-- Copyright (c) 2010, Diego Souza
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module Yql.UI.CLI.Commands.SetEnv
       ( setenv
       ) where

import qualified Yql.Core.Backend as Y
import Yql.UI.CLI.Command

-- | Modifies the env parameters that are sent to yql
setenv :: Y.Yql y => y -> Command (Either String y)
setenv be0 = Command (doc, const exe)
  where doc n  = unlines [ "Modifies the env parameters that are sent to yql"
                         , "Examples:"
                         , "    :"++n++" +foobar  :: Appends the `foobar' string to the env list"
                         , "    :"++n++" -foobar  :: Removes the `foobar' string from the env list"
                         , "    :"++n++" foobar   :: Resets the env, leaving only `foobar' string defined"
                         , "    :"++n++"          :: Dump the current env list"
                         ]
        exe [] = return (Left $ unlines (Y.getenv be0))
        exe es = return (Right $ foldr fold be0 es)
          where fold ('+':env) be = Y.setenv be env
                fold ('-':env) be = Y.unsetenv be env
                fold (env) be     = Y.setenv (foldr (flip Y.unsetenv) be (Y.getenv be)) env