{- | A Go-like EDSL to make working with concurrent in-process code a bit
   easier to read.

This module is expected to be imported qualified as `Go`.

$example
-}
{-# LANGUAGE NoImplicitPrelude #-}
module Com.Simatime.Go
  (
  -- * Running and forking
    Go
  , run
  , fork
  -- * Channels
  , Channel
  , chan
  , read
  , write
  )
where

import           Control.Concurrent             ( forkIO
                                                , ThreadId
                                                )
import           Control.Concurrent.STM.TChan   ( newTChan
                                                , readTChan
                                                , writeTChan
                                                , TChan
                                                )
import           GHC.Conc                       ( STM
                                                , atomically
                                                )
import           Protolude                      ( IO()
                                                , MonadIO(liftIO)
                                                , flip
                                                , (.)
                                                )
type Go = STM
type Channel = TChan

-- | Runs a Go command in IO.
run :: Go a -> IO a
run = atomically

-- | Starts a background process.
fork :: IO () -> IO ThreadId
fork = forkIO

-- | Make a new channel.
chan :: Go (Channel a)
chan = newTChan

-- | Take from a channel. Blocks until a value is received.
read :: Channel a -> Go a
read = readTChan

-- | Write to a channel.
write :: Channel a -> a -> Go ()
write = writeTChan

{- $example

A simple example from ghci:

>>> import qualified Com.Simatime.Go as Go
>>> c <- Go.run Go.chan :: IO (Go.Channel Text)
>>> Go.run $ Go.write c "test"
>>> Go.run $ Go.read c
"test"
-}