FreemarkerWhere.java

/*
   Copyright 2014 base2Services

   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.
 */
package com.base2.kagura.core.report.freemarker;

import freemarker.core.Environment;
import freemarker.template.*;
import org.apache.commons.lang3.StringUtils;

import java.io.IOException;
import java.io.StringWriter;
import java.util.Arrays;
import java.util.List;
import java.util.Map;

/**
 * Where tag. Has two functions:
 * 1. Inserts WHERE if not nested and contains content.
 * 2. Acts like a JOIN statement for clauses, so that if a you have a couple of children clause statements some of which
 *      do return results, others that don't, it will insert an AND or OR between each one.
 *
 * For complicated logic, WHERE tags can be nested, the parent one provides the WHERE clause if required. Each where
 * clause allows you to specify if elements should be joined with a "AND" or an "OR" by specifying the "type" attribute.
 * User: aubels
 * Date: 29/07/13
 * Time: 2:50 PM
 */
public class FreemarkerWhere implements TemplateDirectiveModel
{
    private final List<String> errors;

    /**
     * Constructor
     * @param errors Location to append errors if there are any.
     */
    public FreemarkerWhere(List<String> errors) {
        this.errors = errors;
    }

    /**
     * Detects if it's a child where or a parent where, runs the child clauses and where statements, if there are any
     * results, adds a WHERE at the start if it's a parent, then adds the selected operator (and or or ) between each
     * clause.
     *
     * {@inheritDoc}
     */
    @Override
    public void execute(Environment env, Map params, TemplateModel[] loopVars, TemplateDirectiveBody body) throws TemplateException, IOException {
        StringWriter stringWriter = new StringWriter();
        WhereContext whereContext = new WhereContext(env.getCustomAttribute("whereTag"));
        env.setCustomAttribute("whereTag", whereContext);
        body.render(stringWriter);
        if (params.size() != 0 && !((Map.Entry)params.entrySet().toArray()[0]).getKey().equals("type"))
        {
            String message = "This directive only takes 'type' with a value of either 'AND' or 'OR'.";
            errors.add(message);
            throw new TemplateModelException(message);
        }
        Object typeParam = params.get("type");
        if (typeParam instanceof TemplateScalarModel)
        {
            TemplateScalarModel typeScalar = (TemplateScalarModel) typeParam;
            if (StringUtils.isNotBlank(typeScalar.getAsString()))
                whereContext.setConnector(typeScalar.getAsString().toUpperCase());
        }
        if (!Arrays.asList("AND", "OR").contains(whereContext.getConnector()))
        {
            String message = "This directive only takes 'type' with a value of either 'AND' or 'OR'.";
            errors.add(message);
            throw new TemplateModelException(message);
        }

        String outputBody = StringUtils.join(whereContext.getFreemarkerWhereClauses(), " " + whereContext.getConnector() + " ");
        if (whereContext.getFreemarkerWhereClauses().size() > 1 && whereContext.getParent() != null && !whereContext.getParent().getConnector().equals(whereContext.getConnector()))
            outputBody = "(" + outputBody + ")";
        if (StringUtils.isNotBlank(outputBody)) {
            if (whereContext.getParent() == null)
                env.getOut().write(" WHERE ");
            if (whereContext.getParent() != null)
                whereContext.getParent().addWhereBody(outputBody);
            else
                env.getOut().write(outputBody);
        }
        env.setCustomAttribute("whereTag", whereContext.getParent());
    }

}