From 54c2ddfd9922525926d0a1259cc1da855db205a2 Mon Sep 17 00:00:00 2001
From: Tony Garnock-Jones <tonyg@leastfixedpoint.com>
Date: Tue, 31 Jan 2023 16:22:09 +0100
Subject: [PATCH] Try multiple transports in order

---
 packages/ws-relay/src/index.ts | 113 +++++++++++++++++++++------------
 1 file changed, 73 insertions(+), 40 deletions(-)

diff --git a/packages/ws-relay/src/index.ts b/packages/ws-relay/src/index.ts
index decd0e5..87435b3 100644
--- a/packages/ws-relay/src/index.ts
+++ b/packages/ws-relay/src/index.ts
@@ -1,7 +1,7 @@
 /// SPDX-License-Identifier: GPL-3.0-or-later
 /// SPDX-FileCopyrightText: Copyright © 2016-2023 Tony Garnock-Jones <tonyg@leastfixedpoint.com>
 
-import { QuasiValue as Q, Assertion, Bytes, Ref, Relay, Turn, Supervisor, SupervisorRestartPolicy, Observe, Schemas, assertionFacetObserver, canonicalEncode, isEmbedded, underlying } from "@syndicate-lang/core";
+import { QuasiValue as Q, Assertion, Bytes, Ref, Relay, Turn, Supervisor, SupervisorRestartPolicy, Observe, Schemas, assertionFacetObserver, canonicalEncode, fromJS, isEmbedded, underlying } from "@syndicate-lang/core";
 import * as G from "./gen/ws";
 export * from "./gen/ws";
 import * as N from "@syndicate-lang/core/lib/gen/noise";
@@ -18,55 +18,88 @@ export function boot(ds: Ref, debug: boolean = false) {
             }) }) => {
                 const route = Q.drop_lit(routePatValue, N.toRoute);
                 if (!route) return;
-                let addr0: G.RelayAddress | undefined;
-                route.transports.forEach(t => addr0 = addr0 ?? G.toRelayAddress(t));
-                if (!addr0) return;
-                const addr = addr0;
-                wsConnect(addr, e => resolve(e, route.steps, e => {
-                    assert G.Resolved({
-                        "route": route,
-                        "addr": addr,
-                        "resolved": e,
+                const addrs: G.RelayAddress[] = [];
+                route.transports.forEach(t => {
+                    const a = G.toRelayAddress(t);
+                    if (a) addrs.push(a);
+                });
+                wsConnect(addrs, (e, addr) => {
+                    at ds {
+                        stop on message G.ForceRelayDisconnect(addr);
+                    }
+                    resolve(e, route.steps, e => {
+                        assert G.Resolved({
+                            "route": route,
+                            "addr": addr,
+                            "resolved": e,
+                        });
                     });
-                }));
-                at ds {
-                    stop on message G.ForceRelayDisconnect(addr);
-                }
+                });
             }
         }
 
-        function wsConnect(addr: G.RelayAddress, k: (e: Ref) => void) {
-            console.log('wsConnect', addr);
+        function tryConnection(addr: G.RelayAddress): Promise<WebSocket> {
+            return new Promise((resolve, reject) => {
+                console.log('trying', addr);
+                const ws = new WebSocket(addr.url);
+                ws.binaryType = 'arraybuffer';
+                ws.onopen = () => resolve(ws);
+                ws.onclose = () => reject(null);
+                ws.onerror = (e) => reject(e);
+            });
+        }
+
+        async function establishConnection(
+            addrs: G.RelayAddress[],
+        ): Promise<{ws: WebSocket, addr: G.RelayAddress} | null> {
+            for (let i = 0; i < addrs.length; i++) {
+                const addr = addrs[i];
+                try {
+                    return { ws: await tryConnection(addr), addr };
+                } catch (e) {
+                    console.log('attempt to contact', addr.url, 'failed with', e);
+                }
+            }
+            return null;
+        }
+
+        function wsConnect(addrs: G.RelayAddress[], k: (e: Ref, addr: G.RelayAddress) => void) {
+            console.log('wsConnect', addrs);
             let counter = 0;
             new Supervisor({
                 restartPolicy: SupervisorRestartPolicy.ALWAYS,
-            }, () => ['wsRelay', G.fromRelayAddress(addr), counter++], () => {
+            }, () => ['wsRelay', fromJS(addrs), counter++], () => {
                 console.log('try!', counter - 1);
                 const facet = Turn.activeFacet;
-                const ws = new WebSocket(addr.url);
                 facet.preventInertCheck();
-                on stop {
-                    console.log('on stop triggered');
-                    ws.close();
-                }
-                ws.binaryType = 'arraybuffer';
-                ws.onclose = () => facet.turn(() => { stop {} });
-                ws.onerror = () => facet.turn(() =>
-                    Turn.active.crash(new Error("WebSocket error")));
-                ws.onopen = () => facet.turn(() => {
-                    console.log('hey cool');
-                    const relay = new Relay.Relay({
-                        debug,
-                        trustPeer: true,
-                        packetWriter: bs => ws.send(bs),
-                        setup(r: Relay.Relay) {
-                            ws.onmessage = e => facet.turn(() =>
-                                r.accept(new Uint8Array(e.data)));
-                        },
-                        initialOid: 0,
-                    });
-                    k(relay.peer!);
-                });
+
+                establishConnection(addrs).then(result => facet.turn(() => {
+                    if (result === null) {
+                        console.log('no successful connection');
+                        stop {}
+                    } else {
+                        const {ws, addr} = result;
+                        console.log('hey cool', addr);
+                        on stop {
+                            console.log('on stop triggered');
+                            ws.close();
+                        }
+                        ws.onclose = () => facet.turn(() => { stop {} });
+                        ws.onerror = () => facet.turn(() =>
+                            Turn.active.crash(new Error("WebSocket error")));
+                        const relay = new Relay.Relay({
+                            debug,
+                            trustPeer: true,
+                            packetWriter: bs => ws.send(bs),
+                            setup(r: Relay.Relay) {
+                                ws.onmessage = e => facet.turn(() =>
+                                    r.accept(new Uint8Array(e.data)));
+                            },
+                            initialOid: 0,
+                        });
+                        k(relay.peer!, addr);
+                    }
+                }));
             });
         }