import {useCallback,useEffect,useRef,useState} from 'react';
import type {Sensor} from './contracts';
import {observationSession} from './observationStart';

/** One automatic activation per mounted view/session; failures require explicit retry. */
export function useObservationStart(device:Sensor,enabled:boolean,active:boolean,start:()=>Promise<unknown>){
 const scope=observationSession(device),latest=useRef({scope,enabled,start});latest.current={scope,enabled,start};
 const mounted=useRef(false),attempted=useRef(''),running=useRef(false);
 const [pending,setPending]=useState(false),[error,setError]=useState('');
 useEffect(()=>{mounted.current=true;return()=>{mounted.current=false;};},[]);
 useEffect(()=>{setError('');},[scope]);
 const retry=useCallback(async()=>{
  const value=latest.current;if(!value.enabled||running.current)return;
  attempted.current=value.scope;running.current=true;setPending(true);setError('');
  try{await value.start();}catch(reason){if(mounted.current&&latest.current.scope===value.scope)setError(reason instanceof Error?reason.message:'Не удалось начать просмотр.');}
  finally{running.current=false;if(mounted.current)setPending(false);}
 },[]);
 useEffect(()=>{
  if(!enabled){attempted.current='';return;}
  if(active){attempted.current=scope;setError('');return;}
  if(attempted.current!==scope)void retry();
 },[scope,enabled,active,retry,pending]);
 return {pending,error,retry};
}