danbooru::http: support tracking cookies between requests.

Allow cookies to be saved and sent back when making several requests in
a row. Usage:

    http = Danbooru::Http.use(:session)

    # saves the foo=42 cookie sent by the response.
    http.get("https://httpbin.org/cookies/set/foo/42")

    # sends back the foo=42 cookie from the previous request.
    http.get("https://httpbin.org/cookies")

app/logical/danbooru/http.rb

@@ -1,6 +1,7 @@
 require "danbooru/http/html_adapter"
 require "danbooru/http/xml_adapter"
 require "danbooru/http/retriable"
+require "danbooru/http/session"
 
 module Danbooru
   class Http
@@ -13,7 +14,7 @@ module Danbooru
     attr_writer :cache, :max_size, :http
 
     class << self
-      delegate :get, :head, :put, :post, :delete, :cache, :follow, :max_size, :timeout, :auth, :basic_auth, :headers, :public_only, :download_media, to: :new
+      delegate :get, :head, :put, :post, :delete, :cache, :follow, :max_size, :timeout, :auth, :basic_auth, :headers, :cookies, :use, :public_only, :download_media, to: :new
     end
 
     def get(url, **options)
@@ -64,6 +65,14 @@ module Danbooru
       dup.tap { |o| o.http = o.http.headers(*args) }
     end
 
+    def cookies(*args)
+      dup.tap { |o| o.http = o.http.cookies(*args) }
+    end
+
+    def use(*args)
+      dup.tap { |o| o.http = o.http.use(*args) }
+    end
+
     # allow requests only to public IPs, not to local or private networks.
     def public_only
       dup.tap do |o|
@@ -143,6 +152,7 @@ module Danbooru
       @http ||=
         ::Danbooru::Http::ApplicationClient.new
         .follow(strict: false, max_hops: MAX_REDIRECTS)
+        .use(:session)
         .timeout(DEFAULT_TIMEOUT)
         .use(:auto_inflate)
         .headers(Danbooru.config.http_headers)

app/logical/danbooru/http/session.rb

@@ -0,0 +1,37 @@
+module Danbooru
+  class Http
+    class Session < HTTP::Feature
+      HTTP::Options.register_feature :session, self
+
+      attr_reader :cookie_jar
+
+      def initialize(cookie_jar: HTTP::CookieJar.new)
+        @cookie_jar = cookie_jar
+      end
+
+      def perform(request)
+        add_cookies(request)
+        response = yield request
+        save_cookies(response)
+        response
+      end
+
+      def add_cookies(request)
+        cookies = cookies_for_request(request)
+        request.headers["Cookie"] = cookies if cookies.present?
+      end
+
+      def cookies_for_request(request)
+        saved_cookies = cookie_jar.each(request.uri).map { |c| [c.name, c.value] }.to_h
+        request_cookies = HTTP::Cookie.cookie_value_to_hash(request.headers["Cookie"].to_s)
+        saved_cookies.merge(request_cookies).map { |name, value| "#{name}=#{value}" }.join("; ")
+      end
+
+      def save_cookies(response)
+        response.cookies.each do |cookie|
+          cookie_jar.add(cookie)
+        end
+      end
+    end
+  end
+end

test/unit/danbooru_http_test.rb

@@ -51,6 +51,18 @@ class DanbooruHttpTest < ActiveSupport::TestCase
         assert_equal(true, response.parse[:slideshow].present?)
       end
 
+      should "track cookies between requests" do
+        http = Danbooru::Http.use(:session)
+
+        resp1 = http.get("https://httpbin.org/cookies/set/abc/1")
+        resp2 = http.get("https://httpbin.org/cookies/set/def/2")
+        resp3 = http.get("https://httpbin.org/cookies")
+        assert_equal({ abc: "1", def: "2" }, resp3.parse["cookies"].symbolize_keys)
+
+        resp4 = http.cookies(def: 3, ghi: 4).get("https://httpbin.org/cookies")
+        assert_equal({ abc: "1", def: "3", ghi: "4" }, resp4.parse["cookies"].symbolize_keys)
+      end
+
       should "cache requests" do
         response1 = Danbooru::Http.cache(1.minute).get("https://httpbin.org/uuid")
         assert_equal(200, response1.status)