module Model.User exposing
  ( Users
  , usersDecoder
  , User
  , userDecoder
  , UserId
  , userIdDecoder
  , getUserName
  )

import Json.Decode as Decode exposing (Decoder)
import Dict exposing (Dict)

type alias Users = Dict UserId User

type alias UserId = Int

type alias User =
  { name : String
  , email : String
  }

usersDecoder : Decoder Users
usersDecoder = Decode.map Dict.fromList (Decode.list userWithIdDecoder)

userWithIdDecoder : Decode.Decoder (UserId, User)
userWithIdDecoder =
  Decode.map2 (,)
    (Decode.field "id" userIdDecoder)
    userDecoder

userIdDecoder : Decoder UserId
userIdDecoder = Decode.int

userDecoder : Decoder User
userDecoder =
  Decode.map2 User
    (Decode.field "name" Decode.string)
    (Decode.field "email" Decode.string)

getUserName : Users -> UserId -> Maybe String
getUserName users userId =
  Dict.get userId users
    |> Maybe.map .name