dbwrapper.js

let typeforce = require('typeforce')
let NIL = Buffer.alloc(0)

function atomic () {
  let batch = this.batch()

  return {
    del: del.bind(batch),
    put: put.bind(batch),
    write: (callback) => batch.write(callback)
  }
}

function del (type, key, callback) {
  typeforce(type.keyType, key)
  key = type.key.encode(key)

  return this.del(key, callback)
}

function get (type, key, callback) {
  typeforce(type.keyType, key)
  key = type.key.encode(key)

  this.get(key, (err, value) => {
    if (err && (/NotFound/).test(err)) return callback()
    if (err) return callback(err)
    if (!type.value) return callback()

    callback(null, type.value.decode(value))
  })
}

function put (type, key, value, callback) {
  typeforce(type.keyType, key)
  typeforce(type.valueType, value)

  key = type.key.encode(key)
  value = type.value ? type.value.encode(value) : NIL

  return this.put(key, value, callback)
}

function iterator (type, options, forEach, callback) {
  typeforce({
    gt: typeforce.maybe(type.keyType),
    gte: typeforce.maybe(type.keyType),
    lt: typeforce.maybe(type.keyType),
    lte: typeforce.maybe(type.keyType),
    limit: typeforce.maybe(typeforce.UInt53)
  }, options)

  // don't mutate
  options = Object.assign({}, options)
  options.gt = options.gt && type.key.encode(options.gt)
  options.gte = options.gte && type.key.encode(options.gte)
  options.lt = options.lt && type.key.encode(options.lt)
  options.lte = options.lte && type.key.encode(options.lte)

  let iterator = this.iterator(options)

  function loop (err, key, value) {
    // NOTE: ignores .end errors, if they occur
    if (err) return iterator.end(() => callback(err))
    if (key === undefined || value === undefined) return iterator.end(callback)

    key = type.key.decode(key)
    value = type.value ? type.value.decode(value) : null

    forEach(key, value)
    iterator.next(loop)
  }

  iterator.next(loop)
}

module.exports = function wrap (db) {
  return {
    atomic: atomic.bind(db),
    del: del.bind(db),
    get: get.bind(db),
    iterator: iterator.bind(db),
    put: put.bind(db)
  }
}