Main.hs

-- | This module defines the main entry point for the application.
module CabalGild.Main where

import qualified CabalGild.Action.AttachComments as AttachComments
import qualified CabalGild.Action.EvaluatePragmas as EvaluatePragmas
import qualified CabalGild.Action.ExtractComments as ExtractComments
import qualified CabalGild.Action.FormatFields as FormatFields
import qualified CabalGild.Action.GetCabalVersion as GetCabalVersion
import qualified CabalGild.Action.ReflowText as ReflowText
import qualified CabalGild.Action.RemovePositions as RemovePositions
import qualified CabalGild.Action.Render as Render
import qualified CabalGild.Action.StripBlanks as StripBlanks
import qualified CabalGild.Class.MonadLog as MonadLog
import qualified CabalGild.Class.MonadRead as MonadRead
import qualified CabalGild.Class.MonadWalk as MonadWalk
import qualified CabalGild.Class.MonadWrite as MonadWrite
import qualified CabalGild.Exception.CheckFailure as CheckFailure
import qualified CabalGild.Exception.ParseError as ParseError
import qualified CabalGild.Type.Config as Config
import qualified CabalGild.Type.Context as Context
import qualified CabalGild.Type.Flag as Flag
import qualified CabalGild.Type.Input as Input
import qualified CabalGild.Type.Mode as Mode
import qualified Control.Monad as Monad
import qualified Control.Monad.Catch as Exception
import qualified Data.ByteString as ByteString
import qualified Data.ByteString.Char8 as Latin1
import qualified Distribution.Fields as Fields
import qualified System.Environment as Environment
import qualified System.Exit as Exit
import qualified System.IO as IO

-- | This is the main entry point for the application. It gets the command line
-- arguments and then hands things off to 'mainWith'. If any exceptions are
-- thrown, they will be handled by 'onException'.
defaultMain :: IO ()
defaultMain = Exception.handle onException $ do
  arguments <- Environment.getArgs
  mainWith arguments

-- | If the exception was an 'Exit.ExitCode', simply exit with that code.
-- Otherwise handle exceptions by printing them to STDERR using
-- 'Exception.displayException' instead of 'show'. Then exit with a failing
-- status code.
onException :: Exception.SomeException -> IO a
onException e = case Exception.fromException e of
  Just exitCode -> Exit.exitWith exitCode
  Nothing -> do
    IO.hPutStrLn IO.stderr $ Exception.displayException e
    Exit.exitFailure

-- | The actual logic for the command line application. This is written using
-- constraints so that it can be run in pure code if so desired. But most often
-- this will be run in 'IO'.
mainWith ::
  ( MonadLog.MonadLog m,
    MonadRead.MonadRead m,
    Exception.MonadThrow m,
    MonadWalk.MonadWalk m,
    MonadWrite.MonadWrite m
  ) =>
  [String] ->
  m ()
mainWith arguments = do
  flags <- Flag.fromArguments arguments
  config <- Config.fromFlags flags
  context <- Context.fromConfig config

  let source = Context.input context
  input <- MonadRead.read source
  fields <-
    either (Exception.throwM . ParseError.ParseError) pure $
      Fields.readFields input
  let csv = GetCabalVersion.fromFields fields
      comments = ExtractComments.fromByteString input
      path = case source of
        Input.Stdin -> Context.stdin context
        Input.File f -> f
  output <-
    ( StripBlanks.run
        Monad.>=> AttachComments.run
        Monad.>=> ReflowText.run csv
        Monad.>=> RemovePositions.run
        Monad.>=> EvaluatePragmas.run path
        Monad.>=> FormatFields.run csv
        Monad.>=> Render.run
      )
      (fields, comments)

  case Context.mode context of
    Mode.Check -> do
      -- The input might have CRLF ("\r\n", 0x0d 0x0a) line endings, but the
      -- output will always have LF line endings. For the purposes of the check
      -- command, we'll consider the input formatted if it only differs from
      -- the output in line endings.
      let outputLines = Latin1.lines output
          stripCR x = case ByteString.unsnoc x of
            Just (y, 0x0d) -> y
            _ -> x
          inputLines = stripCR <$> Latin1.lines input
      Monad.when (outputLines /= inputLines) $
        Exception.throwM CheckFailure.CheckFailure
    Mode.Format -> do
      let target = Context.output context
      MonadWrite.write target output