/*
 * 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.http.header;

import static org.apache.juneau.commons.utils.Shorts.*;

import java.util.*;
import java.util.function.*;

import org.apache.juneau.http.*;

/**
 * A mutable, ordered list of {@link HttpHeader} instances.
 *
 * <p>
 * Mirrors the semantics of {@code HeaderList} from {@code juneau-rest-common-classic} without the
 * Apache HttpCore dependency. Header-name comparisons are case-insensitive by default.
 *
 * <h5 class='figure'>Example</h5>
 * <p class='bjava'>
 *    HttpHeaderList <jv>headers</jv> = HttpHeaderList.<jsm>create</jsm>()
 *       .append(HttpHeaderBean.<jsm>of</jsm>(<js>"Accept"</js>, <js>"text/xml"</js>))
 *       .append(<js>"Content-Type"</js>, <js>"text/xml"</js>);
 * </p>
 *
 * <h5 class='section'>See Also:</h5><ul>
 *    <li class='link'><a class="doclink" href="https://juneau.apache.org/docs/topics/NextGenRestClient">Next-Generation REST Client</a>
 * </ul>
 *
 * @since 10.0.0
 */
@SuppressWarnings({
   "java:S2160" // equals() inherited from ArrayList; list equality is element-based which is correct
})
public class HttpHeaderList extends ArrayList<HttpHeader> {

   private static final long serialVersionUID = 1L;

   /** Represents no header list in annotations. */
   public static final class Void extends HttpHeaderList {
      private static final long serialVersionUID = 1L;
   }

   private boolean caseSensitive;

   /**
    * Creates a new empty {@link HttpHeaderList}.
    *
    * @return A new instance. Never <jk>null</jk>.
    */
   public static HttpHeaderList create() {
      return new HttpHeaderList();
   }

   /**
    * Creates a new {@link HttpHeaderList} initialized with the given headers.
    *
    * @param headers The headers to include. {@code null} entries are ignored.
    * @return A new instance. Never <jk>null</jk>.
    */
   public static HttpHeaderList of(HttpHeader...headers) {
      return new HttpHeaderList().append(headers);
   }

   /**
    * Creates a new {@link HttpHeaderList} initialized with the given headers.
    *
    * @param headers The headers to include. {@code null} entries are ignored.
    * @return A new instance. Never <jk>null</jk>.
    */
   public static HttpHeaderList of(List<HttpHeader> headers) {
      return new HttpHeaderList().append(headers);
   }

   /**
    * Creates a new {@link HttpHeaderList} initialized with the given alternating {@code name}/{@code value} pairs.
    *
    * @param pairs Alternating name/value strings. Can be <jk>null</jk> (treated as empty). Length must be even.
    * @return A new instance. Never <jk>null</jk>.
    * @throws IllegalArgumentException If the number of arguments is odd.
    */
   public static HttpHeaderList ofPairs(String...pairs) {
      var x = new HttpHeaderList();
      if (pairs == null)
         pairs = new String[0];
      req(pairs.length % 2 == 0, "Odd number of parameters passed into HttpHeaderList.ofPairs()");
      for (var i = 0; i < pairs.length; i += 2)
         x.add(HttpHeaderBean.of(pairs[i], pairs[i + 1]));
      return x;
   }

   /** Constructor. */
   public HttpHeaderList() {
      super();
   }

   /**
    * Copy constructor.
    *
    * @param copyFrom The list to copy. Must not be <jk>null</jk>.
    */
   protected HttpHeaderList(HttpHeaderList copyFrom) {
      super(copyFrom);
      this.caseSensitive = copyFrom.caseSensitive;
   }

   /**
    * Sets whether header-name comparisons are case-sensitive. Defaults to {@code false}.
    *
    * @param value New value.
    * @return This object.
    */
   public HttpHeaderList caseSensitive(boolean value) {
      this.caseSensitive = value;
      return this;
   }

   /**
    * Appends the given header.
    *
    * @param value The header to add. {@code null} is ignored.
    * @return This object.
    */
   public HttpHeaderList append(HttpHeader value) {
      if (value != null)
         add(value);
      return this;
   }

   /**
    * Appends the given headers in order.
    *
    * @param values The headers to add. {@code null} entries are ignored.
    * @return This object.
    */
   public HttpHeaderList append(HttpHeader...values) {
      if (values != null)
         for (var v : values)
            append(v);
      return this;
   }

   /**
    * Appends the given headers in order.
    *
    * @param values The headers to add. {@code null} entries are ignored.
    * @return This object.
    */
   public HttpHeaderList append(List<HttpHeader> values) {
      if (values != null)
         values.forEach(this::append);
      return this;
   }

   /**
    * Appends a header constructed from the given name and string value.
    *
    * @param name The header name. Must not be <jk>null</jk>.
    * @param value The header value. Can be <jk>null</jk> to omit the header from the request.
    * @return This object.
    */
   public HttpHeaderList append(String name, String value) {
      return append(HttpHeaderBean.of(name, value));
   }

   /**
    * Appends a header constructed from the given name and lazy value supplier.
    *
    * @param name The header name. Must not be <jk>null</jk>.
    * @param value Supplier of the header value. Must not be <jk>null</jk>.
    * @return This object.
    */
   public HttpHeaderList append(String name, Supplier<String> value) {
      return append(HttpHeaderBean.of(name, value));
   }

   /**
    * Sets the given header as a default. If a header with the same name already exists, this is a no-op
    * (first-in-chain wins per name).
    *
    * @param value The header to set. {@code null} is ignored.
    * @return This object.
    */
   public HttpHeaderList setDefault(HttpHeader value) {
      if (value != null && !contains(value.getName()))
         add(value);
      return this;
   }

   /**
    * Sets the given headers as defaults, in order. For each, if a header with the same name already exists,
    * the entry is skipped (first-in-chain wins per name).
    *
    * @param values The headers to set. {@code null} entries are ignored.
    * @return This object.
    */
   public HttpHeaderList setDefault(HttpHeader...values) {
      if (values != null)
         for (var v : values)
            setDefault(v);
      return this;
   }

   /**
    * Sets a default header with the given name and value (first-in-chain wins per name).
    *
    * @param name The header name. Must not be <jk>null</jk>.
    * @param value The header value. Can be <jk>null</jk> to omit the header from the request.
    * @return This object.
    */
   public HttpHeaderList setDefault(String name, String value) {
      return setDefault(HttpHeaderBean.of(name, value));
   }

   /**
    * Sets the given header, replacing any prior entry with the same name.
    *
    * @param value The header to set. {@code null} is ignored.
    * @return This object.
    */
   public HttpHeaderList set(HttpHeader value) {
      if (value == null)
         return this;
      removeAll(value.getName());
      add(value);
      return this;
   }

   /**
    * Sets the given headers, each replacing any prior entry with the same name.
    *
    * @param values The headers to set. {@code null} entries are ignored.
    * @return This object.
    */
   public HttpHeaderList set(HttpHeader...values) {
      if (values != null)
         for (var v : values)
            set(v);
      return this;
   }

   /**
    * Sets a header with the given name and value, replacing any prior entry with the same name.
    *
    * @param name The header name. Must not be <jk>null</jk>.
    * @param value The header value. Can be <jk>null</jk> to omit the header from the request.
    * @return This object.
    */
   public HttpHeaderList set(String name, String value) {
      return set(HttpHeaderBean.of(name, value));
   }

   /**
    * Removes all headers with the given name.
    *
    * @param name The header name. Must not be <jk>null</jk>.
    * @return This object.
    */
   public HttpHeaderList removeAll(String name) {
      reqnn("name", name);
      removeIf(h -> nameMatches(h, name));
      return this;
   }

   /**
    * Returns {@code true} if a header with the given name is present.
    *
    * @param name The header name.
    * @return {@code true} if present.
    */
   public boolean contains(String name) {
      return stream().anyMatch(h -> nameMatches(h, name));
   }

   /**
    * Returns the first header with the given name, or {@code null} if absent.
    *
    * @param name The header name.
    * @return The first matching header, or {@code null}.
    */
   public HttpHeader getFirst(String name) {
      return stream().filter(h -> nameMatches(h, name)).findFirst().orElse(null);
   }

   /**
    * Returns the last header with the given name, or {@code null} if absent.
    *
    * @param name The header name.
    * @return The last matching header, or {@code null}.
    */
   public HttpHeader getLast(String name) {
      HttpHeader last = null;
      for (var h : this)
         if (nameMatches(h, name))
            last = h;
      return last;
   }

   /**
    * Returns all headers with the given name in insertion order.
    *
    * @param name The header name.
    * @return A new list of matching headers. Never <jk>null</jk>.
    */
   public List<HttpHeader> getAll(String name) {
      return stream().filter(h -> nameMatches(h, name)).toList();
   }

   /**
    * Returns all headers in this list as a typed array.
    *
    * <p>
    * Mirrors {@code HeaderList.getAll()} from {@code juneau-rest-common-classic}.
    *
    * @return A new array. Never <jk>null</jk>.
    */
   public HttpHeader[] getAll() {
      return toHeaderArray();
   }

   /**
    * Performs an action on each header whose name matches.
    *
    * @param name The header name.
    * @param action The action.
    * @return This object.
    */
   public HttpHeaderList forEach(String name, Consumer<HttpHeader> action) {
      for (var h : this)
         if (nameMatches(h, name))
            action.accept(h);
      return this;
   }

   /**
    * Returns a copy of this list.
    *
    * @return A new copy. Never <jk>null</jk>.
    */
   public HttpHeaderList copy() {
      return new HttpHeaderList(this);
   }

   /**
    * Returns an unmodifiable snapshot of this list.
    *
    * <p>
    * Idempotency: if this list is already an {@link Unmodifiable} snapshot, it is returned as-is.
    *
    * @return An unmodifiable snapshot of this list, or this list if it is already unmodifiable.
    */
   public HttpHeaderList unmodifiable() {
      return this instanceof Unmodifiable ? this : new Unmodifiable(this);
   }

   /**
    * Returns <jk>true</jk> if this list is an unmodifiable snapshot.
    *
    * @return <jk>true</jk> if this list is an {@link UnmodifiableBean} snapshot.
    */
   public boolean isUnmodifiable() {
      return this instanceof UnmodifiableBean;
   }

   /**
    * Returns the headers in this list as a typed array.
    *
    * @return A new array. Never <jk>null</jk>.
    */
   public HttpHeader[] toHeaderArray() {
      return toArray(new HttpHeader[0]);
   }

   private boolean nameMatches(HttpHeader h, String name) {
      return caseSensitive ? eq(h.getName(), name) : eqic(h.getName(), name);
   }

   /**
    * An unmodifiable snapshot of a {@link HttpHeaderList}.
    *
    * <p>
    * This is the "collection-mutator-override" variant of the immutability paradigm.  Because {@link HttpHeaderList}
    * extends {@link ArrayList}, a single funnel cannot intercept the inherited {@code ArrayList} mutators, so this
    * subclass snapshot-copies the elements in its constructor and overrides the entire collection-mutator surface — its
    * own fluent mutators plus the inherited {@code ArrayList} mutators (including the {@code iterator()} /
    * {@code listIterator()} mutators) — to throw {@link UnsupportedOperationException}.  Read operations and
    * non-mutating iteration continue to work.
    */
   public static class Unmodifiable extends HttpHeaderList implements UnmodifiableBean {

      private static final long serialVersionUID = 1L;

      /**
       * Constructor.
       *
       * @param copyFrom The list to snapshot-copy. Must not be <jk>null</jk>.
       */
      Unmodifiable(HttpHeaderList copyFrom) {
         super(copyFrom);
      }

      // --- Fluent mutators -----------------------------------------------------------------------------------------

      @Override public HttpHeaderList append(HttpHeader value) { throw uoex(RO); }
      @Override public HttpHeaderList append(HttpHeader...values) { throw uoex(RO); }
      @Override public HttpHeaderList append(List<HttpHeader> values) { throw uoex(RO); }
      @Override public HttpHeaderList append(String name, String value) { throw uoex(RO); }
      @Override public HttpHeaderList append(String name, Supplier<String> value) { throw uoex(RO); }
      @Override public HttpHeaderList caseSensitive(boolean value) { throw uoex(RO); }
      @Override public HttpHeaderList removeAll(String name) { throw uoex(RO); }
      @Override public HttpHeaderList set(HttpHeader value) { throw uoex(RO); }
      @Override public HttpHeaderList set(HttpHeader...values) { throw uoex(RO); }
      @Override public HttpHeaderList set(String name, String value) { throw uoex(RO); }
      @Override public HttpHeaderList setDefault(HttpHeader value) { throw uoex(RO); }
      @Override public HttpHeaderList setDefault(HttpHeader...values) { throw uoex(RO); }
      @Override public HttpHeaderList setDefault(String name, String value) { throw uoex(RO); }

      // --- Inherited ArrayList collection mutators -----------------------------------------------------------------

      @Override public boolean add(HttpHeader e) { throw uoex(RO); }
      @Override public void add(int index, HttpHeader element) { throw uoex(RO); }
      @Override public boolean addAll(Collection<? extends HttpHeader> c) { throw uoex(RO); }
      @Override public boolean addAll(int index, Collection<? extends HttpHeader> c) { throw uoex(RO); }
      @Override public void clear() { throw uoex(RO); }
      @Override public boolean remove(Object o) { throw uoex(RO); }
      @Override public HttpHeader remove(int index) { throw uoex(RO); }
      @Override public boolean removeAll(Collection<?> c) { throw uoex(RO); }
      @Override public boolean removeIf(Predicate<? super HttpHeader> filter) { throw uoex(RO); }
      @Override public void replaceAll(UnaryOperator<HttpHeader> operator) { throw uoex(RO); }
      @Override public boolean retainAll(Collection<?> c) { throw uoex(RO); }
      @Override public HttpHeader set(int index, HttpHeader element) { throw uoex(RO); }
      @Override public void sort(Comparator<? super HttpHeader> c) { throw uoex(RO); }

      @Override public Iterator<HttpHeader> iterator() {
         var i = super.iterator();
         return new Iterator<>() {
            @Override public boolean hasNext() { return i.hasNext(); }
            @Override public HttpHeader next() { return i.next(); }
            @Override public void remove() { throw uoex(RO); }
         };
      }

      @Override public ListIterator<HttpHeader> listIterator() { return listIterator(0); }

      @Override public ListIterator<HttpHeader> listIterator(int index) {
         var i = super.listIterator(index);
         return new ListIterator<>() {
            @Override public boolean hasNext() { return i.hasNext(); }
            @Override public HttpHeader next() { return i.next(); }
            @Override public boolean hasPrevious() { return i.hasPrevious(); }
            @Override public HttpHeader previous() { return i.previous(); }
            @Override public int nextIndex() { return i.nextIndex(); }
            @Override public int previousIndex() { return i.previousIndex(); }
            @Override public void add(HttpHeader e) { throw uoex(RO); }
            @Override public void set(HttpHeader e) { throw uoex(RO); }
            @Override public void remove() { throw uoex(RO); }
         };
      }
   }

   private static final String RO = "Bean is unmodifiable.";
}