lib/cdxjEntry.js

/**
 * @type {Buffer}
 */
const spaceBuffer = Buffer.from('20', 'hex')

/**
 * @type {Buffer}
 */
const jsonStartBuffer = Buffer.from('7b', 'hex')

/**
 * @desc A CDXJ Entry (a single in a .cdxj file)
 */
class CDXJEntry {
  /**
   * @desc Create a new CDXJEntry
   * @param {Buffer} linebuf
   */
  constructor (linebuf) {
    let fspace = linebuf.indexOf(spaceBuffer)
    let jsonStart = linebuf.indexOf(jsonStartBuffer)
    this._surtb = linebuf.slice(0, fspace)
    this._surt = null
    this._surtDidConvert = false
    this._dtb = linebuf.slice(fspace + 1, linebuf.indexOf(spaceBuffer, this._surtb.length + spaceBuffer.length))
    this._dt = null
    this._dtDidConvert = false
    this._jsonb = linebuf.slice(jsonStart)
    this._json = null
    this._jsonDidConvert = false
  }

  /**
   * @desc The SURT key for this cdxj entry
   * @return {String}
   */
  get surt () {
    if (!this._surtDidConvert) {
      this._surtDidConvert = true
      this._surt = this._surtb.toString('utf8')
    }
    return this._surt
  }

  /**
   * @desc The raw string datetime portion of this cdxj entry
   * @return {String}
   */
  get dt () {
    if (!this._dtDidConvert) {
      this._dtDidConvert = true
      this._dt = this._dtb.toString('utf8')
    }
    return this._dt
  }

  /**
   * @desc The json data portion of this cdxj entry
   * @return {Object}
   */
  get json () {
    if (!this._jsonDidConvert) {
      this._jsonDidConvert = true
      this._json = JSON.parse(this._jsonb.toString('utf8'))
    }
    return this._json
  }

  /**
   * @desc Returns a buffer for writing this CDXJEntry back to a file
   * @return {Buffer}
   */
  writeable () {
    return Buffer.concat([this._surtb, spaceBuffer, this._dtb, spaceBuffer, this._jsonb])
  }
}

module.exports = CDXJEntry