class ElasticAPM::ContextBuilder

def apply_to_request(context, rack_env)
  req = rails_req?(rack_env) ? rack_env : Rack::Request.new(rack_env)
  context.request = Context::Request.new unless context.request
  request = context.request
  request.socket = Context::Request::Socket.new(req).to_h
  request.http_version = build_http_version rack_env
  request.method = req.request_method
  request.url = Context::Request::Url.new(req).to_h
  request.headers, request.env = get_headers_and_env(rack_env)
  request.body = get_body(req)
  context
end

def build(rack_env)
  context = Context.new
  apply_to_request(context, rack_env)
  context
end

def build_http_version(rack_env)
  return unless (http_version = rack_env['HTTP_VERSION'])
  http_version.gsub(%r{HTTP/}, '')
end

def camel_key(key)
  key.gsub(/^HTTP_/, '').split('_').map(&:capitalize).join('-')
end

def get_body(req)
  return req.POST if req.form_data?
  body = req.body.read
  req.body.rewind
  body
end

def get_headers_and_env(rack_env)
  # In Rails < 5 ActionDispatch::Request inherits from Hash
  headers =
    rack_env.respond_to?(:headers) ? rack_env.headers : rack_env
  headers.each_with_object([{}, {}]) do |(key, value), (http, env)|
    next unless key == key.upcase
    if key.start_with?('HTTP_')
      http[camel_key(key)] = value
    else
      env[key] = value
    end
  end
end

def initialize(_agent); end

def rails_req?(env)
  defined?(ActionDispatch::Request) &&
    env.is_a?(ActionDispatch::Request)
end