feat: implement cookie_from and csrf_token_from

blog_giveaway_worker.rb

@@ -0,0 +1,76 @@
+# One entrant's attempt to claim a limited giveaway slot, run as its own,
+# completely independent `ruby` process - a real second (third, fourth...)
+# `Prism::Server` instance booted against the SAME shared database file as
+# every other worker (see blog_giveaway_demo.rb, which spawns several of
+# these at once and only then releases them all together), not just
+# another thread inside one process. This is the scenario
+# ClaimsController#create's `post.with_lock` (Prism::Orm::Pessimistic) has
+# to hold up against for real: several independent app-server processes -
+# think several Puma/Unicorn workers behind a load balancer, all pointed
+# at the same database - racing the same "claim now" button on the same
+# post at (as close to) the same instant as this demo can arrange.
+#
+# ARGV: label email password slug go_file
+$LOAD_PATH.unshift(File.expand_path('lib', __dir__))
+require 'prism'
+require 'net/http'
+require_relative 'examples/blog/app'
+
+label, email, password, slug, go_file = ARGV
+
+def cookie_from(response)
+  (response.get_fields('set-cookie') || []).map { |line| line.split(';').first }.join('; ')
+end
+
+def csrf_token_from(html)
+  html[/name="csrf-token" content="([^"]+)"/, 1]
+end
+
+server = Prism::Server.new(Blog, port: 0).start
+port = server.port
+
+Net::HTTP.start('127.0.0.1', port) do |http|
+  sign_in_page = http.get('/session/new')
+  cookie = cookie_from(sign_in_page)
+  token = csrf_token_from(sign_in_page.body)
+  login_body = URI.encode_www_form('user[email]' => email, 'user[password]' => password, 'authenticity_token' => token)
+  signed_in = http.post('/session', login_body, 'Content-Type' => 'application/x-www-form-urlencoded', 'Cookie' => cookie)
+  raise "#{label}: sign-in failed (#{signed_in.code})" unless signed_in.code == '302'
+  new_cookie = cookie_from(signed_in)
+  cookie = new_cookie unless new_cookie.empty?
+
+  show_page = http.get("/posts/#{slug}", 'Cookie' => cookie)
+  raise "#{label}: could not load post page (#{show_page.code})" unless show_page.code == '200'
+  claim_token = csrf_token_from(show_page.body)
+
+  # Every worker reaches this point at its own pace (fresh Ruby boot, fresh
+  # Prism::Server, its own sign-in round trip) - spin-waiting on a file the
+  # demo only creates once ALL workers have been spawned turns "started at
+  # roughly the same time" into "fires the actual claim request at
+  # (approximately) the same instant", which is the moment that actually
+  # needs to race for this demo to mean anything.
+  sleep(0.01) until File.exist?(go_file)
+
+  claim_body = URI.encode_www_form('authenticity_token' => claim_token)
+  response = http.post("/posts/#{slug}/claims", claim_body,
+                        'Content-Type' => 'application/x-www-form-urlencoded', 'Cookie' => cookie)
+  raise "#{label}: claim request failed (#{response.code})" unless response.code == '302'
+  # The flash notice this redirect just set lives in the session cookie
+  # itself (see Prism::Session) - the Set-Cookie on THIS response, not the
+  # one from the earlier sign-in, is what carries it forward.
+  post_claim_cookie = cookie_from(response)
+  cookie = post_claim_cookie unless post_claim_cookie.empty?
+
+  landed = http.get(response['location'], 'Cookie' => cookie)
+  outcome =
+    if landed.body.include?('You claimed a giveaway slot!')
+      'claimed'
+    elsif landed.body.include?('Sorry, this giveaway is sold out')
+      'sold_out'
+    elsif landed.body.include?('You already claimed a slot for this giveaway')
+      'already_claimed'
+    else
+      'unknown'
+    end
+  puts "#{label}:#{outcome}"
+end