{-# LANGUAGE DataKinds #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE NamedFieldPuns #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeFamilies #-}
{-# OPTIONS_HADDOCK prune not-home #-}

{- |
Copyright   : (c) 2020-2021 Tim Emiola
SPDX-License-Identifier: BSD3
Maintainer  : Tim Emiola <adetokunbo@users.noreply.github.com >

Provides an instance of 'Proc' that launches @postgres@ as a @tmp proc@.

The instance this module provides can be used in integration tests as is.

It's also possible to write other instances that launch @postgres@ in different
ways; for those, this instance can be used as a reference example.
-}
module System.TmpProc.Docker.Postgres
  ( -- * 'Proc' instance
    TmpPostgres (..)

    -- * Useful definitions
  , aProc
  , aHandle

    -- * Re-exports
  , module System.TmpProc
  )
where

import Control.Exception (catch)
import qualified Data.ByteString.Char8 as C8
import Data.String (fromString)
import Data.Text (Text)
import qualified Data.Text as Text
import Database.PostgreSQL.Simple
  ( Connection
  , SqlError
  , close
  , connectPostgreSQL
  , execute_
  )
import System.TmpProc
  ( Connectable (..)
  , HList (..)
  , HandlesOf
  , HostIpAddress
  , Pinged (..)
  , Proc (..)
  , ProcHandle (..)
  , SvcURI
  , only
  , startupAll
  , withTmpConn
  )


-- | A singleton 'HList' containing a 'TmpPostgres'.
aProc :: HList '[TmpPostgres]
aProc = only $ TmpPostgres []


-- | An 'HList' that contains the handle created from 'aProc'.
aHandle :: IO (HandlesOf '[TmpPostgres])
aHandle = startupAll aProc


{- | Provides the capability to launch a Postgres database as a @tmp proc@.

The constructor receives the names of the tables to be dropped on 'reset'.
-}
newtype TmpPostgres = TmpPostgres [Text]


-- | Specifies how to run @postgres@ as a @tmp proc@.
instance Proc TmpPostgres where
  type Image TmpPostgres = "postgres:10.6"
  type Name TmpPostgres = "a-postgres-db"
  uriOf = mkUri'
  runArgs = runArgs'
  ping = toPinged . connectPostgreSQL . hUri
  reset = reset'


-- | Specifies how to connect to a tmp @postgres@ db.
instance Connectable TmpPostgres where
  type Conn TmpPostgres = Connection
  openConn = connectPostgreSQL . hUri
  closeConn = close


-- | Makes a uri whose password matches the one specified in 'runArgs''.
mkUri' :: HostIpAddress -> SvcURI
mkUri' ip =
  "postgres://postgres:"
    <> dbPassword
    <> "@"
    <> C8.pack (Text.unpack ip)
    <> "/postgres"


dbPassword :: C8.ByteString
dbPassword = "mysecretpassword"


-- | Match the password used in 'mkUri''.
runArgs' :: [Text]
runArgs' =
  [ "-e"
  , "POSTGRES_PASSWORD=" <> Text.pack (C8.unpack dbPassword)
  ]


toPinged :: IO a -> IO Pinged
toPinged action =
  ( (action >> pure OK)
      `catch` (\(_ :: SqlError) -> pure NotOK)
  )
    `catch` (\(_ :: IOError) -> pure NotOK)


-- | Empty all rows in the tables, if any are specified.
reset' :: ProcHandle TmpPostgres -> IO ()
reset' handle@(ProcHandle {hProc}) =
  let go (TmpPostgres []) = pure ()
      go (TmpPostgres tables) = withTmpConn handle $ \c ->
        mapM_ (execute_ c . (fromString . (++) "DELETE FROM ") . Text.unpack) tables
   in go hProc