# frozen_string_literal: true

# Released under the MIT License.
# Copyright, 2019-2024, by Samuel Williams.
# Copyright, 2023, by Thomas Morgan.

require 'protocol/http/body/readable'

module Protocol
	module HTTP1
		module Body
			class Chunked < HTTP::Body::Readable
				CRLF = "\r\n"
				
				def initialize(stream, headers)
					@stream = stream
					@finished = false
					
					@headers = headers
					
					@length = 0
					@count = 0
				end
				
				def empty?
					@stream.nil?
				end
				
				def close(error = nil)
					if @stream
						# We only close the connection if we haven't completed reading the entire body:
						unless @finished
							@stream.close_read
						end
						
						@stream = nil
					end
					
					super
				end
				
				VALID_CHUNK_LENGTH = /\A[0-9a-fA-F]+\z/
				
				# Follows the procedure outlined in https://tools.ietf.org/html/rfc7230#section-4.1.3
				def read
					if !@finished
						if @stream
							length, _extensions = read_line.split(";", 2)
							
							unless length =~ VALID_CHUNK_LENGTH
								raise BadRequest, "Invalid chunk length: #{length.inspect}"
							end
							
							# It is possible this line contains chunk extension, so we use `to_i` to only consider the initial integral part:
							length = Integer(length, 16)
							
							if length == 0
								read_trailer
								
								# The final chunk has been read and the stream is now closed:
								@stream = nil
								@finished = true
								
								return nil
							end
							
							# Read trailing CRLF:
							chunk = @stream.read(length + 2)
							
							# ...and chomp it off:
							chunk.chomp!(CRLF)
							
							@length += length
							@count += 1
							
							return chunk
						end
						
						# If the stream has been closed before we have read the final chunk, raise an error:
						raise EOFError, "Stream closed before expected length was read!"
					end
				end
				
				def inspect
					"\#<#{self.class} #{@length} bytes read in #{@count} chunks>"
				end
				
				private
				
				def read_line?
					@stream.gets(CRLF, chomp: true)
				end
				
				def read_line
					read_line? or raise EOFError
				end
				
				def read_trailer
					while line = read_line?
						# Empty line indicates end of trailer:
						break if line.empty?
						
						if match = line.match(HEADER)
							@headers.add(match[1], match[2])
						else
							raise BadHeader, "Could not parse header: #{line.inspect}"
						end
					end
				end
			end
		end
	end
end