/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.jena.permissions.query.rewriter;

import java.util.List;

import org.apache.jena.graph.Node;
import org.apache.jena.graph.Triple;
import org.apache.jena.permissions.SecurityEvaluator;
import org.apache.jena.permissions.SecurityEvaluator.Action;
import org.apache.jena.shared.AuthenticationRequiredException;
import org.apache.jena.sparql.core.Var;
import org.apache.jena.sparql.engine.binding.Binding;
import org.apache.jena.sparql.expr.*;
import org.apache.jena.sparql.function.FunctionEnv;
import org.apache.jena.sparql.graph.NodeTransform;

public class SecuredFunction extends ExprFunctionN {
	private final SecurityEvaluator securityEvaluator;
	private final List<Node> variables;
	private final List<Triple> bgp;
	private final Node graphIRI;

	private static ExprList createArgs(List<Node> variables) {
		ExprList retval = new ExprList();
		for (Node n : variables) {
			retval.add(new ExprVar(n));
		}
		return retval;
	}

	public SecuredFunction(final Node graphIRI,
			final SecurityEvaluator securityEvaluator,
			final List<Node> variables, final List<Triple> bgp) {
		super(String.format("<java:%s>", SecuredFunction.class.getName()),
				createArgs(variables));
		this.securityEvaluator = securityEvaluator;
		this.variables = variables;
		this.bgp = bgp;
		this.graphIRI = graphIRI;
	}

	private boolean checkAccess(Binding values)
			throws AuthenticationRequiredException {
		Object principal = securityEvaluator.getPrincipal();
		for (final Triple t : bgp) {
			final Triple secT = resolveTriple(t, values);
			if (!securityEvaluator.evaluate(principal, Action.Read, graphIRI,
					secT)) {
				return false;
			}
		}
		return true;
	}

	private Triple resolveTriple(final Triple t, final Binding values) {
		int idx = variables.indexOf(t.getSubject());

		final Node s = idx == -1 ? t.getSubject() : values.get(Var
				.alloc(variables.get(idx)));

		idx = variables.indexOf(t.getPredicate());
		final Node p = idx == -1 ? t.getPredicate() : values.get(Var
				.alloc(variables.get(idx)));
		idx = variables.indexOf(t.getObject());
		final Node o = idx == -1 ? t.getObject() : values.get(Var
				.alloc(variables.get(idx)));
		return new Triple(s, p, o);
	}

	@Override
	public Expr copySubstitute(Binding binding) {
		return this;
	}

	@Override
	public Expr applyNodeTransform(NodeTransform transform) {
		return this;
	}

	@Override
	public void visit(ExprVisitor visitor) {
		visitor.visit(this);
	}

	@Override
	public NodeValue eval(List<NodeValue> args) {
		// TODO Auto-generated method stub
		return null;
	}

	@Override
	public Expr copy(ExprList newArgs) {
		return this;
	}

	@Override
	protected NodeValue evalSpecial(Binding binding, FunctionEnv env) {
		return NodeValue.booleanReturn(checkAccess(binding));
	}

}