EFP #8

pizza_party.elm

import Html.App exposing (beginnerProgram)
import Html exposing(Html, Attribute, button, div, text, span, label, input, p)
import Html.Attributes exposing(value, style, placeholder)
import Html.Events exposing(onClick, onInput)
import String exposing(toFloat)


main =
  beginnerProgram {model = model, view = view, update = update}
  

-- types

type Msg = 
  NoOp
  | NumberOfPeople String
  | NumberOfPizzas String
  | NumberOfSlicesPerPizza String
  | CalculatePiecesPerPerson


type alias Model =
  { numberOfPeople: String
  , numberOfPizzas: String
  , numberOfSlicesPerPizza: String
  , piecesPerPerson: Int  
  , leftovers: Int
  }
 
 
-- model

model: Model
model =
  { numberOfPeople = "2"
  , numberOfPizzas = "2"
  , numberOfSlicesPerPizza = "8"
  , piecesPerPerson = 0
  , leftovers = 0
  }


  
-- view

view: Model -> Html Msg
view model = 
  div [] [
    div [] [
      label [labelStyle] [text "Number Of People"]
    , input [placeholder "0", onInput NumberOfPeople, value model.numberOfPeople] []
    ]
  , div [] [
      label [labelStyle] [text "Number of pizzas"]
    , input [placeholder "0", onInput NumberOfPizzas, value model.numberOfPizzas] []
    ]
  , div [] [
      label [labelStyle] [text "Number of slices per person"]
    , input [onInput NumberOfSlicesPerPizza, value model.numberOfSlicesPerPizza] []
    ]
  , p [] [
    text "Each person gets "
    , text (toString model.piecesPerPerson)
    ]
  , p [] [
      text (toString model.leftovers)
    , text " left over"
    ]
  , button [onClick CalculatePiecesPerPerson] [text "Calculate"]
  ]
 
 
-- update

update: Msg -> Model -> Model
update message model = 
  case message of
    NoOp -> model
    
    NumberOfPeople p ->
      { model | numberOfPeople = p }
      
    NumberOfPizzas p ->
      { model | numberOfPizzas = p }
      
    NumberOfSlicesPerPizza s ->
      { model | numberOfSlicesPerPizza = s }
    
    CalculatePiecesPerPerson ->
      let 
        (pieces, leftovers) = calculateSlices model
      in
        { model | piecesPerPerson = pieces, leftovers = leftovers  }
      
 
-- work

calculateSlices: Model -> (Int, Int)
calculateSlices model = 
  let
    numberOfPeople         = convertToInt model.numberOfPeople
    numberOfPizzas         = convertToInt model.numberOfPizzas
    numberOfSlicesPerPizza = convertToInt model.numberOfSlicesPerPizza

  in
  -- return (piences, leftovers)
    ( ((numberOfPizzas * numberOfSlicesPerPizza) // numberOfPeople)
    , ((numberOfPizzas * numberOfSlicesPerPizza) % numberOfPeople) 
    )
  

-- Custom label style. Can be used as an attribute in HTML.
labelStyle: Attribute Msg
labelStyle =
  style
    [ ("width", "200px")
    , ("padding", "10px")
    , ("text-align", "right")
    , ("display", "inline-block")
    ]


convertToInt: String -> Int
convertToInt number =
  case String.toInt number of
    Err msg -> 0
    Ok val -> val