/*
 * 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.el.lang;

import java.io.StringReader;
import java.lang.reflect.Method;
import java.security.AccessController;
import java.security.PrivilegedAction;

import javax.el.ELContext;
import javax.el.ELException;
import javax.el.FunctionMapper;
import javax.el.MethodExpression;
import javax.el.ValueExpression;
import javax.el.VariableMapper;

import org.apache.el.MethodExpressionImpl;
import org.apache.el.MethodExpressionLiteral;
import org.apache.el.ValueExpressionImpl;
import org.apache.el.parser.AstDeferredExpression;
import org.apache.el.parser.AstDynamicExpression;
import org.apache.el.parser.AstFunction;
import org.apache.el.parser.AstIdentifier;
import org.apache.el.parser.AstLiteralExpression;
import org.apache.el.parser.AstValue;
import org.apache.el.parser.ELParser;
import org.apache.el.parser.Node;
import org.apache.el.parser.NodeVisitor;
import org.apache.el.util.ConcurrentCache;
import org.apache.el.util.MessageFactory;

/**
 * @author Jacob Hookom [[email protected]]
 */
public final class ExpressionBuilder implements NodeVisitor {

	private static final int CACHE_SIZE;
	private static final String CACHE_SIZE_PROP = "org.apache.el.ExpressionBuilder.CACHE_SIZE";

	static {
		String cacheSizeStr;
		if (System.getSecurityManager() == null) {
			cacheSizeStr = System.getProperty(CACHE_SIZE_PROP, "5000");
		} else {
			cacheSizeStr = AccessController.doPrivileged(new PrivilegedAction<String>() {

				@Override
				public String run() {
					return System.getProperty(CACHE_SIZE_PROP, "5000");
				}
			});
		}
		CACHE_SIZE = Integer.parseInt(cacheSizeStr);
	}

	private static final ConcurrentCache<String, Node> cache = new ConcurrentCache<String, Node>(CACHE_SIZE);

	private FunctionMapper fnMapper;

	private VariableMapper varMapper;

	private String expression;

	/**
	 *
	 */
	public ExpressionBuilder(String expression, ELContext ctx) throws ELException {
		this.expression = expression;

		FunctionMapper ctxFn = ctx.getFunctionMapper();
		VariableMapper ctxVar = ctx.getVariableMapper();

		if (ctxFn != null) {
			this.fnMapper = new FunctionMapperFactory(ctxFn);
		}
		if (ctxVar != null) {
			this.varMapper = new VariableMapperFactory(ctxVar);
		}
	}

	public static final Node createNode(String expr) throws ELException {
		Node n = createNodeInternal(expr);
		return n;
	}

	private static final Node createNodeInternal(String expr) throws ELException {
		if (expr == null) {
			throw new ELException(MessageFactory.get("error.null"));
		}

		Node n = cache.get(expr);
		if (n == null) {
			try {
				n = (new ELParser(new StringReader(expr))).CompositeExpression();

				// validate composite expression
				int numChildren = n.jjtGetNumChildren();
				if (numChildren == 1) {
					n = n.jjtGetChild(0);
				} else {
					Class<?> type = null;
					Node child = null;
					for (int i = 0; i < numChildren; i++) {
						child = n.jjtGetChild(i);
						if (child instanceof AstLiteralExpression)
							continue;
						if (type == null)
							type = child.getClass();
						else {
							if (!type.equals(child.getClass())) {
								throw new ELException(MessageFactory.get("error.mixed", expr));
							}
						}
					}
				}

				if (n instanceof AstDeferredExpression || n instanceof AstDynamicExpression) {
					n = n.jjtGetChild(0);
				}
				cache.put(expr, n);
			} catch (Exception e) {
				throw new ELException(MessageFactory.get("error.parseFail", expr), e);
			}
		}
		return n;
	}

	private void prepare(Node node) throws ELException {
		try {
			node.accept(this);
		} catch (Exception e) {
			if (e instanceof ELException) {
				throw (ELException) e;
			} else {
				throw (new ELException(e));
			}
		}
		if (this.fnMapper instanceof FunctionMapperFactory) {
			this.fnMapper = ((FunctionMapperFactory) this.fnMapper).create();
		}
		if (this.varMapper instanceof VariableMapperFactory) {
			this.varMapper = ((VariableMapperFactory) this.varMapper).create();
		}
	}

	private Node build() throws ELException {
		Node n = createNodeInternal(this.expression);
		this.prepare(n);
		if (n instanceof AstDeferredExpression || n instanceof AstDynamicExpression) {
			n = n.jjtGetChild(0);
		}
		return n;
	}

	/*
	 * (non-Javadoc)
	 *
	 * @see com.sun.el.parser.NodeVisitor#visit(com.sun.el.parser.Node)
	 */
	@Override
	public void visit(Node node) throws ELException {
		if (node instanceof AstFunction) {

			AstFunction funcNode = (AstFunction) node;

			if (this.fnMapper == null) {
				throw new ELException(MessageFactory.get("error.fnMapper.null"));
			}
			Method m = fnMapper.resolveFunction(funcNode.getPrefix(), funcNode.getLocalName());
			if (m == null) {
				throw new ELException(MessageFactory.get("error.fnMapper.method", funcNode.getOutputName()));
			}
			int methodParameterCount = m.getParameterTypes().length;
			int inputParameterCount = node.jjtGetNumChildren();
			if (m.isVarArgs() && inputParameterCount < methodParameterCount - 1
					|| !m.isVarArgs() && inputParameterCount != methodParameterCount) {
				throw new ELException(MessageFactory.get("error.fnMapper.paramcount", funcNode.getOutputName(),
						"" + methodParameterCount, "" + node.jjtGetNumChildren()));
			}
		} else if (node instanceof AstIdentifier && this.varMapper != null) {
			String variable = ((AstIdentifier) node).getImage();

			// simply capture it
			this.varMapper.resolveVariable(variable);
		}
	}

	public ValueExpression createValueExpression(Class<?> expectedType) throws ELException {
		Node n = this.build();
		return new ValueExpressionImpl(this.expression, n, this.fnMapper, this.varMapper, expectedType);
	}

	public MethodExpression createMethodExpression(Class<?> expectedReturnType, Class<?>[] expectedParamTypes)
			throws ELException {
		Node n = this.build();
		if (!n.isParametersProvided() && expectedParamTypes == null) {
			throw new NullPointerException(MessageFactory.get("error.method.nullParms"));
		}
		if (n instanceof AstValue || n instanceof AstIdentifier) {
			return new MethodExpressionImpl(expression, n, this.fnMapper, this.varMapper, expectedReturnType,
					expectedParamTypes);
		} else if (n instanceof AstLiteralExpression) {
			return new MethodExpressionLiteral(expression, expectedReturnType, expectedParamTypes);
		} else {
			throw new ELException("Not a Valid Method Expression: " + expression);
		}
	}
}