/*
    * Copyright 2014 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.netty.handler.codec.http2;
  
  import io.netty.handler.codec.CharSequenceValueConverter;
  import io.netty.handler.codec.DefaultHeaders;
  import io.netty.handler.codec.http.HttpHeaderValidationUtil;
  import io.netty.util.AsciiString;
  import io.netty.util.ByteProcessor;
  import io.netty.util.internal.PlatformDependent;
  
  import static io.netty.handler.codec.http2.Http2Error.PROTOCOL_ERROR;
  import static io.netty.handler.codec.http2.Http2Exception.connectionError;
  import static io.netty.handler.codec.http2.Http2Headers.PseudoHeaderName.hasPseudoHeaderFormat;
  import static io.netty.handler.codec.http2.Http2Headers.PseudoHeaderName.isPseudoHeader;
  import static io.netty.util.AsciiString.CASE_INSENSITIVE_HASHER;
  import static io.netty.util.AsciiString.CASE_SENSITIVE_HASHER;
  import static io.netty.util.AsciiString.isUpperCase;
  
  public class DefaultHttp2Headers
          extends DefaultHeaders<CharSequence, CharSequence, Http2Headers> implements Http2Headers {
      private static final ByteProcessor HTTP2_NAME_VALIDATOR_PROCESSOR = new ByteProcessor() {
          @Override
          public boolean process(byte value) {
              return !isUpperCase(value);
          }
      };
      static final NameValidator<CharSequence> HTTP2_NAME_VALIDATOR = new NameValidator<CharSequence>() {
          @Override
          public void validateName(CharSequence name) {
              if (name == null || name.length() == 0) {
                  PlatformDependent.throwException(connectionError(PROTOCOL_ERROR,
                          "empty headers are not allowed [%s]", name));
              }
  
              if (hasPseudoHeaderFormat(name)) {
                  if (!isPseudoHeader(name)) {
                      PlatformDependent.throwException(connectionError(
                              PROTOCOL_ERROR, "Invalid HTTP/2 pseudo-header '%s' encountered.", name));
                  }
                  // no need for lower-case validation, we trust our own pseudo header constants
                  return;
              }
  
              // RFC 9113 Section 8.2.1: HTTP/2 field names are valid HTTP/1.1 tokens (RFC 7230 Section 3.2.6)
              // with the additional constraint that they MUST be lowercase. Reject anything outside the token
              // grammar (non-ASCII, control characters, SP/HTAB, separators) before the lowercase check.
              int tokenIndex = HttpHeaderValidationUtil.validateToken(name);
              if (tokenIndex != -1) {
                  PlatformDependent.throwException(connectionError(PROTOCOL_ERROR,
                          "invalid header name [%s]", name));
              }
  
              if (name instanceof AsciiString) {
                  final int index;
                  try {
                      index = ((AsciiString) name).forEachByte(HTTP2_NAME_VALIDATOR_PROCESSOR);
                  } catch (Http2Exception e) {
                      PlatformDependent.throwException(e);
                      return;
                  } catch (Throwable t) {
                      PlatformDependent.throwException(connectionError(PROTOCOL_ERROR, t,
                              "unexpected error. invalid header name [%s]", name));
                      return;
                  }
  
                  if (index != -1) {
                      PlatformDependent.throwException(connectionError(PROTOCOL_ERROR,
                              "invalid header name [%s]", name));
                  }
              } else {
                  for (int i = 0; i < name.length(); ++i) {
                      if (isUpperCase(name.charAt(i))) {
                          PlatformDependent.throwException(connectionError(PROTOCOL_ERROR,
                                  "invalid header name [%s]", name));
                      }
                  }
              }
          }
      };
  
      private static final ValueValidator<CharSequence> VALUE_VALIDATOR = new ValueValidator<CharSequence>() {
          @Override
          public void validate(CharSequence value) {
              int index = HttpHeaderValidationUtil.validateValidHeaderValue(value);
              if (index != -1) {
                  throw new IllegalArgumentException("a header value contains prohibited character 0x" +
                         Integer.toHexString(value.charAt(index)) + " at index " + index + '.');
             }
         }
     };
 
     private HeaderEntry<CharSequence, CharSequence> firstNonPseudo = head;
 
     /**
      * Create a new instance.
      * <p>
      * Header names will be validated according to
      * <a href="https://tools.ietf.org/html/rfc7540">rfc7540</a>.
      */
     public DefaultHttp2Headers() {
         this(true);
     }
 
     /**
      * Create a new instance.
      * @param validate {@code true} to validate header names according to
      * <a href="https://tools.ietf.org/html/rfc7540">rfc7540</a>. {@code false} to not validate header names.
      */
     @SuppressWarnings("unchecked")
     public DefaultHttp2Headers(boolean validate) {
         // Case sensitive compare is used because it is cheaper, and header validation can be used to catch invalid
         // headers.
         super(CASE_SENSITIVE_HASHER,
               CharSequenceValueConverter.INSTANCE,
               validate ? HTTP2_NAME_VALIDATOR : NameValidator.NOT_NULL);
     }
 
     /**
      * Create a new instance.
      * @param validate {@code true} to validate header names according to
      * <a href="https://tools.ietf.org/html/rfc7540">rfc7540</a>. {@code false} to not validate header names.
      * @param arraySizeHint A hint as to how large the hash data structure should be.
      * The next positive power of two will be used. An upper bound may be enforced.
      * @see DefaultHttp2Headers#DefaultHttp2Headers(boolean, boolean, int)
      */
     @SuppressWarnings("unchecked")
     public DefaultHttp2Headers(boolean validate, int arraySizeHint) {
         // Case sensitive compare is used because it is cheaper, and header validation can be used to catch invalid
         // headers.
         super(CASE_SENSITIVE_HASHER,
               CharSequenceValueConverter.INSTANCE,
               validate ? HTTP2_NAME_VALIDATOR : NameValidator.NOT_NULL,
               arraySizeHint);
     }
 
     /**
      * Create a new instance.
      * @param validate {@code true} to validate header names according to
      * <a href="https://tools.ietf.org/html/rfc7540">rfc7540</a>. {@code false} to not validate header names.
      * @param validateValues {@code true} to validate header values according to
      * <a href="https://datatracker.ietf.org/doc/html/rfc7230#section-3.2">rfc7230</a> and
      * <a href="https://datatracker.ietf.org/doc/html/rfc5234#appendix-B.1">rfc5234</a>. Otherwise, {@code false}
      * (the default) to not validate values.
      * @param arraySizeHint A hint as to how large the hash data structure should be.
      * The next positive power of two will be used. An upper bound may be enforced.
      */
     @SuppressWarnings("unchecked")
     public DefaultHttp2Headers(boolean validate, boolean validateValues, int arraySizeHint) {
         // Case sensitive compare is used because it is cheaper, and header validation can be used to catch invalid
         // headers.
         super(CASE_SENSITIVE_HASHER,
                 CharSequenceValueConverter.INSTANCE,
                 validate ? HTTP2_NAME_VALIDATOR : NameValidator.NOT_NULL,
                 arraySizeHint,
                 validateValues ? VALUE_VALIDATOR : (ValueValidator<CharSequence>) ValueValidator.NO_VALIDATION);
     }
 
     @Override
     protected void validateName(NameValidator<CharSequence> validator, boolean forAdd, CharSequence name) {
         super.validateName(validator, forAdd, name);
         if (nameValidator() == HTTP2_NAME_VALIDATOR && forAdd && hasPseudoHeaderFormat(name)) {
             if (contains(name)) {
                 PlatformDependent.throwException(connectionError(
                         PROTOCOL_ERROR, "Duplicate HTTP/2 pseudo-header '%s' encountered.", name));
             }
         }
     }
 
     @Override
     protected void validateValue(ValueValidator<CharSequence> validator, CharSequence name, CharSequence value) {
         // This method has a noop override for backward compatibility, see https://github.com/netty/netty/pull/12975
         super.validateValue(validator, name, value);
         // https://datatracker.ietf.org/doc/html/rfc9113#section-8.3.1
         // pseudo headers must not be empty
         if (nameValidator() == HTTP2_NAME_VALIDATOR && (value == null || value.length() == 0) &&
                 hasPseudoHeaderFormat(name)) {
             PlatformDependent.throwException(connectionError(
                     PROTOCOL_ERROR, "HTTP/2 pseudo-header '%s' must not be empty.", name));
         }
     }
 
     @Override
     public Http2Headers clear() {
         firstNonPseudo = head;
         return super.clear();
     }
 
     @Override
     public boolean equals(Object o) {
         return o instanceof Http2Headers && equals((Http2Headers) o, CASE_SENSITIVE_HASHER);
     }
 
     @Override
     public int hashCode() {
         return hashCode(CASE_SENSITIVE_HASHER);
     }
 
     @Override
     public Http2Headers method(CharSequence value) {
         set(PseudoHeaderName.METHOD.value(), value);
         return this;
     }
 
     @Override
     public Http2Headers scheme(CharSequence value) {
         set(PseudoHeaderName.SCHEME.value(), value);
         return this;
     }
 
     @Override
     public Http2Headers authority(CharSequence value) {
         set(PseudoHeaderName.AUTHORITY.value(), value);
         return this;
     }
 
     @Override
     public Http2Headers path(CharSequence value) {
         set(PseudoHeaderName.PATH.value(), value);
         return this;
     }
 
     @Override
     public Http2Headers status(CharSequence value) {
         set(PseudoHeaderName.STATUS.value(), value);
         return this;
     }
 
     @Override
     public CharSequence method() {
         return get(PseudoHeaderName.METHOD.value());
     }
 
     @Override
     public CharSequence scheme() {
         return get(PseudoHeaderName.SCHEME.value());
     }
 
     @Override
     public CharSequence authority() {
         return get(PseudoHeaderName.AUTHORITY.value());
     }
 
     @Override
     public CharSequence path() {
         return get(PseudoHeaderName.PATH.value());
     }
 
     @Override
     public CharSequence status() {
         return get(PseudoHeaderName.STATUS.value());
     }
 
     @Override
     public boolean contains(CharSequence name, CharSequence value) {
         return contains(name, value, false);
     }
 
     @Override
     public boolean contains(CharSequence name, CharSequence value, boolean caseInsensitive) {
         return contains(name, value, caseInsensitive ? CASE_INSENSITIVE_HASHER : CASE_SENSITIVE_HASHER);
     }
 
     @Override
     protected final HeaderEntry<CharSequence, CharSequence> newHeaderEntry(int h, CharSequence name, CharSequence value,
                                                            HeaderEntry<CharSequence, CharSequence> next) {
         return new Http2HeaderEntry(h, name, value, next);
     }
 
     private final class Http2HeaderEntry extends HeaderEntry<CharSequence, CharSequence> {
         Http2HeaderEntry(int hash, CharSequence key, CharSequence value,
                 HeaderEntry<CharSequence, CharSequence> next) {
             super(hash, key);
             this.value = value;
             this.next = next;
 
             // Make sure the pseudo headers fields are first in iteration order
             if (hasPseudoHeaderFormat(key)) {
                 after = firstNonPseudo;
                 before = firstNonPseudo.before();
             } else {
                 after = head;
                 before = head.before();
                 if (firstNonPseudo == head) {
                     firstNonPseudo = this;
                 }
             }
             pointNeighborsToThis();
         }
 
         @Override
         protected void remove() {
             if (this == firstNonPseudo) {
                 firstNonPseudo = firstNonPseudo.after();
             }
             super.remove();
         }
     }
 }