paint_calculator.elm

module PaintCalculator where

import Html exposing (..)
import Html.Attributes exposing(..)
import Html.Events exposing(..)
import String exposing (..)
import Signal exposing (Address)

import StartApp.Simple as StartApp

type alias Model = 
  {
    length: String,
    width: String,
    gallons: Int
  }
  
  
initialModel : Model
initialModel = 
  { 
    length = "0",
    width = "0",
    gallons = 0
  }
  


type Action
  = NoOp 
  | SetLength String
  | SetWidth String
  | Calculate

update action model = 
  case action of
    NoOp ->
      model
      
    SetLength length ->
      {model | length = length }
      
    SetWidth width ->
      {model | width = width }
      
    Calculate ->
      {model | gallons = (calculateGallons model.length model.width) }
      
calculateGallons : String -> String -> Int
calculateGallons length width = 
  let l = 
        case String.toFloat length of
          Ok n -> n
          Err _ -> 0.0
      w = 
        case String.toFloat width of
          Ok n -> n
          Err _ -> 0.0
  


  in
    ceiling ((l * w) / 350)
  
  

view : Address Action -> Model -> Html
view address model =
  div [] [
    h1 [] [text "Ceiling Paint Calculator"],
    p [] [text "Enter dimensions of the ceiling to determine gallons of paint needed."],
    div [] [
  
      label 
        [for "length"] [text "Length"],
    
      input 
        [id "length",
        on "input" targetValue (\value -> Signal.message address (SetLength value))   
        ] []
    ],
  
    div [] [
      label 
        [for "width"] [text "width"],
    
      input 
        [
          id "width", 
          on "input" targetValue (\value -> Signal.message address (SetWidth value))   
        ] []
     ],
     
     div [] [
      button [onClick address Calculate] [text "Calculate"],
      div [] [
        span [] [text (toString model.gallons)],
        span [] [text " gallons of paint needed."]
      ]
    ]
  ]

main =
 StartApp.start { model = initialModel, view = view, update = update }