Internal.hs

{-# LANGUAGE OverloadedStrings #-}

{- |
Module      : Data.Rfc5280.Internal
Copyright   : (c) 2026 Tim Emiola
Maintainer  : Tim Emiola <adetokunbo@emio.la>
SPDX-License-Identifier: BSD3

Internal helpers shared across X.509 extension modules. Not part of the
public API stability guarantee.
-}
module Data.Rfc5280.Internal
  ( -- * Rendering
    RenderConfig (..)

    -- * OID
  , OID
  , OIDError (..)
  , mkOID
  , oidBuilder

    -- * Builder helpers
  , intersperseCommas
  , intersperseWith
  )
where

import Data.ByteString.Builder (Builder, intDec)
import Data.Foldable (foldl')
import Data.List.NonEmpty (NonEmpty (..))


{- | Types that can be rendered to a configuration value as a 'Builder'.
Implemented by all extension types; used by 'Data.Rfc5280.renderConfig'.
-}
class RenderConfig a where
  -- | Render a value as a 'Builder' in OpenSSL extension configuration format.
  renderBuilder :: a -> Builder


-- | An ASN.1 object identifier. Construct with 'mkOID'.
type OID = NonEmpty Int


-- | Failure modes for 'mkOID'.
data OIDError
  = -- | First arc is not 0, 1, or 2.
    InvalidFirstArc
  | -- | One or more subsequent arcs are negative.
    NegativeArc
  deriving (Eq, Show)


{- | Construct an 'OID', validating that the first arc is 0–2 and all arcs
are non-negative.

The second-arc ≤ 39 constraint from X.660 is not enforced; it only applies
under first arcs 0 and 1 and is rarely violated in practice.
-}
mkOID :: Int -> [Int] -> Either OIDError OID
mkOID first rest
  | first < 0 || first > 2 = Left InvalidFirstArc
  | any (< 0) rest = Left NegativeArc
  | otherwise = Right (first :| rest)


-- | Render an 'OID' as a dot-separated sequence of integers.
oidBuilder :: OID -> Builder
oidBuilder = intersperseWith "." . fmap intDec


-- | Render a non-empty list of 'Builder' values separated by commas.
intersperseCommas :: NonEmpty Builder -> Builder
intersperseCommas = intersperseWith ","


-- | Render a non-empty list of 'Builder' values separated by @sep@.
intersperseWith :: Builder -> NonEmpty Builder -> Builder
intersperseWith sep (x :| xs) = x <> foldl' (\acc y -> acc <> sep <> y) "" xs