fix: make getPeerId return the target peer id from relay addrs (#325)

If a p2p-circuit address doesn't contain the `/p2p/QmFoo` tuple for
the target peer, `getPeerId` returns the peer id of the relay which
is not what you'd expect.

The fix here is for relay addresses, to return the peer id of the
target and never the relay.

Fixes #319

src/index.ts

@@ -635,14 +635,21 @@ class DefaultMultiaddr implements Multiaddr {
 
   getPeerId (): string | null {
     try {
-      const tuples = this.stringTuples().filter((tuple) => {
-        if (tuple[0] === names.ipfs.code) {
-          return true
+      let tuples: Array<[number, string | undefined]> = []
+
+      this.stringTuples().forEach(([code, name]) => {
+        if (code === names.p2p.code) {
+          tuples.push([code, name])
+        }
+
+        // if this is a p2p-circuit address, return the target peer id if present
+        // not the peer id of the relay
+        if (code === names['p2p-circuit'].code) {
+          tuples = []
         }
-        return false
       })
 
-      // Get the last ipfs tuple ['ipfs', 'peerid string']
+      // Get the last ipfs tuple ['p2p', 'peerid string']
       const tuple = tuples.pop()
       if (tuple?.[1] != null) {
         const peerIdStr = tuple[1]

test/index.spec.ts

@@ -997,6 +997,11 @@ describe('helpers', () => {
         multiaddr('/p2p-circuit/p2p/12D3KooWNvSZnPi3RrhrTwEY4LuuBeB6K6facKUCJcyWG1aoDd2p').getPeerId()
       ).to.equal('12D3KooWNvSZnPi3RrhrTwEY4LuuBeB6K6facKUCJcyWG1aoDd2p')
     })
+    it('does not extract a peer Id from a circuit relay multiaddr where only the relay peer id is present', () => {
+      expect(
+        multiaddr('/ip4/127.0.0.1/tcp/123/p2p/bafzbeigweq4zr4x4ky2dvv7nanbkw6egutvrrvzw6g3h2rftp7gidyhtt4/p2p-circuit').getPeerId()
+      ).to.be.null()
+    })
   })
 
   describe('.getPeerId should return null on missing peer id in multiaddr', () => {