class Ractor
  # Create a new Ractor with args and a block.
  # args are passed via incoming channel.
  # A block (Proc) will be isolated (can't access to outer variables)
  #
  # A ractor has default two channels:
  # an incoming channel and an outgoing channel.
  #
  # Other ractors send objects to the ractor via the incoming channel and
  # the ractor receives them.
  # The ractor send objects via the outgoing channel and other ractors can
  # receive them.
  #
  # The result of the block is sent via the outgoing channel
  # and other
  #
  #   r = Ractor.new do
  #     Ractor.receive # receive via r's mailbox => 1
  #     Ractor.receive # receive via r's mailbox => 2
  #     Ractor.yield 3 # yield a message (3) and wait for taking by another ractor.
  #     'ok'           # the return value will be yielded.
  #                    # and r's incoming/outgoing ports are closed automatically.
  #   end
  #   r.send 1 # send a message (1) into r's mailbox.
  #   r <<   2 # << is an alias of `send`.
  #   p r.take   # take a message from r's outgoing port => 3
  #   p r.take   # => 'ok'
  #   p r.take   # raise Ractor::ClosedError
  #
  # other options:
  #   name: Ractor's name
  #
  def self.new(*args, name: nil, &block)
    b = block # TODO: builtin bug
    raise ArgumentError, "must be called with a block" unless block
    loc = caller_locations(1, 1).first
    loc = "#{loc.path}:#{loc.lineno}"
    __builtin_ractor_create(loc, name, args, b)
  end

  # return current Ractor
  def self.current
    __builtin_cexpr! %q{
      rb_ec_ractor_ptr(ec)->self
    }
  end

  def self.count
    __builtin_cexpr! %q{
      ULONG2NUM(GET_VM()->ractor.cnt);
    }
  end

  # Multiplex multiple Ractor communications.
  #
  #   r, obj = Ractor.select(r1, r2)
  #   #=> wait for taking from r1 or r2
  #   #   returned obj is a taken object from Ractor r
  #
  #   r, obj = Ractor.select(r1, r2, Ractor.current)
  #   #=> wait for taking from r1 or r2
  #   #         or receive from incoming queue
  #   #   If receive is succeed, then obj is received value
  #   #   and r is :receive (Ractor.current)
  #
  #   r, obj = Ractor.select(r1, r2, Ractor.current, yield_value: obj)
  #   #=> wait for taking from r1 or r2
  #   #         or receive from incoming queue
  #   #         or yield (Ractor.yield) obj
  #   #   If yield is succeed, then obj is nil
  #   #   and r is :yield
  #
  def self.select(*ractors, yield_value: yield_unspecified = true, move: false)
    raise ArgumentError, 'specify at least one ractor or `yield_value`' if yield_unspecified && ractors.empty?

    __builtin_cstmt! %q{
      const VALUE *rs = RARRAY_CONST_PTR_TRANSIENT(ractors);
      VALUE rv;
      VALUE v = ractor_select(ec, rs, RARRAY_LENINT(ractors),
                              yield_unspecified == Qtrue ? Qundef : yield_value,
                              (bool)RTEST(move) ? true : false, &rv);
      return rb_ary_new_from_args(2, rv, v);
    }
  end

  # Receive an incoming message from Ractor's incoming queue.
  def self.receive
    __builtin_cexpr! %q{
      ractor_receive(ec, rb_ec_ractor_ptr(ec))
    }
  end

  class << self
    alias recv receive
  end

  # same as Ractor.receive
  private def receive
    __builtin_cexpr! %q{
      ractor_receive(ec, rb_ec_ractor_ptr(ec))
    }
  end
  alias recv receive

  # Receive only a specific message.
  #
  # Instead of Ractor.receive, Ractor.receive_if can provide a pattern
  # by a block and you can choose the receiving message.
  #
  # # Example:
  # r = Ractor.new do
  #   p Ractor.receive_if{|msg| /foo/ =~ msg} #=> "foo3"
  #   p Ractor.receive_if{|msg| /bar/ =~ msg} #=> "bar1"
  #   p Ractor.receive_if{|msg| /baz/ =~ msg} #=> "baz2"
  # end
  # r << "bar1"
  # r << "baz2"
  # r << "foo3"
  # r.take
  #
  # If the block returns truthy, the message will be removed from incoming queue
  # and return this method with the message.
  # When the block is escaped by break/return/exception and so on, the message also
  # removed from the incoming queue.
  # Otherwise, the messsage is remained in the incoming queue and check next received
  # message by the given block.
  #
  # If there is no messages in the incoming queue, wait until arrival of other messages.
  #
  # Note that you can not call receive/receive_if in the given block recursively.
  # It means that you should not do any tasks in the block.
  #
  # # Example:
  # Ractor.current << true
  # Ractor.receive_if{|msg| Ractor.receive}
  # #=> `receive': can not call receive/receive_if recursively (Ractor::Error)
  #
  def self.receive_if &b
    Primitive.ractor_receive_if b
  end

  private def receive_if &b
    Primitive.ractor_receive_if b
  end

  # Send a message to a Ractor's incoming queue.
  #
  # # Example:
  #   r = Ractor.new do
  #     p Ractor.receive #=> 'ok'
  #   end
  #   r.send 'ok' # send to r's incoming queue.
  def send(obj, move: false)
    __builtin_cexpr! %q{
      ractor_send(ec, RACTOR_PTR(self), obj, move)
    }
  end
  alias << send

  # yield a message to the ractor's outgoing port.
  def self.yield(obj, move: false)
    __builtin_cexpr! %q{
      ractor_yield(ec, rb_ec_ractor_ptr(ec), obj, move)
    }
  end

  # Take a message from ractor's outgoing port.
  #
  # Example:
  #   r = Ractor.new{ 'oK' }
  #   p r.take #=> 'ok'
  def take
    __builtin_cexpr! %q{
      ractor_take(ec, RACTOR_PTR(self))
    }
  end

  def inspect
    loc  = __builtin_cexpr! %q{ RACTOR_PTR(self)->loc }
    name = __builtin_cexpr! %q{ RACTOR_PTR(self)->name }
    id   = __builtin_cexpr! %q{ INT2FIX(RACTOR_PTR(self)->id) }
    status = __builtin_cexpr! %q{
      rb_str_new2(ractor_status_str(RACTOR_PTR(self)->status_))
    }
    "#<Ractor:##{id}#{name ? ' '+name : ''}#{loc ? " " + loc : ''} #{status}>"
  end

  def name
    __builtin_cexpr! %q{ RACTOR_PTR(self)->name }
  end

  class RemoteError
    attr_reader :ractor
  end

  # Closes the incoming port and returns its previous state.
  def close_incoming
    __builtin_cexpr! %q{
      ractor_close_incoming(ec, RACTOR_PTR(self));
    }
  end

  # Closes the outgoing port and returns its previous state.
  def close_outgoing
    __builtin_cexpr! %q{
      ractor_close_outgoing(ec, RACTOR_PTR(self));
    }
  end

  # utility method
  def self.shareable? obj
    __builtin_cexpr! %q{
      rb_ractor_shareable_p(obj) ? Qtrue : Qfalse;
    }
  end

  # make obj sharable.
  #
  # Basically, traverse referring objects from obj and freeze them.
  #
  # When a sharable object is found in traversing, stop traversing
  # from this shareable object.
  #
  # If copy keyword is true, it makes a deep copied object
  # and make it sharable. This is safer option (but it can take more time).
  #
  # Note that the specification and implementation of this method are not
  # matured and can be changed in a future.
  #
  def self.make_shareable obj, copy: false
    if copy
      __builtin_cexpr! %q{
        rb_ractor_make_copy_shareable(obj);
      }
    else
      __builtin_cexpr! %q{
        rb_ractor_make_shareable(obj);
      }
    end
  end
end