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 FlexibleContexts  #-}
  13 {-# LANGUAGE NoImplicitPrelude #-}
  14 {-# LANGUAGE OverloadedStrings #-}
  15 {-# LANGUAGE QuasiQuotes       #-}
  16 {-# LANGUAGE RankNTypes        #-}
  17
  18 module Gargantext.Database.Query.Tree.Error
  19   where
  20
  21 import Control.Lens (Prism', (#))
  22 import Control.Monad.Error.Class (MonadError(throwError))
  23 import Gargantext.Prelude
  24
  25 ------------------------------------------------------------------------
  26 data TreeError = NoRoot
  27                | EmptyRoot
  28                | TooManyRoots
  29
  30 instance Show TreeError
  31   where
  32     show NoRoot       = "Root node not found"
  33     show EmptyRoot    = "Root node should not be empty"
  34     show TooManyRoots = "Too many root nodes"
  35
  36 class HasTreeError e where
  37   _TreeError :: Prism' e TreeError
  38
  39 treeError :: ( MonadError e m
  40              , HasTreeError e)
  41              => TreeError
  42              -> m a
  43 treeError te = throwError $ _TreeError # te
  44