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#
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# Copyright (c) 2004 David R. Halliday
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# All rights reserved.
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#
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# This SNMP library is free software.  Redistribution is permitted under the
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# same terms and conditions as the standard Ruby distribution.  See the
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# COPYING file in the Ruby distribution for details.
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#
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require 'snmp/varbind'
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require 'fileutils'
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require 'yaml'
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module SNMP
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class MIB
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    DEFAULT_MIB_PATH = File.expand_path(
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        File.join(File.dirname(__FILE__), "..", "..", "data", "snmp", "mibs")
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    )
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    #:startdoc:
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    MODULE_EXT = 'yaml'
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    class ModuleNotLoadedError < RuntimeError; end
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    class << self
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        ##
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        # Import an SMIv2 MIB file for later loading.  A module only needs to
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        # be installed once.
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        #
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        #   module_file - the filename of the module to be imported
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        #   mib_dir - the output directory for the serialized MIB data
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        #
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        # NOTE: This implementation requires that the 'smidump' tool is available
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        # in the PATH.  This tool can be obtained from the libsmi website at
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        # http://http://www.ibr.cs.tu-bs.de/projects/libsmi/ .
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        #
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        # ALSO NOTE: The file format in future releases is subject to
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        # change.  For now, it is a simple YAML hash with the MIB symbol
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        # as the key and the OID as the value.  These files could be
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        # generated manually if 'smidump' is not available.
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        #
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        # Here is an example of the contents of an output file:
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        #
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        #   --- 
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        #   ipDefaultTTL: 1.3.6.1.2.1.4.2
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        #   ipForwDatagrams: 1.3.6.1.2.1.4.6
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        #   ipOutRequests: 1.3.6.1.2.1.4.10
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        #   ipOutNoRoutes: 1.3.6.1.2.1.4.12
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        #   ipReasmTimeout: 1.3.6.1.2.1.4.13
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        #   icmpInDestUnreachs: 1.3.6.1.2.1.5.3
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        #
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        def import_module(module_file, mib_dir=DEFAULT_MIB_PATH)
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            raise "smidump tool must be installed" unless import_supported?
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            FileUtils.makedirs mib_dir
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            mib_hash = `smidump -f python #{module_file}`
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            mib = eval_mib_data(mib_hash)
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            if mib
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                module_name = mib["moduleName"]
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                raise "#{module_file}: invalid file format; no module name" unless module_name
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                if mib["nodes"]
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                    oid_hash = {}
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                    mib["nodes"].each { |key, value| oid_hash[key] = value["oid"] }
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                    if mib["notifications"]
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                        mib["notifications"].each { |key, value| oid_hash[key] = value["oid"] }
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                    end
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                    File.open(module_file_name(module_name, mib_dir), 'w') do |file|
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                        YAML.dump(oid_hash, file)
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                        file.puts
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                    end
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                    module_name
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                else
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                    warn "*** No nodes defined in: #{module_file} ***"
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                    nil
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                end
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            else
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                warn "*** Import failed for: #{module_file} ***"
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                nil
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            end
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        end
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        ##
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        # Returns the full filename of the imported MIB file for the given
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        # module name.
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        #
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        def module_file_name(module_name, mib_dir=DEFAULT_MIB_PATH)
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            File.join(mib_dir, module_name + "." + MODULE_EXT)
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        end
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        ##
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        # The MIB.import_module method is only supported if the external
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        # 'smidump' tool is available.  This method returns true if a
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        # known version of the tool is available.
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        #
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        def import_supported?
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            `smidump --version` =~ /^smidump 0.4/  && $? == 0 
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        end
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        ##
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        # Returns a list of MIB modules that have been imported.  All of
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        # the current IETF MIBs should be available from the default
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        # MIB directory. 
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        #
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        # If a regex is provided, then the module names are matched
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        # against that pattern.
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        #
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        def list_imported(regex=//, mib_dir=DEFAULT_MIB_PATH)
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            list = []
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            Dir["#{mib_dir}/*.#{MODULE_EXT}"].each do |name|
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                module_name = File.basename(name, ".*")
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                list << module_name if module_name =~ regex
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            end
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            list
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        end
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        private 
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        def eval_mib_data(mib_hash)
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            ruby_hash = mib_hash.
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                gsub(':', '=>').                  # fix hash syntax
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                gsub('(', '[').gsub(')', ']').    # fix tuple syntax
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                sub('FILENAME =', 'filename =').  # get rid of constants
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                sub('MIB =', 'mib =')
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            mib = nil
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            eval(ruby_hash)
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            mib
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        end
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    end # class methods
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    def initialize
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        @by_name = {}
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        @by_module_by_name = {}
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    end
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    ##
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    # Loads a module into this MIB.  The module must be imported before it
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    # can be loaded.  See MIB.import_module .
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    #
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    def load_module(module_name, mib_dir=DEFAULT_MIB_PATH)
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        oid_hash = nil
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        File.open(MIB.module_file_name(module_name, mib_dir)) do |file|
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            oid_hash = YAML.load(file.read)
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        end
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        @by_name.merge!(oid_hash) do |key, old, value|
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            warn "warning: overwriting old MIB name '#{key}'"
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        end
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        @by_module_by_name[module_name] = {}
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        @by_module_by_name[module_name].merge!(oid_hash)
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    end
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    ##
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    # Returns a VarBindList for the provided list of objects.  If a
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    # string is provided it is interpreted as a symbolic OID.
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    #
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    # This method accepts many different kinds of objects:
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    # - single string object IDs e.g. "1.3.6.1" or "IF-MIB::ifTable.1.1"
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    # - single ObjectId
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    # - list of string object IDs
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    # - list of ObjectIds
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    # - list of VarBinds
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    # 
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    def varbind_list(object_list, option=:KeepValue)
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        vb_list = VarBindList.new
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        if object_list.respond_to? :to_str
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            vb_list << oid(object_list).to_varbind
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        elsif object_list.respond_to? :to_varbind
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            vb_list << apply_option(object_list.to_varbind, option)
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        else
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            object_list.each do |item|
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                if item.respond_to? :to_str
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                    varbind = oid(item).to_varbind
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                else
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                    varbind = item.to_varbind
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                end
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                vb_list << apply_option(varbind, option)
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            end
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        end
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        vb_list
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    end
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    def apply_option(varbind, option)
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        if option == :NullValue
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            varbind.value = Null
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        elsif option != :KeepValue
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            raise ArgumentError, "invalid option: #{option.to_s}", caller
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        end
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        varbind
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    end
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    private :apply_option
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    ##
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    # Returns a VarBind object for the given name and value.  The name
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    # can be a String, ObjectId, or anything that responds to :to_varbind.
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    #
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    # String names are in the format <ModuleName>::<NodeName>.<Index> with
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    # ModuleName and Index being optional.
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    #
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    def varbind(name, value=Null)
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        if name.respond_to? :to_str
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            vb = VarBind.new(oid(name), value)
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        else
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            vb = name.to_varbind
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            vb.value = value
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        end
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        vb
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    end
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    ##
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    # Returns an ObjectId for the given name.  Names are in the format
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    # <ModuleName>::<NodeName>.<Index> with ModuleName and Index being
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    # optional.
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    # 
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    def oid(name)
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        module_parts = name.to_str.split("::")
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        if module_parts.length == 1
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            parse_oid(@by_name, name.to_str)
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        elsif module_parts.length == 2
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            module_name = module_parts[0]
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            oid = module_parts[1]
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            module_hash = @by_module_by_name[module_name]
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            if module_hash
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                parse_oid(module_hash, oid)
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            else
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                raise ModuleNotLoadedError, "module '#{module_name}' not loaded"
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            end
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        else
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            raise ArgumentError, "invalid format: #{name.to_str}"
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        end
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    end
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    def parse_oid(node_hash, name)
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        oid_parts = name.split(".")
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        first_part = oid_parts.shift
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        oid_string = node_hash[first_part]
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        if oid_string
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            oid_array = oid_string.split(".")
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        else
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            oid_array = [first_part]
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        end
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        oid_array.concat(oid_parts)
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        ObjectId.new(oid_array)
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    end
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    private :parse_oid
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end
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end # module SNMP
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