/*
    * Copyright 2015 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:
    *
    *   https://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 io.netty5.handler.codec.http.cookie;
  
  import io.netty5.handler.codec.DateFormatter;
  import io.netty5.handler.codec.http.cookie.CookieHeaderNames.SameSite;
  
  import java.util.Date;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * A <a href="https://tools.ietf.org/html/rfc6265">RFC6265</a> compliant cookie decoder to be used client side.
   *
   * It will store the way the raw value was wrapped in {@link Cookie#setWrap(boolean)} so it can be
   * eventually sent back to the Origin server as is.
   *
   * @see ClientCookieEncoder
   */
  public final class ClientCookieDecoder extends CookieDecoder {
  
      /**
       * Strict encoder that validates that name and value chars are in the valid scope
       * defined in RFC6265
       */
      public static final ClientCookieDecoder STRICT = new ClientCookieDecoder(true);
  
      /**
       * Lax instance that doesn't validate name and value
       */
      public static final ClientCookieDecoder LAX = new ClientCookieDecoder(false);
  
      private ClientCookieDecoder(boolean strict) {
          super(strict);
      }
  
      /**
       * Decodes the specified Set-Cookie HTTP header value into a {@link Cookie}.
       *
       * @return the decoded {@link Cookie}
       */
      public Cookie decode(String header) {
          final int headerLen = requireNonNull(header, "header").length();
  
          if (headerLen == 0) {
              return null;
          }
  
          CookieBuilder cookieBuilder = null;
  
          loop: for (int i = 0;;) {
  
              // Skip spaces and separators.
              for (;;) {
                  if (i == headerLen) {
                      break loop;
                  }
                  char c = header.charAt(i);
                  if (c == ',') {
                      // Having multiple cookies in a single Set-Cookie header is
                      // deprecated, modern browsers only parse the first one
                      break loop;
  
                  } else if (c == '\t' || c == '\n' || c == 0x0b || c == '\f'
                          || c == '\r' || c == ' ' || c == ';') {
                      i++;
                      continue;
                  }
                  break;
              }
  
              int nameBegin = i;
              int nameEnd;
              int valueBegin;
              int valueEnd;
  
              for (;;) {
                  char curChar = header.charAt(i);
                  if (curChar == ';') {
                      // NAME; (no value till ';')
                      nameEnd = i;
                      valueBegin = valueEnd = -1;
                      break;
  
                  } else if (curChar == '=') {
                      // NAME=VALUE
                     nameEnd = i;
                     i++;
                     if (i == headerLen) {
                         // NAME= (empty value, i.e. nothing after '=')
                         valueBegin = valueEnd = 0;
                         break;
                     }
 
                     valueBegin = i;
                     // NAME=VALUE;
                     int semiPos = header.indexOf(';', i);
                     valueEnd = i = semiPos > 0 ? semiPos : headerLen;
                     break;
                 } else {
                     i++;
                 }
 
                 if (i == headerLen) {
                     // NAME (no value till the end of string)
                     nameEnd = headerLen;
                     valueBegin = valueEnd = -1;
                     break;
                 }
             }
 
             if (valueEnd > 0 && header.charAt(valueEnd - 1) == ',') {
                 // old multiple cookies separator, skipping it
                 valueEnd--;
             }
 
             if (cookieBuilder == null) {
                 // cookie name-value pair
                 DefaultCookie cookie = initCookie(header, nameBegin, nameEnd, valueBegin, valueEnd);
 
                 if (cookie == null) {
                     return null;
                 }
 
                 cookieBuilder = new CookieBuilder(cookie, header);
             } else {
                 // cookie attribute
                 cookieBuilder.appendAttribute(nameBegin, nameEnd, valueBegin, valueEnd);
             }
         }
         return cookieBuilder != null ? cookieBuilder.cookie() : null;
     }
 
     private static class CookieBuilder {
 
         private final String header;
         private final DefaultCookie cookie;
         private String domain;
         private String path;
         private long maxAge = Long.MIN_VALUE;
         private int expiresStart;
         private int expiresEnd;
         private boolean secure;
         private boolean httpOnly;
         private SameSite sameSite;
 
         CookieBuilder(DefaultCookie cookie, String header) {
             this.cookie = cookie;
             this.header = header;
         }
 
         private long mergeMaxAgeAndExpires() {
             // max age has precedence over expires
             if (maxAge != Long.MIN_VALUE) {
                 return maxAge;
             } else if (isValueDefined(expiresStart, expiresEnd)) {
                 Date expiresDate = DateFormatter.parseHttpDate(header, expiresStart, expiresEnd);
                 if (expiresDate != null) {
                     long maxAgeMillis = expiresDate.getTime() - System.currentTimeMillis();
                     return maxAgeMillis / 1000 + (maxAgeMillis % 1000 != 0 ? 1 : 0);
                 }
             }
             return Long.MIN_VALUE;
         }
 
         Cookie cookie() {
             cookie.setDomain(domain);
             cookie.setPath(path);
             cookie.setMaxAge(mergeMaxAgeAndExpires());
             cookie.setSecure(secure);
             cookie.setHttpOnly(httpOnly);
             cookie.setSameSite(sameSite);
             return cookie;
         }
 
         /**
          * Parse and store a key-value pair. First one is considered to be the
          * cookie name/value. Unknown attribute names are silently discarded.
          *
          * @param keyStart
          *            where the key starts in the header
          * @param keyEnd
          *            where the key ends in the header
          * @param valueStart
          *            where the value starts in the header
          * @param valueEnd
          *            where the value ends in the header
          */
         void appendAttribute(int keyStart, int keyEnd, int valueStart, int valueEnd) {
             int length = keyEnd - keyStart;
 
             if (length == 4) {
                 parse4(keyStart, valueStart, valueEnd);
             } else if (length == 6) {
                 parse6(keyStart, valueStart, valueEnd);
             } else if (length == 7) {
                 parse7(keyStart, valueStart, valueEnd);
             } else if (length == 8) {
                 parse8(keyStart, valueStart, valueEnd);
             }
         }
 
         private void parse4(int nameStart, int valueStart, int valueEnd) {
             if (header.regionMatches(true, nameStart, CookieHeaderNames.PATH, 0, 4)) {
                 path = computeValue(valueStart, valueEnd);
             }
         }
 
         private void parse6(int nameStart, int valueStart, int valueEnd) {
             if (header.regionMatches(true, nameStart, CookieHeaderNames.DOMAIN, 0, 5)) {
                 domain = computeValue(valueStart, valueEnd);
             } else if (header.regionMatches(true, nameStart, CookieHeaderNames.SECURE, 0, 5)) {
                 secure = true;
             }
         }
 
         private void setMaxAge(String value) {
             try {
                 maxAge = Math.max(Long.parseLong(value), 0L);
             } catch (NumberFormatException e1) {
                 // ignore failure to parse -> treat as session cookie
             }
         }
 
         private void parse7(int nameStart, int valueStart, int valueEnd) {
             if (header.regionMatches(true, nameStart, CookieHeaderNames.EXPIRES, 0, 7)) {
                 expiresStart = valueStart;
                 expiresEnd = valueEnd;
             } else if (header.regionMatches(true, nameStart, CookieHeaderNames.MAX_AGE, 0, 7)) {
                 setMaxAge(computeValue(valueStart, valueEnd));
             }
         }
 
         private void parse8(int nameStart, int valueStart, int valueEnd) {
             if (header.regionMatches(true, nameStart, CookieHeaderNames.HTTPONLY, 0, 8)) {
                 httpOnly = true;
             } else if (header.regionMatches(true, nameStart, CookieHeaderNames.SAMESITE, 0, 8)) {
                 sameSite = SameSite.of(computeValue(valueStart, valueEnd));
             }
         }
 
         private static boolean isValueDefined(int valueStart, int valueEnd) {
             return valueStart != -1 && valueStart != valueEnd;
         }
 
         private String computeValue(int valueStart, int valueEnd) {
             return isValueDefined(valueStart, valueEnd) ? header.substring(valueStart, valueEnd) : null;
         }
     }
 }