//
// Copyright (C) 2015 The Android Open Source Project
//
// 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.
//

#ifndef DHCP_CLIENT_DHCP_MESSAGE_H_
#define DHCP_CLIENT_DHCP_MESSAGE_H_

#include <map>
#include <memory>
#include <set>
#include <string>
#include <vector>

#include <base/macros.h>
#include <shill/net/byte_string.h>

#include "dhcp_client/dhcp_options_parser.h"

namespace dhcp_client {

static const uint8_t kDHCPMessageTypeDiscover = 1;
static const uint8_t kDHCPMessageTypeOffer = 2;
static const uint8_t kDHCPMessageTypeRequest = 3;
static const uint8_t kDHCPMessageTypeDecline = 4;
static const uint8_t kDHCPMessageTypeAck = 5;
static const uint8_t kDHCPMessageTypeNak = 6;
static const uint8_t kDHCPMessageTypeRelease = 7;
static const uint8_t kDHCPMessageTypeInform = 8;

typedef std::unique_ptr<DHCPOptionsParser> ParserPtr;

struct ParserContext{
  ParserPtr parser;
  void* output;
  ParserContext(DHCPOptionsParser* parser_ptr, void* output_ptr)
      : parser(parser_ptr),
        output(output_ptr) {}
};

class DHCPMessage {
 public:
  DHCPMessage();
  ~DHCPMessage();
  // Initialize the data fields from a buffer with existing DHCP message.
  // This is used for inbound DHCP message.
  static bool InitFromBuffer(const unsigned char* buffer,
                             size_t length,
                             DHCPMessage* message);
  static DHCPMessage InitRequest();
  static uint16_t ComputeChecksum(const uint8_t* data, size_t len);
  // Initialize part of the data fields for outbound DHCP message.
  // Serialize the message to a buffer
  bool Serialize(shill::ByteString* data) const;

  // DHCP option and field setters
  void SetClientHardwareAddress(
      const shill::ByteString& client_hardware_address);
  void SetClientIdentifier(const shill::ByteString& client_identifier);
  void SetClientIPAddress(uint32_t client_ip_address);
  void SetErrorMessage(const std::string& error_message);
  void SetLeaseTime(uint32_t lease_time);
  void SetMessageType(uint8_t message_type);
  void SetParameterRequestList(
      const std::vector<uint8_t>& parameter_request_list);
  void SetRequestedIpAddress(uint32_t requested_ip_address);
  void SetServerIdentifier(uint32_t server_identifier);
  void SetTransactionID(uint32_t transaction_id);
  void SetVendorSpecificInfo(const shill::ByteString& vendor_specific_info);

  // DHCP option and field getters
  const shill::ByteString& client_hardware_address() const {
    return client_hardware_address_;
  }
  const shill::ByteString& client_identifier() const {
    return client_identifier_;
  }
  uint32_t client_ip_address() const { return client_ip_address_; }
  const std::vector<uint32_t>& dns_server() const { return dns_server_; }
  const std::string& domain_name() const { return domain_name_; }
  const std::string& error_message() const { return error_message_; }
  uint32_t lease_time() const { return lease_time_; }
  uint8_t message_type() const { return message_type_; }
  uint32_t rebinding_time() const { return rebinding_time_; }
  uint32_t renewal_time() const { return renewal_time_; }
  const std::vector<uint32_t>& router() const { return router_; }
  uint32_t server_identifier() const { return server_identifier_; }
  uint32_t subnet_mask() const { return subnet_mask_; }
  uint32_t transaction_id() const { return transaction_id_; }
  const shill::ByteString& vendor_specific_info() const {
    return vendor_specific_info_;
  }
  uint32_t your_ip_address() const { return your_ip_address_; }

 private:
  bool ParseDHCPOptions(const uint8_t* options, size_t options_length);
  bool IsValid();
  bool ContainsValidOptions(const std::set<uint8_t>& options_set);

  // Message type: request or reply.
  uint8_t opcode_;
  // Hardware address type.
  uint8_t hardware_address_type_;
  // Hardware address length.
  uint8_t hardware_address_length_;
  // Client sets to zero, optionally used by relay agents
  // when booting via a relay agent.
  uint8_t relay_hops_;
  // Transaction id.
  uint32_t transaction_id_;
  // Elapsed time from boot in seconds.
  uint16_t seconds_;
  // Broadcast flag
  uint16_t flags_;
  // Previously allocated client IP.
  uint32_t client_ip_address_;
  // Client IP address.
  uint32_t your_ip_address_;
  // IP address of next server to use in bootstrap;
  // returned in DHCPOFFER, DHCPACK by server.
  // It should be zero in client's messages.
  uint32_t next_server_ip_address_;
  // Relay agent IP address, used in booting via a relay agent.
  // It should be zero in client's messages.
  uint32_t agent_ip_address_;
  // Client's hardware address.
  shill::ByteString client_hardware_address_;
  // Server host name.
  std::string servername_;
  // Boot file name.
  std::string bootfile_;
  uint32_t cookie_;

  // A map from DHCP Options number to corresponding callbacks.
  std::map<uint8_t, ParserContext> options_map_;

  // Fields for DHCP Options.
  // Option 1: Subnet Mask.
  uint32_t subnet_mask_;
  // Option 3: Router(Default Gateway).
  std::vector<uint32_t> router_;
  // Option 6: Domain Name Server.
  std::vector<uint32_t> dns_server_;
  // Option 15: Domain Name.
  std::string domain_name_;
  // Option 43: Vendor Specific Information.
  shill::ByteString vendor_specific_info_;
  // Option 50: Requested IP Address.
  uint32_t requested_ip_address_;
  // Option 51: IP address lease time in unit of seconds.
  uint32_t lease_time_;
  // Option 53: DHCP message type.
  uint8_t message_type_;
  // Option 54: Server Identifier.
  uint32_t server_identifier_;
  // Option 55: Parameter Request List.
  std::vector<uint8_t> parameter_request_list_;
  // Option 56: (Error) Message.
  std::string error_message_;
  // Option 58: Renewal time value in unit of seconds.
  uint32_t renewal_time_;
  // Option 59: Rebinding time value in unit of seconds.
  uint32_t rebinding_time_;
  // Option 61: Client identifier.
  shill::ByteString client_identifier_;

  DISALLOW_COPY_AND_ASSIGN(DHCPMessage);
};

}  // namespace dhcp_client

#endif  // DHCP_CLIENT_DHCP_MESSAGE_H_