Fix BLE stream crashes and gossip sync races (#663)

* Handle long BLE packets safely

* Keep BLE stream aligned after partial drops

---------

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

bitchatTests/GCSFilterTests.swift

@@ -0,0 +1,22 @@
+import XCTest
+@testable import bitchat
+
+final class GCSFilterTests: XCTestCase {
+    func testBuildFilterWithDuplicateIdsProducesStableEncoding() {
+        let id = Data(repeating: 0xAB, count: 16)
+        let ids = Array(repeating: id, count: 64)
+
+        let params = GCSFilter.buildFilter(ids: ids, maxBytes: 128, targetFpr: 0.01)
+        XCTAssertGreaterThanOrEqual(params.m, 1)
+
+        let decoded = GCSFilter.decodeToSortedSet(p: params.p, m: params.m, data: params.data)
+        XCTAssertLessThanOrEqual(decoded.count, 1)
+    }
+
+    func testBucketAvoidsZeroCandidate() {
+        let id = Data(repeating: 0x01, count: 16)
+        let bucket = GCSFilter.bucket(for: id, modulus: 2)
+        XCTAssertNotEqual(bucket, 0)
+        XCTAssertLessThan(bucket, 2)
+    }
+}

bitchatTests/GossipSyncManagerTests.swift

@@ -0,0 +1,70 @@
+import Foundation
+import XCTest
+@testable import bitchat
+
+final class GossipSyncManagerTests: XCTestCase {
+    func testConcurrentPacketIntakeAndSyncRequest() {
+        let manager = GossipSyncManager(myPeerID: "0102030405060708")
+        let delegate = RecordingDelegate()
+        let sendExpectation = expectation(description: "sync request sent")
+        delegate.onSend = { sendExpectation.fulfill() }
+        manager.delegate = delegate
+
+        let iterations = 200
+        let group = DispatchGroup()
+
+        for i in 0..<iterations {
+            group.enter()
+            DispatchQueue.global(qos: .userInitiated).async {
+                let packet = BitchatPacket(
+                    type: MessageType.message.rawValue,
+                    senderID: Data(hexString: "1122334455667788") ?? Data(),
+                    recipientID: nil,
+                    timestamp: 1_000_000 + UInt64(i),
+                    payload: Data([UInt8(truncatingIfNeeded: i)]),
+                    signature: nil,
+                    ttl: 1
+                )
+                manager.onPublicPacketSeen(packet)
+                Thread.sleep(forTimeInterval: 0.001)
+                group.leave()
+            }
+        }
+
+        DispatchQueue.global(qos: .userInitiated).asyncAfter(deadline: .now() + 0.002) {
+            manager.scheduleInitialSyncToPeer("FFFFFFFFFFFFFFFF", delaySeconds: 0.0)
+        }
+
+        group.wait()
+        wait(for: [sendExpectation], timeout: 2.0)
+
+        guard let lastPacket = delegate.lastPacket else {
+            XCTFail("Expected sync packet to be sent")
+            return
+        }
+
+        XCTAssertEqual(lastPacket.type, MessageType.requestSync.rawValue)
+        XCTAssertNotNil(RequestSyncPacket.decode(from: lastPacket.payload))
+    }
+}
+
+private final class RecordingDelegate: GossipSyncManager.Delegate {
+    var onSend: (() -> Void)?
+    private(set) var lastPacket: BitchatPacket?
+    private let lock = NSLock()
+
+    func sendPacket(_ packet: BitchatPacket) {
+        lock.lock()
+        lastPacket = packet
+        lock.unlock()
+        onSend?()
+    }
+
+    func sendPacket(to peerID: String, packet: BitchatPacket) {
+        sendPacket(packet)
+    }
+
+    func signPacketForBroadcast(_ packet: BitchatPacket) -> BitchatPacket {
+        packet
+    }
+}

bitchatTests/NotificationStreamAssemblerTests.swift

@@ -0,0 +1,111 @@
+import XCTest
+@testable import bitchat
+
+final class NotificationStreamAssemblerTests: XCTestCase {
+    private func makePacket(timestamp: UInt64 = 0x0102030405) -> BitchatPacket {
+        let sender = Data([0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77])
+        return BitchatPacket(
+            type: MessageType.message.rawValue,
+            senderID: sender,
+            recipientID: nil,
+            timestamp: timestamp,
+            payload: Data([0xDE, 0xAD, 0xBE, 0xEF]),
+            signature: nil,
+            ttl: 3
+        )
+    }
+
+    func testAssemblesSingleFrameAcrossChunks() {
+        var assembler = NotificationStreamAssembler()
+        let packet = makePacket()
+        guard let frame = packet.toBinaryData(padding: false) else {
+            return XCTFail("Failed to encode packet")
+        }
+        XCTAssertNotNil(BinaryProtocol.decode(frame))
+        let payloadLen = (Int(frame[12]) << 8) | Int(frame[13])
+        XCTAssertEqual(payloadLen, packet.payload.count)
+
+        let splitIndex = min(20, max(1, frame.count / 2))
+        let first = frame.prefix(splitIndex)
+        let second = frame.suffix(from: splitIndex)
+        XCTAssertEqual(first.count + second.count, frame.count)
+
+        var result = assembler.append(first)
+        XCTAssertTrue(result.frames.isEmpty)
+        XCTAssertTrue(result.droppedPrefixes.isEmpty)
+        XCTAssertFalse(result.reset)
+
+        result = assembler.append(second)
+        XCTAssertEqual(result.frames.count, 1)
+        XCTAssertTrue(result.droppedPrefixes.isEmpty)
+        XCTAssertFalse(result.reset)
+
+        guard let frameData = result.frames.first else {
+            return XCTFail("Missing frame data")
+        }
+        if frameData.count != frame.count {
+            XCTFail("Frame size mismatch: expected \(frame.count) got \(frameData.count)\nframe=\(Array(frame))\nassembled=\(Array(frameData))")
+            return
+        }
+        guard let decoded = BinaryProtocol.decode(frameData) else {
+            return XCTFail("Failed to decode frame")
+        }
+        XCTAssertEqual(decoded.type, packet.type)
+        XCTAssertEqual(decoded.payload, packet.payload)
+        XCTAssertEqual(decoded.senderID, packet.senderID)
+        XCTAssertEqual(decoded.timestamp, packet.timestamp)
+
+        var directAssembler = NotificationStreamAssembler()
+        let directResult = directAssembler.append(frame)
+        XCTAssertEqual(directResult.frames.first?.count, frame.count)
+    }
+
+    func testAssemblesMultipleFramesSequentially() {
+        var assembler = NotificationStreamAssembler()
+        let packet1 = makePacket(timestamp: 0xABC)
+        let packet2 = makePacket(timestamp: 0xDEF)
+
+        guard let frame1 = packet1.toBinaryData(padding: false),
+              let frame2 = packet2.toBinaryData(padding: false) else {
+            return XCTFail("Failed to encode packets")
+        }
+
+        var combined = Data()
+        combined.append(frame1)
+        combined.append(frame2)
+        let firstChunk = combined.prefix(20)
+        let secondChunk = combined.suffix(from: 20)
+
+        var result = assembler.append(firstChunk)
+        XCTAssertTrue(result.frames.isEmpty)
+
+        result = assembler.append(secondChunk)
+        XCTAssertEqual(result.frames.count, 2)
+        guard let decoded1 = BinaryProtocol.decode(result.frames[0]),
+              let decoded2 = BinaryProtocol.decode(result.frames[1]) else {
+            return XCTFail("Failed to decode frames")
+        }
+        XCTAssertEqual(decoded1.timestamp, packet1.timestamp)
+        XCTAssertEqual(decoded2.timestamp, packet2.timestamp)
+    }
+
+    func testDropsInvalidPrefixByte() {
+        var assembler = NotificationStreamAssembler()
+        let packet = makePacket(timestamp: 0xF00)
+        guard let frame = packet.toBinaryData(padding: false) else {
+            return XCTFail("Failed to encode packet")
+        }
+        var noisyFrame = Data([0x00])
+        noisyFrame.append(frame)
+
+        let result = assembler.append(noisyFrame)
+        XCTAssertEqual(result.droppedPrefixes, [0x00])
+        XCTAssertEqual(result.frames.count, 1)
+        XCTAssertFalse(result.reset)
+
+        guard let decoded = BinaryProtocol.decode(result.frames[0]) else {
+            return XCTFail("Failed to decode frame after drop")
+        }
+        XCTAssertEqual(decoded.timestamp, packet.timestamp)
+    }
+}