examjam-frontend/context/TimerContext.tsx

"use client";

import React, {
  createContext,
  useContext,
  useState,
  useEffect,
  useRef,
} from "react";

interface TimerContextType {
  timeRemaining: number;
  resetTimer: (duration: number) => void;
  stopTimer: () => void;
  setInitialTime: (duration: number) => void;
}

const TimerContext = createContext<TimerContextType | undefined>(undefined);

export const TimerProvider: React.FC<{ children: React.ReactNode }> = ({
  children,
}) => {
  const [timeRemaining, setTimeRemaining] = useState<number>(0);
  const timerRef = useRef<NodeJS.Timeout | null>(null);

  // Effect: run interval whenever timeRemaining is set > 0
  useEffect(() => {
    if (timeRemaining > 0 && !timerRef.current) {
      timerRef.current = setInterval(() => {
        setTimeRemaining((prev) => {
          if (prev <= 1) {
            clearInterval(timerRef.current!);
            timerRef.current = null;
            return 0;
          }
          return prev - 1;
        });
      }, 1000);
    }

    return () => {
      if (timerRef.current && timeRemaining <= 0) {
        clearInterval(timerRef.current);
        timerRef.current = null;
      }
    };
  }, [timeRemaining]); // 👈 depend on timeRemaining

  const resetTimer = (duration: number) => {
    if (timerRef.current) {
      clearInterval(timerRef.current);
      timerRef.current = null;
    }
    setTimeRemaining(duration);
  };

  const stopTimer = () => {
    if (timerRef.current) {
      clearInterval(timerRef.current);
      timerRef.current = null;
    }
    setTimeRemaining(0);
  };

  const setInitialTime = (duration: number) => {
    if (timerRef.current) {
      clearInterval(timerRef.current);
      timerRef.current = null;
    }
    setTimeRemaining(duration);
  };

  return (
    <TimerContext.Provider
      value={{ timeRemaining, resetTimer, stopTimer, setInitialTime }}
    >
      {children}
    </TimerContext.Provider>
  );
};

export const useTimer = (): TimerContextType => {
  const context = useContext(TimerContext);
  if (!context) {
    throw new Error("useTimer must be used within a TimerProvider");
  }
  return context;
};