{-# LANGUAGE DeriveGeneric         #-}
{-# LANGUAGE FlexibleInstances     #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE OverloadedStrings     #-}

-- | Module supporting the use of docker containers as external tasks.
--
--   In general, an external task can be any command. This module just makes it
--   easier to specify certain tasks which will run inside docker containers. It
--   handles constructing the call to docker, mounting input and output
--   directories, and specifying the docker image and version to use.
module Control.Funflow.External.Docker where

import           Control.Funflow.ContentHashable
import           Control.Funflow.External
import           Data.Map.Strict                 (Map)
import qualified Data.Map.Strict                 as Map
import           Data.Semigroup                  ((<>))
import qualified Data.Text                       as T
import           GHC.Generics                    (Generic)
import           System.FilePath

data Bind
  -- | Single input, will get mounted to @/input@ on the image.
  = SingleInput InputPath
  -- | Multiple inputs, each gets mouted into a subdirectory under
  -- @/input@ as described by the given mapping.
  | MultiInput (Map FilePath InputPath)
  deriving Generic

instance ContentHashable IO Bind

data Config = Config
  { image      :: T.Text
  , optImageID :: Maybe T.Text
  , input      :: Bind
  , command    :: FilePath
  , args       :: [T.Text]
  } deriving Generic

instance ContentHashable IO Config

toExternal :: Config -> ExternalTask
toExternal cfg = ExternalTask
  -- XXX: Allow to configure the path to the docker executable.
  { _etCommand = "docker"
  , _etParams =
      [ "run"
      , "--user=" <> uidParam
      ] ++ mounts ++
      [ imageArg
      , stringParam (command cfg)
      ] ++ map textParam (args cfg)
  , _etWriteToStdOut = False
  }
  where
    mounts = outputMount : inputMounts
    mount src dst =
      "--volume=" <> pathParam src <> ":" <> stringParam dst
    outputMount = "--volume=" <> outParam <> ":/output"
    inputMounts = case input cfg of
      SingleInput chash -> [ mount chash "/input" ]
      MultiInput cmap ->
        [ mount chash ("/input" </> dest)
        | (dest, chash) <- Map.toList cmap
        ]
    imageArg = textParam $ case optImageID cfg of
      Nothing  -> image cfg
      Just id' -> image cfg <> ":" <> id'