{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE OverloadedStrings #-}
module Main where

import qualified Data.Text as T
import Lens.Micro ((^.))
import Lens.Micro.TH
import Data.Monoid ((<>))

import qualified Graphics.Vty as V
import Brick
import Brick.Forms
  ( Form
  , newForm
  , formState
  , formFocus
  , setFieldValid
  , renderForm
  , handleFormEvent
  , invalidFields
  , allFieldsValid
  , focusedFormInputAttr
  , invalidFormInputAttr
  , checkboxField
  , radioField
  , editShowableField
  , editTextField
  , editPasswordField
  , (@@=)
  )
import Brick.Focus
  ( focusGetCurrent
  , focusRingCursor
  )
import qualified Brick.Widgets.Edit as E
import qualified Brick.Widgets.Border as B
import qualified Brick.Widgets.Center as C

data Name = NameField
          | AgeField
          | BikeField
          | HandedField
          | PasswordField
          | LeftHandField
          | RightHandField
          | AmbiField
          | AddressField
          deriving (Eq, Ord, Show)

data Handedness = LeftHanded | RightHanded | Ambidextrous
                deriving (Show, Eq)

data UserInfo =
    UserInfo { _name      :: T.Text
             , _age       :: Int
             , _address   :: T.Text
             , _ridesBike :: Bool
             , _handed    :: Handedness
             , _password  :: T.Text
             }
             deriving (Show)

makeLenses ''UserInfo

-- This form is covered in the Brick User Guide; see the "Input Forms"
-- section.
mkForm :: UserInfo -> Form UserInfo e Name
mkForm =
    let label s w = padBottom (Pad 1) $
                    (vLimit 1 $ hLimit 15 $ str s <+> fill ' ') <+> w
    in newForm [ label "Name" @@=
                   editTextField name NameField (Just 1)
               , label "Address" @@=
                 B.borderWithLabel (str "Mailing") @@=
                   editTextField address AddressField (Just 3)
               , label "Age" @@=
                   editShowableField age AgeField
               , label "Password" @@=
                   editPasswordField password PasswordField
               , label "Dominant hand" @@=
                   radioField handed [ (LeftHanded, LeftHandField, "Left")
                                     , (RightHanded, RightHandField, "Right")
                                     , (Ambidextrous, AmbiField, "Both")
                                     ]
               , label "" @@=
                   checkboxField ridesBike BikeField "Do you ride a bicycle?"
               ]

theMap :: AttrMap
theMap = attrMap V.defAttr
  [ (E.editAttr, V.white `on` V.black)
  , (E.editFocusedAttr, V.black `on` V.yellow)
  , (invalidFormInputAttr, V.white `on` V.red)
  , (focusedFormInputAttr, V.black `on` V.yellow)
  ]

draw :: Form UserInfo e Name -> [Widget Name]
draw f = [C.vCenter $ C.hCenter form <=> C.hCenter help]
    where
        form = B.border $ padTop (Pad 1) $ hLimit 50 $ renderForm f
        help = padTop (Pad 1) $ B.borderWithLabel (str "Help") body
        body = str $ "- Name is free-form text\n" <>
                     "- Age must be an integer (try entering an\n" <>
                     "  invalid age!)\n" <>
                     "- Handedness selects from a list of options\n" <>
                     "- The last option is a checkbox\n" <>
                     "- Enter/Esc quit, mouse interacts with fields"

app :: App (Form UserInfo e Name) e Name
app =
    App { appDraw = draw
        , appHandleEvent = \s ev ->
            case ev of
                VtyEvent (V.EvResize {})     -> continue s
                VtyEvent (V.EvKey V.KEsc [])   -> halt s
                -- Enter quits only when we aren't in the multi-line editor.
                VtyEvent (V.EvKey V.KEnter [])
                    | focusGetCurrent (formFocus s) /= Just AddressField -> halt s
                _ -> do
                    s' <- handleFormEvent ev s

                    -- Example of external validation:
                    -- Require age field to contain a value that is at least 18.
                    continue $ setFieldValid ((formState s')^.age >= 18) AgeField s'

        , appChooseCursor = focusRingCursor formFocus
        , appStartEvent = return
        , appAttrMap = const theMap
        }

main :: IO ()
main = do
    let buildVty = do
          v <- V.mkVty =<< V.standardIOConfig
          V.setMode (V.outputIface v) V.Mouse True
          return v

        initialUserInfo = UserInfo { _name = ""
                                   , _address = ""
                                   , _age = 0
                                   , _handed = RightHanded
                                   , _ridesBike = False
                                   , _password = ""
                                   }
        f = setFieldValid False AgeField $
            mkForm initialUserInfo

    f' <- customMain buildVty Nothing app f

    putStrLn "The starting form state was:"
    print initialUserInfo

    putStrLn "The final form state was:"
    print $ formState f'

    if allFieldsValid f'
       then putStrLn "The final form inputs were valid."
       else putStrLn $ "The final form had invalid inputs: " <> show (invalidFields f')