compression: added custom transcoders for gzip and deflate; extending response to mask the buffer with an equally streamable decoder, after the response is fully buffered; request now adds accept-encoding automatically

lib/httpx/plugins/compression.rb

@@ -1,8 +1,99 @@
 # frozen_string_literal: true
 
 module HTTPX
+  module Transcoder
+    module GZIP
+      module_function
+      def encode(payload)
+
+      end
+      
+      def decode(io)
+        Zlib::GzipReader.new(io, window_size: 32 + Zlib::MAX_WBITS)
+      end
+    end
+
+    module Deflate
+      module_function
+
+      class Decoder
+        def initialize(io)
+          @io = io
+          @inflater = Zlib::Inflate.new(32 + Zlib::MAX_WBITS)
+          @buffer = StringIO.new
+        end
+       
+        def rewind
+          @buffer.rewind
+        end
+
+        def read(*args)
+          return @buffer.read(*args) if @io.eof?
+          chunk = @io.read(*args)
+          inflated_chunk = @inflater.inflate(chunk)
+          inflated_chunk << @inflater.finish if @io.eof?
+          @buffer << chunk
+          inflated_chunk
+        end
+
+        def close
+          @io.close
+          @io.unlink if @io.respond_to?(:unlink)
+          @inflater.close
+        end
+      end
+
+      def decode(io)
+        Decoder.new(io)
+      end
+    end
+
+    register "gzip", GZIP
+    register "deflate", Deflate
+  end
+
   module Plugins
     module Compression
+      ACCEPT_ENCODING = %w[gzip deflate].freeze
+
+      def self.load_dependencies(*)
+        require "zlib"
+      end
+
+      module RequestMethods
+        def initialize(*)
+          super
+          ACCEPT_ENCODING.each do |enc|
+            @headers.add("accept-encoding", enc)
+          end
+        end
+      end
+
+      module ResponseBodyMethods
+        def initialize(*)
+          super
+          @_decoders = @headers.get("content-encoding").map do |encoding|
+            Transcoder.registry(encoding)
+          end
+        end
+
+        def write(*)
+          super
+          if @length == @headers["content-length"].to_i
+            @buffer.rewind
+            @buffer = decompress(@buffer)
+          end
+        end
+
+        private
+
+        def decompress(buffer)
+          @_decoders.reverse_each do |decoder|
+            buffer = decoder.decode(buffer)
+          end
+          buffer
+        end 
+      end
     end
     register_plugin :compression, Compression
   end