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{-| Some common types.

-}

{-

Copyright (C) 2009 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.HTools.Types

    ( Idx

    , Ndx

    , NameAssoc

    , Result(..)

    , Element(..)

    ) where

-- | The instance index type.

type Idx = Int

-- | The node index type.

type Ndx = Int

-- | The type used to hold name-to-idx mappings.

type NameAssoc = [(String, Int)]

{-|

This is similar to the JSON library Result type - *very* similar, but

we want to use it in multiple places, so we abstract it into a

mini-library here

-}

data Result a

    = Bad String

    | Ok a

    deriving (Show)

instance Monad Result where

    (>>=) (Bad x) _ = Bad x

    (>>=) (Ok x) fn = fn x

    return = Ok

    fail = Bad

-- | A generic class for items that have updateable names and indices.

class Element a where

    -- | Returns the name of the element

    nameOf  :: a -> String

    -- | Returns the index of the element

    idxOf   :: a -> Int

    -- | Updates the name of the element

    setName :: a -> String -> a

    -- | Updates the index of the element

    setIdx  :: a -> Int -> a