feat: make libp2p a state machine (#257)

* docs: add events to readme

test/fsm.spec.js

@@ -0,0 +1,118 @@
+/* eslint-env mocha */
+'use strict'
+
+const chai = require('chai')
+chai.use(require('dirty-chai'))
+chai.use(require('chai-checkmark'))
+const expect = chai.expect
+const sinon = require('sinon')
+const series = require('async/series')
+const createNode = require('./utils/create-node')
+
+describe('libp2p state machine (fsm)', () => {
+  describe('starting and stopping', () => {
+    let node
+    beforeEach((done) => {
+      createNode([], (err, _node) => {
+        node = _node
+        done(err)
+      })
+    })
+    afterEach(() => {
+      node.removeAllListeners()
+    })
+    after((done) => {
+      node.stop(done)
+      node = null
+    })
+
+    it('should be able to start and stop several times', (done) => {
+      node.on('start', (err) => {
+        expect(err).to.not.exist().mark()
+      })
+      node.on('stop', (err) => {
+        expect(err).to.not.exist().mark()
+      })
+
+      expect(4).checks(done)
+
+      series([
+        (cb) => node.start(cb),
+        (cb) => node.stop(cb),
+        (cb) => node.start(cb),
+        (cb) => node.stop(cb)
+      ], () => {})
+    })
+
+    it('should noop when stopping a stopped node', (done) => {
+      node.once('start', node.stop)
+      node.once('stop', () => {
+        node.state.on('STOPPING', () => {
+          throw new Error('should not stop a stopped node')
+        })
+        node.once('stop', done)
+
+        // stop the stopped node
+        node.stop()
+      })
+      node.start()
+    })
+
+    it('should noop when starting a started node', (done) => {
+      node.once('start', () => {
+        node.state.on('STARTING', () => {
+          throw new Error('should not start a started node')
+        })
+        node.once('start', () => {
+          node.once('stop', done)
+          node.stop()
+        })
+
+        // start the started node
+        node.start()
+      })
+      node.start()
+    })
+
+    it('should error on start with no transports', (done) => {
+      let transports = node._modules.transport
+      node._modules.transport = null
+
+      node.on('stop', () => {
+        node._modules.transport = transports
+        expect(node._modules.transport).to.exist().mark()
+      })
+      node.on('error', (err) => {
+        expect(err).to.exist().mark()
+      })
+      node.on('start', () => {
+        throw new Error('should not start')
+      })
+
+      expect(2).checks(done)
+
+      node.start()
+    })
+
+    it('should not start if the switch fails to start', (done) => {
+      const error = new Error('switch didnt start')
+      const stub = sinon.stub(node._switch, 'start')
+        .callsArgWith(0, error)
+
+      node.on('stop', () => {
+        expect(stub.calledOnce).to.eql(true).mark()
+        stub.restore()
+      })
+      node.on('error', (err) => {
+        expect(err).to.eql(error).mark()
+      })
+      node.on('start', () => {
+        throw new Error('should not start')
+      })
+
+      expect(2).checks(done)
+
+      node.start()
+    })
+  })
+})