module Lib.Error

import Prelude
import Lib.Common

-- I'll want to get Context / Val in some of these
-- and a pretty printer in the monad
data Error
  = E FC String
  | ENotInScope FC String
  | Postpone FC QName String


instance HasFC Error where
  getFC (E x str) = x
  getFC (ENotInScope x _) = x
  getFC (Postpone x k str) = x

errorMsg : Error -> String
errorMsg (E x str) = str
errorMsg (ENotInScope x nm) = "\{nm} not in scope"
errorMsg (Postpone x k str) = str

showError : (src : String) -> Error -> String
showError src err =
  let fc = getFC err
  in "ERROR at \{show $ getFC err}: \{errorMsg err}\n" ++ go fc 0 (lines src)
  where
    go : FC → Int → List String → String
    go fc l Nil = ""
    go fc l (x :: xs) =
      if l == fcLine fc then
        let width = fc.bnds.endCol - fc.bnds.startCol in
        "  \{x}\n  \{padding (fcCol fc) ' '}\{padding width '^'}\n"
      else if fcLine fc - 3 < l then "  " ++ x ++ "\n" ++ go fc (l + 1) xs
      else go fc (l + 1) xs