Customers.elm

module Customers exposing (Error, Customers, init, toLoading, toFailure, toSuccess)

type alias Error = String

type Customers
  = NotAsked
  | Loading (Maybe Error) (Maybe (List Customer))
  | Failure Error (Maybe (List Customer))
  | Success (List Customer)
    
    
init : Customers
init = NotAsked
      
toLoading : Customers -> Customers
toLoading current =                                 
  case current of
    NotAsked -> Loading Nothing Nothing             
    Loading me ml -> Loading me ml
    Failure e ml -> Loading (Just e) ml
    Success l -> Loading Nothing (Just l)
    
toFailure : Error -> Customers -> Customers         
toFailure error current =                           
  case current of
    NotAsked -> Failure error Nothing
    Loading _ ml -> Failure error ml
    Failure _ ml -> Failure error ml                
    Success l -> Failure error (Just l)             
    
toSuccess : LIst Customer -> Customers -> Customers
toSuccess list current =
  Success list