content: {-# LANGUAGE OverloadedStrings #-}
  {-| Parser for the output of the @xl list --long@ command of Xen
  
  -}
  {-
  
  Copyright (C) 2013 Google Inc.
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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
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  -}
  module Ganeti.Hypervisor.Xen.XlParser
    ( xlListParser
    , lispConfigParser
    , xlUptimeParser
    , uptimeLineParser
    ) where
  
  import Control.Applicative
  import Control.Monad
  import qualified Data.Attoparsec.Combinator as AC
  import qualified Data.Attoparsec.Text as A
  import Data.Attoparsec.Text (Parser)
  import Data.Char
  import Data.List
  import Data.Text (unpack)
  import qualified Data.Map as Map
  
  import Ganeti.BasicTypes
  import Ganeti.Hypervisor.Xen.Types
  
  -- | A parser for parsing generic config files written in the (LISP-like)
  -- format that is the output of the @xl list --long@ command.
  -- This parser only takes care of the syntactic parse, but does not care
  -- about the semantics.
  -- Note: parsing the double requires checking for the next character in order
  -- to prevent string like "9a" to be recognized as the number 9.
  lispConfigParser :: Parser LispConfig
  lispConfigParser =
    A.skipSpace *>
      (   listConfigP
      <|> doubleP
      <|> stringP
      )
    <* A.skipSpace
      where listConfigP = LCList <$> (A.char '(' *> liftA2 (++)
              (many middleP)
              (((:[]) <$> finalP) <|> (rparen *> pure [])))
            doubleP = LCDouble <$> A.rational <* A.skipSpace <* A.endOfInput
            innerDoubleP = LCDouble <$> A.rational
            stringP = LCString . unpack <$> A.takeWhile1 (not . (\c -> isSpace c
              || c `elem` ("()" :: String)))
            wspace = AC.many1 A.space
            rparen = A.skipSpace *> A.char ')'
            finalP =   listConfigP <* rparen
                   <|> innerDoubleP <* rparen
                   <|> stringP <* rparen
            middleP =   listConfigP <* wspace
                    <|> innerDoubleP <* wspace
                    <|> stringP <* wspace
  
  
  -- | Find a configuration having the given string as its first element,
  -- from a list of configurations.
  findConf :: String -> [LispConfig] -> Result LispConfig
  findConf key configs =
    case find (isNamed key) configs of
      (Just c) -> Ok c
      _ -> Bad "Configuration not found"
  
  -- | Get the value of of a configuration having the given string as its
  -- first element.
  -- The value is the content of the configuration, discarding the name itself.
  getValue :: (FromLispConfig a) => String -> [LispConfig] -> Result a
  getValue key configs = findConf key configs >>= fromLispConfig
  
  -- | Extract the values of a configuration containing a list of them.
  extractValues :: LispConfig -> Result [LispConfig]
  extractValues c = tail `fmap` fromLispConfig c
  
  -- | Verify whether the given configuration has a certain name or not.fmap
  -- The name of a configuration is its first parameter, if it is a string.
  isNamed :: String -> LispConfig -> Bool
  isNamed key (LCList (LCString x:_)) = x == key
  isNamed _ _ = False
  
  -- | Parser for recognising the current state of a Xen domain.
  parseState :: String -> ActualState
  parseState s =
    case s of
      "r-----" -> ActualRunning
      "-b----" -> ActualBlocked
      "--p---" -> ActualPaused
      "---s--" -> ActualShutdown
      "----c-" -> ActualCrashed
      "-----d" -> ActualDying
      _ -> ActualUnknown
  
  -- | Extract the configuration data of a Xen domain from a generic LispConfig
  -- data structure. Fail if the LispConfig does not represent a domain.
  getDomainConfig :: LispConfig -> Result Domain
  getDomainConfig configData = do
    domainConf <-
      if isNamed "domain" configData
        then extractValues configData
        else Bad $ "Not a domain configuration: " ++ show configData
    domid <- getValue "domid" domainConf
    name <- getValue "name" domainConf
    cpuTime <- getValue "cpu_time" domainConf
    state <- getValue "state" domainConf
    let actualState = parseState state
    return $ Domain domid name cpuTime actualState Nothing
  
  -- | A parser for parsing the output of the @xl list --long@ command.
  -- It adds the semantic layer on top of lispConfigParser.
  -- It returns a map of domains, with their name as the key.
  -- FIXME: This is efficient under the assumption that only a few fields of the
  -- domain configuration are actually needed. If many of them are required, a
  -- parser able to directly extract the domain config would actually be better.
  xlListParser :: Parser (Map.Map String Domain)
  xlListParser = do
    configs <- lispConfigParser `AC.manyTill` A.endOfInput
    let domains = map getDomainConfig configs
        foldResult m (Ok val) = Ok $ Map.insert (domName val) val m
        foldResult _ (Bad msg) = Bad msg
    case foldM foldResult Map.empty domains of
      Ok d -> return d
      Bad msg -> fail msg
  
  -- | A parser for parsing the output of the @xl uptime@ command.
  xlUptimeParser :: Parser (Map.Map Int UptimeInfo)
  xlUptimeParser = do
    _ <- headerParser
    uptimes <- uptimeLineParser `AC.manyTill` A.endOfInput
    return $ Map.fromList [(uInfoID u, u) | u <- uptimes]
      where headerParser = A.string "Name" <* A.skipSpace <* A.string "ID"
              <* A.skipSpace <* A.string "Uptime" <* A.skipSpace
  
  -- | A helper for parsing a single line of the @xl uptime@ output.
  uptimeLineParser :: Parser UptimeInfo
  uptimeLineParser = do
    name <- A.takeTill isSpace <* A.skipSpace
    idNum <- A.decimal <* A.skipSpace
    uptime <- A.takeTill (`elem` ("\n\r" :: String)) <* A.skipSpace
    return . UptimeInfo (unpack name) idNum $ unpack uptime
  