module Main exposing (main)

{-| Exercise 3: Temperature Converter

Build a temperature converter:

Exercise 3.1: Convert Celsius to Fahrenheit (F = C × 9/5 + 32)
Exercise 3.2: Add Fahrenheit to Celsius conversion
Exercise 3.3: Handle invalid input gracefully

Run with: elm reactor
Then open http://localhost:8000/src/Main.elm

-}

import Browser
import Html exposing (Html, div, input, text)
import Html.Attributes exposing (placeholder, value)
import Html.Events exposing (onInput)



-- MODEL


type alias Model =
    { celsius : String
    }


init : Model
init =
    { celsius = ""
    }



-- UPDATE


type Msg
    = UpdateCelsius String


update : Msg -> Model -> Model
update msg model =
    case msg of
        UpdateCelsius value ->
            { model | celsius = value }



-- HELPER FUNCTIONS


celsiusToFahrenheit : Float -> Float
celsiusToFahrenheit c =
    -- TODO: Implement the conversion formula
    0



-- VIEW


view : Model -> Html Msg
view model =
    let
        fahrenheit =
            case String.toFloat model.celsius of
                Just c ->
                    -- TODO: Call celsiusToFahrenheit and format the result
                    "TODO"

                Nothing ->
                    "Enter a valid number"
    in
    div []
        [ input
            [ placeholder "Enter Celsius"
            , value model.celsius
            , onInput UpdateCelsius
            ]
            []
        , text " °C = "
        , text fahrenheit
        ]



-- MAIN


main : Program () Model Msg
main =
    Browser.sandbox
        { init = init
        , update = update
        , view = view
        }