# Copyright, 2017, by Samuel G. D. Williams. <http://www.codeotaku.com>
# 
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
# 
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
# 
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.

require_relative 'wrapper'

require 'forwardable'

module Async
	# Represents an asynchronous IO within a reactor.
	class IO < Wrapper
		extend Forwardable
		
		WRAPPERS = {}
		
		# Return the wrapper for a given native IO instance.
		def self.[] instance
			WRAPPERS[instance.class]
		end
		
		class << self
			# @!macro [attach] wrap_blocking_method
			#   @method $1
			#   Invokes `$2` on the underlying {io}. If the operation would block, the current task is paused until the operation can succeed, at which point it's resumed and the operation is completed.
			def wrap_blocking_method(new_name, method_name, &block)
				if block_given?
					define_method(new_name, &block)
				else
					define_method(new_name) do |*args|
						async_send(method_name, *args)
					end
				end
			end
			
			def wraps(klass, *additional_methods)
				WRAPPERS[klass] = self
				
				# klass.instance_methods(false).grep(/(.*)_nonblock/) do |method_name|
				# 	wrap_blocking_method($1, method_name)
				# end
				
				def_delegators :@io, *(additional_methods - instance_methods(false))
			end
		end
		
		wraps ::IO
		
		# @example
		#   data = io.read(512)
		wrap_blocking_method :read, :read_nonblock
		
		# @example
		#   io.write("Hello World")
		wrap_blocking_method :write, :write_nonblock
		
		protected
		
		if RUBY_VERSION >= "2.3"
			def async_send(*args)
				async do
					@io.__send__(*args, exception: false)
				end
			end
		else
			def async_send(*args)
				async do
					@io.__send__(*args)
				end
			end
		end
		
		def async
			while true
				begin
					result = yield
					
					case result
					when :wait_readable
						wait_readable
					when :wait_writable
						wait_writable
					else
						return result
					end
				rescue ::IO::WaitReadable
					wait_readable
				rescue ::IO::WaitWritable
					wait_writable
				end
			end
		end
	end
end