-- | This module defines a data type and various functions for interacting
-- | with the `Storage` interface of the Web Storage API.
-- | For example:
-- |
-- | ```purescript
-- | import Prelude
-- | import Effect (Effect)
-- | import Effect.Console (log, logShow)
-- | import Web.HTML (window)
-- | import Web.HTML.Window (localStorage)
-- | import Web.Storage.Storage (clear, getItem, removeItem, setItem)
-- |
-- | main :: Effect Unit
-- | main = do
-- |   w <- window
-- |   s <- localStorage w
-- |   setItem "this-is-my-key" "Here is my value." s
-- |   v <- getItem "this-is-my-key" s
-- |   logShow v
-- |
-- |   removeItem "this-is-my-key" s
-- |   v' <- getItem "this-is-my-key" s
-- |   log "It is gone!"
-- |   logShow v'
-- |
-- |   clear s
-- | ```

module Web.Storage.Storage
  ( Storage
  , length
  , key
  , getItem
  , setItem
  , removeItem
  , clear
  ) where

import Prelude

import Data.Maybe (Maybe)
import Data.Nullable (Nullable, toMaybe)
import Effect (Effect)

foreign import data Storage :: Type

-- | Returns the number of items in the storage.
foreign import length :: Storage -> Effect Int

foreign import _key :: Int -> Storage -> Effect (Nullable String)

-- | Retrieves the key at the given index in the storage, if one exists.
key :: Int -> Storage -> Effect (Maybe String)
key i = map toMaybe <<< _key i

foreign import _getItem :: String -> Storage -> Effect (Nullable String)

-- | Retrieves the value stored at the given key, if one exists.
getItem :: String -> Storage -> Effect (Maybe String)
getItem s = map toMaybe <<< _getItem s

-- | Given a key name and a value (in that order), adds that key to the
-- | storage or updates its value if it already exists.
foreign import setItem :: String -> String -> Storage -> Effect Unit

-- | Removes the given key from the storage.
foreign import removeItem :: String -> Storage -> Effect Unit

-- | Clears all keys from the storage.
foreign import clear :: Storage -> Effect Unit