refactor: extract PeerSessionManager for testable ICE buffering and glare handling
Extract the ICE candidate buffering, answer routing, and renegotiation glare logic from CallController into a platform-independent PeerSessionManager in commons/. This makes the three most critical NIP-AC spec requirements testable as JVM unit tests with FakePeerSession: 1. Two-layer ICE candidate buffering (global + per-session) - Global buffer: candidates arriving before any PeerConnection exists - Per-session buffer: candidates arriving before setRemoteDescription - Candidates buffered while ringing are preserved when accepting 2. Renegotiation glare handling (pubkey comparison tiebreaker) - Higher pubkey wins, lower pubkey rolls back local offer - Full glare scenario test with two PeerSessionManagers 3. Callee-to-callee mesh initiation (lower pubkey initiates) CallController now delegates to PeerSessionManager via a PeerSession interface, with WebRtcPeerSessionAdapter bridging to WebRtcCallSession. https://claude.ai/code/session_01AfRYTRCvtKqqDxeKQujUrx
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Claude
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/*
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* Copyright (c) 2025 Vitor Pamplona
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy of
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* this software and associated documentation files (the "Software"), to deal in
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* the Software without restriction, including without limitation the rights to use,
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* copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
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* Software, and to permit persons to whom the Software is furnished to do so,
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* subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
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* AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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package com.vitorpamplona.amethyst.commons.call
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import com.vitorpamplona.quartz.nip01Core.core.HexKey
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/**
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* Represents a single ICE candidate received from a peer.
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* Platform-neutral — does not depend on org.webrtc.
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*/
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data class IceCandidateData(
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val sdp: String,
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val sdpMid: String,
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val sdpMLineIndex: Int,
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)
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/**
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* Represents the signaling state of a peer connection.
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* Maps 1:1 with WebRTC's PeerConnection.SignalingState.
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*/
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enum class SignalingState {
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STABLE,
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HAVE_LOCAL_OFFER,
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HAVE_REMOTE_OFFER,
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HAVE_LOCAL_PRANSWER,
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HAVE_REMOTE_PRANSWER,
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CLOSED,
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}
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/**
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* Abstraction over a single peer connection's signaling operations.
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* Implemented by the platform-specific WebRTC wrapper.
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*/
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interface PeerSession {
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fun getSignalingState(): SignalingState?
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fun setRemoteDescription(
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type: SdpType,
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sdp: String,
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)
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fun addIceCandidate(candidate: IceCandidateData)
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fun createOffer(onSdpCreated: (String) -> Unit)
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fun createAnswer(onSdpCreated: (String) -> Unit)
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fun rollback(onDone: () -> Unit)
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fun dispose()
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}
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enum class SdpType {
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OFFER,
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ANSWER,
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}
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/**
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* Manages per-peer session state and ICE candidate buffering.
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*
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* This class encapsulates the NIP-AC spec requirements for:
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* - **Two-layer ICE buffering**: global buffer (before session exists) and
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* per-session buffer (before remote description is set)
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* - **Renegotiation glare handling**: pubkey comparison tiebreaker
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* - **Callee-to-callee mesh**: lower pubkey initiates
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*
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* It is platform-independent and testable without real WebRTC.
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*/
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class PeerSessionManager(
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private val localPubKey: HexKey,
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) {
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data class SessionEntry(
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val session: PeerSession,
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var remoteDescriptionSet: Boolean = false,
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val pendingIceCandidates: MutableList<IceCandidateData> = mutableListOf(),
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)
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private val sessions = mutableMapOf<HexKey, SessionEntry>()
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/** Candidates received before a session exists for the sender. */
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private val globalPendingIce = mutableMapOf<HexKey, MutableList<IceCandidateData>>()
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// ---- Session management ----
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fun registerSession(
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peerPubKey: HexKey,
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session: PeerSession,
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): SessionEntry {
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val globalPending = globalPendingIce.remove(peerPubKey) ?: emptyList()
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val entry = SessionEntry(session)
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entry.pendingIceCandidates.addAll(globalPending)
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sessions[peerPubKey] = entry
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return entry
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}
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fun getSession(peerPubKey: HexKey): SessionEntry? = sessions[peerPubKey]
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fun hasSession(peerPubKey: HexKey): Boolean = sessions.containsKey(peerPubKey)
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fun removeSession(peerPubKey: HexKey): SessionEntry? {
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globalPendingIce.remove(peerPubKey)
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return sessions.remove(peerPubKey)
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}
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fun allSessionKeys(): Set<HexKey> = sessions.keys.toSet()
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// ---- ICE candidate routing (two-layer buffering) ----
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/**
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* Routes an incoming ICE candidate to the correct destination:
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* 1. If session exists AND remote description is set → add directly
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* 2. If session exists but remote description NOT set → buffer per-session
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* 3. If no session exists → buffer globally (keyed by sender)
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*
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* Returns the action taken for testability.
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*/
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fun routeIceCandidate(
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senderPubKey: HexKey,
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candidate: IceCandidateData,
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): IceRouteAction {
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val entry = sessions[senderPubKey]
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if (entry != null && entry.remoteDescriptionSet) {
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entry.session.addIceCandidate(candidate)
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return IceRouteAction.ADDED_DIRECTLY
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} else if (entry != null) {
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entry.pendingIceCandidates.add(candidate)
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return IceRouteAction.BUFFERED_PER_SESSION
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} else {
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globalPendingIce.getOrPut(senderPubKey) { mutableListOf() }.add(candidate)
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return IceRouteAction.BUFFERED_GLOBALLY
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}
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}
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/**
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* Flushes all per-session buffered candidates into the PeerConnection.
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* Called after setRemoteDescription succeeds.
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*/
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fun flushPendingIceCandidates(peerPubKey: HexKey): Int {
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val entry = sessions[peerPubKey] ?: return 0
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entry.remoteDescriptionSet = true
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val candidates = entry.pendingIceCandidates.toList()
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entry.pendingIceCandidates.clear()
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candidates.forEach { entry.session.addIceCandidate(it) }
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return candidates.size
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}
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fun globalPendingCount(peerPubKey: HexKey): Int = globalPendingIce[peerPubKey]?.size ?: 0
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fun sessionPendingCount(peerPubKey: HexKey): Int = sessions[peerPubKey]?.pendingIceCandidates?.size ?: 0
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// ---- Renegotiation glare handling ----
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/**
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* Determines how to handle a renegotiation offer when we may have a pending
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* local offer (glare condition).
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*
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* Per NIP-AC spec: "the peer with the higher pubkey wins (their offer takes priority).
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* The losing peer MUST roll back their local offer."
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*/
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fun resolveRenegotiationGlare(
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peerPubKey: HexKey,
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remoteSdpOffer: String,
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onAcceptRemote: (SessionEntry) -> Unit,
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): GlareResolution {
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val entry = sessions[peerPubKey] ?: return GlareResolution.NO_SESSION
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val signalingState = entry.session.getSignalingState()
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if (signalingState != SignalingState.HAVE_LOCAL_OFFER) {
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// No glare — accept the remote offer directly
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onAcceptRemote(entry)
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return GlareResolution.NO_GLARE
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}
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// Glare detected: both sides sent offers simultaneously
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return if (localPubKey > peerPubKey) {
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// We win — our offer takes priority, ignore remote
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GlareResolution.LOCAL_WINS
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} else {
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// We lose — rollback our local offer, accept remote
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entry.session.rollback {
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onAcceptRemote(entry)
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}
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GlareResolution.REMOTE_WINS_ROLLBACK
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}
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}
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// ---- Callee-to-callee mesh ----
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/**
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* Determines if the local peer should initiate the offer to [peerPubKey].
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* Per NIP-AC spec: "the peer with the lexicographically lower pubkey initiates."
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*/
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fun shouldInitiateOffer(peerPubKey: HexKey): Boolean = localPubKey < peerPubKey
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// ---- Answer routing ----
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/**
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* Routes an incoming SDP answer to the correct session.
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* Returns the action taken.
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*/
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fun routeAnswer(
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peerPubKey: HexKey,
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sdpAnswer: String,
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): AnswerRouteAction {
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val entry = sessions[peerPubKey] ?: return AnswerRouteAction.NO_SESSION
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val signalingState = entry.session.getSignalingState()
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if (signalingState != SignalingState.HAVE_LOCAL_OFFER) {
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return AnswerRouteAction.IGNORED_WRONG_STATE
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}
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entry.session.setRemoteDescription(SdpType.ANSWER, sdpAnswer)
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flushPendingIceCandidates(peerPubKey)
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return AnswerRouteAction.APPLIED
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}
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// ---- Cleanup ----
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fun disposeAll() {
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for (entry in sessions.values) {
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entry.session.dispose()
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}
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sessions.clear()
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globalPendingIce.clear()
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}
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}
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enum class IceRouteAction {
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ADDED_DIRECTLY,
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BUFFERED_PER_SESSION,
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BUFFERED_GLOBALLY,
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}
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enum class GlareResolution {
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NO_SESSION,
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NO_GLARE,
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LOCAL_WINS,
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REMOTE_WINS_ROLLBACK,
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}
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enum class AnswerRouteAction {
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APPLIED,
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NO_SESSION,
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IGNORED_WRONG_STATE,
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}
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