#
# Copyright (c) 2004-2014 David R. Halliday
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
#

require 'snmp/pdu'
require 'snmp/mib'
require 'snmp/options'
require 'socket'
require 'timeout'
require 'thread'

module SNMP

  class RequestTimeout < RuntimeError;
  end

  ##
  # Wrap socket so that it can be easily substituted for testing or for
  # using other transport types (e.g. TCP)
  #
  class UDPTransport
    def initialize(address_family)
      @socket = UDPSocket.open(address_family)
    end

    def close
      @socket.close
    end

    def send(data, host, port)
      @socket.send(data, 0, host, port)
    end

    def recv(max_bytes)
      @socket.recv(max_bytes)
    end
  end

  ##
  # Manage a request-id in the range 1..2**31-1
  #
  class RequestId
    MAX_REQUEST_ID = 2**31

    def initialize
      @lock = Mutex.new
      @request_id = rand(MAX_REQUEST_ID)
    end

    def next
      @lock.synchronize do
        @request_id += 1
        @request_id = 1 if @request_id == MAX_REQUEST_ID
        return @request_id
      end
    end

    def force_next(next_id)
      new_request_id = next_id.to_i
      if new_request_id < 1 || new_request_id >= MAX_REQUEST_ID
        raise "Invalid request id: #{new_request_id}"
      end
      new_request_id = MAX_REQUEST_ID if new_request_id == 1
      @lock.synchronize do
        @request_id = new_request_id - 1
      end
    end
  end


  ##
  # This class provides a manager for interacting with a single SNMP agent.
  #
  # == Example
  #
  #    require 'snmp'
  #
  #    manager = SNMP::Manager.new(:host => 'localhost', :port => 1061)
  #    response = manager.get(["1.3.6.1.2.1.1.1.0", "1.3.6.1.2.1.1.2.0"])
  #    response.each_varbind {|vb| puts vb.inspect}
  #    manager.close
  #
  # == Symbolic Object Names
  #
  # Symbolic names for SNMP object IDs can be used as parameters to the
  # APIs in this class if the MIB modules are imported and the names of the
  # MIBs are included in the MibModules configuration parameter.
  #
  # See MIB.varbind_list for a description of valid parameter formats.
  #
  # The following modules are loaded by default: "SNMPv2-SMI", "SNMPv2-MIB",
  # "IF-MIB", "IP-MIB", "TCP-MIB", "UDP-MIB".  All of the current IETF MIBs
  # have been imported and are available for loading.
  #
  # Additional modules may be imported using the MIB class.  The
  # current implementation of the importing code requires that the
  # external 'smidump' tool is available in your PATH. This tool can be
  # obtained from the libsmi website at
  # http://www.ibr.cs.tu-bs.de/projects/libsmi/ .
  #
  # == Example
  #
  # Do this once:
  #
  #   SNMP::MIB.import_module(MY_MODULE_FILENAME, MIB_OUTPUT_DIR)
  #
  # Include your module in MibModules each time you create a Manager:
  #
  #   SNMP::Manager.new(:host => 'localhost', :mib_dir => MIB_OUTPUT_DIR,
  #                     :mib_modules => ["MY-MODULE-MIB", "SNMPv2-MIB", ...])
  #

  class Manager

    class Config < Options
      option :host, :Host, 'localhost'
      option :port, :Port, 161
      option :trap_port, :TrapPort, 162
      option :community, :Community, 'public'
      option :write_community, :WriteCommunity, lambda { |c| c.community }
      option :version, :Version, :SNMPv2c
      option :timeout, :Timeout, 1
      option :retries, :Retries, 5
      option :transport, :Transport, UDPTransport
      option :max_recv_bytes, :MaxReceiveBytes, 8000
      option :mib_dir, :MibDir, MIB::DEFAULT_MIB_PATH
      option :mib_modules, :MibModules, default_modules
      option :use_IPv6, :use_IPv6, lambda { |c| ipv6_address?(c) }

      def create_transport
        transport.respond_to?(:new) ? transport.new(socket_address_family) : transport
      end
    end

    @@request_id = RequestId.new

    ##
    # Retrieves the current configuration of this Manager.
    #
    attr_reader :config

    ##
    # Retrieves the MIB for this Manager.
    #
    attr_reader :mib

    ##
    # Creates a Manager. The following are valid options and their default values.
    #
    # <b>Note: The upper-case options supported in previous versions of this library are
    # deprecated, but still supported for now.  Use at your own risk.</b>
    #
    #   Option              Default Value
    #   --------------------------------------
    #   :host               'localhost'
    #   :port               161
    #   :trap_port          162
    #   :community          'public'
    #   :write_community    Same as :community
    #   :version            :SNMPv2c
    #   :timeout            1 (timeout units are seconds)
    #   :retries            5
    #   :transport          UDPTransport
    #   :max_recv_bytes     8000 bytes
    #   :mib_dir            MIB::DEFAULT_MIB_PATH
    #   :mib_modules        SNMPv2-SMI, SNMPv2-MIB, IF-MIB, IP-MIB, TCP-MIB, UDP-MIB
    #   :use_IPv6           false, unless :host is formatted like an IPv6 address
    #
    # Use {:version => :SNMPv1} for SNMP v1.  SNMP v3 is not supported.
    #
    def initialize(options = {})
      if block_given?
        warn "SNMP::Manager.new() does not take block; use SNMP::Manager.open() instead"
      end
      config = Config.new(options)
      @host = config.host
      @port = config.port
      @trap_port = config.trap_port
      @community = config.community
      @write_community = config.write_community
      @snmp_version = config.version
      @timeout = config.timeout
      @retries = config.retries
      @transport = config.create_transport
      @max_bytes = config.max_recv_bytes
      @mib = MIB.new
      load_modules(config.mib_modules, config.mib_dir)
      @config = config.applied_config
    end

    ##
    # Creates a Manager but also takes an optional block and automatically
    # closes the transport connection used by this manager after the block
    # completes.
    #
    def self.open(config = {})
      manager = Manager.new(config)
      if block_given?
        begin
          yield manager
        ensure
          manager.close
        end
      end
    end

    ##
    # Close the transport connection for this manager.
    #
    def close
      @transport.close
    end

    def load_module(name)
      @mib.load_module(name)
    end

    ##
    # Sends a get request for the supplied list of ObjectId or VarBind
    # objects.
    #
    # Returns a Response PDU with the results of the request.
    #
    def get(object_list)
      varbind_list = @mib.varbind_list(object_list, :NullValue)
      request = GetRequest.new(@@request_id.next, varbind_list)
      try_request(request)
    end

    ##
    # Sends a get request for the supplied list of ObjectId or VarBind
    # objects.
    #
    # Returns a list of the varbind values only, not the entire response,
    # in the same order as the initial object_list.  This method is
    # useful for retrieving scalar values.
    #
    # For example:
    #
    #   SNMP::Manager.open(:host => "localhost") do |manager|
    #     puts manager.get_value("sysDescr.0")
    #   end
    #
    def get_value(object_list)
      if object_list.respond_to? :to_ary
        get(object_list).vb_list.collect { |vb| vb.value }
      else
        get(object_list).vb_list.first.value
      end
    end

    ##
    # Sends a get-next request for the supplied list of ObjectId or VarBind
    # objects.
    #
    # Returns a Response PDU with the results of the request.
    #
    def get_next(object_list)
      varbind_list = @mib.varbind_list(object_list, :NullValue)
      request = GetNextRequest.new(@@request_id.next, varbind_list)
      try_request(request)
    end

    ##
    # Sends a get-bulk request.  The non_repeaters parameter specifies
    # the number of objects in the object_list to be retrieved once.  The
    # remaining objects in the list will be retrieved up to the number of
    # times specified by max_repetitions.
    #
    def get_bulk(non_repeaters, max_repetitions, object_list)
      varbind_list = @mib.varbind_list(object_list, :NullValue)
      request = GetBulkRequest.new(
          @@request_id.next,
          varbind_list,
          non_repeaters,
          max_repetitions)
      try_request(request)
    end

    ##
    # Sends a set request using the supplied list of VarBind objects.
    #
    # Returns a Response PDU with the results of the request.
    #
    def set(object_list)
      varbind_list = @mib.varbind_list(object_list, :KeepValue)
      request = SetRequest.new(@@request_id.next, varbind_list)
      try_request(request, @write_community)
    end

    ##
    # Sends an SNMPv1 style trap.
    #
    # enterprise: The enterprise OID from the IANA assigned numbers
    # (http://www.iana.org/assignments/enterprise-numbers) as a String or
    # an ObjectId.
    #
    # agent_addr: The IP address of the SNMP agent as a String or IpAddress.
    #
    # generic_trap: The generic trap identifier.  One of :coldStart,
    # :warmStart, :linkDown, :linkUp, :authenticationFailure,
    # :egpNeighborLoss, or :enterpriseSpecific
    #
    # specific_trap: An integer representing the specific trap type for
    # an enterprise-specific trap.
    #
    # timestamp: An integer respresenting the number of hundredths of
    # a second that this system has been up.
    #
    # object_list: A list of additional varbinds to send with the trap.
    #
    # For example:
    #
    #   Manager.open(:Version => :SNMPv1) do |snmp|
    #     snmp.trap_v1(
    #       "enterprises.9",
    #       "10.1.2.3",
    #       :enterpriseSpecific,
    #        42,
    #       12345,
    #       [VarBind.new("1.3.6.1.2.3.4", Integer.new(1))])
    #  end
    #
    def trap_v1(enterprise, agent_addr, generic_trap, specific_trap, timestamp, object_list=[])
      vb_list = @mib.varbind_list(object_list, :KeepValue)
      ent_oid = @mib.oid(enterprise)
      agent_ip = IpAddress.new(agent_addr)
      specific_int = Integer(specific_trap)
      ticks = TimeTicks.new(timestamp)
      trap = SNMPv1_Trap.new(ent_oid, agent_ip, generic_trap, specific_int, ticks, vb_list)
      send_request(trap, @community, @host, @trap_port)
    end

    ##
    # Sends an SNMPv2c style trap.
    #
    # sys_up_time: An integer respresenting the number of hundredths of
    # a second that this system has been up.
    #
    # trap_oid: An ObjectId or String with the OID identifier for this
    # trap.
    #
    # object_list: A list of additional varbinds to send with the trap.
    #
    def trap_v2(sys_up_time, trap_oid, object_list=[])
      vb_list = create_trap_vb_list(sys_up_time, trap_oid, object_list)
      trap = SNMPv2_Trap.new(@@request_id.next, vb_list)
      send_request(trap, @community, @host, @trap_port)
    end

    ##
    # Sends an inform request using the supplied varbind list.
    #
    # sys_up_time: An integer respresenting the number of hundredths of
    # a second that this system has been up.
    #
    # trap_oid: An ObjectId or String with the OID identifier for this
    # inform request.
    #
    # object_list: A list of additional varbinds to send with the inform.
    #
    def inform(sys_up_time, trap_oid, object_list=[])
      vb_list = create_trap_vb_list(sys_up_time, trap_oid, object_list)
      request = InformRequest.new(@@request_id.next, vb_list)
      try_request(request, @community, @host, @trap_port)
    end

    ##
    # Helper method for building VarBindList for trap and inform requests.
    #
    def create_trap_vb_list(sys_up_time, trap_oid, object_list)
      vb_args = @mib.varbind_list(object_list, :KeepValue)
      uptime_vb = VarBind.new(SNMP::SYS_UP_TIME_OID, TimeTicks.new(sys_up_time.to_int))
      trap_vb = VarBind.new(SNMP::SNMP_TRAP_OID_OID, @mib.oid(trap_oid))
      VarBindList.new([uptime_vb, trap_vb, *vb_args])
    end

    ##
    # Walks a list of ObjectId or VarBind objects using get_next until
    # the response to the first OID in the list reaches the end of its
    # MIB subtree.
    #
    # The varbinds from each get_next are yielded to the given block as
    # they are retrieved.  The result is yielded as a VarBind when walking
    # a single object or as a VarBindList when walking a list of objects.
    #
    # Normally this method is used for walking tables by providing an
    # ObjectId for each column of the table.
    #
    # For example:
    #
    #   SNMP::Manager.open(:host => "localhost") do |manager|
    #     manager.walk("ifTable") { |vb| puts vb }
    #   end
    #
    #   SNMP::Manager.open(:host => "localhost") do |manager|
    #     manager.walk(["ifIndex", "ifDescr"]) do |index, descr|
    #       puts "#{index.value} #{descr.value}"
    #     end
    #   end
    #
    # The index_column identifies the column that will provide the index
    # for each row.  This information is used to deal with "holes" in a
    # table (when a row is missing a varbind for one column).  A missing
    # varbind is replaced with a varbind with the value NoSuchInstance.
    #
    # Note: If you are getting back rows where all columns have a value of
    # NoSuchInstance then your index column is probably missing one of the
    # rows.  Choose an index column that includes all indexes for the table.
    #
    def walk(object_list, index_column=0)
      raise ArgumentError, "expected a block to be given" unless block_given?
      vb_list = @mib.varbind_list(object_list, :NullValue)
      raise ArgumentError, "index_column is past end of varbind list" if index_column >= vb_list.length
      is_single_vb = object_list.respond_to?(:to_str) ||
          object_list.respond_to?(:to_varbind)
      start_list = vb_list
      start_oid = vb_list[index_column].name
      last_oid = start_oid
      loop do
        vb_list = get_next(vb_list).vb_list
        index_vb = vb_list[index_column]
        break if EndOfMibView == index_vb.value
        stop_oid = index_vb.name
        if stop_oid <= last_oid
          warn "OIDs are not increasing, #{last_oid} followed by #{stop_oid}"
          break
        end
        break unless stop_oid.subtree_of?(start_oid)
        last_oid = stop_oid
        if is_single_vb
          yield index_vb
        else
          vb_list = validate_row(vb_list, start_list, index_column)
          yield vb_list
        end
      end
    end

    ##
    # Helper method for walk.  Checks all of the VarBinds in vb_list to
    # make sure that the row indices match.  If the row index does not
    # match the index column, then that varbind is replaced with a varbind
    # with a value of NoSuchInstance.
    #
    def validate_row(vb_list, start_list, index_column)
      start_vb = start_list[index_column]
      index_vb = vb_list[index_column]
      row_index = index_vb.name.index(start_vb.name)
      vb_list.each_index do |i|
        if i != index_column
          expected_oid = start_list[i].name + row_index
          if vb_list[i].name != expected_oid
            vb_list[i] = VarBind.new(expected_oid, NoSuchInstance).with_mib(@mib)
          end
        end
      end
      vb_list
    end

    private :validate_row

    ##
    # Set the next request-id instead of letting it be generated
    # automatically. This method is useful for testing and debugging.
    #
    def next_request_id=(request_id)
      @@request_id.force_next(request_id)
    end

    def load_modules(module_list, mib_dir)
      module_list.each { |m| @mib.load_module(m, mib_dir) }
    end

    private

    def warn(message)
      trace = caller(2)
      location = trace[0].sub(/:in.*/, '')
      Kernel::warn "#{location}: warning: #{message}"
    end

    def try_request(request, community=@community, host=@host, port=@port)
      (@retries + 1).times do |n|
        send_request(request, community, host, port)
        begin
          Timeout.timeout(@timeout) do
            return get_response(request)
          end
        rescue Timeout::Error
          # no action - try again
        rescue => e
          warn e.to_s
        end
      end
      raise RequestTimeout, "host #{config[:host]} not responding", caller
    end

    def send_request(request, community, host, port)
      message = Message.new(@snmp_version, community, request)
      @transport.send(message.encode, host, port)
    end

    ##
    # Wait until response arrives.  Ignore responses with mismatched IDs;
    # these responses are typically from previous requests that timed out
    # or almost timed out.
    #
    def get_response(request)
      begin
        data = @transport.recv(@max_bytes)
        message = Message.decode(data, @mib)
        response = message.pdu
      end until request.request_id == response.request_id
      response
    end
  end

  class UDPServerTransport
    def initialize(host, port, address_family)
      @socket = UDPSocket.open(address_family)
      @socket.bind(host, port)
    end

    def close
      @socket.close
    end

    def send(data, host, port)
      @socket.send(data, 0, host, port)
    end

    def recvfrom(max_bytes)
      data, host_info = @socket.recvfrom(max_bytes)
      _, host_port, _, host_ip = host_info
      return data, host_ip, host_port
    end
  end

  ##
  # == SNMP Trap Listener
  #
  # Listens to a socket and processes received traps and informs in a separate
  # thread.
  #
  # === Example
  #
  #   require 'snmp'
  #
  #   m = SNMP::TrapListener.new(:Port => 1062, :Community => 'public') do |manager|
  #     manager.on_trap_default { |trap| p trap }
  #   end
  #   m.join
  #
  class TrapListener
    class Config < Options
      option :host, :Host, 'localhost'
      option :port, :Port, 162
      option :community, :Community, nil
      option :server_transport, :ServerTransport, UDPServerTransport
      option :max_recv_bytes, :MaxReceiveBytes, 8000
      option :mib_dir, :MibDir, MIB::DEFAULT_MIB_PATH
      option :mib_modules, :MibModules, default_modules
      option :use_IPv6, :use_IPv6, false

      def create_transport
        server_transport.respond_to?(:new) ?
            server_transport.new(host, port, socket_address_family) : server_transport
      end
    end

    NULL_HANDLER = Proc.new {}

    ##
    # Retrieves the current configuration of this TrapListener.
    #
    attr_reader :config

    ##
    # Start a trap handler thread.  If a block is provided then the block
    # is executed before trap handling begins.  This block is typically used
    # to define the trap handler blocks.
    #
    # The trap handler blocks execute in the context of the trap handler thread.
    #
    # The most specific trap handler is executed when a trap arrives.  Only one
    # handler is executed.  The handlers are checked in the following order:
    #
    # 1. handler for a specific OID
    # 2. handler for a specific SNMP version
    # 3. default handler
    #
    # The default for the :community option is 'nil' allows traps with any
    # community to be accepted. To only accept traps from a specific community,
    # the community may also be set to a string (e.g. 'public') or a list of
    # strings (e.g. ['public', 'my_private_community'] ).
    #
    def initialize(options={}, &block)
      config = Config.new(options)
      @transport = config.create_transport
      @community = config.community
      @max_bytes = config.max_recv_bytes
      @mib = MIB.new
      load_modules(config.mib_modules, config.mib_dir)
      @config = config.applied_config

      @handler_init = block
      @oid_handler = {}
      @v1_handler = nil
      @v2c_handler = nil
      @default_handler = nil
      @lock = Mutex.new
      @handler_thread = Thread.new(self) { |m| process_traps(m) }
    end

    ##
    # Define the default trap handler.  The default trap handler block is
    # executed only if no other block is applicable.  This handler should
    # expect to receive both SNMPv1_Trap and SNMPv2_Trap objects.
    #
    def on_trap_default(&block)
      raise ArgumentError, "a block must be provided" unless block
      @lock.synchronize { @default_handler = block }
    end

    ##
    # Define a trap handler block for a specific trap ObjectId.  This handler
    # only applies to SNMPv2 traps.  Note that symbolic OIDs are not
    # supported by this method (like in the SNMP.Manager class).
    #
    def on_trap(object_id, &block)
      raise ArgumentError, "a block must be provided" unless block
      @lock.synchronize { @oid_handler[ObjectId.new(object_id)] = block }
    end

    ##
    # Define a trap handler block for all SNMPv1 traps.  The trap yielded
    # to the block will always be an SNMPv1_Trap.
    #
    def on_trap_v1(&block)
      raise ArgumentError, "a block must be provided" unless block
      @lock.synchronize { @v1_handler = block }
    end

    ##
    # Define a trap handler block for all SNMPv2c traps.  The trap yielded
    # to the block will always be an SNMPv2_Trap.  Note that InformRequest
    # is a subclass of SNMPv2_Trap, so inform PDUs are also received by
    # this handler.
    #
    def on_trap_v2c(&block)
      raise ArgumentError, "a block must be provided" unless block
      @lock.synchronize { @v2c_handler = block }
    end

    ##
    # Joins the current thread to the trap handler thread.
    #
    # See also Thread#join.
    #
    def join
      @handler_thread.join
    end

    ##
    # Stops the trap handler thread and releases the socket.
    #
    # See also Thread#exit.
    #
    def exit
      @handler_thread.exit
      @transport.close
    end

    alias kill exit
    alias terminate exit

    private

    def load_modules(module_list, mib_dir)
      module_list.each { |m| @mib.load_module(m, mib_dir) }
    end

    def process_traps(trap_listener)
      @handler_init.call(trap_listener) if @handler_init
      loop do
        data, source_ip, source_port = @transport.recvfrom(@max_bytes)
        begin
          message = Message.decode(data, @mib)
          if community_allowed? message.community
            trap = message.pdu
            if trap.kind_of?(InformRequest)
              @transport.send(message.response.encode, source_ip, source_port)
            end
            trap.source_ip = source_ip
            select_handler(trap).call(trap)
          end
        rescue => e
          puts "Error handling trap: #{e}"
          puts e.backtrace.join("\n")
          puts "Received data:"
          p data
        end
      end
    end

    def community_allowed?(msg_community)
      @community.nil? || @community == msg_community || !(Array(@community) & Array(msg_community)).empty?
    end

    def select_handler(trap)
      @lock.synchronize do
        if trap.kind_of?(SNMPv2_Trap)
          oid = trap.trap_oid
          if @oid_handler[oid]
            return @oid_handler[oid]
          elsif @v2c_handler
            return @v2c_handler
          elsif @default_handler
            return @default_handler
          else
            return NULL_HANDLER
          end
        elsif trap.kind_of?(SNMPv1_Trap)
          if @v1_handler
            return @v1_handler
          elsif @default_handler
            return @default_handler
          else
            return NULL_HANDLER
          end
        else
          return NULL_HANDLER
        end
      end
    end
  end

end
