be tested.
	 * @return <tt>true</tt> if this map contains a mapping for the specified key.
	 * @throws ClassCastException   if the key is of an inappropriate type for this
	 *                              map (optional).
	 * @throws NullPointerException if the key is <tt>null</tt> and this map does
	 *                              not permit <tt>null</tt> keys (optional).
	 */
	public boolean containsKey(Object key) {
		if (key instanceof String) {
			return context.getAttributesScope((String) key) != -1;
		}
		return false;
	}


	/**
	 * Returns <tt>true</tt> if this map maps one or more keys to the specified
	 * value.  More formally, returns <tt>true</tt> if and only if this map
	 * contains at least one mapping to a value <tt>v</tt> such that
	 * <tt>(value==null ? v==null : value.equals(v))</tt>.  This operation will
	 * probably require time linear in the map size for most implementations of the
	 * <tt>Map</tt> interface.
	 *
	 * @param value value whose presence in this map is to be tested.
	 * @return <tt>true</tt> if this map maps one or more keys to the specified
	 *         value.
	 * @throws ClassCastException   if the value is of an inappropriate type for this
	 *                              map (optional).
	 * @throws NullPointerException if the value is <tt>null</tt> and this map does
	 *                              not permit <tt>null</tt> values (optional).
	 */
	public boolean containsValue(Object value) {
		Set values = totalValueSet();
		return values.contains(value);
	}


	/**
	 * Returns the value bound in the most specific (lowest numbered)
	 * bindings space for this key.
	 * key must be a String.
	 *
	 * @param key key whose associated value is to be returned.
	 * @return the value to which this map maps the specified key, or <tt>null</tt>
	 *         if the map contains no mapping for this key.
	 * @throws ClassCastException   if the key is of an inappropriate type for this
	 *                              map (optional).
	 * @throws NullPointerException if the key is <tt>null</tt> and this map does
	 *                              not permit <tt>null</tt> keys (optional).
	 * @see #containsKey(Object)
	 */
	public Object get(Object key) {
		return context.getAttribute((String) key);
	}


	/**
	 * Set the key, value binding in the ENGINE_SCOPE of the context.
	 *
	 * @param key   key with which the specified value is to be associated.
	 * @param value value to be associated with the specified key.
	 * @return previous value associated with specified key, or <tt>null</tt> if
	 *         there was no mapping for key.  A <tt>null</tt> return can also
	 *         indicate that the map previously associated <tt>null</tt> with the
	 *         specified key, if the implementation supports <tt>null</tt> values.
	 * @throws UnsupportedOperationException if the <tt>put</tt> operation is not
	 *                                       supported by this map.
	 * @throws ClassCastException			if the class of the specified key or value
	 *                                       prevents it from being stored in this map.
	 * @throws IllegalArgumentException	  if some aspect of this key or value
	 *                                       prevents it from being stored in this map.
	 * @throws NullPointerException		  if this map does not permit <tt>null</tt> keys
	 *                                       or values, and the specified key or value is <tt>null</tt>.
	 */
	public Object put(String key, Object value) {
		Object oldValue = context.getAttribute(key, ENGINE_SCOPE);
		context.setAttribute(key, value, ENGINE_SCOPE);
		return oldValue;
	}


	/**
	 * Put the bindings into the ENGINE_SCOPE of the context.
	 *
	 * @param t Mappings to be stored in this map.
	 * @throws UnsupportedOperationException if the <tt>putAll</tt> method is not
	 *                                       supported by this map.
	 * @throws ClassCastException			if the class of a key or value in the specified
	 *                                       map prevents it from being stored in this map.
	 * @throws IllegalArgumentException	  some aspect of a key or value in the
	 *                                       specified map prevents it from being stored in this map.
	 * @throws NullPointerException		  if the specified map is <tt>null</tt>, or if
	 *                                       this map does not permit <tt>null</tt> keys or values, and the specified map
	 *                                       contains <tt>null</tt> keys or values.
	 */
	public void putAll(Map<? extends String, ? extends Object> t) {
		context.getBindings(ENGINE_SCOPE).putAll(t);
	}


	/**
	 * Removes the mapping from the engine scope.
	 * <p/>
	 * <p>Returns the value to which the map previously associated the key, or
	 * <tt>null</tt> if the map contained no mapping for this key.  (A
	 * <tt>null</tt> return can also indicate that the map previously associated
	 * <tt>null</tt> with the specified key if the implementation supports
	 * <tt>null</tt> values.)  The map will not contain a mapping for the specified
	 * key once the call returns.
	 *
	 * @param okey key whose mapping is to be removed from the map.
	 * @return previous value associated with specified key, or <tt>null</tt> if
	 *         there was no mapping for key.
	 * @throws ClassCastException			if the key is of an inappropriate type for this
	 *                                       map (optional).
	 * @throws NullPointerException		  if the key is <tt>null</tt> and this map does
	 *                                       not permit <tt>null</tt> keys (optional).
	 * @throws UnsupportedOperationException if the <tt>remove</tt> method is not
	 *                                       supported by this map.
	 */
	// Why is the compiler complaining about this?
	//public Object remove( String key )
	public Object remove(Object okey) {
		// This shouldn't be necessary... we don't map Objects, Strings.
		String key = (String) okey;
		Object oldValue = context.getAttribute(key, ENGINE_SCOPE);
		context.removeAttribute(key, ENGINE_SCOPE);
		return oldValue;
	}


	/**
	 * Removes all mappings from this map (optional operation).
	 *
	 * @throws UnsupportedOperationException clear is not supported by this map.
	 */
	public void clear() {
		context.getBindings(ENGINE_SCOPE).clear();
	}


	/**
	 * Returns the total key set of all scopes.
	 * This method violates the Map contract by returning an unmodifiable set.
	 *
	 * @return a set view of the keys contained in this map.
	 */
	public Set<String> keySet() {
		return totalKeySet();
	}


	/**
	 * Returns the total values set of all scopes.
	 * This method violates the Map contract by returning an unmodifiable set.
	 *
	 * @return a collection view of the values contained in this map.
	 */
	public Collection<Object> values() {
		return totalValueSet();
	}


	/**
	 * Returns a set view of the mappings contained in this map.  Each element in
	 * the returned set is a {@link java.util.Map.Entry}.  The set is backed by the
	 * map, so changes to the map are reflected in the set, and vice-versa. If the
	 * map is modified while an iteration over the set is in progress (except
	 * through the iterator's own <tt>remove</tt> operation, or through the
	 * <tt>setValue</tt> operation on a map entry returned by the iterator) the
	 * results of the iteration are undefined.  The set supports element removal,
	 * which removes the corresponding mapping from the map, via the
	 * <tt>Iterator.remove</tt>, <tt>Set.remove</tt>, <tt>removeAll</tt>,
	 * <tt>retainAll</tt> and <tt>clear</tt> operations.  It does not support the
	 * <tt>add</tt> or <tt>addAll</tt> operations.
	 *
	 * @return a set view of the mappings contained in this map.
	 */
	public Set<Entry<String, Object>> entrySet() {
		throw new Error("unimplemented");
	}


	private Set<String> totalKeySet() {
		Set<String> keys = new HashSet<String>();
		List<Integer> scopes = context.getScopes();
		for (int i : scopes) {
			keys.addAll(context.getBindings(i).keySet());
		}
		return Collections.unmodifiableSet(keys);
	}


	private Set<Object> totalValueSet() {
		Set<Object> values = new HashSet<Object>();
		List<Integer> scopes = context.getScopes();
		for (int i : scopes) {
			values.addAll(context.getBindings(i).values());
		}
		return Collections.unmodifiableSet(values);
	}

}

