{-| This module contains the top-level entrypoint and options parsing for the
    @dhall@ executable
-}

{-# LANGUAGE DeriveAnyClass    #-}
{-# LANGUAGE LambdaCase        #-}
{-# LANGUAGE NamedFieldPuns    #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE RecordWildCards   #-}

module Dhall.Main
    ( -- * Options
      Options(..)
    , Mode(..)
    , parseOptions
    , parserInfoOptions

      -- * Execution
    , command
    , main
    ) where

import Control.Applicative (optional, (<|>))
import Control.Exception (Handler(..), SomeException)
import Control.Monad (when)
import Data.List.NonEmpty (NonEmpty(..))
import Data.Monoid ((<>))
import Data.Text (Text)
import Data.Text.Prettyprint.Doc (Doc, Pretty)
import Data.Void (Void)
import Dhall.Core (Expr(Annot), Import, pretty)
import Dhall.Freeze (Intent(..), Scope(..))
import Dhall.Import (Imported(..), Depends(..), SemanticCacheMode(..), _semanticCacheMode)
import Dhall.Parser (Src)
import Dhall.Pretty (Ann, CharacterSet(..), annToAnsiStyle)
import Dhall.TypeCheck (Censored(..), DetailedTypeError(..), TypeError)
import Dhall.Util (Censor(..), Header (..), Input(..), Output(..))
import Dhall.Version (dhallVersionString)
import Options.Applicative (Parser, ParserInfo)
import System.Exit (ExitCode, exitFailure)
import System.IO (Handle)
import Text.Dot ((.->.))

import qualified Codec.CBOR.JSON
import qualified Codec.CBOR.Read
import qualified Codec.CBOR.Write
import qualified Control.Exception
import qualified Control.Monad.Trans.State.Strict          as State
import qualified Data.Aeson
import qualified Data.Aeson.Encode.Pretty
import qualified Data.ByteString.Lazy
import qualified Data.ByteString.Lazy.Char8
import qualified Data.Map
import qualified Data.Text
import qualified Data.Text.IO
import qualified Data.Text.Prettyprint.Doc                 as Pretty
import qualified Data.Text.Prettyprint.Doc.Render.Terminal as Pretty
import qualified Data.Text.Prettyprint.Doc.Render.Text     as Pretty.Text
import qualified Dhall
import qualified Dhall.Binary
import qualified Dhall.Core
import qualified Dhall.Diff
import qualified Dhall.Format
import qualified Dhall.Freeze
import qualified Dhall.Import
import qualified Dhall.Import.Types
import qualified Dhall.Lint
import qualified Dhall.Map
import qualified Dhall.Tags
import qualified Dhall.Pretty
import qualified Dhall.Repl
import qualified Dhall.TypeCheck
import qualified Dhall.Util
import qualified GHC.IO.Encoding
import qualified Options.Applicative
import qualified System.AtomicWrite.Writer.LazyText        as AtomicWrite.LazyText
import qualified System.Console.ANSI
import qualified System.Exit                               as Exit
import qualified System.IO
import qualified System.FilePath
import qualified Text.Dot
import qualified Text.Pretty.Simple

-- | Top-level program options
data Options = Options
    { mode    :: Mode
    , explain :: Bool
    , plain   :: Bool
    , ascii   :: Bool
    , censor  :: Censor
    }

ignoreSemanticCache :: Mode -> Bool
ignoreSemanticCache Default {..} = semanticCacheMode == IgnoreSemanticCache
ignoreSemanticCache Resolve {..} = semanticCacheMode == IgnoreSemanticCache
ignoreSemanticCache Type {..}    = semanticCacheMode == IgnoreSemanticCache
ignoreSemanticCache _            = False

-- | The subcommands for the @dhall@ executable
data Mode
    = Default
          { file :: Input
          , output :: Output
          , annotate :: Bool
          , alpha :: Bool
          , semanticCacheMode :: SemanticCacheMode
          , version :: Bool
          }
    | Version
    | Resolve
          { file :: Input
          , resolveMode :: Maybe ResolveMode
          , semanticCacheMode :: SemanticCacheMode
          }
    | Type
          { file :: Input
          , quiet :: Bool
          , semanticCacheMode :: SemanticCacheMode
          }
    | Normalize { file :: Input , alpha :: Bool }
    | Repl
    | Format { formatMode :: Dhall.Format.FormatMode }
    | Freeze { inplace :: Input, all_ :: Bool, cache :: Bool }
    | Hash { file :: Input }
    | Diff { expr1 :: Text, expr2 :: Text }
    | Lint { inplace :: Input }
    | Tags
          { input :: Input
          , output :: Output
          , suffixes :: Maybe [Text]
          , followSymlinks :: Bool
          }
    | Encode { file :: Input, json :: Bool }
    | Decode { file :: Input, json :: Bool }
    | Text { file :: Input }
    | SyntaxTree { file :: Input }

data ResolveMode
    = Dot
    | ListTransitiveDependencies
    | ListImmediateDependencies


-- | `Parser` for the `Options` type
parseOptions :: Parser Options
parseOptions =
        Options
    <$> parseMode
    <*> switch "explain" "Explain error messages in more detail"
    <*> switch "plain" "Disable syntax highlighting"
    <*> switch "ascii" "Format code using only ASCII syntax"
    <*> parseCensor
  where
    switch name description =
        Options.Applicative.switch
            (   Options.Applicative.long name
            <>  Options.Applicative.help description
            )

    parseCensor = fmap f (switch "censor" "Hide source code in error messages")
      where
        f True  = Censor
        f False = NoCensor

subcommand' :: Bool -> String -> String -> Parser a -> Parser a
subcommand' internal name description parser =
    Options.Applicative.hsubparser
        (   Options.Applicative.command name parserInfo
        <>  Options.Applicative.metavar name
        <>  if internal then Options.Applicative.internal else mempty
        )
  where
    parserInfo =
        Options.Applicative.info parser
            (   Options.Applicative.fullDesc
            <>  Options.Applicative.progDesc description
            )

subcommand :: String -> String -> Parser a -> Parser a
subcommand = subcommand' False

internalSubcommand :: String -> String -> Parser a -> Parser a
internalSubcommand = subcommand' True

parseMode :: Parser Mode
parseMode =
        subcommand
            "version"
            "Display version"
            (pure Version)
    <|> subcommand
            "resolve"
            "Resolve an expression's imports"
            (Resolve <$> parseFile <*> parseResolveMode <*> parseSemanticCacheMode)
    <|> subcommand
            "type"
            "Infer an expression's type"
            (Type <$> parseFile <*> parseQuiet <*> parseSemanticCacheMode)
    <|> subcommand
            "normalize"
            "Normalize an expression"
            (Normalize <$> parseFile <*> parseAlpha)
    <|> subcommand
            "repl"
            "Interpret expressions in a REPL"
            (pure Repl)
    <|> subcommand
            "diff"
            "Render the difference between the normal form of two expressions"
            (Diff <$> argument "expr1" <*> argument "expr2")
    <|> subcommand
            "hash"
            "Compute semantic hashes for Dhall expressions"
            (Hash <$> parseFile)
    <|> subcommand
            "lint"
            "Improve Dhall code by using newer language features and removing dead code"
            (Lint <$> parseInplace)
    <|> subcommand
            "tags"
            "Generate etags file"
            (Tags <$> parseInput <*> parseTagsOutput <*> parseSuffixes <*> parseFollowSymlinks)
    <|> subcommand
            "format"
            "Standard code formatter for the Dhall language"
            (Format <$> parseFormatMode)
    <|> subcommand
            "freeze"
            "Add integrity checks to remote import statements of an expression"
            (Freeze <$> parseInplace <*> parseAllFlag <*> parseCacheFlag)
    <|> subcommand
            "encode"
            "Encode a Dhall expression to binary"
            (Encode <$> parseFile <*> parseJSONFlag)
    <|> subcommand
            "decode"
            "Decode a Dhall expression from binary"
            (Decode <$> parseFile <*> parseJSONFlag)
    <|> subcommand
            "text"
            "Render a Dhall expression that evaluates to a Text literal"
            (Text <$> parseFile)
    <|> internalSubcommand
            "haskell-syntax-tree"
            "Output the parsed syntax tree (for debugging)"
            (SyntaxTree <$> parseFile)
    <|> (   Default
        <$> parseFile
        <*> parseOutput
        <*> parseAnnotate
        <*> parseAlpha
        <*> parseSemanticCacheMode
        <*> parseVersion
        )
  where
    argument =
            fmap Data.Text.pack
        .   Options.Applicative.strArgument
        .   Options.Applicative.metavar

    parseFile = fmap f (optional p)
      where
        f  Nothing    = StandardInput
        f (Just file) = InputFile file

        p = Options.Applicative.strOption
                (   Options.Applicative.long "file"
                <>  Options.Applicative.help "Read expression from a file instead of standard input"
                <>  Options.Applicative.metavar "FILE"
                )

    parseOutput = fmap f (optional p)
      where
        f Nothing = StandardOutput
        f (Just file) = OutputFile file

        p = Options.Applicative.strOption
                (   Options.Applicative.long "output"
                <>  Options.Applicative.help "Write result to a file instead of standard output"
                <>  Options.Applicative.metavar "FILE"
                )

    parseAlpha =
        Options.Applicative.switch
            (   Options.Applicative.long "alpha"
            <>  Options.Applicative.help "α-normalize expression"
            )

    parseAnnotate =
        Options.Applicative.switch
            (   Options.Applicative.long "annotate"
            <>  Options.Applicative.help "Add a type annotation to the output"
            )

    parseSemanticCacheMode =
        Options.Applicative.flag
            UseSemanticCache
            IgnoreSemanticCache
            (   Options.Applicative.long "no-cache"
            <>  Options.Applicative.help
                  "Handle protected imports as if the cache was empty"
            )

    parseVersion =
        Options.Applicative.switch
            (   Options.Applicative.long "version"
            <>  Options.Applicative.help "Display version"
            )

    parseResolveMode =
          Options.Applicative.flag' (Just Dot)
              (   Options.Applicative.long "dot"
              <>  Options.Applicative.help
                    "Output import dependency graph in dot format"
              )
        <|>
          Options.Applicative.flag' (Just ListImmediateDependencies)
              (   Options.Applicative.long "immediate-dependencies"
              <>  Options.Applicative.help
                    "List immediate import dependencies"
              )
        <|>
          Options.Applicative.flag' (Just ListTransitiveDependencies)
              (   Options.Applicative.long "transitive-dependencies"
              <>  Options.Applicative.help
                    "List transitive import dependencies in post-order"
              )
        <|> pure Nothing

    parseQuiet =
        Options.Applicative.switch
            (   Options.Applicative.long "quiet"
            <>  Options.Applicative.help "Don't print the inferred type"
            )

    parseInplace = fmap f (optional p)
      where
        f  Nothing    = StandardInput
        f (Just file) = InputFile file

        p = Options.Applicative.strOption
            (   Options.Applicative.long "inplace"
            <>  Options.Applicative.help "Modify the specified file in-place"
            <>  Options.Applicative.metavar "FILE"
            )

    parseInput = fmap f (optional p)
      where
        f  Nothing    = StandardInput
        f (Just path) = InputFile path

        p = Options.Applicative.strOption
            (   Options.Applicative.long "path"
            <>  Options.Applicative.help "Index all files in path recursively. Will get list of files from STDIN if omitted."
            <>  Options.Applicative.metavar "PATH"
            )

    parseTagsOutput = fmap f (optional p)
      where
        f  Nothing    = OutputFile "tags"
        f (Just file) = OutputFile file

        p = Options.Applicative.strOption
            (   Options.Applicative.long "output"
            <>  Options.Applicative.help "The name of the file that the tags are written to. Defaults to \"tags\""
            <>  Options.Applicative.metavar "FILENAME"
            )

    parseSuffixes = fmap f (optional p)
      where
        f  Nothing    = Just [".dhall"]
        f (Just "")   = Nothing
        f (Just line) = Just (Data.Text.splitOn " " line)

        p = Options.Applicative.strOption
            (   Options.Applicative.long "suffixes"
            <>  Options.Applicative.help "Index only files with suffixes. \"\" to index all files."
            <>  Options.Applicative.metavar "SUFFIXES"
            )

    parseFollowSymlinks =
        Options.Applicative.switch
        (   Options.Applicative.long "follow-symlinks"
        <>  Options.Applicative.help "Follow symlinks when recursing directories"
        )

    parseJSONFlag =
        Options.Applicative.switch
        (   Options.Applicative.long "json"
        <>  Options.Applicative.help "Use JSON representation of CBOR"
        )

    parseAllFlag =
        Options.Applicative.switch
        (   Options.Applicative.long "all"
        <>  Options.Applicative.help "Add integrity checks to all imports (not just remote imports)"
        )

    parseCacheFlag =
        Options.Applicative.switch
        (   Options.Applicative.long "cache"
        <>  Options.Applicative.help "Add fallback unprotected imports when using integrity checks purely for caching purposes"
        )

    parseCheck =
        Options.Applicative.switch
        (   Options.Applicative.long "check"
        <>  Options.Applicative.help "Only check if the input is formatted"
        )

    parseFormatMode = adapt <$> parseCheck <*> parseInplace
      where
        adapt True  path    = Dhall.Format.Check {..}
        adapt False inplace = Dhall.Format.Modify {..}

-- | `ParserInfo` for the `Options` type
parserInfoOptions :: ParserInfo Options
parserInfoOptions =
    Options.Applicative.info
        (Options.Applicative.helper <*> parseOptions)
        (   Options.Applicative.progDesc "Interpreter for the Dhall language"
        <>  Options.Applicative.fullDesc
        )

-- | Run the command specified by the `Options` type
command :: Options -> IO ()
command (Options {..}) = do
    let characterSet = case ascii of
            True  -> ASCII
            False -> Unicode

    GHC.IO.Encoding.setLocaleEncoding System.IO.utf8

    let rootDirectory = \case
            InputFile f   -> System.FilePath.takeDirectory f
            StandardInput -> "."

    let toStatus = Dhall.Import.emptyStatus . rootDirectory

    let getExpression          = Dhall.Util.getExpression          censor
    let getExpressionAndHeader = Dhall.Util.getExpressionAndHeader censor

    let handle io =
            Control.Exception.catches io
                [ Handler handleTypeError
                , Handler handleImported
                , Handler handleExitCode
                ]
          where
            handleAll e = do
                let string = show (e :: SomeException)

                if not (null string)
                    then System.IO.hPutStrLn System.IO.stderr string
                    else return ()

                System.Exit.exitFailure

            handleTypeError e = Control.Exception.handle handleAll $ do
                let _ = e :: TypeError Src Void
                System.IO.hPutStrLn System.IO.stderr ""
                if explain
                    then
                        case censor of
                            Censor   -> Control.Exception.throwIO (CensoredDetailed (DetailedTypeError e))
                            NoCensor -> Control.Exception.throwIO (DetailedTypeError e)

                    else do
                        Data.Text.IO.hPutStrLn System.IO.stderr "\ESC[2mUse \"dhall --explain\" for detailed errors\ESC[0m"
                        case censor of
                            Censor   -> Control.Exception.throwIO (Censored e)
                            NoCensor -> Control.Exception.throwIO e

            handleImported (Imported ps e) = Control.Exception.handle handleAll $ do
                let _ = e :: TypeError Src Void
                System.IO.hPutStrLn System.IO.stderr ""
                if explain
                    then Control.Exception.throwIO (Imported ps (DetailedTypeError e))
                    else do
                        Data.Text.IO.hPutStrLn System.IO.stderr "\ESC[2mUse \"dhall --explain\" for detailed errors\ESC[0m"
                        Control.Exception.throwIO (Imported ps e)

            handleExitCode e = do
                Control.Exception.throwIO (e :: ExitCode)

    let renderDoc :: Handle -> Doc Ann -> IO ()
        renderDoc h doc = do
            let stream = Dhall.Pretty.layout doc

            supportsANSI <- System.Console.ANSI.hSupportsANSI h
            let ansiStream =
                    if supportsANSI && not plain
                    then fmap annToAnsiStyle stream
                    else Pretty.unAnnotateS stream

            Pretty.renderIO h ansiStream
            Data.Text.IO.hPutStrLn h ""

    let render :: Pretty a => Handle -> Expr Src a -> IO ()
        render h expression = do
            let doc = Dhall.Pretty.prettyCharacterSet characterSet expression

            renderDoc h doc

    let writeDocToFile :: FilePath -> Doc ann -> IO ()
        writeDocToFile file doc = do
            let stream = Dhall.Pretty.layout (doc <> "\n")

            AtomicWrite.LazyText.atomicWriteFile file (Pretty.Text.renderLazy stream)

    when (not $ ignoreSemanticCache mode) Dhall.Import.warnAboutMissingCaches

    handle $ case mode of
        Version -> do
            putStrLn dhallVersionString

        Default {..} -> do
            if version
                then do
                    putStrLn dhallVersionString
                    Exit.exitSuccess
                else return ()

            expression <- getExpression file

            resolvedExpression <-
                Dhall.Import.loadRelativeTo (rootDirectory file) semanticCacheMode expression

            inferredType <- Dhall.Core.throws (Dhall.TypeCheck.typeOf resolvedExpression)

            let normalizedExpression = Dhall.Core.normalize resolvedExpression

            let alphaNormalizedExpression =
                    if alpha
                    then Dhall.Core.alphaNormalize normalizedExpression
                    else normalizedExpression

            let annotatedExpression =
                    if annotate
                        then Annot alphaNormalizedExpression inferredType
                        else alphaNormalizedExpression

            case output of
                StandardOutput -> render System.IO.stdout annotatedExpression

                OutputFile file_ ->
                    writeDocToFile
                        file_
                        (Dhall.Pretty.prettyCharacterSet characterSet annotatedExpression)

        Resolve { resolveMode = Just Dot, ..} -> do
            expression <- getExpression file

            (Dhall.Import.Types.Status { _graph, _stack }) <-
                State.execStateT (Dhall.Import.loadWith expression) (toStatus file) { _semanticCacheMode = semanticCacheMode }

            let (rootImport :| _) = _stack
                imports = rootImport : map parent _graph ++ map child _graph
                importIds = Data.Map.fromList (zip imports [Text.Dot.userNodeId i | i <- [0..]])

            let dotNode (i, nodeId) =
                    Text.Dot.userNode
                        nodeId
                        [ ("label", Data.Text.unpack $ pretty i)
                        , ("shape", "box")
                        , ("style", "rounded")
                        ]

            let dotEdge (Depends parent child) =
                    case (Data.Map.lookup parent importIds, Data.Map.lookup child importIds) of
                        (Just from, Just to) -> from .->. to
                        _                    -> pure ()

            let dot = do Text.Dot.attribute ("rankdir", "LR")
                         mapM_ dotNode (Data.Map.assocs importIds)
                         mapM_ dotEdge _graph

            putStr . ("strict " <>) . Text.Dot.showDot $ dot

        Resolve { resolveMode = Just ListImmediateDependencies, ..} -> do
            expression <- getExpression file

            mapM_ (print
                        . Pretty.pretty
                        . Dhall.Core.importHashed) expression

        Resolve { resolveMode = Just ListTransitiveDependencies, ..} -> do
            expression <- getExpression file

            (Dhall.Import.Types.Status { _cache }) <-
                State.execStateT (Dhall.Import.loadWith expression) (toStatus file) { _semanticCacheMode = semanticCacheMode }

            mapM_ print
                 .   fmap (   Pretty.pretty
                          .   Dhall.Core.importType
                          .   Dhall.Core.importHashed
                          .   Dhall.Import.chainedImport )
                 .   reverse
                 .   Dhall.Map.keys
                 $   _cache

        Resolve { resolveMode = Nothing, ..} -> do
            expression <- getExpression file

            resolvedExpression <-
                Dhall.Import.loadRelativeTo (rootDirectory file) semanticCacheMode expression

            render System.IO.stdout resolvedExpression

        Normalize {..} -> do
            expression <- getExpression file

            resolvedExpression <- Dhall.Import.assertNoImports expression

            _ <- Dhall.Core.throws (Dhall.TypeCheck.typeOf resolvedExpression)

            let normalizedExpression = Dhall.Core.normalize resolvedExpression

            let alphaNormalizedExpression =
                    if alpha
                    then Dhall.Core.alphaNormalize normalizedExpression
                    else normalizedExpression

            render System.IO.stdout alphaNormalizedExpression

        Type {..} -> do
            expression <- getExpression file

            resolvedExpression <-
                Dhall.Import.loadRelativeTo (rootDirectory file) semanticCacheMode expression

            inferredType <- Dhall.Core.throws (Dhall.TypeCheck.typeOf resolvedExpression)

            if quiet
                then return ()
                else render System.IO.stdout inferredType

        Repl -> do
            Dhall.Repl.repl characterSet explain

        Diff {..} -> do
            expression1 <- Dhall.inputExpr expr1

            expression2 <- Dhall.inputExpr expr2

            let diff = Dhall.Diff.diffNormalized expression1 expression2

            renderDoc System.IO.stdout (Dhall.Diff.doc diff)

            if Dhall.Diff.same diff
                then return ()
                else Exit.exitFailure

        Format {..} -> do
            Dhall.Format.format (Dhall.Format.Format {..})

        Freeze {..} -> do
            let scope = if all_ then AllImports else OnlyRemoteImports

            let intent = if cache then Cache else Secure

            Dhall.Freeze.freeze inplace scope intent characterSet censor

        Hash {..} -> do
            expression <- getExpression file

            resolvedExpression <-
                Dhall.Import.loadRelativeTo (rootDirectory file) UseSemanticCache expression

            _ <- Dhall.Core.throws (Dhall.TypeCheck.typeOf resolvedExpression)

            let normalizedExpression =
                    Dhall.Core.alphaNormalize (Dhall.Core.normalize resolvedExpression)

            Data.Text.IO.putStrLn (Dhall.Import.hashExpressionToCode normalizedExpression)

        Lint {..} -> do
            (Header header, expression) <- getExpressionAndHeader inplace

            let lintedExpression = Dhall.Lint.lint expression

            let doc =   Pretty.pretty header
                    <>  Dhall.Pretty.prettyCharacterSet characterSet lintedExpression

            case inplace of
                InputFile file -> writeDocToFile file doc

                StandardInput -> renderDoc System.IO.stdout doc

        Encode {..} -> do
            expression <- getExpression file

            let bytes = Dhall.Binary.encodeExpression (Dhall.Core.denote expression)

            if json
                then do
                    let decoder = Codec.CBOR.JSON.decodeValue False

                    (_, value) <- Dhall.Core.throws (Codec.CBOR.Read.deserialiseFromBytes decoder bytes)

                    let jsonBytes = Data.Aeson.Encode.Pretty.encodePretty value

                    Data.ByteString.Lazy.Char8.putStrLn jsonBytes

                else do
                    Data.ByteString.Lazy.putStr bytes

        Decode {..} -> do
            bytes <- do
                case file of
                    InputFile f   -> Data.ByteString.Lazy.readFile f
                    StandardInput -> Data.ByteString.Lazy.getContents

            expression <- do
                if json
                    then do
                        value <- case Data.Aeson.eitherDecode' bytes of
                            Left  string -> fail string
                            Right value  -> return value

                        let encoding = Codec.CBOR.JSON.encodeValue value

                        let cborgBytes = Codec.CBOR.Write.toLazyByteString encoding

                        Dhall.Core.throws (Dhall.Binary.decodeExpression cborgBytes)
                    else do
                        Dhall.Core.throws (Dhall.Binary.decodeExpression bytes)


            let doc = Dhall.Pretty.prettyCharacterSet characterSet (Dhall.Core.renote expression :: Expr Src Import)

            renderDoc System.IO.stdout doc

        Text {..} -> do
            expression <- getExpression file

            resolvedExpression <-
                Dhall.Import.loadRelativeTo (rootDirectory file) UseSemanticCache expression

            _ <- Dhall.Core.throws (Dhall.TypeCheck.typeOf (Annot resolvedExpression Dhall.Core.Text))

            let normalizedExpression = Dhall.Core.normalize resolvedExpression

            case normalizedExpression of
                Dhall.Core.TextLit (Dhall.Core.Chunks [] text) -> do
                    Data.Text.IO.putStr text
                _ -> do
                    let invalidDecoderExpected :: Expr Void Void
                        invalidDecoderExpected = Dhall.Core.Text

                    let invalidDecoderExpression :: Expr Void Void
                        invalidDecoderExpression = normalizedExpression

                    Control.Exception.throwIO (Dhall.InvalidDecoder {..})

        Tags {..} -> do
            tags <- Dhall.Tags.generate input suffixes followSymlinks

            case output of
                OutputFile file ->
                    System.IO.withFile file System.IO.WriteMode (`Data.Text.IO.hPutStr` tags)

                StandardOutput -> Data.Text.IO.putStrLn tags

        SyntaxTree {..} -> do
            expression <- getExpression file

            let denoted :: Expr Void Import
                denoted = Dhall.Core.denote expression

            Text.Pretty.Simple.pPrintNoColor denoted

-- | Entry point for the @dhall@ executable
main :: IO ()
main = do
    options <- Options.Applicative.execParser parserInfoOptions
    command options