/*
    * Copyright 2012 The Netty Project
    *
    * The Netty Project 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.jboss.netty.handler.codec.spdy;
  
  import java.util.LinkedList;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  import java.util.TreeSet;
  
  import org.jboss.netty.handler.codec.http.HttpMethod;
  import org.jboss.netty.handler.codec.http.HttpResponseStatus;
  import org.jboss.netty.handler.codec.http.HttpVersion;
  
  /**
   * Provides the constants for the standard SPDY HTTP header names and commonly
   * used utility methods that access a {@link SpdyHeaderBlock}.
   * @apiviz.stereotype static
   */
  public class SpdyHeaders {
  
      /**
       * SPDY HTTP header names
       * @apiviz.stereotype static
       */
      public static final class HttpNames {
          /**
           * {@code ":host"}
           */
          public static final String HOST = ":host";
          /**
           * {@code ":method"}
           */
          public static final String METHOD = ":method";
          /**
           * {@code ":path"}
           */
          public static final String PATH = ":path";
          /**
           * {@code ":scheme"}
           */
          public static final String SCHEME = ":scheme";
          /**
           * {@code ":status"}
           */
          public static final String STATUS = ":status";
          /**
           * {@code ":version"}
           */
          public static final String VERSION = ":version";
  
          private HttpNames() {
          }
      }
  
      /**
       * SPDY/2 HTTP header names
       * @apiviz.stereotype static
       */
      public static final class Spdy2HttpNames {
          /**
           * {@code "method"}
           */
          public static final String METHOD = "method";
          /**
           * {@code "scheme"}
           */
          public static final String SCHEME = "scheme";
          /**
           * {@code "status"}
           */
          public static final String STATUS = "status";
          /**
           * {@code "url"}
           */
          public static final String URL = "url";
          /**
           * {@code "version"}
           */
          public static final String VERSION = "version";
  
          private Spdy2HttpNames() {
          }
      }
  
  
     /**
      * Returns the header value with the specified header name.  If there are
      * more than one header value for the specified header name, the first
      * value is returned.
      *
      * @return the header value or {@code null} if there is no such header
      */
     public static String getHeader(SpdyHeaderBlock block, String name) {
         return block.getHeader(name);
     }
 
     /**
      * Returns the header value with the specified header name.  If there are
      * more than one header value for the specified header name, the first
      * value is returned.
      *
      * @return the header value or the {@code defaultValue} if there is no such
      *         header
      */
     public static String getHeader(SpdyHeaderBlock block, String name, String defaultValue) {
         String value = block.getHeader(name);
         if (value == null) {
             return defaultValue;
         }
         return value;
     }
 
     /**
      * Sets a new header with the specified name and value.  If there is an
      * existing header with the same name, the existing header is removed.
      */
     public static void setHeader(SpdyHeaderBlock block, String name, Object value) {
         block.setHeader(name, value);
     }
 
     /**
      * Sets a new header with the specified name and values.  If there is an
      * existing header with the same name, the existing header is removed.
      */
     public static void setHeader(SpdyHeaderBlock block, String name, Iterable<?> values) {
         block.setHeader(name, values);
     }
 
     /**
      * Adds a new header with the specified name and value.
      */
     public static void addHeader(SpdyHeaderBlock block, String name, Object value) {
         block.addHeader(name, value);
     }
 
     /**
      * Removes the SPDY host header.
      */
     public static void removeHost(SpdyHeaderBlock block) {
         block.removeHeader(HttpNames.HOST);
     }
 
     /**
      * Returns the SPDY host header.
      */
     public static String getHost(SpdyHeaderBlock block) {
         return block.getHeader(HttpNames.HOST);
     }
 
     /**
      * Set the SPDY host header.
      */
     public static void setHost(SpdyHeaderBlock block, String host) {
         block.setHeader(HttpNames.HOST, host);
     }
 
     /**
      * Removes the HTTP method header.
      */
     @Deprecated
     public static void removeMethod(SpdyHeaderBlock block) {
         removeMethod(2, block);
     }
 
     /**
      * Removes the HTTP method header.
      */
     public static void removeMethod(int spdyVersion, SpdyHeaderBlock block) {
         if (spdyVersion < 3) {
             block.removeHeader(Spdy2HttpNames.METHOD);
         } else {
             block.removeHeader(HttpNames.METHOD);
         }
     }
 
     /**
      * Returns the {@link HttpMethod} represented by the HTTP method header.
      */
     @Deprecated
     public static HttpMethod getMethod(SpdyHeaderBlock block) {
         return getMethod(2, block);
     }
 
     /**
      * Returns the {@link HttpMethod} represented by the HTTP method header.
      */
     public static HttpMethod getMethod(int spdyVersion, SpdyHeaderBlock block) {
         try {
             if (spdyVersion < 3) {
                 return HttpMethod.valueOf(block.getHeader(Spdy2HttpNames.METHOD));
             } else {
                 return HttpMethod.valueOf(block.getHeader(HttpNames.METHOD));
             }
         } catch (Exception e) {
             return null;
         }
     }
 
     /**
      * Sets the HTTP method header.
      */
     @Deprecated
     public static void setMethod(SpdyHeaderBlock block, HttpMethod method) {
         setMethod(2, block, method);
     }
 
     /**
      * Sets the HTTP method header.
      */
     public static void setMethod(int spdyVersion, SpdyHeaderBlock block, HttpMethod method) {
         if (spdyVersion < 3) {
             block.setHeader(Spdy2HttpNames.METHOD, method.getName());
         } else {
             block.setHeader(HttpNames.METHOD, method.getName());
         }
     }
 
     /**
      * Removes the URL scheme header.
      */
     @Deprecated
     public static void removeScheme(SpdyHeaderBlock block) {
         removeMethod(2, block);
     }
 
     /**
      * Removes the URL scheme header.
      */
     public static void removeScheme(int spdyVersion, SpdyHeaderBlock block) {
         if (spdyVersion < 2) {
             block.removeHeader(Spdy2HttpNames.SCHEME);
         } else {
             block.removeHeader(HttpNames.SCHEME);
         }
     }
 
     /**
      * Returns the value of the URL scheme header.
      */
     @Deprecated
     public static String getScheme(SpdyHeaderBlock block) {
         return getScheme(2, block);
     }
 
     /**
      * Returns the value of the URL scheme header.
      */
     public static String getScheme(int spdyVersion, SpdyHeaderBlock block) {
         if (spdyVersion < 3) {
             return block.getHeader(Spdy2HttpNames.SCHEME);
         } else {
             return block.getHeader(HttpNames.SCHEME);
         }
     }
 
     /**
      * Sets the URL scheme header.
      */
     @Deprecated
     public static void setScheme(SpdyHeaderBlock block, String scheme) {
         setScheme(2, block, scheme);
     }
 
     /**
      * Sets the URL scheme header.
      */
     public static void setScheme(int spdyVersion, SpdyHeaderBlock block, String scheme) {
         if (spdyVersion < 3) {
             block.setHeader(Spdy2HttpNames.SCHEME, scheme);
         } else {
             block.setHeader(HttpNames.SCHEME, scheme);
         }
     }
 
     /**
      * Removes the HTTP response status header.
      */
     @Deprecated
     public static void removeStatus(SpdyHeaderBlock block) {
         removeMethod(2, block);
     }
 
     /**
      * Removes the HTTP response status header.
      */
     public static void removeStatus(int spdyVersion, SpdyHeaderBlock block) {
         if (spdyVersion < 3) {
             block.removeHeader(Spdy2HttpNames.STATUS);
         } else {
             block.removeHeader(HttpNames.STATUS);
         }
     }
 
     /**
      * Returns the {@link HttpResponseStatus} represented by the HTTP response status header.
      */
     @Deprecated
     public static HttpResponseStatus getStatus(SpdyHeaderBlock block) {
         return getStatus(2, block);
     }
 
     /**
      * Returns the {@link HttpResponseStatus} represented by the HTTP response status header.
      */
     public static HttpResponseStatus getStatus(int spdyVersion, SpdyHeaderBlock block) {
         try {
             String status;
             if (spdyVersion < 3) {
                 status = block.getHeader(Spdy2HttpNames.STATUS);
             } else {
                 status = block.getHeader(HttpNames.STATUS);
             }
             int space = status.indexOf(' ');
             if (space == -1) {
                 return HttpResponseStatus.valueOf(Integer.parseInt(status));
             } else {
                 int code = Integer.parseInt(status.substring(0, space));
                 String reasonPhrase = status.substring(space + 1);
                 HttpResponseStatus responseStatus = HttpResponseStatus.valueOf(code);
                 if (responseStatus.getReasonPhrase().equals(reasonPhrase)) {
                     return responseStatus;
                 } else {
                     return new HttpResponseStatus(code, reasonPhrase);
                 }
             }
         } catch (Exception e) {
             return null;
         }
     }
 
     /**
      * Sets the HTTP response status header.
      */
     @Deprecated
     public static void setStatus(SpdyHeaderBlock block, HttpResponseStatus status) {
         setStatus(2, block, status);
     }
 
     /**
      * Sets the HTTP response status header.
      */
     public static void setStatus(int spdyVersion, SpdyHeaderBlock block, HttpResponseStatus status) {
         if (spdyVersion < 3) {
             block.setHeader(Spdy2HttpNames.STATUS, status.toString());
         } else {
             block.setHeader(HttpNames.STATUS, status.toString());
         }
     }
 
     /**
      * Removes the URL path header.
      */
     @Deprecated
     public static void removeUrl(SpdyHeaderBlock block) {
         removeUrl(2, block);
     }
 
     /**
      * Removes the URL path header.
      */
     public static void removeUrl(int spdyVersion, SpdyHeaderBlock block) {
         if (spdyVersion < 3) {
             block.removeHeader(Spdy2HttpNames.URL);
         } else {
             block.removeHeader(HttpNames.PATH);
         }
     }
 
     /**
      * Returns the value of the URL path header.
      */
     @Deprecated
     public static String getUrl(SpdyHeaderBlock block) {
         return getUrl(2, block);
     }
 
     /**
      * Returns the value of the URL path header.
      */
     public static String getUrl(int spdyVersion, SpdyHeaderBlock block) {
         if (spdyVersion < 3) {
             return block.getHeader(Spdy2HttpNames.URL);
         } else {
             return block.getHeader(HttpNames.PATH);
         }
     }
 
     /**
      * Sets the URL path header.
      */
     @Deprecated
     public static void setUrl(SpdyHeaderBlock block, String path) {
         setUrl(2, block, path);
     }
 
     /**
      * Sets the URL path header.
      */
     public static void setUrl(int spdyVersion, SpdyHeaderBlock block, String path) {
         if (spdyVersion < 3) {
             block.setHeader(Spdy2HttpNames.URL, path);
         } else {
             block.setHeader(HttpNames.PATH, path);
         }
     }
 
     /**
      * Removes the HTTP version header.
      */
     @Deprecated
     public static void removeVersion(SpdyHeaderBlock block) {
         removeVersion(2, block);
     }
 
     /**
      * Removes the HTTP version header.
      */
     public static void removeVersion(int spdyVersion, SpdyHeaderBlock block) {
         if (spdyVersion < 3) {
             block.removeHeader(Spdy2HttpNames.VERSION);
         } else {
             block.removeHeader(HttpNames.VERSION);
         }
     }
 
     /**
      * Returns the {@link HttpVersion} represented by the HTTP version header.
      */
     @Deprecated
     public static HttpVersion getVersion(SpdyHeaderBlock block) {
         return getVersion(2, block);
     }
 
     /**
      * Returns the {@link HttpVersion} represented by the HTTP version header.
      */
     public static HttpVersion getVersion(int spdyVersion, SpdyHeaderBlock block) {
         try {
             if (spdyVersion < 3) {
                 return HttpVersion.valueOf(block.getHeader(Spdy2HttpNames.VERSION));
             } else {
                 return HttpVersion.valueOf(block.getHeader(HttpNames.VERSION));
             }
         } catch (Exception e) {
             return null;
         }
     }
 
     /**
      * Sets the HTTP version header.
      */
     @Deprecated
     public static void setVersion(SpdyHeaderBlock block, HttpVersion httpVersion) {
         setVersion(2, block, httpVersion);
     }
 
     /**
      * Sets the HTTP version header.
      */
     public static void setVersion(int spdyVersion, SpdyHeaderBlock block, HttpVersion httpVersion) {
         if (spdyVersion < 3) {
             block.setHeader(Spdy2HttpNames.VERSION, httpVersion.getText());
         } else {
             block.setHeader(HttpNames.VERSION, httpVersion.getText());
         }
     }
 
 
     private static final int BUCKET_SIZE = 17;
 
     private static int hash(String name) {
         int h = 0;
         for (int i = name.length() - 1; i >= 0; i --) {
             char c = name.charAt(i);
             if (c >= 'A' && c <= 'Z') {
                 c += 32;
             }
             h = 31 * h + c;
         }
 
         if (h > 0) {
             return h;
         } else if (h == Integer.MIN_VALUE) {
             return Integer.MAX_VALUE;
         } else {
             return -h;
         }
     }
 
     private static boolean eq(String name1, String name2) {
         int nameLen = name1.length();
         if (nameLen != name2.length()) {
             return false;
         }
 
         for (int i = nameLen - 1; i >= 0; i --) {
             char c1 = name1.charAt(i);
             char c2 = name2.charAt(i);
             if (c1 != c2) {
                 if (c1 >= 'A' && c1 <= 'Z') {
                     c1 += 32;
                 }
                 if (c2 >= 'A' && c2 <= 'Z') {
                     c2 += 32;
                 }
                 if (c1 != c2) {
                     return false;
                 }
             }
         }
         return true;
     }
 
     private static int index(int hash) {
         return hash % BUCKET_SIZE;
     }
 
     private final Entry[] entries = new Entry[BUCKET_SIZE];
     private final Entry head = new Entry(-1, null, null);
 
     SpdyHeaders() {
         head.before = head.after = head;
     }
 
     void addHeader(final String name, final Object value) {
         String lowerCaseName = name.toLowerCase();
         SpdyCodecUtil.validateHeaderName(lowerCaseName);
         String strVal = toString(value);
         SpdyCodecUtil.validateHeaderValue(strVal);
         int h = hash(lowerCaseName);
         int i = index(h);
         addHeader0(h, i, lowerCaseName, strVal);
     }
 
     private void addHeader0(int h, int i, final String name, final String value) {
         // Update the hash table.
         Entry e = entries[i];
         Entry newEntry;
         entries[i] = newEntry = new Entry(h, name, value);
         newEntry.next = e;
 
         // Update the linked list.
         newEntry.addBefore(head);
     }
 
     void removeHeader(final String name) {
         if (name == null) {
             throw new NullPointerException("name");
         }
         String lowerCaseName = name.toLowerCase();
         int h = hash(lowerCaseName);
         int i = index(h);
         removeHeader0(h, i, lowerCaseName);
     }
 
     private void removeHeader0(int h, int i, String name) {
         Entry e = entries[i];
         if (e == null) {
             return;
         }
 
         for (;;) {
             if (e.hash == h && eq(name, e.key)) {
                 e.remove();
                 Entry next = e.next;
                 if (next != null) {
                     entries[i] = next;
                     e = next;
                 } else {
                     entries[i] = null;
                     return;
                 }
             } else {
                 break;
             }
         }
 
         for (;;) {
             Entry next = e.next;
             if (next == null) {
                 break;
             }
             if (next.hash == h && eq(name, next.key)) {
                 e.next = next.next;
                 next.remove();
             } else {
                 e = next;
             }
         }
     }
 
     void setHeader(final String name, final Object value) {
         String lowerCaseName = name.toLowerCase();
         SpdyCodecUtil.validateHeaderName(lowerCaseName);
         String strVal = toString(value);
         SpdyCodecUtil.validateHeaderValue(strVal);
         int h = hash(lowerCaseName);
         int i = index(h);
         removeHeader0(h, i, lowerCaseName);
         addHeader0(h, i, lowerCaseName, strVal);
     }
 
     void setHeader(final String name, final Iterable<?> values) {
         if (values == null) {
             throw new NullPointerException("values");
         }
 
         String lowerCaseName = name.toLowerCase();
         SpdyCodecUtil.validateHeaderName(lowerCaseName);
 
         int h = hash(lowerCaseName);
         int i = index(h);
 
         removeHeader0(h, i, lowerCaseName);
         for (Object v: values) {
             if (v == null) {
                 break;
             }
             String strVal = toString(v);
             SpdyCodecUtil.validateHeaderValue(strVal);
             addHeader0(h, i, lowerCaseName, strVal);
         }
     }
 
     void clearHeaders() {
         for (int i = 0; i < entries.length; i ++) {
             entries[i] = null;
         }
         head.before = head.after = head;
     }
 
     String getHeader(final String name) {
         if (name == null) {
             throw new NullPointerException("name");
         }
 
         int h = hash(name);
         int i = index(h);
         Entry e = entries[i];
         while (e != null) {
             if (e.hash == h && eq(name, e.key)) {
                 return e.value;
             }
 
             e = e.next;
         }
         return null;
     }
 
     List<String> getHeaders(final String name) {
         if (name == null) {
             throw new NullPointerException("name");
         }
 
         LinkedList<String> values = new LinkedList<String>();
 
         int h = hash(name);
         int i = index(h);
         Entry e = entries[i];
         while (e != null) {
             if (e.hash == h && eq(name, e.key)) {
                 values.addFirst(e.value);
             }
             e = e.next;
         }
         return values;
     }
 
     List<Map.Entry<String, String>> getHeaders() {
         List<Map.Entry<String, String>> all =
             new LinkedList<Map.Entry<String, String>>();
 
         Entry e = head.after;
         while (e != head) {
             all.add(e);
             e = e.after;
         }
         return all;
     }
 
     boolean containsHeader(String name) {
         return getHeader(name) != null;
     }
 
     Set<String> getHeaderNames() {
         Set<String> names = new TreeSet<String>();
 
         Entry e = head.after;
         while (e != head) {
             names.add(e.key);
             e = e.after;
         }
         return names;
     }
 
     private static String toString(Object value) {
         if (value == null) {
             return null;
         }
         return value.toString();
     }
 
     private static final class Entry implements Map.Entry<String, String> {
         final int hash;
         final String key;
         String value;
         Entry next;
         Entry before, after;
 
         Entry(int hash, String key, String value) {
             this.hash = hash;
             this.key = key;
             this.value = value;
         }
 
         void remove() {
             before.after = after;
             after.before = before;
         }
 
         void addBefore(Entry e) {
             after  = e;
             before = e.before;
             before.after = this;
             after.before = this;
         }
 
         public String getKey() {
             return key;
         }
 
         public String getValue() {
             return value;
         }
 
         public String setValue(String value) {
             if (value == null) {
                 throw new NullPointerException("value");
             }
             SpdyCodecUtil.validateHeaderValue(value);
             String oldValue = this.value;
             this.value = value;
             return oldValue;
         }
 
         @Override
         public String toString() {
             return key + '=' + value;
         }
     }
 }