import assert from 'assert'
import fs from 'fs'
import path from 'path'
import walk from 'walk-sync'
import yaml from 'js-yaml'
import { isRegExp, set } from 'lodash-es'
import filenameToKey from './filename-to-key.js'

export default function dataDirectory(dir, opts = {}) {
  const defaultOpts = {
    preprocess: (content) => {
      return content
    },
    ignorePatterns: [/README\.md$/i],
    extensions: ['.json', '.md', '.markdown', '.yaml', '.yml'],
  }

  opts = Object.assign({}, defaultOpts, opts)

  // validate input
  assert(Array.isArray(opts.ignorePatterns))
  assert(opts.ignorePatterns.every(isRegExp))
  assert(Array.isArray(opts.extensions))
  assert(opts.extensions.length)

  // start with an empty data object
  const data = {}

  // find YAML and Markdown files in the given directory, recursively
  const filenames = walk(dir, { includeBasePath: true }).filter((filename) => {
    // ignore files that match any of ignorePatterns regexes
    if (opts.ignorePatterns.some((pattern) => pattern.test(filename))) return false

    // ignore files that don't have a whitelisted file extension
    return opts.extensions.includes(path.extname(filename).toLowerCase())
  })

  const files = filenames.map((filename) => [filename, fs.readFileSync(filename, 'utf8')])
  files.forEach(([filename, fileContent]) => {
    // derive `foo.bar.baz` object key from `foo/bar/baz.yml` filename
    const key = filenameToKey(path.relative(dir, filename))
    const extension = path.extname(filename).toLowerCase()

    if (opts.preprocess) fileContent = opts.preprocess(fileContent)

    // add this file's data to the global data object
    switch (extension) {
      case '.json':
        set(data, key, JSON.parse(fileContent))
        break
      case '.yaml':
      case '.yml':
        set(data, key, yaml.load(fileContent, { filename }))
        break
      case '.md':
      case '.markdown':
        set(data, key, fileContent)
        break
    }
  })

  return data
}