org-meta-filter/index.js

pandoc filter to use org-mode custom keywords as metadata

#!/usr/bin/env node

const getStdin = require('get-stdin')
const {
  complement,
  equals,
  filter,
  head,
  ifElse,
  join,
  map,
  mergeAll,
  nth,
  pipe,
  prop,
  replace,
  splitWhen,
  tail,
  // tap,
  trim,
  where,
} = require('ramda')

/*
const { writeFileSync } = require('fs')
const debug = (subject, chunk) =>
  writeFileSync(`debug-${subject}.json`, JSON.stringify(chunk))
const debugPipe = subject => tap(chunk => debug(subject, chunk))
*/

const beforeChar = char => pipe(splitWhen(equals(char)), head, join(''))
const afterChar = char => pipe(splitWhen(equals(char)), nth(1), tail, join(''))

const getPandocValue = prop('c')
const getPandocRawBlockValue = pipe(getPandocValue, nth(1))

// '#+key:value' => ['key', 'value']
const getOrgMetadata = rawMetadata => {
  const key = pipe(beforeChar(':'), replace('#+', ''))(rawMetadata)
  const value = pipe(afterChar(':'), trim)(rawMetadata)
  return [key, value]
}

const toPandocStr = str => [{ t: 'Str', c: str }]
const toPandocMetaInlines = str => ({ t: 'MetaInlines', c: toPandocStr(str) })
const toPandocMetaBool = bool => ({ t: 'MetaBool', c: Boolean(bool) })
const isBoolString = str => ['true', 'false'].includes(str)
const toPandocMetaValue = ifElse(
  isBoolString,
  toPandocMetaBool,
  toPandocMetaInlines
)
const toPandocMeta = ([key, value]) => ({ [key]: toPandocMetaValue(value) })

const isMetadata = where({
  t: equals('RawBlock'),
  c: pipe(head, equals('org')),
})
const removeMetadata = filter(complement(isMetadata))

const main = async () => {
  let ast = JSON.parse(await getStdin())

  const rawMetadata = filter(isMetadata, ast.blocks)
  if (rawMetadata.length > 0) {
    // extract keywords
    ast.blocks = removeMetadata(ast.blocks)

    const metadata = pipe(
      map(pipe(getPandocRawBlockValue, getOrgMetadata, toPandocMeta)),
      mergeAll
    )(rawMetadata)

    // and add as metadata
    ast.meta = mergeAll([metadata, ast.meta])
  }

  process.stdout.write(JSON.stringify(ast))
}

main()