require 'rs_232/version'
require 'rs_232_native.so'
require 'forwardable'

module Rs232
  # public accessible factory method
  #
  # @example
  #
  #   > include Rs232
  #   > port = new_serial_port('/dev/tty.ACM0', baud_rate: 9600)
  #   #=> #<Rs232::Impl @port='/dev/tty.ACM0'>
  #   > port.open?
  #   #=> false
  #   > port.connect # rasing IOError in case of port couldn't be opened.
  #   #=> #<Rs232::Impl @port='/dev/tty.ACM0'>
  #   > port.pending_bytes
  #   #=> 15
  #   > port.read(15)
  #   #=> 'Hello, World!!!'
  #   > port.write("Hi")
  #   #=> 2
  #   > port.close
  #   #=> true
  #   > port.open?
  #   #=> false
  #
  # @param [String] port name
  # @param [Hash] opts with such keys as: baud_rate, parity, data_bits, stop_bits, flow_control, timeout
  # @param [Proc] block is a function to apply on constructor finish
  def new_serial_port(port, opts = {}, &block)
    Impl.new(port, opts, &block)
  end

  # the following class represents ruby public interface
  # to native Rs232 implementation
  #
  # There no public instantiation, can be instantiate through
  # the factory method @see Rs232.new
  #
  class Impl
    include Rs232::Constants

    STD_OPTS = {
        baud_rate: BAUD_115200,
        parity: PAR_NONE,
        data_bits: DATA_BITS_8,
        stop_bits: STOP_BITS_1,
        flow_control: FLOW_OFF,
        timeout: 10
    }.freeze

    extend Forwardable

    def_delegators :@impl,
                   :read,
                   :write,
                   :flush,
                   :open?,
                   :set_rts,
                   :set_dtr

    def initialize(name, opts = {})
      @impl = Rs232::Native.new(name)
      @opts = STD_OPTS.merge(opts).freeze
      freeze
      yield self if block_given?
    end

    # @raise IOError in case of port was not open.
    # @return [Impl] instance
    def connect
      return self if open?
      @impl.open.tap do |io|
        io.baud_rate = @opts[:baud_rate]
        io.parity = @opts[:parity]
        io.data_bits = @opts[:data_bits]
        io.stop_bits = @opts[:stop_bits]
        io.flow_control = @opts[:flow_control]
        io.timeout = @opts[:timeout]
      end
      self
    end

    # @return [Boolean]
    def close
      return !open? unless open?
      0 == @impl.close
    end

    # @return [Fixnum] representing count of bytes in the buffer
    def pending_bytes
      @impl.available?
    end

    # @return [Hash] of configurations on the OS side.
    def settings
      {}.tap do |o|
        o[:baud_rate] = @impl.baud_rate
        o[:parity] = @impl.parity
        o[:data_bits] = @impl.data_bits
        o[:stop_bits] = @impl.stop_bits
        o[:flow_control] = @impl.flow_control
        o[:timeout] = @impl.timeout
        o[:line_status] = @impl.line_status
      end.freeze
    end
  end

  private_constant :Impl
end