import type { JsonValue } from '../json-value.ts'
import { carryFencePrefix } from './opaque-carry.ts'
import { infoStringCarries } from './commonmark/grammar.ts'

export type LanguageSlot = { info: string; kind: 'fence' } | { kind: 'attribute' } | { kind: 'none' }

// spec/flavour.md, The CommonMark blocks: the one slot a codeBlock's language rides.
export function languageSlot(language: JsonValue | undefined): LanguageSlot {
  if (language === undefined) return { kind: 'none' }
  if (typeof language !== 'string' || language.startsWith(carryFencePrefix) || !infoStringCarries(language)) return { kind: 'attribute' }
  return { info: language, kind: 'fence' }
}