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.Error.Class (MonadError(throwError))
  19 import Gargantext.Prelude
  20
  21 ------------------------------------------------------------------------
  22 data TreeError = NoRoot
  23                | EmptyRoot
  24                | TooManyRoots
  25
  26 instance Show TreeError
  27   where
  28     show NoRoot       = "Root node not found"
  29     show EmptyRoot    = "Root node should not be empty"
  30     show TooManyRoots = "Too many root nodes"
  31
  32 class HasTreeError e where
  33   _TreeError :: Prism' e TreeError
  34
  35 treeError :: ( MonadError e m
  36              , HasTreeError e)
  37              => TreeError
  38              -> m a
  39 treeError te = throwError $ _TreeError # te
  40