/**
 * 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.ambari.server.api.services;

import org.apache.ambari.server.api.handlers.RequestHandler;
import org.apache.ambari.server.api.predicate.InvalidQueryException;
import org.apache.ambari.server.api.predicate.PredicateCompiler;
import org.apache.ambari.server.api.resources.*;
import org.apache.ambari.server.controller.internal.PageRequestImpl;
import org.apache.ambari.server.controller.internal.TemporalInfoImpl;
import org.apache.ambari.server.controller.spi.PageRequest;
import org.apache.ambari.server.controller.spi.Predicate;
import org.apache.ambari.server.controller.spi.TemporalInfo;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.ws.rs.core.HttpHeaders;
import javax.ws.rs.core.UriInfo;
import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import java.util.*;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Request implementation.
 */
public abstract class BaseRequest implements Request {

  /**
   * URI information
   */
  private UriInfo m_uriInfo;

  /**
   * Http headers
   */
  private HttpHeaders m_headers;

  /**
   * Http Body
   */
  private RequestBody m_body;

  /**
   * Query Predicate
   */
  private Predicate m_predicate;

  /**
   * Associated resource definition
   */
  private ResourceInstance m_resource;

  /**
   * Default page size for pagination request.
   */
  private static final int DEFAULT_PAGE_SIZE = 20;

  /**
   *  Logger instance.
   */
  private final static Logger LOG = LoggerFactory.getLogger(Request.class);


  /**
   * Constructor.
   *
   * @param headers           http headers
   * @param body              http body
   * @param uriInfo           uri information
   * @param resource          associated resource definition
   *
   */
  public BaseRequest(HttpHeaders headers, RequestBody body, UriInfo uriInfo, ResourceInstance resource) {
    m_headers     = headers;
    m_uriInfo     = uriInfo;
    m_resource    = resource;
    m_body        = body;
  }

  @Override
  public Result process() {
    if (LOG.isDebugEnabled()) {
      LOG.debug("Handling API Request: '" + getURI() + "'");
    }

    Result result;
    try {
      parseQueryPredicate();
      result = getRequestHandler().handleRequest(this);
    } catch (InvalidQueryException e) {
      result =  new ResultImpl(new ResultStatus(ResultStatus.STATUS.BAD_REQUEST,
          "Unable to compile query predicate: " + e.getMessage()));
    }

    if (! result.getStatus().isErrorState()) {
      getResultPostProcessor().process(result);
    }

    return result;
  }

  @Override
  public ResourceInstance getResource() {
    return m_resource;
  }

  @Override
  public String getURI() {
    try {
      return URLDecoder.decode(m_uriInfo.getRequestUri().toASCIIString(), "UTF-8");
    } catch (UnsupportedEncodingException e) {
      throw new RuntimeException("Unable to decode URI: " + e, e);
    }
  }

  @Override
  public int getAPIVersion() {
    return 1;
  }

  @Override
  public Predicate getQueryPredicate() {
    return m_predicate;
  }

  @Override
  public Map<String, TemporalInfo> getFields() {
    Map<String, TemporalInfo> mapProperties;
    String partialResponseFields = m_uriInfo.getQueryParameters().getFirst("fields");
    if (partialResponseFields == null) {
      mapProperties = Collections.emptyMap();
    } else {
      Set<String> setMatches = new HashSet<String>();
      // Pattern basically splits a string using ',' as the deliminator unless ',' is between '[' and ']'.
      // Actually, captures char sequences between ',' and all chars between '[' and ']' including ','.
      Pattern re = Pattern.compile("[^,\\[]*?\\[[^\\]]*?\\]|[^,]+");
      Matcher m = re.matcher(partialResponseFields);
      while (m.find()){
        for (int groupIdx = 0; groupIdx < m.groupCount() + 1; groupIdx++) {
          setMatches.add(m.group(groupIdx));
        }
      }

      mapProperties = new HashMap<String, TemporalInfo>(setMatches.size());
      for (String field : setMatches) {
        TemporalInfo temporalInfo = null;
        if (field.contains("[")) {
          String[] temporalData = field.substring(field.indexOf('[') + 1,
              field.indexOf(']')).split(",");
          field = field.substring(0, field.indexOf('['));
          long start = Long.parseLong(temporalData[0].trim());
          long end   = -1;
          long step  = -1;
          if (temporalData.length >= 2) {
            end = Long.parseLong(temporalData[1].trim());
            if (temporalData.length == 3) {
              step = Long.parseLong(temporalData[2].trim());
            }
          }
          temporalInfo = new TemporalInfoImpl(start, end, step);
        }
        mapProperties.put(field, temporalInfo);
      }
    }

    return mapProperties;
  }

  @Override
  public Map<String, List<String>> getHttpHeaders() {
    return m_headers.getRequestHeaders();
  }

  @Override
  public PageRequest getPageRequest() {

    String pageSize = m_uriInfo.getQueryParameters().getFirst("page_size");
    String from     = m_uriInfo.getQueryParameters().getFirst("from");
    String to       = m_uriInfo.getQueryParameters().getFirst("to");

    if (pageSize == null && from == null && to == null) {
      return null;
    }

    int offset = 0;
    PageRequest.StartingPoint startingPoint;

    // TODO : support other starting points
    if (from != null) {
      if(from.equals("start")) {
        startingPoint = PageRequest.StartingPoint.Beginning;
      } else {
        offset = Integer.valueOf(from);
        startingPoint = PageRequest.StartingPoint.OffsetStart;
      }
    } else if (to != null ) {
      if (to.equals("end")) {
        startingPoint = PageRequest.StartingPoint.End;
      } else {
        offset = Integer.valueOf(to);
        startingPoint = PageRequest.StartingPoint.OffsetEnd;
      }
    } else {
      startingPoint = PageRequest.StartingPoint.Beginning;
    }

    // TODO : support predicate and comparator
    return new PageRequestImpl(startingPoint,
        pageSize == null ? DEFAULT_PAGE_SIZE : Integer.valueOf(pageSize), offset, null, null);
  }

  @Override
  public RequestBody getBody() {
    return m_body;
  }


  /**
   * Obtain the result post processor for the request.
   *
   * @return the result post processor
   */
  protected ResultPostProcessor getResultPostProcessor() {
    //todo: inject
    return new ResultPostProcessorImpl(this);
  }

  /**
   * Obtain the predicate compiler which is used to compile the query string into
   * a predicate.
   *
   * @return the predicate compiler
   */
  protected PredicateCompiler getPredicateCompiler() {
    return new PredicateCompiler();
  }


  /**
   * Parse the query string and compile it into a predicate.
   * The query string may have already been extracted from the http body.
   * If the query string didn't exist in the body use the query string in the URL.
   *
   * @throws InvalidQueryException  if unable to parse a non-null query string into a predicate
   */
  private void parseQueryPredicate() throws InvalidQueryException {
    String queryString = m_body.getQueryString();
    if (queryString == null) {
      String uri     = getURI();
      int    qsBegin = uri.indexOf("?");

      queryString = (qsBegin == -1) ? null : uri.substring(qsBegin + 1);
    }

    if (queryString != null) {
      m_predicate = getPredicateCompiler().compile(queryString);
    }
  }

  /**
   * Obtain the underlying request handler for the request.
   *
   * @return  the request handler
   */
  protected abstract RequestHandler getRequestHandler();
}