/*
 * 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.creadur.tentacles;

import java.io.File;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.StringWriter;
import java.io.Writer;
import java.net.URL;
import java.util.HashMap;
import java.util.Map;
import java.util.Properties;

import org.apache.velocity.VelocityContext;
import org.apache.velocity.app.VelocityEngine;
import org.apache.velocity.runtime.log.CommonsLogLogChute;

public final class Templates {

    private static final Templates INSTANCE = new Templates();

    private final VelocityEngine engine;

    private Templates() {
        Properties properties = new Properties();
        properties.setProperty("file.resource.loader.cache", "true");
        properties.setProperty("resource.loader", "file, class");
        properties.setProperty("class.resource.loader.description", "Velocity Classpath Resource Loader");
        properties.setProperty("class.resource.loader.class", "org.apache.velocity.runtime.resource.loader.ClasspathResourceLoader");
        properties.setProperty("runtime.log.logsystem.class", CommonsLogLogChute.class.getName());
        properties.setProperty("runtime.log.logsystem.commons.logging.name", Templates.class.getName());

        engine = new VelocityEngine();
        engine.init(properties);
    }

    private void evaluate(String template, Map<String, Object> mapContext, Writer writer) throws IOException {

        URL resource = Thread.currentThread().getContextClassLoader().getResource(template);

        if (resource == null) throw new IllegalStateException(template);

        VelocityContext context = new VelocityContext(mapContext);
        engine.evaluate(context, writer, Templates.class.getName(), new InputStreamReader(resource.openStream()));
    }

    public static Builder template(String name) {
        return INSTANCE.new Builder(name);
    }

    public class Builder {
        private final String template;
        private final Map<String, Object> map = new HashMap<String, Object>();

        public Builder(String template) {
            this.template = template;
        }

        public Builder add(String key, Object value) {
            map.put(key, value);
            return this;
        }

        public Builder addAll(Map<String, Object> map) {
            this.map.putAll(map);
            return this;
        }

        public String apply() {
            final StringWriter writer = new StringWriter();

            try {
                evaluate(template, map, writer);
            } catch (IOException ioe) {
                throw new RuntimeException("can't apply template " + template, ioe);
            }

            return writer.toString();
        }

        public File write(File file) throws IOException {
            IO.writeString(file, apply());
            return file;
        }
    }
}