class Vernier::Middleware

def call(env)
  request = Rack::Request.new(env)
  return @app.call(env) unless request.GET.has_key?("vernier")
  permitted = @permit.call(request)
  return @app.call(env) unless permitted
  interval = request.GET.fetch("vernier_interval", 200).to_i
  allocation_interval = request.GET.fetch("vernier_allocation_interval", 200).to_i
  result = Vernier.trace(interval:, allocation_interval:, hooks: [:rails]) do
    @app.call(env)
  end
  body = result.to_firefox(gzip: true)
  filename = "#{request.path.gsub("/", "_")}_#{DateTime.now.strftime("%Y-%m-%d-%H-%M-%S")}.vernier.json.gz"
  headers = {
    "Content-Type" => "application/octet-stream",
    "Content-Disposition" => "attachment; filename=\"#{filename}\"",
    "Content-Length" => body.bytesize.to_s
  }
  Rack::Response.new(body, 200, headers).finish
end

def initialize(app, permit: ->(_env) { true })
  @app = app
  @permit = permit
end