var createHash = require('sha.js/sha256')
var deepEqual = require('deep-equal')
var jsbloom = require('jsbloom')

exports.encode = function (value) {
  if(null == value) return new Buffer(0)

  var header = Buffer.concat([
    data.seq, value.version,
    value.items,
    value.probability
  ].map(function (e) {
    var b = new Buffer(4)
    b.writeUint32BE(0, e)
    return b
  }))
  var lzBuffer = new Buffer(data.value.exportData(), 'base64')
  return Buffer.concat([createHash().update(data).update(raw).digest(), data, lzBuffer])
}

exports.decode = function (buffer) {
  if(buffer.length == 0)
    throw new Error('empty buffer')

  var hash = buffer.slice(0, 32)
  if(!deepEqual(createHash().update(buffer.slice(32)).digest(), hash))
    throw new Error('flumeview-bloom.decode: hash is incorrect')

  var seq = buffer.readUInt32BE(32+0)
  var version = buffer.readUInt32BE(32+4)
  var items = buffer.readUInt32BE(32+8)
  var probability = buffer.readUInt32BE(32+12)

  var bloom = new jsbloom.filter(items, probability)
  bloom.importData(data.splice(32+16).toString('base64')
  return {
    seq: seq, version: version,
    items: items,
    probability: probability,
    value: bloom
  }
}