{-|
Generates a conditional expression in Cabal _only_ if there the
`minimumGhcVersion` is less than the version it’s conditinolazed on.

__TODO__: If this doesn’t create the conditional, then the caller needs to
          manually add the `body` to the containing section.
-}
let Pvp = ../../PVP/package.dhall

let Alternative = ../Alternative/Type

let Conditional = ./Type

in  λ(ghcVersion : Pvp.Version) →
    λ(minimumGhcVersion : Pvp.Version) →
    λ(body : Alternative) →
    λ(alt : Optional Alternative) →
      if    Pvp.lessThanEqual ghcVersion minimumGhcVersion
      then  [] : List Conditional
      else  [ merge
                { None =
                    Conditional.If
                      (   { condition =
                              "impl(ghc >= " ++ Pvp.show ghcVersion ++ ")"
                          }
                        ⫽ body
                      )
                , Some =
                    λ(els : Alternative) →
                      Conditional.OrElse
                        { condition =
                            "impl(ghc >= " ++ Pvp.show ghcVersion ++ ")"
                        , `then` = body
                        , `else` = els
                        }
                }
                alt
            ]