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/*
 * Copyright 2013 the original author or authors.
 *
 * 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 ratpack.parse;

import com.google.common.reflect.TypeToken;

/**
 * A convenience superclass for {@link Parser} implementations.
 * 
 * Specializations only need to implement the {@link Parser#parse(ratpack.handling.Context, ratpack.http.TypedData, Parse)} method.
 * 
{@code
 * import ratpack.handling.Handler;
 * import ratpack.handling.Context;
 * import ratpack.http.TypedData;
 * import ratpack.parse.Parse;
 * import ratpack.parse.ParserSupport;
 * import ratpack.parse.ParseException;
 * import ratpack.util.Types;
 *
 * import java.io.UnsupportedEncodingException;
 *
 * import ratpack.test.handling.HandlingResult;
 * import ratpack.test.handling.RequestFixture;
 *
 * import static org.junit.Assert.assertEquals;
 *
 * public class Example {
 *
 *   // The parse options
 *   public static class StringParseOpts {
 *     private int maxLength;
 *
 *     public StringParseOpts(int maxLength) {
 *       this.maxLength = maxLength;
 *     }
 *
 *     public int getMaxLength() {
 *       return maxLength;
 *     }
 *   }
 *
 *   // A parser for this type
 *   public static class MaxLengthStringParser extends ParserSupport {
 *     public MaxLengthStringParser() {
 *       super("text/plain");
 *     }
 *
 *     public  T parse(Context context, TypedData requestBody, Parse parse) throws UnsupportedEncodingException {
 *       if (!parse.getType().getRawType().equals(String.class)) {
 *         return null;
 *       }
 *
 *       String rawString = requestBody.getText();
 *       if (rawString.length() < parse.getOpts().getMaxLength()) {
 *         return Types.cast(rawString);
 *       } else {
 *         return Types.cast(rawString.substring(0, parse.getOpts().getMaxLength()));
 *       }
 *     }
 *   }
 *
 *   public static class ToUpperCaseHandler implements Handler {
 *     public void handle(Context context) throws ParseException {
 *       String string = context.parse(String.class, new StringParseOpts(5));
 *       context.render(string);
 *     }
 *   }
 *
 *   // unit test
 *   public static void main(String[] args) throws Exception {
 *     HandlingResult result = RequestFixture.handle(new ToUpperCaseHandler(), fixture ->
 *         fixture
 *           .body("123456", "text/plain")
 *           .registry(registry -> registry.add(new MaxLengthStringParser()))
 *     );
 *
 *     assertEquals("12345", result.rendered(String.class));
 *   }
 * }
 * }
 *
 * @see NoOptParserSupport
 * @param  the type of option object this parser accepts
 */
abstract public class ParserSupport implements Parser {

  private final Class optsType;
  private final String contentType;

  /**
   * Constructor.
   *
   * @param contentType the type of request this parser can handle
   */
  protected ParserSupport(String contentType) {
    this.contentType = contentType;

    TypeToken typeToken = new TypeToken(getClass()) {
    };

    if (typeToken.getType() instanceof Class) {
      @SuppressWarnings("unchecked") Class rawType = (Class) typeToken.getRawType();
      this.optsType = rawType;
    } else {
      throw new IllegalArgumentException("Type parameter O of ParserSupport must be a Class");
    }
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public final String getContentType() {
    return contentType;
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public final Class getOptsType() {
    return optsType;
  }

}