module Page.Register exposing (ExternalMsg(..), Model, Msg, initialModel, update, view)

import Data.Session exposing (Session)
import Data.User exposing (User)
import Html exposing (..)
import Html.Attributes exposing (..)
import Html.Events exposing (..)
import Http
import Json.Decode as Decode exposing (Decoder, decodeString, field, string)
import Json.Decode.Pipeline exposing (decode, optional)
import Request.User exposing (storeSession)
import Route exposing (Route)
import Validate exposing (Validator, ifBlank, validate)
import Views.Form as Form


-- MODEL --


type alias Model =
    { errors : List Error
    , email : String
    , username : String
    , password : String
    }


initialModel : Model
initialModel =
    { errors = []
    , email = ""
    , username = ""
    , password = ""
    }



-- VIEW --


view : Session -> Model -> Html Msg
view session model =
    div [ class "auth-page" ]
        [ div [ class "container page" ]
            [ div [ class "row" ]
                [ div [ class "col-md-6 offset-md-3 col-xs-12" ]
                    [ h1 [ class "text-xs-center" ] [ text "Sign up" ]
                    , p [ class "text-xs-center" ]
                        [ a [ Route.href Route.Login ]
                            [ text "Have an account?" ]
                        ]
                    , Form.viewErrors model.errors
                    , viewForm
                    ]
                ]
            ]
        ]


viewForm : Html Msg
viewForm =
    Html.form [ onSubmit SubmitForm ]
        [ Form.input
            [ class "form-control-lg"
            , placeholder "Username"
            , onInput SetUsername
            ]
            []
        , Form.input
            [ class "form-control-lg"
            , placeholder "Email"
            , onInput SetEmail
            ]
            []
        , Form.password
            [ class "form-control-lg"
            , placeholder "Password"
            , onInput SetPassword
            ]
            []
        , button [ class "btn btn-lg btn-primary pull-xs-right" ]
            [ text "Sign up" ]
        ]



-- UPDATE --


type Msg
    = SubmitForm
    | SetEmail String
    | SetUsername String
    | SetPassword String
    | RegisterCompleted (Result Http.Error User)


type ExternalMsg
    = NoOp
    | SetUser User


update : Msg -> Model -> ( ( Model, Cmd Msg ), ExternalMsg )
update msg model =
    case msg of
        SubmitForm ->
            case validate modelValidator model of
                [] ->
                    ( ( { model | errors = [] }
                      , Http.send RegisterCompleted (Request.User.register model)
                      )
                    , NoOp
                    )

                errors ->
                    ( ( { model | errors = errors }
                      , Cmd.none
                      )
                    , NoOp
                    )

        SetEmail email ->
            ( ( { model | email = email }
              , Cmd.none
              )
            , NoOp
            )

        SetUsername username ->
            ( ( { model | username = username }
              , Cmd.none
              )
            , NoOp
            )

        SetPassword password ->
            ( ( { model | password = password }
              , Cmd.none
              )
            , NoOp
            )

        RegisterCompleted (Err error) ->
            let
                errorMessages =
                    case error of
                        Http.BadStatus response ->
                            response.body
                                |> decodeString (field "errors" errorsDecoder)
                                |> Result.withDefault []

                        _ ->
                            [ "unable to process registration" ]
            in
            ( ( { model | errors = List.map (\errorMessage -> ( Form, errorMessage )) errorMessages }
              , Cmd.none
              )
            , NoOp
            )

        RegisterCompleted (Ok user) ->
            ( ( model
              , Cmd.batch [ storeSession user, Route.modifyUrl Route.Home ]
              )
            , SetUser user
            )



-- VALIDATION --


type Field
    = Form
    | Username
    | Email
    | Password


type alias Error =
    ( Field, String )


modelValidator : Validator Error Model
modelValidator =
    Validate.all
        [ ifBlank .username ( Username, "username can't be blank." )
        , ifBlank .email ( Email, "email can't be blank." )
        , Validate.fromErrors passwordLength
        ]


minPasswordChars : Int
minPasswordChars =
    6


passwordLength : Model -> List Error
passwordLength { password } =
    if String.length password < minPasswordChars then
        [ ( Password, "password must be at least " ++ toString minPasswordChars ++ " characters long." ) ]
    else
        []


errorsDecoder : Decoder (List String)
errorsDecoder =
    decode (\email username password -> List.concat [ email, username, password ])
        |> optionalError "email"
        |> optionalError "username"
        |> optionalError "password"


optionalError : String -> Decoder (List String -> a) -> Decoder a
optionalError fieldName =
    let
        errorToString errorMessage =
            String.join " " [ fieldName, errorMessage ]
    in
    optional fieldName (Decode.list (Decode.map errorToString string)) []