feat: interface pubsub (#60)

* feat: interface pubsub

* chore: pubsub router tests

* chore: move pubsub abstractions from gossipsub

* chore: address review

* chore: revamp docs

* chore: add emit self tests to interface

* chore: refactor base tests

* chore: publish should only accept one topic per api call

* chore: normalize msg before emit

* chore: do not reset inbound stream

* chore: apply suggestions from code review

Co-authored-by: Jacob Heun <jacobheun@gmail.com>

* chore: address review

* fix: remove subscribe handler

* chore: remove bits from create peerId

Co-authored-by: Jacob Heun <jacobheun@gmail.com>

* chore: remove delay from topic validators tests

* chore: add event emitter information

* fix: topic validator docs

Co-authored-by: Jacob Heun <jacobheun@gmail.com>

test/pubsub/utils/index.js

@@ -0,0 +1,85 @@
+'use strict'
+
+const DuplexPair = require('it-pair/duplex')
+
+const PeerId = require('peer-id')
+
+const PubsubBaseProtocol = require('../../../src/pubsub')
+const { message } = require('../../../src/pubsub')
+
+exports.createPeerId = async () => {
+  const peerId = await PeerId.create({ bits: 1024 })
+
+  return peerId
+}
+
+class PubsubImplementation extends PubsubBaseProtocol {
+  constructor (protocol, libp2p, options = {}) {
+    super({
+      debugName: 'libp2p:pubsub',
+      multicodecs: protocol,
+      libp2p,
+      ...options
+    })
+  }
+
+  _publish (message) {
+    // ...
+  }
+
+  _decodeRpc (bytes) {
+    return message.rpc.RPC.decode(bytes)
+  }
+
+  _encodeRpc (rpc) {
+    return message.rpc.RPC.encode(rpc)
+  }
+}
+
+exports.PubsubImplementation = PubsubImplementation
+
+exports.mockRegistrar = {
+  handle: () => {},
+  register: () => {},
+  unregister: () => {}
+}
+
+exports.createMockRegistrar = (registrarRecord) => ({
+  handle: (multicodecs, handler) => {
+    const rec = registrarRecord[multicodecs[0]] || {}
+
+    registrarRecord[multicodecs[0]] = {
+      ...rec,
+      handler
+    }
+  },
+  register: ({ multicodecs, _onConnect, _onDisconnect }) => {
+    const rec = registrarRecord[multicodecs[0]] || {}
+
+    registrarRecord[multicodecs[0]] = {
+      ...rec,
+      onConnect: _onConnect,
+      onDisconnect: _onDisconnect
+    }
+
+    return multicodecs[0]
+  },
+  unregister: (id) => {
+    delete registrarRecord[id]
+  }
+})
+
+exports.ConnectionPair = () => {
+  const [d0, d1] = DuplexPair()
+
+  return [
+    {
+      stream: d0,
+      newStream: () => Promise.resolve({ stream: d0 })
+    },
+    {
+      stream: d1,
+      newStream: () => Promise.resolve({ stream: d1 })
+    }
+  ]
+}