/*
 *
 * Copyright 2016 gRPC authors.
 *
 * Licensed 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.
 *
 */

#include <stdlib.h>
#include <string.h>

#include <grpc/grpc.h>
#include <grpc/support/alloc.h>
#include <grpc/support/port_platform.h>

#include "src/core/lib/iomgr/error.h"
#include "src/core/lib/slice/slice_internal.h"
#include "src/core/lib/slice/slice_string_helpers.h"
#include "src/core/lib/surface/validate_metadata.h"

static grpc_error* conforms_to(grpc_slice slice, const uint8_t* legal_bits,
                               const char* err_desc) {
  const uint8_t* p = GRPC_SLICE_START_PTR(slice);
  const uint8_t* e = GRPC_SLICE_END_PTR(slice);
  for (; p != e; p++) {
    int idx = *p;
    int byte = idx / 8;
    int bit = idx % 8;
    if ((legal_bits[byte] & (1 << bit)) == 0) {
      char* dump = grpc_dump_slice(slice, GPR_DUMP_HEX | GPR_DUMP_ASCII);
      grpc_error* error = grpc_error_set_str(
          grpc_error_set_int(GRPC_ERROR_CREATE_FROM_COPIED_STRING(err_desc),
                             GRPC_ERROR_INT_OFFSET,
                             p - GRPC_SLICE_START_PTR(slice)),
          GRPC_ERROR_STR_RAW_BYTES, grpc_slice_from_copied_string(dump));
      gpr_free(dump);
      return error;
    }
  }
  return GRPC_ERROR_NONE;
}

static int error2int(grpc_error* error) {
  int r = (error == GRPC_ERROR_NONE);
  GRPC_ERROR_UNREF(error);
  return r;
}

grpc_error* grpc_validate_header_key_is_legal(grpc_slice slice) {
  static const uint8_t legal_header_bits[256 / 8] = {
      0x00, 0x00, 0x00, 0x00, 0x00, 0x60, 0xff, 0x03, 0x00, 0x00, 0x00,
      0x80, 0xfe, 0xff, 0xff, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
  if (GRPC_SLICE_LENGTH(slice) == 0) {
    return GRPC_ERROR_CREATE_FROM_STATIC_STRING(
        "Metadata keys cannot be zero length");
  }
  if (GRPC_SLICE_START_PTR(slice)[0] == ':') {
    return GRPC_ERROR_CREATE_FROM_STATIC_STRING(
        "Metadata keys cannot start with :");
  }
  return conforms_to(slice, legal_header_bits, "Illegal header key");
}

int grpc_header_key_is_legal(grpc_slice slice) {
  return error2int(grpc_validate_header_key_is_legal(slice));
}

grpc_error* grpc_validate_header_nonbin_value_is_legal(grpc_slice slice) {
  static const uint8_t legal_header_bits[256 / 8] = {
      0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
      0xff, 0xff, 0xff, 0xff, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
  return conforms_to(slice, legal_header_bits, "Illegal header value");
}

int grpc_header_nonbin_value_is_legal(grpc_slice slice) {
  return error2int(grpc_validate_header_nonbin_value_is_legal(slice));
}

int grpc_is_binary_header(grpc_slice slice) {
  if (GRPC_SLICE_LENGTH(slice) < 5) return 0;
  return 0 == memcmp(GRPC_SLICE_END_PTR(slice) - 4, "-bin", 4);
}