# frozen_string_literal: true

# Released under the MIT License.
# Copyright, 2018-2023, by Samuel Williams.

require_relative 'readable'

module Protocol
	module HTTP
		module Body
			# A dynamic body which you can write to and read from.
			class Writable < Readable
				class Closed < StandardError
				end
				
				# @param [Integer] length The length of the response body if known.
				# @param [Async::Queue] queue Specify a different queue implementation, e.g. `Async::LimitedQueue.new(8)` to enable back-pressure streaming.
				def initialize(length = nil, queue: Thread::Queue.new)
					@queue = queue
					
					@length = length
					
					@count = 0
					
					@finished = false
					
					@closed = false
					@error = nil
				end
				
				def length
					@length
				end
				
				# Stop generating output; cause the next call to write to fail with the given error. Does not prevent existing chunks from being read. In other words, this indicates both that no more data will be or should be written to the body.
				def close(error = nil)
					unless @closed
						@queue.close
						
						@closed = true
						@error = error
					end
					
					super
				end
				
				def closed?
					@closed
				end
				
				def ready?
					!@queue.empty? || @queue.closed?
				end
				
				# Has the producer called #finish and has the reader consumed the nil token?
				def empty?
					@queue.empty? && @queue.closed?
				end
				
				# Read the next available chunk.
				def read
					@queue.pop
				end
				
				# Write a single chunk to the body. Signal completion by calling `#finish`.
				def write(chunk)
					# If the reader breaks, the writer will break.
					# The inverse of this is less obvious (*)
					if @closed
						raise(@error || Closed)
					end
					
					@count += 1
					@queue.push(chunk)
				end
				
				alias << write
				
				def inspect
					"\#<#{self.class} #{@count} chunks written, #{status}>"
				end
				
				private
				
				def status
					if @queue.empty?
						if @queue.closed?
							'closed'
						else
							'waiting'
						end
					else
						if @queue.closed?
							'closing'
						else
							'ready'
						end
					end
				end
			end
		end
	end
end