useLocalStorage.ts

import { useState, useEffect } from 'react';

const subscribers = new Map<string, Set<React.Dispatch<any>>>();

function useLocalStorage<T>(key: string, initialValue: T) {
  // State to store our value
  const [storedValue, setStoredValue] = useState<T>(() => {
    try {
      const item = window.localStorage.getItem(key);
      return item ? (JSON.parse(item) as T) : initialValue;
    } catch (error) {
      console.error(error);
      return initialValue;
    }
  });

  // Manage subscriptions
  useEffect(() => {
    let subs = subscribers.get(key);
    if (!subs) {
      subs = new Set();
      subscribers.set(key, subs);
    }
    subs.add(setStoredValue);

    return () => {
      subs!.delete(setStoredValue);
      if (subs!.size === 0) {
        subscribers.delete(key);
      }
    };
  }, [key]);

  // Update localStorage when storedValue changes
  useEffect(() => {
    try {
      window.localStorage.setItem(key, JSON.stringify(storedValue));
    } catch (error) {
      console.error(error);
    }
  }, [key, storedValue]);

  // Cross-tab synchronization
  useEffect(() => {
    const handleStorageChange = (event: StorageEvent) => {
      if (event.key === key) {
        try {
          const newValue = event.newValue ? (JSON.parse(event.newValue) as T) : initialValue;
          setStoredValue(newValue);

          // Notify subscribers
          const subs = subscribers.get(key);
          if (subs) {
            subs.forEach((sub) => {
              if (sub !== setStoredValue) {
                sub(newValue);
              }
            });
          }
        } catch (error) {
          console.error(error);
        }
      }
    };

    window.addEventListener('storage', handleStorageChange);
    return () => {
      window.removeEventListener('storage', handleStorageChange);
    };
  }, [key, initialValue]);

  // Function to set the value and notify subscribers
  const setValue = (value: T | ((val: T) => T)) => {
    try {
      const valueToStore = value instanceof Function ? value(storedValue) : value;
      setStoredValue(valueToStore);
      window.localStorage.setItem(key, JSON.stringify(valueToStore));

      // Notify other subscribers
      const subs = subscribers.get(key);
      if (subs) {
        subs.forEach((sub) => {
          if (sub !== setStoredValue) {
            sub(valueToStore);
          }
        });
      }
    } catch (error) {
      console.error(error);
    }
  };

  return [storedValue, setValue] as [T, typeof setValue];
}

export default useLocalStorage;