src/Gargantext/Database/Query/Tree/Error.hs

   1 {-|
   2 Module      : Gargantext.Database.Tree.Error
   3 Description :
   4 Copyright   : (c) CNRS, 2017-Present
   5 License     : AGPL + CECILL v3
   6 Maintainer  : team@gargantext.org
   7 Stability   : experimental
   8 Portability : POSIX
   9
  10 -}
  11
  12 {-# LANGUAGE QuasiQuotes       #-}
  13
  14 module Gargantext.Database.Query.Tree.Error
  15   where
  16
  17 import Control.Lens (Prism', (#))
  18 import Control.Monad.Except (MonadError(throwError))
  19
  20 import Gargantext.Prelude
  21
  22 ------------------------------------------------------------------------
  23 data TreeError = NoRoot
  24                | EmptyRoot
  25                | TooManyRoots
  26
  27 instance Show TreeError
  28   where
  29     show NoRoot       = "Root node not found"
  30     show EmptyRoot    = "Root node should not be empty"
  31     show TooManyRoots = "Too many root nodes"
  32
  33 class HasTreeError e where
  34   _TreeError :: Prism' e TreeError
  35
  36 treeError :: ( MonadError e m
  37              , HasTreeError e )
  38              => TreeError
  39              -> m a
  40 treeError te = throwError $ _TreeError # te
  41