/*
    * #%L
    * wcm.io
    * %%
    * Copyright (C) 2014 wcm.io
    * %%
    * 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.
   * #L%
   */
  package io.wcm.caravan.io.http.request;
  
  import static com.google.common.base.Preconditions.checkNotNull;
  
  import java.nio.charset.Charset;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  
  import org.apache.commons.lang3.StringUtils;
  import org.apache.http.client.methods.HttpGet;
  import org.osgi.annotation.versioning.ProviderType;
  
  import com.damnhandy.uri.template.UriTemplate;
  import com.google.common.base.Charsets;
  import com.google.common.base.Strings;
  import com.google.common.collect.ArrayListMultimap;
  import com.google.common.collect.ImmutableList;
  import com.google.common.collect.Lists;
  import com.google.common.collect.Maps;
  import com.google.common.collect.Multimap;
  import com.google.common.collect.Sets;
  
  import io.wcm.caravan.io.http.impl.CaravanHttpHelper;
  
  /**
   * UriTemplate using HTTP request builder.
   */
  @ProviderType
  public final class CaravanHttpRequestBuilder {
  
    private final String serviceId;
    private String method = HttpGet.METHOD_NAME;
    private StringBuilder path = new StringBuilder();
    private Set<String> queryNames = Sets.newHashSet();
    private Map<String, Object> values = Maps.newHashMap();
    private final Multimap<String, String> headers = ArrayListMultimap.create();
    private Charset charset;
    private byte[] body;
    private String bodyTemplate;
  
    /**
     * Default constructor.
     */
    public CaravanHttpRequestBuilder() {
      serviceId = null;
    }
  
    /**
     * @param serviceId Logical service ID. Can be null.
     */
    public CaravanHttpRequestBuilder(String serviceId) {
      this.serviceId = serviceId;
    }
  
    /**
     * @param correlationId Correlation Id. Can be null.
     * @return Builder
     */
    public CaravanHttpRequestBuilder correlationId(String correlationId) {
      if (correlationId != null) {
        header(CaravanHttpRequest.CORRELATION_ID_HEADER_NAME, ImmutableList.of(correlationId));
      }
      return this;
    }
  
    /**
     * @see CaravanHttpRequest#getMethod()
     * @param newMethod HTTP method
     * @return Builder
     */
    public CaravanHttpRequestBuilder method(String newMethod) {
      this.method = checkNotNull(newMethod, "method");
      return this;
    }
  
    /**
     * Adds a header to the HTTP request
    * @see CaravanHttpRequest#getHeaders()
    * @param name Header name
    * @param value Header value
    * @return Builder
    */
   public CaravanHttpRequestBuilder header(String name, String value) {
     headers.put(name, value);
     return this;
   }
 
   /**
    * Sets and replaces a header for the HTTP request
    * @see CaravanHttpRequest#getHeaders()
    * @param name Header name
    * @param headerValues Header values
    * @return Builder
    */
   public CaravanHttpRequestBuilder header(String name, Collection<String> headerValues) {
     headers.putAll(name, headerValues);
     return this;
   }
 
   /**
    * Appends a URL fragment.
    * @param urlFragment URL fragment
    * @return Builder
    */
   public CaravanHttpRequestBuilder append(String urlFragment) {
     this.path.append(urlFragment);
     return this;
   }
 
   /**
    * Adds a query template expression.
    * @param name Query parameter name
    * @return Builder
    */
   public CaravanHttpRequestBuilder query(String name) {
     queryNames.add(name);
     return this;
   }
 
   /**
    * Adds a parameter with value to the request query
    * @see CaravanHttpRequest#getUrl()
    * @param name Parameter name
    * @param value Parameter value
    * @return Builder
    */
   public CaravanHttpRequestBuilder query(String name, Object value) {
     return query(name).value(name, value);
   }
 
   /**
    * Adds a value for any UriTemplate expression in URL, header or body.
    * @param name Parameter name
    * @param value Parameter value
    * @return Builder
    */
   public CaravanHttpRequestBuilder value(String name, Object value) {
     values.put(name, value);
     return this;
   }
 
   /**
    * Sets a template for the HTTP body.
    * @see CaravanHttpRequest#getBody()
    * @param template Body template
    * @return Builder
    */
   public CaravanHttpRequestBuilder body(String template) {
     body = null;
     charset = Charsets.UTF_8;
     bodyTemplate = template;
     return this;
   }
 
   /**
    * Sets the HTTP body and charset.
    * @see CaravanHttpRequest#getBody()
    * @param newBody HTTP body
    * @param newCharset HTTP charset
    * @return Builder
    */
   public CaravanHttpRequestBuilder body(byte[] newBody, Charset newCharset) {
     body = newBody;
     charset = newCharset;
     bodyTemplate = null;
     return this;
   }
 
   /**
    * Creates the request object with no values for the templates.
    * @return Request
    */
   public CaravanHttpRequest build() {
     return build(Collections.emptyMap());
   }
 
   /**
    * Creates the request object with given values for the templates.
    * @param parameters Template values
    * @return Request
    */
   public CaravanHttpRequest build(Map<String, Object> parameters) {
     String expandedUrl = getExpandedUrl(parameters);
     Multimap<String, String> expandedHeaders = getExpandedHeaders(parameters);
     byte[] expandedBody = getExpandedBody(parameters);
     return new CaravanHttpRequest(serviceId, method, expandedUrl, expandedHeaders, expandedBody, charset);
   }
 
   private String getExpandedUrl(Map<String, Object> parameters) {
 
     Map<String, Object> mergedParams = Maps.newHashMap(parameters);
     mergedParams.putAll(values);
     List<String> sortedQueryNames = Lists.newArrayList(queryNames);
     Collections.sort(sortedQueryNames);
     String operator = path.indexOf("?") == -1 ? "?" : "&";
     String query = queryNames.isEmpty() ? "" : ('{' + operator + StringUtils.join(queryNames, ',') + '}');
     return UriTemplate.fromTemplate(path + query).expand(mergedParams);
 
   }
 
   private Multimap<String, String> getExpandedHeaders(Map<String, Object> parameters) {
     Multimap<String, String> expandedHeaders = ArrayListMultimap.create();
     headers.entries().forEach(entry -> {
       String template = entry.getValue();
       String expanded = UriTemplate.expand(template, parameters);
       if (!Strings.isNullOrEmpty(expanded)) {
         expandedHeaders.put(entry.getKey(), expanded);
       }
     });
     return expandedHeaders;
   }
 
   private byte[] getExpandedBody(Map<String, Object> parameters) {
     if (bodyTemplate == null) {
       return body;
     }
     return CaravanHttpHelper.urlDecode(UriTemplate.expand(bodyTemplate, parameters)).getBytes(Charsets.UTF_8);
   }
 
 }