{-# LANGUAGE DeriveAnyClass     #-}
{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE DeriveGeneric      #-}
{-# LANGUAGE OverloadedStrings  #-}
{-# LANGUAGE TemplateHaskell    #-}

-- | This module provides the `Src` type used for source spans in error messages

module Dhall.Src
    ( -- * Type
      Src(..)
    ) where

import Control.DeepSeq (NFData)
import Data.Data (Data)
import Data.Monoid ((<>))
import Data.Text (Text)
import Data.Text.Prettyprint.Doc  (Pretty (..))
import GHC.Generics (Generic)
import Instances.TH.Lift ()
import Language.Haskell.TH.Syntax (Lift, lift)
import Text.Megaparsec (SourcePos (SourcePos), mkPos, unPos)

import {-# SOURCE #-} qualified Dhall.Util

import qualified Data.Text       as Text
import qualified Text.Megaparsec as Megaparsec
import qualified Text.Printf     as Printf

-- | Source code extract
data Src = Src
    { srcStart :: !SourcePos
    , srcEnd   :: !SourcePos
    , srcText  :: Text -- Text field is intentionally lazy
    } deriving (Data, Eq, Generic, Ord, Show, NFData)


instance Lift Src where
    lift (Src (SourcePos a b c) (SourcePos d e f) g) =
        [| Src (SourcePos a (mkPos b') (mkPos c')) (SourcePos d (mkPos e') (mkPos f')) g |]
      where
        b' = unPos b
        c' = unPos c
        e' = unPos e
        f' = unPos f


instance Pretty Src where
    pretty (Src begin _ text) =
            pretty (Dhall.Util.snip numberedLines)
        <>  "\n"
        <>  pretty (Megaparsec.sourcePosPretty begin)
      where
        prefix = Text.replicate (n - 1) " "
          where
            n = Megaparsec.unPos (Megaparsec.sourceColumn begin)

        ls = Text.lines (prefix <> text)

        numberOfLines = length ls

        minimumNumber =
            Megaparsec.unPos (Megaparsec.sourceLine begin)

        maximumNumber = minimumNumber + numberOfLines - 1

        numberWidth :: Int
        numberWidth =
            truncate (logBase (10 :: Double) (fromIntegral maximumNumber)) + 1

        adapt n line = Text.pack outputString
          where
            inputString = Text.unpack line

            outputString =
                Printf.printf ("%" <> show numberWidth <> "d│ %s") n inputString

        numberedLines = Text.unlines (zipWith adapt [minimumNumber..] ls)
