{-# OPTIONS_GHC -Wall #-}
module Reporting.Error.Pattern where

import Text.PrettyPrint.ANSI.Leijen (text)

import qualified Nitpick.Pattern as Pattern
import qualified Reporting.Error.Helpers as Help
import qualified Reporting.Render.Type as RenderType
import qualified Reporting.Report as Report



data Error
    = Incomplete Origin [Pattern.Pattern]
    | Redundant


data Origin
    = Arg
    | LetBound
    | Case



-- TO REPORT


toReport :: RenderType.Localizer -> Error -> Report.Report
toReport _localizer err =
  case err of
    Incomplete Arg unhandled ->
        Report.report
          "PARTIAL PATTERN"
          Nothing
          "This pattern does not cover all possible inputs."
          (text (unhandledError unhandled toCaseMessage))

    Incomplete LetBound unhandled ->
        Report.report
          "PARTIAL PATTERN"
          Nothing
          "The pattern used here does not cover all possible values."
          (text (unhandledError unhandled toCaseMessage))

    Incomplete Case unhandled ->
        Report.report
          "MISSING PATTERNS"
          Nothing
          "This `case` does not have branches for all possibilities."
          (text (unhandledError unhandled (missingBranchesMessage (length unhandled))))

    Redundant ->
        Report.report
          "REDUNDANT PATTERN"
          Nothing
          "The following pattern is redundant. Remove it."
          (text "Any value with this shape will be handled by a previous pattern.")


unhandledError :: [Pattern.Pattern] -> String -> String
unhandledError unhandledPatterns relevantMessage =
  let
    (visiblePatterns, rest) =
      splitAt 4 unhandledPatterns

    patternList =
        map (Pattern.toString False) visiblePatterns
        ++ if null rest then [] else ["..."]
  in
    "You need to account for the following values:\n"
    ++ concatMap ("\n    " ++) patternList ++ "\n"
    ++ "\n"
    ++ relevantMessage ++ "\n"
    ++ "\n"
    ++ "If you are seeing this error for the first time, check out these hints:\n"
    ++ Help.hintLink "missing-patterns" ++ "\n"
    ++ "The recommendations about wildcard patterns and `Debug.crash` are important!"


toCaseMessage :: String
toCaseMessage =
  "Switch to a `case` expression to handle all possible patterns."


missingBranchesMessage :: Int -> String
missingBranchesMessage numUnhandled =
  if numUnhandled == 1 then
    "Add a branch to cover this pattern!"

  else
    "Add branches to cover each of these patterns!"