/*
 * 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.juneau.rest.httppart;

import static org.apache.juneau.commons.utils.AssertionUtils.*;
import static org.apache.juneau.commons.utils.CollectionUtils.*;
import static org.apache.juneau.commons.utils.Utils.*;

import java.util.*;

import org.apache.juneau.collections.*;
import org.apache.juneau.commons.collections.*;
import org.apache.juneau.rest.*;
import org.apache.juneau.svl.*;

import jakarta.servlet.http.*;

/**
 * Represents the attributes in an HTTP request.
 *
 * <p>
 *    The {@link RequestAttributes} object is the API for accessing the standard servlet attributes on an HTTP request
 *    (i.e. {@link jakarta.servlet.ServletRequest#getAttribute(String)}).
 * </p>
 *
 * <p class='bjava'>
 *    <ja>@RestPost</ja>(...)
 *    <jk>public</jk> Object myMethod(RequestAttributes <jv>attributes</jv>) {...}
 * </p>
 *
 * <h5 class='figure'>Example:</h5>
 * <p class='bjava'>
 *    <ja>@RestPost</ja>(...)
 *    <jk>public</jk> Object myMethod(RequestAttributes <jv>attributes</jv>) {
 *
 *       <jc>// Add a default value.</jc>
 *       <jv>attributes</jv>.addDefault(<js>"Foo"</js>, 123);
 *
 *       <jc>// Get an attribute value as a POJO.</jc>
 *       UUID <jv>etag</jv> = <jv>attributes</jv>.get(<js>"ETag"</js>).as(UUID.<jk>class</jk>).orElse(<jk>null</jk>);
 *    }
 * </p>
 *
 * <p>
 *    Some important methods on this class are:
 * </p>
 * <ul class='javatree'>
 *    <li class='jc'>{@link RequestHeaders}
 *    <ul class='spaced-list'>
 *       <li>Methods for retrieving request attributes:
 *       <ul class='javatreec'>
 *          <li class='jm'>{@link RequestAttributes#contains(String...) contains(String...)}
 *          <li class='jm'>{@link RequestAttributes#containsAny(String...) containsAny(String...)}
 *          <li class='jm'>{@link RequestAttributes#get(String) get(String)}
 *          <li class='jm'>{@link RequestAttributes#getAll() getAll()}
 *       </ul>
 *       <li>Methods for overriding request attributes:
 *       <ul class='javatreec'>
 *          <li class='jm'>{@link RequestAttributes#addDefault(List) addDefault(List)}
 *          <li class='jm'>{@link RequestAttributes#addDefault(NamedAttribute...) addDefault(NamedAttribute...)}
 *          <li class='jm'>{@link RequestAttributes#addDefault(NamedAttributeMap) addDefault(NamedAttributeMap)}
 *          <li class='jm'>{@link RequestAttributes#addDefault(String,Object) addDefault(String,Object)}
 *          <li class='jm'>{@link RequestAttributes#remove(NamedAttribute...) remove(NamedAttribute...)}
 *          <li class='jm'>{@link RequestAttributes#remove(String...) remove(String...)}
 *          <li class='jm'>{@link RequestAttributes#set(NamedAttribute...) set(NamedAttribute...)}
 *          <li class='jm'>{@link RequestAttributes#set(String,Object) set(String,Object)}
 *       </ul>
 *       <li>Other methods:
 *       <ul class='javatreec'>
 *          <li class='jm'>{@link RequestAttributes#asMap() asMap()}
 *       </ul>
 *    </ul>
 * </ul>
 *
 * <p>
 *    Modifications made to request attributes through the <c>RequestAttributes</c> bean are automatically reflected in
 *    the underlying servlet request attributes making it possible to mix the usage of both APIs.
 * </p>
 *
 * <h5 class='section'>See Also:</h5><ul>
 *    <li class='link'><a class="doclink" href="https://juneau.apache.org/docs/topics/HttpParts">HTTP Parts</a>
 * </ul>
 */
public class RequestAttributes {

   final RestRequest req;
   final HttpServletRequest sreq;
   final VarResolverSession vs;

   /**
    * Constructor.
    *
    * @param req The request creating this bean.
    */
   public RequestAttributes(RestRequest req) {
      this.req = req;
      this.sreq = req.getHttpServletRequest();
      this.vs = req.getVarResolverSession();
   }

   /**
    * Adds default entries to the request attributes.
    *
    * @param pairs
    *    The default entries.
    *    <br>Can be <jk>null</jk>.
    * @return This object.
    */
   public RequestAttributes addDefault(List<NamedAttribute> pairs) {
      for (var p : pairs)
         if (sreq.getAttribute(p.getName()) == null) {
            Object o = p.getValue();
            sreq.setAttribute(p.getName(), o instanceof String ? vs.resolve(o) : o);
         }
      return this;
   }

   /**
    * Adds default entries to the request attributes.
    *
    * @param pairs
    *    The default entries.
    *    <br>Can be <jk>null</jk>.
    * @return This object.
    */
   public RequestAttributes addDefault(NamedAttribute...pairs) {
      return addDefault(l(pairs));
   }

   /**
    * Adds default entries to the request attributes.
    *
    * @param pairs
    *    The default entries.
    *    <br>Can be <jk>null</jk>.
    * @return This object.
    */
   public RequestAttributes addDefault(NamedAttributeMap pairs) {
      for (var p : pairs.values())
         if (sreq.getAttribute(p.getName()) == null) {
            Object o = p.getValue();
            sreq.setAttribute(p.getName(), o instanceof String ? vs.resolve(o) : o);
         }
      return this;
   }

   /**
    * Adds a default entry to the request attributes.
    *
    * @param name The name.
    * @param value The value.
    * @return This object.
    */
   public RequestAttributes addDefault(String name, Object value) {
      return addDefault(BasicNamedAttribute.of(name, value));
   }

   /**
    * Returns the request attributes as a map.
    *
    * @return The request attributes as a map.  Never <jk>null</jk>.
    */
   public Map<String,Object> asMap() {
      var m = new JsonMap();
      Enumeration<String> e = sreq.getAttributeNames();
      while (e.hasMoreElements()) {
         var n = e.nextElement();
         m.put(n, sreq.getAttribute(n));
      }
      return m;
   }

   /**
    * Returns <jk>true</jk> if the attributes with the specified names are present.
    *
    * @param names The attribute names.  Must not be <jk>null</jk>.
    * @return <jk>true</jk> if the parameters with the specified names are present.
    */
   public boolean contains(String...names) {
      assertArgNotNull("names", names);
      for (var n : names)
         if (sreq.getAttribute(n) == null)
            return false;
      return true;
   }

   /**
    * Returns <jk>true</jk> if the attribute with any of the specified names are present.
    *
    * @param names The attribute names.  Must not be <jk>null</jk>.
    * @return <jk>true</jk> if the attribute with any of the specified names are present.
    */
   public boolean containsAny(String...names) {
      assertArgNotNull("names", names);
      for (var n : names)
         if (nn(sreq.getAttribute(n)))
            return true;
      return false;
   }

   /**
    * Returns the request attribute with the specified name.
    *
    * @param name The attribute name.
    * @return The parameter value, or {@link Optional#empty()} if it doesn't exist.
    */
   public RequestAttribute get(String name) {
      return new RequestAttribute(req, name, sreq.getAttribute(name));
   }

   /**
    * Returns all the attribute on this request.
    *
    * @return All the attribute on this request.
    */
   public List<RequestAttribute> getAll() {
      List<RequestAttribute> l = list();
      Enumeration<String> e = sreq.getAttributeNames();
      while (e.hasMoreElements()) {
         var n = e.nextElement();
         l.add(new RequestAttribute(req, n, sreq.getAttribute(n)));
      }
      return l;
   }

   /**
    * Remove request attributes.
    *
    * @param attributes The attributes to remove.  Must not be <jk>null</jk>.
    * @return This object.
    */
   public RequestAttributes remove(NamedAttribute...attributes) {
      for (var p : attributes)
         remove(p.getName());
      return this;
   }

   /**
    * Remove request attributes.
    *
    * @param name The attribute names.  Must not be <jk>null</jk>.
    * @return This object.
    */
   public RequestAttributes remove(String...name) {
      assertArgNotNull("name", name);
      for (var n : name) {
         sreq.removeAttribute(n);
      }
      return this;
   }

   /**
    * Sets request attributes.
    *
    * @param attributes The parameters to set.  Must not be <jk>null</jk> or contain <jk>null</jk>.
    * @return This object.
    */
   public RequestAttributes set(NamedAttribute...attributes) {
      assertArgNotNull("attributes", attributes);
      for (var p : attributes)
         set(p);
      return this;
   }

   /**
    * Sets a request attribute.
    *
    * @param name The attribute name.  Must not be <jk>null</jk>.
    * @param value
    *    The attribute value.
    *    <br>Can be <jk>null</jk>.
    * @return This object.
    */
   public RequestAttributes set(String name, Object value) {
      assertArgNotNull("name", name);
      sreq.setAttribute(name, value);
      return this;
   }

   protected FluentMap<String,Object> properties() {
      // @formatter:off
      return filteredBeanPropertyMap()
         .a("attributes", asMap());
      // @formatter:on
   }

   @Override /* Overridden from Object */
   public String toString() {
      return r(properties());
   }
}