feat: topology

Author: vasco-santos

README.md

@@ -19,6 +19,7 @@
 - [Peer Discovery](./src/peer-discovery)
 - [Peer Routing](./src/peer-routing)
 - [Stream Muxer](./src/stream-muxer)
+- [Topology](./src/topology)
 - [Transport](./src/transport)
 
 ### Origin Repositories

src/topology/README.md

@@ -0,0 +1 @@
+WIP

src/topology/index.js

@@ -0,0 +1,108 @@
+'use strict'
+
+const assert = require('assert')
+
+class Topology {
+  /**
+   * @param {Object} props
+   * @param {number} props.min minimum needed connections (default: 0)
+   * @param {number} props.max maximum needed connections (default: Infinity)
+   * @param {Array<string>} props.multicodecs protocol multicodecs
+   * @param {Object} props.handlers
+   * @param {function} props.handlers.onConnect protocol "onConnect" handler
+   * @param {function} props.handlers.onDisconnect protocol "onDisconnect" handler
+   * @constructor
+   */
+  constructor ({
+    min = 0,
+    max = Infinity,
+    multicodecs,
+    handlers
+  }) {
+    assert(multicodecs, 'one or more multicodec should be provided')
+    assert(handlers, 'the handlers should be provided')
+    assert(handlers.onConnect && typeof handlers.onConnect === 'function',
+      'the \'onConnect\' handler must be provided')
+    assert(handlers.onDisconnect && typeof handlers.onDisconnect === 'function',
+      'the \'onDisconnect\' handler must be provided')
+
+    this.multicodecs = Array.isArray(multicodecs) ? multicodecs : [multicodecs]
+    this.min = min
+    this.max = max
+
+    // Handlers
+    this._onConnect = handlers.onConnect
+    this._onDisconnect = handlers.onDisconnect
+
+    this.peers = new Map()
+    this._registrar = undefined
+
+    this._onProtocolChange = this._onProtocolChange.bind(this)
+  }
+
+  set registrar (registrar) {
+    this._registrar = registrar
+    this._registrar.peerStore.on('change:protocols', this._onProtocolChange)
+
+    // Update topology peers
+    this._updatePeers(this._registrar.peerStore.peers.values())
+  }
+
+  /**
+   * Update topology.
+   * @param {Array<PeerInfo>} peerInfoIterable
+   * @returns {void}
+   */
+  _updatePeers (peerInfoIterable) {
+    for (const peerInfo of peerInfoIterable) {
+      if (this.multicodecs.filter(multicodec => peerInfo.protocols.has(multicodec))) {
+        // Add the peer regardless of whether or not there is currently a connection
+        this.peers.set(peerInfo.id.toB58String(), peerInfo)
+        // If there is a connection, call _onConnect
+        const connection = this._registrar.getConnection(peerInfo)
+        connection && this._onConnect(peerInfo, connection)
+      } else {
+        // Remove any peers we might be tracking that are no longer of value to us
+        this.peers.delete(peerInfo.id.toB58String())
+      }
+    }
+  }
+
+  /**
+   * Notify protocol of peer disconnected.
+   * @param {PeerInfo} peerInfo
+   * @param {Error} [error]
+   * @returns {void}
+   */
+  disconnect (peerInfo, error) {
+    this._onDisconnect(peerInfo, error)
+  }
+
+  /**
+   * Check if a new peer support the multicodecs for this topology.
+   * @param {Object} props
+   * @param {PeerInfo} props.peerInfo
+   * @param {Array<string>} props.protocols
+   */
+  _onProtocolChange ({ peerInfo, protocols }) {
+    const existingPeer = this.peers.get(peerInfo.id.toB58String())
+    const hasProtocol = protocols.filter(protocol => this.multicodecs.includes(protocol))
+
+    // Not supporting the protocol anymore?
+    if (existingPeer && hasProtocol.length === 0) {
+      this._onDisconnect({
+        peerInfo
+      })
+    }
+
+    // New to protocol support
+    for (const protocol of protocols) {
+      if (this.multicodecs.includes(protocol)) {
+        this._updatePeers([peerInfo])
+        return
+      }
+    }
+  }
+}
+
+module.exports = Topology

src/topology/tests/index.js

@@ -0,0 +1,9 @@
+/* eslint-env mocha */
+
+'use strict'
+
+const topologySuite = require('./topology')
+
+module.exports = (test) => {
+  topologySuite(test)
+}

src/topology/tests/topology.js

@@ -0,0 +1,50 @@
+/* eslint-env mocha */
+
+'use strict'
+
+const chai = require('chai')
+const expect = chai.expect
+chai.use(require('dirty-chai'))
+const sinon = require('sinon')
+
+const PeerId = require('peer-id')
+const PeerInfo = require('peer-info')
+const peers = require('../../utils/peers')
+
+module.exports = (test) => {
+  describe('topology', () => {
+    let topology, peer
+
+    describe('mock', () => {
+      beforeEach(async () => {
+        topology = await test.setup()
+        if (!topology) throw new Error('missing topology')
+
+        const id = await PeerId.createFromJSON(peers[0])
+        peer = await PeerInfo.create(id)
+      })
+
+      afterEach(async () => {
+        sinon.restore()
+        await test.teardown()
+      })
+
+      it('should have properties set', () => {
+        expect(topology.multicodecs).to.exist()
+        expect(topology.min).to.exist()
+        expect(topology.max).to.exist()
+        expect(topology._onConnect).to.exist()
+        expect(topology._onDisconnect).to.exist()
+        expect(topology.peers).to.exist()
+        expect(topology._registrar).to.exist()
+      })
+
+      it('should trigger "onDisconnect" on peer disconnected', () => {
+        sinon.spy(topology, '_onDisconnect')
+        topology.disconnect(peer)
+
+        expect(topology._onDisconnect.callCount).to.equal(1)
+      })
+    })
+  })
+}

test/topology/compliance.spec.js

@@ -0,0 +1,40 @@
+/* eslint-env mocha */
+'use strict'
+
+const tests = require('../../src/topology/tests')
+const Topology = require('../../src/topology')
+const MockPeerStore = require('./mock-peer-store')
+
+describe('compliance tests', () => {
+  tests({
+    setup (properties, registrar) {
+      const multicodecs = ['/echo/1.0.0']
+      const handlers = {
+        onConnect: () => { },
+        onDisconnect: () => { }
+      }
+
+      const topology = new Topology({
+        multicodecs,
+        handlers,
+        ...properties
+      })
+
+      if (!registrar) {
+        const peerStore = new MockPeerStore([])
+
+        registrar = {
+          peerStore,
+          getConnection: () => {}
+        }
+      }
+
+      topology.registrar = registrar
+
+      return topology
+    },
+    teardown () {
+      // cleanup resources created by setup()
+    }
+  })
+})

test/topology/mock-peer-store.js

@@ -0,0 +1,12 @@
+'use strict'
+
+const { EventEmitter } = require('events')
+
+class MockPeerStore extends EventEmitter {
+  constructor (peers) {
+    super()
+    this.peers = peers
+  }
+}
+
+module.exports = MockPeerStore