rarity-map.js

const fixtures = require('webtorrent-fixtures')
const randombytes = require('randombytes')
const test = require('tape')
const Wire = require('bittorrent-protocol')
const Torrent = require('../lib/torrent.js')

test('Rarity map usage', t => {
  t.plan(16)

  const numPieces = 4
  const torrentId = Object.assign({}, fixtures.numbers.parsedTorrent, {
    pieces: Array(numPieces)
  })
  const client = {
    listening: true,
    peerId: randombytes(20).toString('hex'),
    torrentPort: 6889,
    dht: false,
    tracker: false,
    lsd: false,
    _remove () {}
  }
  const opts = {}
  const torrent = new Torrent(torrentId, client, opts)
  torrent.on('metadata', () => {
    torrent._onWire(new Wire())
    torrent._onWire(new Wire())

    const rarityMap = torrent._rarityMap

    // test initial / empty case
    validateInitial()

    rarityMap.recalculate()

    // test initial / empty case after recalc
    validateInitial()

    setPiece(torrent.wires[0], 0)
    setPiece(torrent.wires[1], 0)

    setPiece(torrent.wires[0], 1)
    setPiece(torrent.wires[1], 3)

    // test rarest piece after setting pieces and handling 'have' events
    let piece = rarityMap.getRarestPiece()
    t.equal(piece, 2)

    rarityMap.recalculate()

    // test rarest piece after recalc to ensure its the same
    piece = rarityMap.getRarestPiece()
    t.equal(piece, 2)

    addWire()
    addWire()

    // test rarest piece after adding wires
    piece = rarityMap.getRarestPiece()
    t.equal(piece, 3)

    rarityMap.recalculate()

    // test rarest piece after adding wires and recalc
    piece = rarityMap.getRarestPiece()
    t.equal(piece, 3)

    removeWire(3)
    removeWire(1)

    // test rarest piece after removing wires
    piece = rarityMap.getRarestPiece()
    t.equal(piece, 3)

    rarityMap.recalculate()

    // test rarest piece after removing wires and recalc
    piece = rarityMap.getRarestPiece()
    t.equal(piece, 3)

    // test piece filter func
    piece = rarityMap.getRarestPiece(i => i <= 1)
    t.equal(piece, 0)

    piece = rarityMap.getRarestPiece(i => i === 1 || i === 2)
    t.equal(piece, 2)

    function validateInitial () {
      // note that getRarestPiece will return a random piece since they're all equal
      // so repeat the test several times to reasonably ensure its correctness.
      let piece = rarityMap.getRarestPiece()
      t.ok(piece >= 0 && piece < numPieces)

      piece = rarityMap.getRarestPiece()
      t.ok(piece >= 0 && piece < numPieces)

      piece = rarityMap.getRarestPiece()
      t.ok(piece >= 0 && piece < numPieces)

      piece = rarityMap.getRarestPiece()
      t.ok(piece >= 0 && piece < numPieces)
    }

    function setPiece (wire, index) {
      wire.peerPieces.set(index)
      wire.emit('have', index)
    }

    function addWire () {
      const wire = new Wire()
      wire.peerPieces.set(1)
      wire.peerPieces.set(2)
      torrent._onWire(wire)
    }

    function removeWire (index) {
      const wire = torrent.wires.splice(index, 1)[0]
      wire.destroy()
    }
  })

  t.on('end', () => {
    torrent.wires.forEach(wire => {
      wire.destroy()
    })
    torrent.destroy()
  })
})