com.almende.eve.agent.google.GoogleCalculatorAgent.java Source code

Introduction

Here is the source code for com.almende.eve.agent.google.GoogleCalculatorAgent.java

Source

/**
 * @file GoogleCalculatorAgent.java
 * 
 * @brief
 *        GoogleCalculatorAgent can evaluate mathematical expressions.
 *        It uses the Google calculator API.
 * 
 * @license
 *          Licensed 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.
 * 
 *          Copyright  2012 Almende B.V.
 * 
 * @author Jos de Jong, <jos@almende.org>
 * @date 2011-04-13
 */

package com.almende.eve.agent.google;

import java.net.URLEncoder;

import com.almende.eve.agent.Agent;
import com.almende.eve.rpc.annotation.Access;
import com.almende.eve.rpc.annotation.AccessType;
import com.almende.eve.rpc.annotation.Name;
import com.almende.eve.rpc.jsonrpc.jackson.JOM;
import com.almende.util.HttpUtil;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.ObjectNode;

/**
 * The Class GoogleCalculatorAgent.
 */
@Access(AccessType.PUBLIC)
public class GoogleCalculatorAgent extends Agent {
    private static final String CALC_API_URL = "http://www.google.com/ig/calculator";

    /**
     * Evaluate given expression
     * For example expr="2.5 + 3 / sqrt(16)" will return "3.25"
     * 
     * @param expr
     *            the expr
     * @return result
     * @throws Exception
     *             the exception
     */
    public String eval(@Name("expr") final String expr) throws Exception {
        final String url = CALC_API_URL + "?q=" + URLEncoder.encode(expr, "UTF-8");
        String resp = HttpUtil.get(url);

        // the field names in resp are not enclosed by quotes :(
        resp = resp.replaceAll("lhs:", "\"lhs\":");
        resp = resp.replaceAll("rhs:", "\"rhs\":");
        resp = resp.replaceAll("error:", "\"error\":");
        resp = resp.replaceAll("icc:", "\"icc\":");

        final ObjectMapper mapper = JOM.getInstance();
        final ObjectNode json = mapper.readValue(resp, ObjectNode.class);

        final String error = json.get("error").asText();
        if (error != null && !error.isEmpty()) {
            throw new Exception(error);
        }

        final String rhs = json.get("rhs").asText();
        return rhs;
    }

    /*
     * (non-Javadoc)
     * 
     * @see com.almende.eve.agent.Agent#getVersion()
     */
    @Override
    public String getVersion() {
        return "1.0";
    }

    /*
     * (non-Javadoc)
     * 
     * @see com.almende.eve.agent.Agent#getDescription()
     */
    @Override
    public String getDescription() {
        return "GoogleCalculatorEvent can evaluate mathematical expressions. "
                + "It uses the Google calculator API.";
    }
}