@startuml
package com.iluwatar.loadshedding {
  enum Priority {
    + CRITICAL {static}
    + NORMAL {static}
    + LOW {static}
    + valueOf(name : String) : Priority {static}
    + values() : Priority[] {static}
  }
  class Request {
    + Request(id : String, priority : Priority, description : String)
    + id() : String
    + priority() : Priority
    + description() : String
  }
  class Response {
    + Response(requestId : String, status : Status, message : String)
    + requestId() : String
    + status() : Status
    + message() : String
    + accepted(request : Request, result : String) : Response {static}
    + rejected(request : Request, reason : String) : Response {static}
  }
  enum Status {
    + ACCEPTED {static}
    + REJECTED {static}
    + valueOf(name : String) : Status {static}
    + values() : Status[] {static}
  }
  class LoadShedException {
    - requestId : String
    - priority : Priority
    + LoadShedException(request : Request, inFlight : int, limit : int)
    + getRequestId() : String
    + getPriority() : Priority
  }
  class LoadShedder {
    - maxInFlight : int
    - limits : Map<Priority, Integer>
    - inFlight : AtomicInteger
    - accepted : LongAdder
    - shed : Map<Priority, LongAdder>
    + LoadShedder(maxInFlight : int, lowPriorityLimit : int, criticalReserve : int)
    + acquire(request : Request) : int
    + release() : void
    + getMaxInFlight() : int
    + getInFlight() : int
    + getAccepted() : long
    + getShed(priority : Priority) : long
    + getTotalShed() : long
  }
  interface RequestHandler {
    + handle(request : Request) : String {abstract}
  }
  class ShedGuardedService {
    - name : String
    - shedder : LoadShedder
    - handler : RequestHandler
    + ShedGuardedService(name : String, shedder : LoadShedder, handler : RequestHandler)
    + handle(request : Request) : Response
  }
  class App {
    + App()
    + main(args : String[]) : void {static}
    ~ simulatedPaymentProvider(paymentSlow : AtomicBoolean, paymentRecovered : CountDownLatch, entered : Semaphore, recoveryTimeout : Duration) : RequestHandler {static}
    ~ awaitEntered(entered : Semaphore, count : int, timeout : Duration) : void {static}
    ~ result(future : Future<Response>, timeout : Duration) : Response {static}
    ~ shutdown(executor : ExecutorService, timeout : Duration) : void {static}
    ~ report(response : Response) : void {static}
  }
}
Response +-- Status
Request --> Priority
Response --> Status
Response ..> Request
LoadShedException --> Priority
LoadShedException ..> Request
LoadShedder ..> Priority
LoadShedder ..> Request
LoadShedder ..> LoadShedException
RequestHandler ..> Request
ShedGuardedService --> LoadShedder
ShedGuardedService --> RequestHandler
ShedGuardedService ..> Request
ShedGuardedService ..> Response
ShedGuardedService ..> LoadShedException
App ..> LoadShedder
App ..> ShedGuardedService
App ..> RequestHandler
@enduml