feat: peer store (#470)

* feat: peer-store v0

* chore: apply suggestions from code review

Co-Authored-By: Jacob Heun <jacobheun@gmail.com>

src/peer-store/index.js

@@ -0,0 +1,190 @@
+'use strict'
+
+const assert = require('assert')
+const debug = require('debug')
+const log = debug('libp2p:peer-store')
+log.error = debug('libp2p:peer-store:error')
+
+const { EventEmitter } = require('events')
+
+const PeerInfo = require('peer-info')
+
+/**
+ * Responsible for managing known peers, as well as their addresses and metadata
+ * @fires PeerStore#peer Emitted when a peer is connected to this node
+ * @fires PeerStore#change:protocols
+ * @fires PeerStore#change:multiaddrs
+ */
+class PeerStore extends EventEmitter {
+  constructor () {
+    super()
+
+    /**
+     * Map of peers
+     *
+     * @type {Map<string, PeerInfo>}
+     */
+    this.peers = new Map()
+
+    // TODO: Track ourselves. We should split `peerInfo` up into its pieces so we get better
+    // control and observability. This will be the initial step for removing PeerInfo
+    // https://github.com/libp2p/go-libp2p-core/blob/master/peerstore/peerstore.go
+    // this.addressBook = new Map()
+    // this.protoBook = new Map()
+  }
+
+  /**
+   * Stores the peerInfo of a new peer.
+   * If already exist, its info is updated.
+   * @param {PeerInfo} peerInfo
+   */
+  put (peerInfo) {
+    assert(PeerInfo.isPeerInfo(peerInfo), 'peerInfo must be an instance of peer-info')
+
+    // Already know the peer?
+    if (this.peers.has(peerInfo.id.toB58String())) {
+      this.update(peerInfo)
+    } else {
+      this.add(peerInfo)
+
+      // Emit the new peer found
+      this.emit('peer', peerInfo)
+    }
+  }
+
+  /**
+   * Add a new peer to the store.
+   * @param {PeerInfo} peerInfo
+   */
+  add (peerInfo) {
+    assert(PeerInfo.isPeerInfo(peerInfo), 'peerInfo must be an instance of peer-info')
+
+    // Create new instance and add values to it
+    const newPeerInfo = new PeerInfo(peerInfo.id)
+
+    peerInfo.multiaddrs.forEach((ma) => newPeerInfo.multiaddrs.add(ma))
+    peerInfo.protocols.forEach((p) => newPeerInfo.protocols.add(p))
+
+    const connectedMa = peerInfo.isConnected()
+    connectedMa && newPeerInfo.connect(connectedMa)
+
+    const peerProxy = new Proxy(newPeerInfo, {
+      set: (obj, prop, value) => {
+        if (prop === 'multiaddrs') {
+          this.emit('change:multiaddrs', {
+            peerInfo: obj,
+            multiaddrs: value.toArray()
+          })
+        } else if (prop === 'protocols') {
+          this.emit('change:protocols', {
+            peerInfo: obj,
+            protocols: Array.from(value)
+          })
+        }
+        return Reflect.set(...arguments)
+      }
+    })
+
+    this.peers.set(peerInfo.id.toB58String(), peerProxy)
+  }
+
+  /**
+   * Updates an already known peer.
+   * @param {PeerInfo} peerInfo
+   */
+  update (peerInfo) {
+    assert(PeerInfo.isPeerInfo(peerInfo), 'peerInfo must be an instance of peer-info')
+    const id = peerInfo.id.toB58String()
+    const recorded = this.peers.get(id)
+
+    // pass active connection state
+    const ma = peerInfo.isConnected()
+    if (ma) {
+      recorded.connect(ma)
+    }
+
+    // Verify new multiaddrs
+    // TODO: better track added and removed multiaddrs
+    const multiaddrsIntersection = [
+      ...recorded.multiaddrs.toArray()
+    ].filter((m) => peerInfo.multiaddrs.has(m))
+
+    if (multiaddrsIntersection.length !== peerInfo.multiaddrs.size ||
+      multiaddrsIntersection.length !== recorded.multiaddrs.size) {
+      // recorded.multiaddrs = peerInfo.multiaddrs
+      recorded.multiaddrs.clear()
+
+      for (const ma of peerInfo.multiaddrs.toArray()) {
+        recorded.multiaddrs.add(ma)
+      }
+
+      this.emit('change:multiaddrs', {
+        peerInfo: peerInfo,
+        multiaddrs: recorded.multiaddrs.toArray()
+      })
+    }
+
+    // Update protocols
+    // TODO: better track added and removed protocols
+    const protocolsIntersection = new Set(
+      [...recorded.protocols].filter((p) => peerInfo.protocols.has(p))
+    )
+
+    if (protocolsIntersection.size !== peerInfo.protocols.size ||
+      protocolsIntersection.size !== recorded.protocols.size) {
+      recorded.protocols.clear()
+
+      for (const protocol of peerInfo.protocols) {
+        recorded.protocols.add(protocol)
+      }
+
+      this.emit('change:protocols', {
+        peerInfo: peerInfo,
+        protocols: Array.from(recorded.protocols)
+      })
+    }
+
+    // Add the public key if missing
+    if (!recorded.id.pubKey && peerInfo.id.pubKey) {
+      recorded.id.pubKey = peerInfo.id.pubKey
+    }
+  }
+
+  /**
+   * Get the info to the given id.
+   * @param {string} peerId b58str id
+   * @returns {PeerInfo}
+   */
+  get (peerId) {
+    const peerInfo = this.peers.get(peerId)
+
+    if (peerInfo) {
+      return peerInfo
+    }
+
+    return undefined
+  }
+
+  /**
+   * Removes the Peer with the matching `peerId` from the PeerStore
+   * @param {string} peerId b58str id
+   * @returns {boolean} true if found and removed
+   */
+  remove (peerId) {
+    return this.peers.delete(peerId)
+  }
+
+  /**
+   * Completely replaces the existing peers metadata with the given `peerInfo`
+   * @param {PeerInfo} peerInfo
+   * @returns {void}
+   */
+  replace (peerInfo) {
+    assert(PeerInfo.isPeerInfo(peerInfo), 'peerInfo must be an instance of peer-info')
+
+    this.remove(peerInfo.id.toB58String())
+    this.add(peerInfo)
+  }
+}
+
+module.exports = PeerStore