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{-| Provides all lens-related functions.

-}

{-

Copyright (C) 2014 Google Inc.

This program is free software; you can redistribute it and/or modify

it under the terms of the GNU General Public License as published by

the Free Software Foundation; either version 2 of the License, or

(at your option) any later version.

This program is distributed in the hope that it will be useful, but

WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

General Public License for more details.

You should have received a copy of the GNU General Public License

along with this program; if not, write to the Free Software

Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

02110-1301, USA.

-}

module Ganeti.Lens

  ( module Control.Lens

  , makeCustomLenses

  , makeCustomLenses'

  ) where

import Control.Lens

import Control.Monad

import qualified Data.Set as S

import Language.Haskell.TH

lensFieldName :: String -> String

lensFieldName = (++ "L")

-- | Internal helper method for constructing partial set of lenses.

makeCustomLensesFiltered :: (String -> Bool) -> Name -> Q [Dec]

makeCustomLensesFiltered f = makeLensesWith customRules

  where

    customRules :: LensRules

    customRules = set lensField (fmap lensFieldName . mfilter f . Just)

                      defaultRules

-- | Create lenses for all fields of a given data type.

makeCustomLenses :: Name -> Q [Dec]

makeCustomLenses = makeCustomLensesFiltered (const True)

-- | Create lenses for some fields of a given data type.

makeCustomLenses' :: Name -> [Name] -> Q [Dec]

makeCustomLenses' name lst = makeCustomLensesFiltered f name

  where

    allowed = S.fromList . map nameBase $ lst

    f = flip S.member allowed