require 'dns/zonefile_parser'

module DNS
  class ParsingError < RuntimeError ; end
  class UnknownRecordType < RuntimeError ; end
  class Zonefile
    VERSION = "0.5.0"

    attr_reader :origin, :soa

    class << self
      def parse(zone_string)
        parser = DNS::ZonefileParser.new
        if result = parser.parse(zone_string)
          result
        else
          raise ParsingError, parser.failure_reason
        end
      end

      def load(zone_string, alternate_origin=nil)
        Zone.new(parse(zone_string).entries, alternate_origin)
      end
    end
  end
  
  
  class Zone
    attr :records
    
    def initialize(entries, alternate_origin=nil)
      alternate_origin ||= '.'
      @records = []
      @vars = {'origin'=>alternate_origin, :last_host=>'.'}
      entries.each do |e|
        case e.parse_type
        when :variable
          case key = e.name.text_value.downcase
          when 'ttl'
            @vars[key] = e.value.text_value.to_i
          else
            @vars[key] = e.value.text_value
          end
        when :soa
          @records << SOA.new(@vars, e)
        when :record
          case e.record_type
          when 'A'      : @records << A.new(@vars, e)
          when 'AAAA'   : @records << AAAA.new(@vars, e)
          when 'CNAME'  : @records << CNAME.new(@vars, e)
          when 'MX'     : @records << MX.new(@vars, e)
          when 'NAPTR'  : @records << NAPTR.new(@vars, e)
          when 'NS'     : @records << NS.new(@vars, e)
          when 'PTR'    : @records << PTR.new(@vars, e)
          when 'SRV'    : @records << SRV.new(@vars, e)
          when 'SPF'    : @records << SPF.new(@vars, e)
          when 'TXT'    : @records << TXT.new(@vars, e)
          else
            raise UnknownRecordType, "Unknown record type: #{e.record_type}"
          end
        end
      end
    end
    
    def soa
      records_of(SOA).first
    end
    
    def records_of(kl)
      @records.select{|r| r.instance_of? kl}
    end
  end
  
  
  
  class Record

    # assign, with handling for '@'
    def self.writer_for_at(*attribs)
      attribs.each do |attrib|
        c = <<-MTH
          def #{attrib}=(val)
            @#{attrib} = val.gsub('@', @vars['origin'])
          end
        MTH
        class_eval c, __FILE__, __LINE__
      end
    end

    # assign, with handling for '@', with inheritance
    def self.inheriting_writer_for_at(*attribs)
      attribs.each do |attrib|
        c = <<-MTH
          def #{attrib}=(val)
            if val.strip.empty?
              @#{attrib} = @vars[:last_host]
            else
              @#{attrib} = val.gsub('@', @vars['origin'])
            end
          end
        MTH
        class_eval c, __FILE__, __LINE__
      end
    end
    
    # assign, with handling for global TTL
    def self.writer_for_ttl(*attribs)
      attribs.each do |attrib|
        c = <<-MTH
          def #{attrib}=(val)
            @#{attrib} = val || @vars['ttl']
          end
        MTH
        class_eval c, __FILE__, __LINE__
      end
    end
    
    attr_reader :ttl
    attr_writer :klass
    writer_for_ttl :ttl
    
    def klass
      @klass = nil if @klass == ''
      @klass ||= 'IN'
    end
    
  end
  
  class SOA < Record
    attr_accessor :origin, :nameserver, :responsible_party, :serial, :refresh_time, :retry_time, :expiry_time, :nxttl
    
    writer_for_at  :origin, :nameserver, :responsible_party
    
    def initialize(vars, zonefile_soa=nil)
      @vars = vars
      if zonefile_soa
        self.origin            = zonefile_soa.origin.to_s
        @vars[:last_host]      = self.origin
        self.ttl               = zonefile_soa.ttl.to_i
        self.klass             = zonefile_soa.klass.to_s
        self.nameserver        = zonefile_soa.ns.to_s
        self.responsible_party = zonefile_soa.rp.to_s
        self.serial            = zonefile_soa.serial.to_i
        self.refresh_time      = zonefile_soa.refresh.to_i
        self.retry_time        = zonefile_soa.reretry.to_i
        self.expiry_time       = zonefile_soa.expiry.to_i
        self.nxttl             = zonefile_soa.nxttl.to_i
      end
    end
  end
  
  class A < Record
    attr_accessor :host, :address
    
    inheriting_writer_for_at  :host
    
    def initialize(vars, zonefile_record)
      @vars = vars
      if zonefile_record
        self.host         = zonefile_record.host.to_s
        @vars[:last_host] = self.host
        self.ttl          = zonefile_record.ttl.to_i
        self.klass        = zonefile_record.klass.to_s
        self.address      = zonefile_record.ip_address.to_s
      end
    end
  end
  
  class AAAA < A
  end
  
  class CNAME < Record
    attr_accessor :host, :domainname
    
    inheriting_writer_for_at  :host
    writer_for_at :domainname
    
    def initialize(vars, zonefile_record)
      @vars = vars
      if zonefile_record
        self.host         = zonefile_record.host.to_s
        @vars[:last_host] = self.host
        self.ttl          = zonefile_record.ttl.to_i
        self.klass        = zonefile_record.klass.to_s
        self.domainname   = zonefile_record.target.to_s
      end
    end
    
    alias :target :domainname
    alias :alias :host
  end
  
  class MX < Record
    attr_accessor :host, :priority, :domainname
    
    inheriting_writer_for_at  :host
    writer_for_at :domainname
    
    def initialize(vars, zonefile_record)
      @vars = vars
      if zonefile_record
        self.host         = zonefile_record.host.to_s
        @vars[:last_host] = self.host
        self.ttl          = zonefile_record.ttl.to_i
        self.klass        = zonefile_record.klass.to_s
        self.priority     = zonefile_record.priority.to_i
        self.domainname   = zonefile_record.exchanger.to_s
      end
    end
    
    alias :exchange :domainname
    alias :exchanger :domainname
  end
  
  class NAPTR < Record
    attr_accessor :host, :data
    
    inheriting_writer_for_at  :host
    
    def initialize(vars, zonefile_record)
      @vars = vars
      if zonefile_record
        self.host         = zonefile_record.host.to_s
        @vars[:last_host] = self.host
        self.ttl          = zonefile_record.ttl.to_i
        self.klass        = zonefile_record.klass.to_s
        self.data         = zonefile_record.data.to_s
      end
    end
  end
  
  class NS < Record
    attr_accessor :host, :domainname
    
    inheriting_writer_for_at  :host
    writer_for_at :domainname
    
    def initialize(vars, zonefile_record)
      @vars = vars
      if zonefile_record
        self.host         = zonefile_record.host.to_s
        @vars[:last_host] = self.host
        self.ttl          = zonefile_record.ttl.to_i
        self.klass        = zonefile_record.klass.to_s
        self.domainname   = zonefile_record.nameserver.to_s
      end
    end
    
    alias :nameserver :domainname
  end
  
  class PTR < Record
    attr_accessor :host, :domainname
    
    inheriting_writer_for_at  :host
    writer_for_at :domainname
    
    def initialize(vars, zonefile_record)
      @vars = vars
      if zonefile_record
        self.host         = zonefile_record.host.to_s
        @vars[:last_host] = self.host
        self.ttl          = zonefile_record.ttl.to_i
        self.klass        = zonefile_record.klass.to_s
        self.domainname   = zonefile_record.target.to_s
      end
    end

    alias :target :domainname
  end

  class SRV < Record
    attr_accessor :host, :priority, :weight, :port, :domainname
    
    inheriting_writer_for_at  :host
    writer_for_at :domainname
    
    def initialize(vars, zonefile_record)
      @vars = vars
      if zonefile_record
        self.host         = zonefile_record.host.to_s
        @vars[:last_host] = self.host
        self.ttl          = zonefile_record.ttl.to_i
        self.klass        = zonefile_record.klass.to_s
        self.priority     = zonefile_record.priority.to_i
        self.weight       = zonefile_record.weight.to_i
        self.port         = zonefile_record.port.to_i
        self.domainname   = zonefile_record.target.to_s
      end
    end

    alias :target :domainname
  end

  class TXT < Record
    attr_accessor :host, :data
    
    inheriting_writer_for_at  :host
    
    def initialize(vars, zonefile_record)
      @vars = vars
      if zonefile_record
        self.host         = zonefile_record.host.to_s
        @vars[:last_host] = self.host
        self.ttl          = zonefile_record.ttl.to_i
        self.klass        = zonefile_record.klass.to_s
        self.data         = zonefile_record.data.to_s
      end
    end
  end

  class SPF < TXT
  end
  
end