'use strict'

const fs = require('fs')
const path = require('path')
const matter = require('gray-matter')

const options = {
  lang: 'toml',
  delims: '+++'
}

function* lowercaseKeys (iterator) {
  for (let [k, v] of iterator) {
    yield [String(k).toLowerCase(), v]
  }
}

function canonicaliseMetadata (meta) {
  if (meta.data) {
    meta.data = new Map(lowercaseKeys(Object.entries(meta.data)))
  } else {
    meta.data = new Map()
  }
  return meta
}

function readFileMetadata (filename) {
  return canonicaliseMetadata(matter.read(filename, options))
}

function getFileMetadata (filename) {
  const result = readFileMetadata(filename)
  return result && result.data
}

function getFolderMetadata (folder) {
  return fs
    .readdirSync(folder)
    .map(f => path.resolve(folder, f))
    .map(readFileMetadata)
}

module.exports = {
  getFileMetadata,
  getFolderMetadata
}