{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE PackageImports #-}
{-# LANGUAGE QuasiQuotes #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
-- | Parse forms (and query strings).
module Yesod.Form
    ( -- * Data types
      GForm
    , FormResult (..)
    , Enctype (..)
      -- * Unwrapping functions
    , runFormGet
    , runFormPost
    , runFormGet'
    , runFormPost'
      -- * Field/form helpers
    , fieldsToTable
    , fieldsToPlain
    , module Yesod.Form.Fields
      -- * Template Haskell
    , mkToForm
    ) where

import Yesod.Form.Core
import Yesod.Form.Fields
import Yesod.Form.Class

import Text.Hamlet
import Yesod.Request
import Yesod.Handler
import Control.Applicative hiding (optional)
import Data.Maybe (fromMaybe, mapMaybe)
import "transformers" Control.Monad.IO.Class
import Control.Monad ((<=<))
import Control.Monad.Trans.State
import Language.Haskell.TH.Syntax
import Database.Persist.Base (EntityDef (..))
import Data.Char (toUpper, isUpper)
import Yesod.Widget
import Control.Arrow ((&&&))
import Data.List (group, sort)

-- | Display only the actual input widget code, without any decoration.
fieldsToPlain :: [FieldInfo sub y] -> GWidget sub y ()
fieldsToPlain = mapM_ fiInput

-- | Display the label, tooltip, input code and errors in a single row of a
-- table.
fieldsToTable :: [FieldInfo sub y] -> GWidget sub y ()
fieldsToTable = mapM_ go
  where
    go fi = do
        wrapWidget (fiInput fi) $ \w -> [$hamlet|
%tr
    %td
        %label!for=$fiIdent.fi$ $fiLabel.fi$
        .tooltip $fiTooltip.fi$
    %td
        ^w^
    $maybe fiErrors.fi err
        %td.errors $err$
|]

runFormGeneric :: Env
               -> FileEnv
               -> GForm sub y xml a
               -> GHandler sub y (FormResult a, xml, Enctype)
runFormGeneric env fe f = evalStateT (deform f env fe) $ IntSingle 1

-- | Run a form against POST parameters.
runFormPost :: GForm sub y xml a
            -> GHandler sub y (FormResult a, xml, Enctype)
runFormPost f = do
    rr <- getRequest
    (pp, files) <- liftIO $ reqRequestBody rr
    runFormGeneric pp files f

-- | Run a form against POST parameters, disregarding the resulting HTML and
-- returning an error response on invalid input.
runFormPost' :: GForm sub y xml a -> GHandler sub y a
runFormPost' = helper <=< runFormPost

-- | Run a form against GET parameters, disregarding the resulting HTML and
-- returning an error response on invalid input.
runFormGet' :: GForm sub y xml a -> GHandler sub y a
runFormGet' = helper <=< runFormGet

helper :: (FormResult a, b, c) -> GHandler sub y a
helper (FormSuccess a, _, _) = return a
helper (FormFailure e, _, _) = invalidArgs e
helper (FormMissing, _, _) = invalidArgs ["No input found"]

-- | Run a form against GET parameters.
runFormGet :: GForm sub y xml a
           -> GHandler sub y (FormResult a, xml, Enctype)
runFormGet f = do
    gs <- reqGetParams `fmap` getRequest
    runFormGeneric gs [] f

-- | Create 'ToForm' instances for the entities given. In addition to regular 'EntityDef' attributes understood by persistent, it also understands label= and tooltip=.
mkToForm :: [EntityDef] -> Q [Dec]
mkToForm = mapM derive
  where
    afterPeriod s =
        case dropWhile (/= '.') s of
            ('.':t) -> t
            _ -> s
    beforePeriod s =
        case break (== '.') s of
            (t, '.':_) -> Just t
            _ -> Nothing
    getSuperclass (_, _, z) = getTFF' z >>= beforePeriod
    getTFF (_, _, z) = maybe "toFormField" afterPeriod $ getTFF' z
    getTFF' [] = Nothing
    getTFF' (('t':'o':'F':'o':'r':'m':'F':'i':'e':'l':'d':'=':x):_) = Just x
    getTFF' (_:x) = getTFF' x
    getLabel (x, _, z) = fromMaybe (toLabel x) $ getLabel' z
    getLabel' [] = Nothing
    getLabel' (('l':'a':'b':'e':'l':'=':x):_) = Just x
    getLabel' (_:x) = getLabel' x
    getTooltip (_, _, z) = fromMaybe "" $ getTooltip' z
    getTooltip' (('t':'o':'o':'l':'t':'i':'p':'=':x):_) = Just x
    getTooltip' (_:x) = getTooltip' x
    getTooltip' [] = Nothing
    getId (_, _, z) = fromMaybe "" $ getId' z
    getId' (('i':'d':'=':x):_) = Just x
    getId' (_:x) = getId' x
    getId' [] = Nothing
    getName (_, _, z) = fromMaybe "" $ getName' z
    getName' (('n':'a':'m':'e':'=':x):_) = Just x
    getName' (_:x) = getName' x
    getName' [] = Nothing
    derive :: EntityDef -> Q Dec
    derive t = do
        let cols = map ((getId &&& getName) &&& ((getLabel &&& getTooltip) &&& getTFF)) $ entityColumns t
        ap <- [|(<*>)|]
        just <- [|pure|]
        nothing <- [|Nothing|]
        let just' = just `AppE` ConE (mkName $ entityName t)
        string' <- [|string|]
        mfx <- [|mapFormXml|]
        ftt <- [|fieldsToTable|]
        ffs' <- [|FormFieldSettings|]
        let stm "" = nothing
            stm x = just `AppE` LitE (StringL x)
        let go_ = go ap just' ffs' stm string' mfx ftt
        let c1 = Clause [ ConP (mkName "Nothing") []
                        ]
                        (NormalB $ go_ $ zip cols $ map (const nothing) cols)
                        []
        xs <- mapM (const $ newName "x") cols
        let xs' = map (AppE just . VarE) xs
        let c2 = Clause [ ConP (mkName "Just") [ConP (mkName $ entityName t)
                            $ map VarP xs]]
                        (NormalB $ go_ $ zip cols xs')
                        []
        let y = mkName "y"
        let ctx = map (\x -> ClassP (mkName x) [VarT y])
                $ map head $ group $ sort
                $ mapMaybe getSuperclass
                $ entityColumns t
        return $ InstanceD ctx ( ConT ''ToForm
                              `AppT` ConT (mkName $ entityName t)
                              `AppT` VarT y)
            [FunD (mkName "toForm") [c1, c2]]
    go ap just' ffs' stm string' mfx ftt a =
        let x = foldl (ap' ap) just' $ map (go' ffs' stm string') a
         in mfx `AppE` ftt `AppE` x
    go' ffs' stm string' (((theId, name), ((label, tooltip), tff)), ex) =
        let label' = string' `AppE` LitE (StringL label)
            tooltip' = string' `AppE` LitE (StringL tooltip)
            ffs = ffs' `AppE`
                  label' `AppE`
                  tooltip' `AppE`
                  (stm theId) `AppE`
                  (stm name)
         in VarE (mkName tff) `AppE` ffs `AppE` ex
    ap' ap x y = InfixE (Just x) ap (Just y)

toLabel :: String -> String
toLabel "" = ""
toLabel (x:rest) = toUpper x : go rest
  where
    go "" = ""
    go (c:cs)
        | isUpper c = ' ' : c : go cs
        | otherwise = c : go cs