{-| PyValue contains instances for the 'PyValue' typeclass.

The typeclass 'PyValue' converts Haskell values to Python values.
This module contains instances of this typeclass for several generic
types.  These instances are used in the Haskell to Python generation
of opcodes and constants, for example.

-}

{-

Copyright (C) 2013 Google Inc.
All rights reserved.

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modification, are permitted provided that the following conditions are
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1. Redistributions of source code must retain the above copyright notice,
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2. Redistributions in binary form must reproduce the above copyright
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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 HOLDER OR
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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-}
{-# LANGUAGE ExistentialQuantification #-}
module Ganeti.PyValue
  ( PyValue(..)
  , PyValueEx(..)
  ) where

import Data.List (intercalate)
import Data.Map (Map)
import qualified Data.Map as Map
import qualified Data.Set as Set (toList)

import Ganeti.BasicTypes

-- * PyValue represents data types convertible to Python

-- | Converts Haskell values into Python values
--
-- This is necessary for the default values of opcode parameters and
-- return values.  For example, if a default value or return type is a
-- Data.Map, then it must be shown as a Python dictioanry.
class PyValue a where
  showValue :: a -> String

  showValueList :: [a] -> String
  showValueList xs =  "[" ++ intercalate "," (map showValue xs) ++ "]"

instance PyValue Bool where
  showValue = show

instance PyValue Int where
  showValue = show

instance PyValue Integer where
  showValue = show

instance PyValue Double where
  showValue = show

instance PyValue Char where
  showValue = show
  showValueList = show

instance (PyValue a, PyValue b) => PyValue (a, b) where
  showValue (x, y) = "(" ++ showValue x ++ "," ++ showValue y ++ ")"

instance (PyValue a, PyValue b, PyValue c) => PyValue (a, b, c) where
  showValue (x, y, z) =
    "(" ++
    showValue x ++ "," ++
    showValue y ++ "," ++
    showValue z ++
    ")"

instance PyValue a => PyValue [a] where
  showValue = showValueList

instance (PyValue k, PyValue a) => PyValue (Map k a) where
  showValue mp =
    "{" ++ intercalate ", " (map showPair (Map.assocs mp)) ++ "}"
    where showPair (k, x) = showValue k ++ ":" ++ showValue x

instance PyValue a => PyValue (ListSet a) where
  showValue = showValue . Set.toList . unListSet

-- * PyValue represents an unspecified value convertible to Python

-- | Encapsulates Python default values
data PyValueEx = forall a. PyValue a => PyValueEx a

instance PyValue PyValueEx where
  showValue (PyValueEx x) = showValue x
