Add source-based routing support (#862)

* Add source-based routing support

* include neighbors in ANNOUNCE

---------

Co-authored-by: jack <jackjackbits@users.noreply.github.com>
Co-authored-by: callebtc <93376500+callebtc@users.noreply.github.com>

bitchatTests/Services/MeshTopologyTrackerTests.swift

@@ -0,0 +1,86 @@
+//
+// MeshTopologyTrackerTests.swift
+// bitchatTests
+//
+// This is free and unencumbered software released into the public domain.
+// For more information, see <https://unlicense.org>
+//
+
+import Testing
+import Foundation
+@testable import bitchat
+
+struct MeshTopologyTrackerTests {
+    private func hex(_ value: String) throws -> Data {
+        try #require(Data(hexString: value))
+    }
+
+    @Test func directLinkProducesRoute() throws {
+        let tracker = MeshTopologyTracker()
+        let a = try hex("0102030405060708")
+        let b = try hex("1112131415161718")
+
+        tracker.recordDirectLink(between: a, and: b)
+        let route = try #require(tracker.computeRoute(from: a, to: b))
+        #expect(route == [a, b])
+    }
+
+    @Test func multiHopRouteComputation() throws {
+        let tracker = MeshTopologyTracker()
+        let a = try hex("0001020304050607")
+        let b = try hex("1011121314151617")
+        let c = try hex("2021222324252627")
+        let d = try hex("3031323334353637")
+
+        tracker.recordDirectLink(between: a, and: b)
+        tracker.recordDirectLink(between: b, and: c)
+        tracker.recordDirectLink(between: c, and: d)
+
+        let route = try #require(tracker.computeRoute(from: a, to: d))
+        #expect(route == [a, b, c, d])
+    }
+
+    @Test func recordRouteAddsEdges() throws {
+        let tracker = MeshTopologyTracker()
+        var a = Data([0xAA, 0xBB, 0xCC])
+        let b = try hex("4445464748494A4B")
+        let c = try hex("5455565758595A5B")
+
+        tracker.recordRoute([a, b, c])
+
+        a.append(Data(repeating: 0, count: BinaryProtocol.senderIDSize - a.count))
+        let route = try #require(tracker.computeRoute(from: a, to: c))
+        #expect(route.first == a)
+        #expect(route.last == c)
+    }
+
+    @Test func removingDirectLinkBreaksRoute() throws {
+        let tracker = MeshTopologyTracker()
+        let a = try hex("0101010101010101")
+        let b = try hex("0202020202020202")
+        let c = try hex("0303030303030303")
+
+        tracker.recordDirectLink(between: a, and: b)
+        tracker.recordDirectLink(between: b, and: c)
+        let initialRoute = try #require(tracker.computeRoute(from: a, to: c))
+        #expect(initialRoute == [a, b, c])
+
+        tracker.removeDirectLink(between: b, and: c)
+        #expect(tracker.computeRoute(from: a, to: c) == nil)
+    }
+
+    @Test func removingPeerClearsEdges() throws {
+        let tracker = MeshTopologyTracker()
+        let a = try hex("0F0E0D0C0B0A0908")
+        let b = try hex("0A0B0C0D0E0F0001")
+        let c = try hex("0011223344556677")
+
+        tracker.recordRoute([a, b, c])
+        let initialRoute = try #require(tracker.computeRoute(from: a, to: c))
+        #expect(initialRoute == [a, b, c])
+
+        tracker.removePeer(b)
+        #expect(tracker.computeRoute(from: a, to: c) == nil)
+    }
+
+}