{-# LANGUAGE OverloadedStrings #-}

module Main where

import           Data.Text    (Text)

import qualified Data.Text    as T
import qualified Data.Text.IO as TIO
import           Safe

prefixLength :: Text -> Int
prefixLength line = T.length prefix
  where
    (prefix, _) = T.breakOn "=" line

adjustLine :: Int -> Text -> Text
adjustLine desiredPrefixLength oldLine = newLine
  where
    (prefix, suffix) = T.breakOn "=" oldLine

    actualPrefixLength = T.length prefix

    additionalSpaces = desiredPrefixLength - actualPrefixLength

    spaces = T.replicate additionalSpaces " "

    newLine = T.concat [ prefix, spaces, suffix ]

adjustText :: Text -> Text
adjustText oldText = newText
  where
    oldLines = T.lines oldText

    prefixLengths = map prefixLength oldLines

    newLines =
      case maximumMay prefixLengths of
        Nothing ->
          []
        Just desiredPrefixLength ->
          map (adjustLine desiredPrefixLength) oldLines

    newText = T.unlines newLines

main :: IO ()
main = TIO.interact adjustText