class WebConsole::Middleware

def acceptable_content_type?(headers)
  headers[Rack::CONTENT_TYPE].to_s.include?("html")
end

def binding_change_re
  @_binding_change_re ||= %r{#{repl_sessions_re}/trace\z}
end

def call(env)
  app_exception = catch :app_exception do
    request = create_regular_or_whiny_request(env)
    return call_app(env) unless request.permitted?
    if id = id_for_repl_session_update(request)
      return update_repl_session(id, request)
    elsif id = id_for_repl_session_stack_frame_change(request)
      return change_stack_trace(id, request)
    end
    status, headers, body = call_app(env)
    if (session = Session.from(Thread.current)) && acceptable_content_type?(headers)
      headers["x-web-console-session-id"] = session.id
      headers["x-web-console-mount-point"] = mount_point
      template = Template.new(env, session)
      body, headers = Injector.new(body, headers).inject(template.render("index"))
    end
    [ status, headers, body ]
  end
rescue => e
  WebConsole.logger.error("\n#{e.class}: #{e}\n\tfrom #{e.backtrace.join("\n\tfrom ")}")
  raise e
ensure
  # Clean up the fiber locals after the session creation. Object#console
  # uses those to communicate the current binding or exception to the middleware.
  Thread.current[:__web_console_exception] = nil
  Thread.current[:__web_console_binding] = nil
  raise app_exception if Exception === app_exception
end

def call_app(env)
  @app.call(env)
rescue => e
  throw :app_exception, e
end

def change_stack_trace(id, request)
  json_response_with_session(id, request) do |session|
    session.switch_binding_to(request.params[:frame_id], request.params[:exception_object_id])
    { ok: true }
  end
end

def create_regular_or_whiny_request(env)
  request = Request.new(env)
  whiny_requests ? WhinyRequest.new(request) : request
end

def id_for_repl_session_stack_frame_change(request)
  if request.xhr? && request.post?
    binding_change_re.match(request.path) { |m| m[:id] }
  end
end

def id_for_repl_session_update(request)
  if request.xhr? && request.put?
    update_re.match(request.path) { |m| m[:id] }
  end
end

def initialize(app)
  @app = app
end

def json_response(opts = {})
  status  = opts.fetch(:status, 200)
  headers = { Rack::CONTENT_TYPE => "application/json; charset = utf-8" }
  body    = yield.to_json
  [ status, headers, [ body ] ]
end

def json_response_with_session(id, request, opts = {})
  return respond_with_unavailable_session(id) unless session = Session.find(id)
  json_response(opts) { yield session }
end

def repl_sessions_re
  @_repl_sessions_re ||= %r{#{mount_point}/repl_sessions/(?<id>[^/]+)}
end

def respond_with_unacceptable_request
  json_response(status: 406) do
    { output: I18n.t("errors.unacceptable_request") }
  end
end

def respond_with_unavailable_session(id)
  json_response(status: 404) do
    { output: format(I18n.t("errors.unavailable_session"), id: id) }
  end
end

def update_re
  @_update_re ||= %r{#{repl_sessions_re}\z}
end

def update_repl_session(id, request)
  json_response_with_session(id, request) do |session|
    if input = request.params[:input]
      { output: session.eval(input) }
    elsif input = request.params[:context]
      { context: session.context(input) }
    end
  end
end