add filter functionality for multiaddr

package.json

@@ -45,6 +45,7 @@
   },
   "dependencies": {
     "multiaddr": "^4.0.0",
+    "mafmt": "^4.0.0",
     "lodash.uniqby": "^4.7.0",
     "peer-id": "~0.10.7"
   },

src/multiaddr-set.js

@@ -52,6 +52,15 @@ class MultiaddrSet {
     return this._multiaddrs.forEach(fn)
   }
 
+  filterBy (maFmt) {
+    if (typeof maFmt !== 'object' ||
+      typeof maFmt.matches !== 'function' ||
+      typeof maFmt.partialMatch !== 'function' ||
+      typeof maFmt.toString !== 'function') return []
+
+    return this._multiaddrs.filter((ma) => maFmt.matches(ma))
+  }
+
   has (ma) {
     ma = ensureMultiaddr(ma)
     return this._multiaddrs.some((m) => m.equals(ma))

test/index.spec.js

@@ -7,6 +7,7 @@ chai.use(dirtyChai)
 const expect = chai.expect
 const Id = require('peer-id')
 const Multiaddr = require('multiaddr')
+const mafmt = require('mafmt')
 const Info = require('../src')
 const peerIdJSON = require('./peer-test.json')
 
@@ -260,6 +261,16 @@ describe('peer-info', () => {
     })
   })
 
+  it('multiaddrs.filterBy', () => {
+    const ma1 = Multiaddr('/ip4/127.0.0.1/tcp/7000')
+    const ma2 = Multiaddr('/ip4/127.0.0.1/udp/5001')
+    pi.multiaddrs.add(ma1)
+    pi.multiaddrs.add(ma2)
+    const maddrs = pi.multiaddrs.filterBy(mafmt.TCP)
+    expect(maddrs.length).to.eq(1)
+    expect(maddrs[0].equals(ma1)).to.eq(true)
+  })
+
   it('multiaddrs.toArray', () => {
     pi.multiaddrs.add('/ip4/127.0.0.1/tcp/5001')
     pi.multiaddrs.toArray().forEach((ma) => {