require 'iounpack'
require 'stringio'
require_relative 'errors'

module Knot
	class Protocol
	end
end

module Knot::Protocol::Type
	def [] code
		case code
		when 0, End   then return End
		when 1, Data  then return Data
		when 2, Extra then return Extra
		when 3, Block then return Block
		end
	end

	class Base
		def self.expect_data?
			false
		end
		def expect_data?() self.class.expect_data? end
		def code() self.class.code end
	end
	class End < Base
		def self.code() 0 end
	end
	class Data < Base
		def code() 1 end
		def expect_data?
			true
		end
		attr_reader :data
		def initialize data
			@data = data
		end
	end
	class Extra < Base
		def code() 2 end
		def expect_data?
			true
		end
		attr_reader :data
		def initialize data
			@data = data
		end
	end
	class Block < Base
		def code() 3 end
	end
end

#class Knot::KnotC
#	attr_accessor :debug, :binary
#
#	def initialize path = nil, binary: nil
#   @path = path
#		@binary = binary || 'knotc'
#		@conf = Knot::Conf.new self
#		@zones = Hash.new {|h, zone| h[zone] = Knot::Zone.new zone, self }
#	end
#
#	def call command:, flags: nil, section: nil, item: nil, id: nil, zone: nil, owner: nil, ttl: nil, type: nil, data: nil, filter: nil
#		cs =
#			case command.to_s
#			when 'conf-begin', 'conf-commit', 'conf-abort', 'status', 'stop', 'reload'
#				[@binary, command,  ]
#			else raise ArgumentError, "Unknown Command: #{command}"
#			end
#	end
#end

module Knot::Protocol::Idx
	class Id
		include Comparable
		attr_reader :name, :code, :cname, :description

		def initialize name, code, cname, description
			raise ArgumentError, "Expecting Symbol for #{self.class.name} instead of: #{name.inspect}"   unless Symbol === name
			raise ArgumentError, "Expecting Integer for #{self.class.name} instead of: #{code.inspect}"  unless Integer === code
			@name, @code, @cname, @description = name, code, cname, description
			freeze
		end

		def === x
			case x
			when self.class then self == x
			when Symbol then @name == x
			when String then @name == x.to_sym
			when Integer then @code == x
			else nil
			end
		end

		def <=>( x)  @id <=> x.id  end
		def to_s()  @name.to_s  end
		def to_sym()  @name  end
		def to_i()  @code  end
	end

	Idx = [
		Id.new( :command, 0x10, :CMD,     'Control command name.'),
		Id.new( :flags,   0x11, :FLAGS,   'Control command flags.'),
		Id.new( :error,   0x12, :ERROR,   'Error message.'),
		Id.new( :section, 0x13, :SECTION, 'Configuration section name.'),
		Id.new( :item,    0x14, :ITEM,    'Configuration item name.'),
		Id.new( :id,      0x15, :ID,      'Congiguration item identifier.'),
		Id.new( :zone,    0x16, :ZONE,    'Zone name.'),
		Id.new( :owner,   0x17, :OWNER,   'Zone record owner'),
		Id.new( :ttl,     0x18, :TTL,     'Zone record TTL.'),
		Id.new( :type,    0x19, :TYPE,    'Zone record type name.'),
		Id.new( :data,    0x1a, :DATA,    'Configuration item/zone record data.'),
		Id.new( :filter,  0x1b, :FILTER,  'An option or a filter for output data processing.'),
	]
	Name = {}
	Code = {}

	Idx.each do |id|
		Code[id.to_i] = id
		Name[id.to_sym] = id
	end

	class <<self
		def [] k
			case k
			when Symbol
				Name[k] or raise Knot::Errors::EINVAL, "Unknown Idx: #{k}"
			when Integer
				Code[k] or raise Knot::Errors::EINVAL, "Unknown Idx: #{k}"
			else
				raise ArgumentError, "Unknown Idx-Type: #{k}"
			end
		end

		def each &exe
			block_given? ? Idx.each( &exe) : Idx.to_enum( :each)
		end
	end
end

class Knot::Protocol
	attr_reader :sock, :conf, :zones
	attr_accessor :debug

	def initialize path_or_sock = nil
		case path_or_sock
		when String, Pathname
			@sock = UNIXSocket.new path_or_sock.to_s
		when Socket
			@sock = path_or_sock
		when nil
			@sock = UNIXSocket.new '/run/knot/knot.sock'
		end
		@debug = false
		@conf = Knot::Conf.new self
		@zones = Hash.new {|h, zone| h[zone] = Knot::Zone.new zone, self }
	end

	def snd sock: nil, **data
		rsock = sock || @sock
		s = ''.b
		sock = StringIO.new s
		sock.write [1].pack( 'c')
		data[:flags] ||= ''
		Idx::Idx.each do |n|
			v = data[n.to_sym]&.to_s&.b
			sock.write [n.to_i, v.size, v].pack( 'c na*')  if v
		end
		sock.write [3].pack( 'c')
		sock.flush
		STDERR.puts( {send: data, _: s}.inspect)  if @debug
		rsock.write s
		rsock.flush
	end

	class RecordIO
		attr_reader :str

		def initialize sock, str = nil
			@str, @sock = str || ''.b, sock
		end

		def unpack pattern
			IOUnpack.new( pattern).unpack self
		end

		def unpack1 pattern
			IOUnpack.new( pattern).unpack1 self
		end

		def read n
			s = @sock.read n
			@str.insert -1, s
			s
		end
	end

	def rcv sock: nil
		ret, r = [], nil
		sock = sock || @sock
		sock = RecordIO.new sock  if @debug
		loop do
			t = sock.unpack1 'c'
			case t
			when 0, 3
				return ret
			when 1, 2
				type = t
				ret.push( r = {})
			else
				raise Knot::Errors::EINVAL, "Missing Type before: #{t}"  if ret.empty?
				i = Idx::Idx[t - 0x10] or raise Knot::Errors::EINVAL, "Unknown index: #{t-0x10}"
				l = sock.unpack1 'n'
				r[i] = sock.read( l)
			end
		end
	ensure
		STDERR.puts( {rcvd: ret, _: sock.str}.inspect)  if @debug
		ret
	end

	def call sock: nil, **data
		snd sock: sock, **data
		rcv( sock: sock).each do |r|
			if r[:error]
				if e = Knot::Errors.err2exc[r[:error]]
					raise e, r[:error]
				end
				raise Knot::Error, r[:error]
			end
		end
	end

	def zone( zone) @zones[zone.to_s.to_sym] end

	def conf_set( **opts)   call **opts.update( command: 'conf-set')   end
	def conf_unset( **opts) call **opts.update( command: 'conf-unset') end

	def zone_set( **opts)   call **opts.update( command: 'zone-set')   end
	def zone_unset( **opts) call **opts.update( command: 'zone-unset') end
	def zone_get( **opts)   call **opts.update( command: 'zone-get')   end
end