Switch to http-parser (FFI)

Huge sthanks to [@fxposter](https://github.com/fxposter) for helping on
catching and fixing the problem with underlying parser.

This commit is a squashed and enhanced (with some comments) version of
[PR#489](#489).

Closes #489

http.gemspec

@@ -27,7 +27,7 @@ Gem::Specification.new do |gem|
 
   gem.required_ruby_version = ">= 2.3"
 
-  gem.add_runtime_dependency "http_parser.rb", "~> 0.6.0"
+  gem.add_runtime_dependency "http-parser",    "~> 1.2.0"
   gem.add_runtime_dependency "http-form_data", "~> 2.0"
   gem.add_runtime_dependency "http-cookie",    "~> 1.0"
   gem.add_runtime_dependency "addressable",    "~> 2.3"

lib/http.rb

@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require "http/parser"
-
 require "http/errors"
 require "http/timeout/null"
 require "http/timeout/per_operation"

lib/http/response/parser.rb

@@ -1,41 +1,66 @@
 # frozen_string_literal: true
 
+require "http-parser"
+
 module HTTP
   class Response
+    # @api private
+    #
+    # NOTE(ixti): This class is a subject of future refactoring, thus don't
+    #   expect this class API to be stable until this message disappears and
+    #   class is not marked as private anymore.
     class Parser
       attr_reader :headers
 
       def initialize
-        @parser = HTTP::Parser.new(self)
+        @state  = HttpParser::Parser.new_instance { |i| i.type = :response }
+        @parser = HttpParser::Parser.new(self)
+
         reset
       end
 
+      # @return [self]
       def add(data)
-        @parser << data
+        # XXX(ixti): API doc of HttpParser::Parser is misleading, it says that
+        #   it returns boolean true if data was parsed successfully, but instead
+        #   it's response tells if there was an error; So when it's `true` that
+        #   means parse failed, and `false` means parse was successful.
+        #   case of success.
+        return self unless @parser.parse(@state, data)
+
+        raise IOError, "Could not parse data"
       end
       alias << add
 
       def headers?
-        !!@headers
+        @finished[:headers]
       end
 
       def http_version
-        @parser.http_version.join(".")
+        @state.http_version
       end
 
       def status_code
-        @parser.status_code
+        @state.http_status
       end
 
       #
       # HTTP::Parser callbacks
       #
 
-      def on_headers_complete(headers)
-        @headers = headers
+      def on_header_field(_response, field)
+        @field = field
+      end
+
+      def on_header_value(_response, value)
+        @headers.add(@field, value) if @field
+      end
+
+      def on_headers_complete(_reposse)
+        @finished[:headers] = true
       end
 
-      def on_body(chunk)
+      def on_body(_response, chunk)
         if @chunk
           @chunk << chunk
         else
@@ -57,20 +82,21 @@ def read(size)
         chunk
       end
 
-      def on_message_complete
-        @finished = true
+      def on_message_complete(_response)
+        @finished[:message] = true
       end
 
       def reset
-        @parser.reset!
+        @state.reset!
 
-        @finished = false
-        @headers  = nil
+        @finished = Hash.new(false)
+        @headers  = HTTP::Headers.new
+        @field    = nil
         @chunk    = nil
       end
 
       def finished?
-        @finished
+        @finished[:message]
       end
     end
   end

spec/regression_specs.rb

@@ -14,4 +14,11 @@
       expect { HTTP.get(google_uri).to_s }.not_to raise_error
     end
   end
+
+  describe "#422" do
+    it "reads body when 200 OK response contains Upgrade header" do
+      res = HTTP.get("https://httpbin.org/response-headers?Upgrade=h2,h2c")
+      expect(res.parse(:json)).to include("Upgrade" => "h2,h2c")
+    end
+  end
 end