content: -----------------------------------------------------------------------------
  -- |
  -- Module      :  Distribution.Verbosity
  -- Copyright   :  Ian Lynagh 2007
  --
  -- Maintainer  :  cabal-devel@haskell.org
  -- Portability :  portable
  --
  -- A simple 'Verbosity' type with associated utilities. There are 4 standard
  -- verbosity levels from 'silent', 'normal', 'verbose' up to 'deafening'. This
  -- is used for deciding what logging messages to print.
  
  -- Verbosity for Cabal functions
  
  {- Copyright (c) 2007, Ian Lynagh
  All rights reserved.
  
  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are
  met:
  
      * Redistributions of source code must retain the above copyright
        notice, this list of conditions and the following disclaimer.
  
      * Redistributions in binary form must reproduce the above
        copyright notice, this list of conditions and the following
        disclaimer in the documentation and/or other materials provided
        with the distribution.
  
      * Neither the name of Isaac Jones nor the names of other
        contributors may be used to endorse or promote products derived
        from this software without specific prior written permission.
  
  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. -}
  
  module Distribution.Verbosity (
    -- * Verbosity
    Verbosity,
    silent, normal, verbose, deafening,
    moreVerbose, lessVerbose,
    intToVerbosity,
    showForCabal, showForGHC
   ) where
  
  import Data.List (elemIndex)
  
  data Verbosity = Silent | Normal | Verbose | Deafening
      deriving (Show, Read, Eq, Ord, Enum, Bounded)
  
  -- We shouldn't print /anything/ unless an error occurs in silent mode
  silent :: Verbosity
  silent = Silent
  
  -- Print stuff we want to see by default
  normal :: Verbosity
  normal = Normal
  
  -- Be more verbose about what's going on
  verbose :: Verbosity
  verbose = Verbose
  
  -- Not only are we verbose ourselves (perhaps even noisier than when
  -- being "verbose"), but we tell everything we run to be verbose too
  deafening :: Verbosity
  deafening = Deafening
  
  moreVerbose :: Verbosity -> Verbosity
  moreVerbose Silent    = Silent    --silent should stay silent
  moreVerbose Normal    = Verbose
  moreVerbose Verbose   = Deafening
  moreVerbose Deafening = Deafening
  
  lessVerbose :: Verbosity -> Verbosity
  lessVerbose Deafening = Deafening
  lessVerbose Verbose   = Normal
  lessVerbose Normal    = Silent
  lessVerbose Silent    = Silent
  
  intToVerbosity :: Int -> Maybe Verbosity
  intToVerbosity 0 = Just Silent
  intToVerbosity 1 = Just Normal
  intToVerbosity 2 = Just Verbose
  intToVerbosity 3 = Just Deafening
  intToVerbosity _ = Nothing
  
  showForCabal, showForGHC :: Verbosity -> String
  
  showForCabal v = maybe (error "unknown verbosity") show $
      elemIndex v [silent,normal,verbose,deafening]
  showForGHC   v = maybe (error "unknown verbosity") show $
      elemIndex v [silent,normal,__,verbose,deafening]
          where __ = silent -- this will be always ignored by elemIndex
  