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{-| Implementation of the Ganeti Query2 functionality.

 -}

{-

Copyright (C) 2012 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.Query.Query

    ( query

    ) where

import Data.Maybe (fromMaybe)

import qualified Data.Map as Map

import Ganeti.BasicTypes

import Ganeti.HTools.JSON

import Ganeti.Qlang

import Ganeti.Query.Common

import Ganeti.Query.Types

import Ganeti.Query.Node

import Ganeti.Objects

-- * Helper functions

-- | Builds an unknown field definition.

mkUnknownFDef :: String -> FieldData a b

mkUnknownFDef name =

  ( FieldDefinition name name QFTUnknown ("Unknown field '" ++ name ++ "'")

  , FieldUnknown )

-- | Runs a field getter on the existing contexts.

execGetter :: ConfigData -> b -> a -> FieldGetter a b -> ResultEntry

execGetter _   _ item (FieldSimple getter)  = getter item

execGetter cfg _ item (FieldConfig getter)  = getter cfg item

execGetter _  rt item (FieldRuntime getter) = getter rt item

execGetter _   _ _    FieldUnknown          = rsUnknown

-- * Main query execution

-- | Helper to build the list of requested fields. This transforms the

-- list of string fields to a list of field defs and getters, with

-- some of them possibly being unknown fields.

getSelectedFields :: FieldMap a b  -- ^ Defined fields

                  -> [String]      -- ^ Requested fields

                  -> FieldList a b -- ^ Selected fields

getSelectedFields defined =

  map (\name -> fromMaybe (mkUnknownFDef name) $ name `Map.lookup` defined)

-- | Main query execution function.

query :: ConfigData   -- ^ The current configuration

      -> Query        -- ^ The query (item, fields, filter)

      -> IO (Result QueryResult) -- ^ Result

query cfg (Query QRNode fields _) = return $ do

  let selected = getSelectedFields nodeFieldsMap fields

      (fdefs, fgetters) = unzip selected

      nodes = Map.elems . fromContainer $ configNodes cfg

      fdata = map (\node -> map (execGetter cfg NodeRuntime node) fgetters)

              nodes

  return QueryResult { qresFields = fdefs, qresData = fdata }

query _ (Query qkind _ _) =

  return . Bad $ "Query '" ++ show qkind ++ "' not supported"