module Propellor.Property.Cron (
        Times(..),
        job,
        niceJob,
        jobDropped,
        Propellor.Property.Cron.runPropellor
) where

import Propellor.Base
import qualified Propellor.Property.File as File
import qualified Propellor.Property.Apt as Apt
import Propellor.Bootstrap

import Data.Char

-- | When to run a cron job.
--
-- The Daily, Monthly, and Weekly options allow the cron job to be run
-- by anacron, which is useful for non-servers.
data Times
        = Times String -- ^ formatted as in crontab(5)
        | Daily
        | Weekly
        | Monthly

-- | Installs a cron job, that will run as a specified user in a particular
-- directory. Note that the Desc must be unique, as it is used for the
-- cron job filename.
--
-- Only one instance of the cron job is allowed to run at a time, no matter
-- how long it runs. This is accomplished using flock locking of the cron
-- job file.
--
-- The cron job's output will only be emailed if it exits nonzero.
job :: Desc -> Times -> User -> FilePath -> String -> Property DebianLike
job desc times (User u) cddir command = combineProperties ("cronned " ++ desc) $ props
        & Apt.serviceInstalledRunning "cron"
        & Apt.installed ["util-linux", "moreutils"]
        & cronjobfile desc times `File.hasContent`
                [ case times of
                        Times _ -> ""
                        _ -> "#!/bin/sh\nset -e"
                , "# Generated by propellor"
                , ""
                , "SHELL=/bin/sh"
                , "PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin"
                , ""
                , case times of
                        Times t -> t ++ "\t" ++ u ++ "\tchronic "
                                ++ shellEscape (scriptfile desc)
                        _ -> case u of
                                "root" -> "chronic " ++ shellEscape (scriptfile desc)
                                _ -> "chronic su " ++ u ++ " -c "
                                        ++ shellEscape (scriptfile desc)
                ]
        & case times of
                Times _ -> doNothing
                _ -> (cronjobfile desc times)
                        `File.mode` combineModes (readModes ++ executeModes)
        -- Use a separate script because it makes the cron job name
        -- prettier in emails, and also allows running the job manually.
        & scriptfile desc `File.hasContent`
                [ "#!/bin/sh"
                , "# Generated by propellor"
                , "set -e"
                , "flock -n " ++ shellEscape (cronjobfile desc times)
                        ++ " sh -c " ++ shellEscape cmdline
                ]
        & scriptfile desc `File.mode` combineModes (readModes ++ executeModes)
  where
        cmdline = "cd " ++ cddir ++ " && ( " ++ command ++ " )"

-- | Removes a cron job created by 'job' or 'niceJob', as identified by the
-- 'Desc' passed to those properties when the cronjob was set up
--
-- Those properties are not revertable because simply removing a cronjob does
-- not undo the changes it might have made to the system, i.e., 'jobDropped' is
-- not in the general case a reversion of 'job' or 'niceJob'
jobDropped :: Desc -> Times -> Property UnixLike
jobDropped desc times = combineProperties ("uncronned " ++ desc) $ props
        & File.notPresent (scriptfile desc)
        & File.notPresent (cronjobfile desc times)

-- | Installs a cron job, and runs it niced and ioniced.
niceJob :: Desc -> Times -> User -> FilePath -> String -> Property DebianLike
niceJob desc times user cddir command = job desc times user cddir
        ("nice ionice -c 3 sh -c " ++ shellEscape command)

-- | Installs a cron job to run propellor.
runPropellor :: Times -> RevertableProperty DebianLike UnixLike
runPropellor times = cronned <!> uncronned
  where
        cronned = withOS "propellor cron job" $ \w o -> do
                bootstrapper <- getBootstrapper
                ensureProperty w $
                        niceJob "propellor" times (User "root") localdir
                                (bootstrapPropellorCommand bootstrapper o ++ "; ./propellor")
        uncronned = jobDropped "propellor" times

-- Utility functions

cronjobname :: Desc -> String
cronjobname d = map sanitize d
  where
        sanitize c
                | isAlphaNum c = c
                | otherwise = '_'

scriptfile :: Desc -> FilePath
scriptfile d = "/usr/local/bin/" ++ (cronjobname d) ++ "_cronjob"

cronjobfile :: Desc -> Times -> FilePath
cronjobfile d times = "/etc" </> cronjobdir </> (cronjobname d)
  where
        cronjobdir = case times of
                Times _ -> "cron.d"
                Daily -> "cron.daily"
                Weekly -> "cron.weekly"
                Monthly -> "cron.monthly"