# Copyright, 2018, 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 'async/io/buffer'

require 'async/http/body'
require 'async/http/body/rewindable'

module Falcon
	module Adapters
		# The input stream is an IO-like object which contains the raw HTTP POST data. When applicable, its external encoding must be “ASCII-8BIT” and it must be opened in binary mode, for Ruby 1.9 compatibility. The input stream must respond to gets, each, read and rewind.
		class Input
			def initialize(body)
				@body = body
				
				# Will hold remaining data in `#read`.
				@buffer = nil
				@finished = @body.nil?
			end
			
			attr :body
			
			# each must be called without arguments and only yield Strings.
			def each(&block)
				return to_enum unless block_given?
				
				while chunk = gets
					yield chunk
				end
			end
			
			# rewind must be called without arguments. It rewinds the input stream back to the beginning. It must not raise Errno::ESPIPE: that is, it may not be a pipe or a socket. Therefore, handler developers must buffer the input data into some rewindable object if the underlying input stream is not rewindable.
			def rewind
				if @body
					# If the body is not rewindable, this will fail.
					@body.rewind
					@buffer = nil
					@finished = false
				end
			end
			
			def respond_to?(name, *)
				if name == :rewind
					@body.respond_to?(:rewind)
				else
					super
				end
			end
			
			# read behaves like IO#read. Its signature is read([length, [buffer]]). If given, length must be a non-negative Integer (>= 0) or nil, and buffer must be a String and may not be nil. If length is given and not nil, then this method reads at most length bytes from the input stream. If length is not given or nil, then this method reads all data until EOF. When EOF is reached, this method returns nil if length is given and not nil, or “” if length is not given or is nil. If buffer is given, then the read data will be placed into buffer instead of a newly created String object.
			# @param length [Integer] the amount of data to read
			# @param buffer [String] the buffer which will receive the data
			# @return a buffer containing the data
			def read(length = nil, buffer = nil)
				buffer ||= Async::IO::Buffer.new
				buffer.clear
				
				until buffer.bytesize == length
					@buffer = read_next if @buffer.nil?
					break if @buffer.nil?
					
					remaining_length = length - buffer.bytesize if length
					
					if remaining_length && remaining_length < @buffer.bytesize
						# We know that we are not going to reuse the original buffer.
						# But byteslice will generate a hidden copy. So let's freeze it first:
						@buffer.freeze
						
						buffer << @buffer.byteslice(0, remaining_length)
						@buffer = @buffer.byteslice(remaining_length, @buffer.bytesize)
					else
						buffer << @buffer
						@buffer = nil
					end
				end
				
				return nil if buffer.empty? && length && length > 0
				
				return buffer
			end
			
			def eof?
				@finished and @buffer.nil?
			end
			
			# gets must be called without arguments and return a string, or nil on EOF.
			# @return [String, nil] The next chunk from the body.
			def gets
				if @buffer.nil?
					return read_next
				else
					buffer = @buffer
					@buffer = nil
					return buffer
				end
			end
			
			# close must never be called on the input stream. huh?
			def close
				@body.finish
			end
			
			private
			
			def read_next
				return nil if @finished
				
				if chunk = @body.read
					return chunk
				else
					@finished = true
					return nil
				end
			end
		end
	end
end