/**
 * @description Get the number of key-value pairs currently stored in local storage.
 */
export const getLengthOfLocalStorage = (): number => {
  return localStorage.length
}

/**
 * @description Get an array of all keys currently stored in local storage.
 */
export const getAllKeysFromLocalStorage = (): string[] => {
  const keys: string[] = []
  for (let i = 0; i < localStorage.length; i = i + 1) {
    const key = localStorage.key(i)
    if (key !== null) {
      keys.push(key)
    }
  }
  return keys
}

/**
 * @description Check if a specific key exists in local storage.
 */
export const hasKeyInLocalStorage = (key: string): boolean => {
  return localStorage.getItem(key) !== null
}

/**
 * @description Retrieve a value from local storage by its key.
 */
export const getFromLocalStorage = (key: string): string | null => {
  return localStorage.getItem(key)
}

/**
 * @description Set a value in local storage by its key.
 * If the value is null, the key will be removed from local storage.
 */
export const setToLocalStorage = (key: string, value: string | null): string | null => {
  if (value !== null) {
    localStorage.setItem(key, value)
  } else {
    localStorage.removeItem(key)
  }
  return value
}

/**
 * @description Remove a value from local storage by its key.
 * Returns the removed value, or null if the key did not exist.
 */
export const removeFromLocalStorage = (key: string): string | null => {
  const value = localStorage.getItem(key)
  localStorage.removeItem(key)
  return value
}

/**
 * @description Clear all key-value pairs from local storage.
 */
export const clearLocalStorage = (): void => {
  localStorage.clear()
}

/**
 * @description Subscribe to changes in local storage. The callback will be
 * invoked whenever any key-value pair in local storage changes.
 * Returns a function to unsubscribe from the changes.
 */
export const subscribeAllChangesOfLocalStorage = (
  subscriber: (event: StorageEvent) => void,
): (() => void) => {
  const internalSubscriber = (event: StorageEvent): void => {
    subscriber(event)
  }
  const subscribe = (): void => {
    window.addEventListener("storage", internalSubscriber)
  }
  const unsubscribe = (): void => {
    window.removeEventListener("storage", internalSubscriber)
  }

  subscribe()
  return unsubscribe
}

/**
 * @description Subscribe to changes in a specific key in local storage.
 * The callback will be invoked whenever the value of the key changes.
 * Returns a function to unsubscribe from the changes.
 */
export const subscribeKeyChangesOfLocalStorage = (
  key: string,
  subscriber: (event: StorageEvent) => void,
): (() => void) => {
  const internalSubscriber = (event: StorageEvent): void => {
    if (event.key === key) {
      subscriber(event)
    }
  }
  const subscribe = (): void => {
    window.addEventListener("storage", internalSubscriber)
  }
  const unsubscribe = (): void => {
    window.removeEventListener("storage", internalSubscriber)
  }

  subscribe()
  return unsubscribe
}