/*
 *  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.synapse.mediators;

import org.apache.axiom.om.*;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.synapse.MessageContext;
import org.apache.synapse.SynapseException;
import org.apache.synapse.config.xml.SynapsePath;
import org.apache.synapse.util.synapse.expression.constants.ExpressionConstants;
import org.apache.synapse.util.xpath.SynapseJsonPath;
import org.apache.synapse.util.xpath.SynapseXPath;
import org.apache.synapse.util.xpath.SynapseExpression;
import org.jaxen.JaxenException;

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

/**
 * Represents a Value
 * Handling both static and dynamic(Xpath) keys.
 * User can give Xpath expression as a key and derive
 * real key based on message context
 */
public class Value {
    private static final Log log = LogFactory.getLog(Value.class);

    /**
     * Name of the value attribute
     */
    private String name = null;

    /**
     * The static key value 
     */
    private String keyValue = null;
    /**
     * the dynamic key
     */
    private SynapsePath expression = null;

    private List<OMNamespace> namespaceList = new ArrayList<OMNamespace>();
    /**
     * Create a key instance using a static key
     *
     * @param staticKey static key
     */
    public Value(String staticKey) {
        this.keyValue = staticKey;
    }

    /**
     * Create a key instance using a dynamic key (Xpath or JsonPath Expression)
     *
     * @param expression SynapsePath for dynamic key
     */
    public Value(SynapsePath expression) {
        this.expression = expression;
    }

    /**
     * Retrieving static key
     *
     * @return static key
     */
    public String getKeyValue() {
        return keyValue;
    }

    /**
     * Retrieving dynamic key
     *
     * @return SynapsePath
     */
    public SynapsePath getExpression() {
        if (expression == null && keyValue != null && hasExprTypeKey()) {
            try {
                String expressionString = keyValue.substring(1, keyValue.length() - 1);

                if (expressionString.startsWith("json-eval(")) {

                    // Remove "json-eval" and extract the json expression
                    SynapseJsonPath expressionTypeKey =
                            new SynapseJsonPath(expressionString.substring(10, expressionString.length() - 1));
                    expression = expressionTypeKey;

                } else if (expressionString.startsWith(ExpressionConstants.SYNAPSE_EXPRESSION_IDENTIFIER_START) &&
                        expressionString.endsWith(ExpressionConstants.SYNAPSE_EXPRESSION_IDENTIFIER_END)) {
                    expression = new SynapseExpression(
                            expressionString.substring(2, expressionString.length() - 1));
                } else {
                    SynapseXPath expressionTypeKey = new SynapseXPath(expressionString);
                    for (OMNamespace aNamespaceList : namespaceList) {
                        expressionTypeKey.addNamespace(aNamespaceList);
                    }
                    expression = expressionTypeKey;
                }

            } catch (JaxenException e) {
                expression = null;
                handleException("Can not evaluate escaped expression..");

            }
        }
        return expression;
    }

    /**
     * Evaluating key based on message context
     * used when key is a xpath expression
     *
     * @param synCtx message context
     * @return string value of evaluated key
     */
    public String evaluateValue(MessageContext synCtx) {
        if (keyValue != null) {
            //if static kry: return static key
            return keyValue;
        } else if (expression != null) {
            //if dynamic key return evaluated value
            return expression.stringValueOf(synCtx);
        } else {
            handleException("Can not evaluate the key: " +
                            "key should be static or dynamic key");
            return null;
        }

    }

    public Object evaluateObjectValue(MessageContext synCtx) {
        if (keyValue != null) {
            return keyValue;
        } else if (expression != null) {
            return getObjectValue(synCtx);
        } else {
            handleException("Unable to resolve the value: " + toString());
            return null;
        }
    }

    /**
     * Resolve the object defined in the Value
     *
     * @param synCtx Message Context
     * @return Object defined in the Value
     */
    public Object resolveObject(MessageContext synCtx) {
        if (keyValue != null) {
            return keyValue;
        } else if (expression != null) {
            try {
                return expression.selectSingleNode(synCtx);
            } catch (JaxenException e) {
                handleException("Failed to evaluate the XPath expression: " + expression, e);
            }
        } else {
            handleException("Unable to resolve the object: " + toString());
        }
        return null;
    }

    private Object getObjectValue(MessageContext synCtx) {
        try {
            Object result = expression.selectSingleNode(synCtx);

            if (result instanceof OMText) {
                return ((OMText) result).getText();
            } else if (result instanceof OMElement) {
                return ((OMElement) result).getText();
            } else if (result instanceof OMDocument) {
                return ((OMDocument) result).getOMDocumentElement().toString();
            } else if (result instanceof OMAttribute) {
                return ((OMAttribute) result).getAttributeValue();
            } else {
                return result;
            }
        } catch (JaxenException e) {
            handleException("Failed to evaluate the XPath expression: " + expression, e);
        }
        return null;
    }

    /**
     * Get the name of the value attribute
     *
     * @return name of the value attribute
     */
    public String getName() {
        return name;
    }

    /**
     * Handle exceptions
     *
     * @param msg error message
     */
    private void handleException(String msg) {
        log.error(msg);
        throw new SynapseException(msg);
    }

    private void handleException(String msg, Exception e) {
        log.error(msg, e);
        throw new SynapseException(msg, e);
    }

    /**
     * checks whether key returned by #getKeyValue() is a string of an expression type.
     * @return if true if this is an expression
     */
    public boolean hasExprTypeKey() {
        return keyValue != null && keyValue.startsWith("{") && keyValue.endsWith("}");
    }
    
    public boolean hasPropertyEvaluateExpr(){
    	return keyValue != null && keyValue.contains("get-property");
    }
    
	public Object evalutePropertyExpression(MessageContext synCtx) {
		//this.keyValue = null;
		//String evaluatedProperty = this.evaluateValue(synCtx);
		SynapseXPath _expression = null;
		try {
			_expression = new SynapseXPath(this.keyValue.substring(1, keyValue.length() - 1));
			for (OMNamespace aNamespaceList : namespaceList) {
				_expression.addNamespace(aNamespaceList);
			}
			String result =_expression.stringValueOf(synCtx);
			
			SynapseXPath expression = new SynapseXPath(result);
			for (OMNamespace aNamespaceList : namespaceList) {
				expression.addNamespace(aNamespaceList);
			}
			return expression;
			
		} catch (Exception e) {
			  handleException("Can not evaluate escaped expression..");
		}
		return this.expression;

	}

    public void setNamespaces(OMElement elem){
        Iterator namespaces = elem.getAllDeclaredNamespaces();
        while (namespaces.hasNext()){
            OMNamespace ns = (OMNamespace) namespaces.next();
            namespaceList.add(ns);
        }
    }

    @Override
    public String toString() {
        return "Value {" +
                "name ='" + name + '\'' +
                (keyValue != null ? ", keyValue ='" + keyValue + '\'' : "") +
                (expression != null ? ", expression =" + expression : "") +
                '}';
    }

}


