import db from 'mime-db'
import { extname } from 'path'

const EXTRACT_TYPE_REGEXP = /^\s*([^;\s]*)(?:;|\s|$)/
const TEXT_TYPE_REGEXP = /^text\//i

function populateMaps(extensions: string[], types: string[]) {
  // source preference (least -> most)
  const preference = ['nginx', 'apache', undefined, 'iana']

  Object.keys(db).forEach((type) => {
    const mime = db[type]
    const exts = mime.extensions

    if (!exts || !exts.length) {
      return
    }

    // mime -> extensions
    extensions[type] = exts

    // extension -> mime
    for (const extension of exts) {
      if (types[extension]) {
        const from = preference.indexOf(db[types[extension]].source)
        const to = preference.indexOf(mime.source)

        if (
          types[extension] !== 'application/octet-stream' &&
          (from > to ||
            (from === to && types[extension].substr(0, 12) === 'application/'))
        ) {
          // skip the remapping
          continue
        }
      }

      // set the extension -> mime
      types[extension] = type
    }
  })
}

const extensions = Object.create(null)

const types = Object.create(null)

populateMaps(extensions, types)

export { extensions, types }

/**
 * Get the default charset for a MIME type.
 */
export function charset(type: string): boolean | string {
  if (!type || typeof type !== 'string') {
    return false
  }

  // TODO: use media-typer
  const match = EXTRACT_TYPE_REGEXP.exec(type)
  const mime = match && db[match[1].toLowerCase()]

  if (mime && mime.charset) {
    return mime.charset
  }

  // default text/* to utf-8
  if (match && TEXT_TYPE_REGEXP.test(match[1])) {
    return 'UTF-8'
  }

  return false
}

/**
 * Create a full Content-Type header given a MIME type or extension.
 */
export function contentType(str: string) {
  // TODO: should this even be in this module?
  if (!str || typeof str !== 'string') {
    return false
  }

  let mime = str.indexOf('/') === -1 ? exports.lookup(str) : str

  if (!mime) {
    return false
  }

  // TODO: use content-type or other module
  if (mime.indexOf('charset') === -1) {
    const charset = exports.charset(mime)
    if (charset) mime += '; charset=' + charset.toLowerCase()
  }

  return mime
}

/**
 * Get the default extension for a MIME type.
 */
export function extension(type: string | unknown) {
  if (!type || typeof type !== 'string') {
    return false
  }

  // TODO: use media-typer
  const match = EXTRACT_TYPE_REGEXP.exec(type)

  // get extensions
  const exts = match && exports.extensions[match[1].toLowerCase()]

  if (!exts || !exts.length) {
    return false
  }

  return exts[0]
}

/**
 * Lookup the MIME type for a file path/extension.
 */
export function lookup(path: string | unknown) {
  if (!path || typeof path !== 'string') {
    return false
  }

  // get the extension ("ext" or ".ext" or full path)
  const extension = extname('x.' + path)
    .toLowerCase()
    .substr(1)

  if (!extension) {
    return false
  }

  return exports.types[extension] || false
}