mirror of
https://github.com/permissionlesstech/bitchat.git
synced 2026-07-24 21:45:20 +00:00
announce and read presence
This commit is contained in:
callebtc
@@ -18,6 +18,7 @@ struct NostrProtocol {
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case seal = 13 // NIP-17 sealed event
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case giftWrap = 1059 // NIP-59 gift wrap
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case ephemeralEvent = 20000
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case geohashPresence = 20001
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}
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/// Create a NIP-17 private message
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@@ -125,6 +126,24 @@ struct NostrProtocol {
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return try event.sign(with: schnorrKey)
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}
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/// Create a geohash presence heartbeat (kind 20001)
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/// Must contain empty content and NO nickname tag
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static func createGeohashPresenceEvent(
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geohash: String,
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senderIdentity: NostrIdentity
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) throws -> NostrEvent {
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let tags = [["g", geohash]]
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let event = NostrEvent(
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pubkey: senderIdentity.publicKeyHex,
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createdAt: Date(),
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kind: .geohashPresence,
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tags: tags,
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content: ""
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)
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let schnorrKey = try senderIdentity.schnorrSigningKey()
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return try event.sign(with: schnorrKey)
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}
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/// Create a persistent location note (kind 1: text note) tagged to a street-level geohash.
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static func createGeohashTextNote(
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content: String,
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@@ -887,10 +887,10 @@ struct NostrFilter: Encodable {
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return filter
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}
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// For location channels: geohash-scoped ephemeral events (kind 20000)
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// For location channels: geohash-scoped ephemeral events (kind 20000) and presence (kind 20001)
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static func geohashEphemeral(_ geohash: String, since: Date? = nil, limit: Int = 200) -> NostrFilter {
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var filter = NostrFilter()
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filter.kinds = [20000]
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filter.kinds = [20000, 20001]
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filter.since = since?.timeIntervalSince1970.toInt()
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filter.tagFilters = ["g": [geohash]]
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filter.limit = limit
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@@ -0,0 +1,171 @@
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//
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// GeohashPresenceService.swift
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// bitchat
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//
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// Manages the broadcasting of ephemeral presence heartbeats (Kind 20001)
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// to geohash location channels.
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//
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// This is free and unencumbered software released into the public domain.
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//
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import Foundation
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import Combine
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import BitLogger
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import Tor
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/// Service that coordinates the broadcasting of presence heartbeats.
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///
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/// Behavior:
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/// - Monitors location changes via LocationStateManager
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/// - Broadcasts Kind 20001 events to low-precision geohash channels
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/// - Uses randomized timing (40-80s loop) and decorrelated bursts
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/// - Respects privacy by NOT broadcasting to Neighborhood/Block/Building levels
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@MainActor
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final class GeohashPresenceService: ObservableObject {
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static let shared = GeohashPresenceService()
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private var subscriptions = Set<AnyCancellable>()
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private var heartbeatTimer: Timer?
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private let idBridge = NostrIdentityBridge()
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// MARK: - Constants
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// Loop interval range in seconds
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private let loopMinInterval: TimeInterval = 40.0
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private let loopMaxInterval: TimeInterval = 80.0
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// Per-broadcast decorrelation delay range in seconds
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private let burstMinDelay: TimeInterval = 2.0
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private let burstMaxDelay: TimeInterval = 5.0
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// Privacy: Only broadcast to these levels
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private let allowedPrecisions: Set<Int> = [
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GeohashChannelLevel.region.precision, // 2
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GeohashChannelLevel.province.precision, // 4
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GeohashChannelLevel.city.precision // 5
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]
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private init() {
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setupObservers()
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}
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/// Start the service (safe to call multiple times)
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func start() {
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SecureLogger.info("Presence: service starting...", category: .session)
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scheduleNextHeartbeat()
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}
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private func setupObservers() {
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// Monitor location channel changes
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LocationStateManager.shared.$availableChannels
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.dropFirst()
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.sink { [weak self] _ in
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self?.handleLocationChange()
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}
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.store(in: &subscriptions)
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// Monitor Tor readiness to kick off heartbeat if it was stalled
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NotificationCenter.default.publisher(for: .TorDidBecomeReady)
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.sink { [weak self] _ in
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self?.handleConnectivityChange()
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}
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.store(in: &subscriptions)
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}
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private func handleLocationChange() {
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// When location changes, we trigger an immediate (but slightly delayed) heartbeat
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// to announce presence in the new zone, then reset the loop.
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SecureLogger.debug("Presence: location changed, scheduling update", category: .session)
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heartbeatTimer?.invalidate()
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// Small delay to allow location state to settle
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heartbeatTimer = Timer.scheduledTimer(withTimeInterval: 5.0, repeats: false) { [weak self] _ in
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Task { @MainActor [weak self] in
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self?.performHeartbeat()
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}
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}
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}
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private func handleConnectivityChange() {
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SecureLogger.debug("Presence: connectivity restored, triggering heartbeat", category: .session)
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// If we were waiting for network, do it now
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if heartbeatTimer == nil || !heartbeatTimer!.isValid {
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scheduleNextHeartbeat()
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}
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}
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private func scheduleNextHeartbeat() {
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heartbeatTimer?.invalidate()
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let interval = TimeInterval.random(in: loopMinInterval...loopMaxInterval)
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heartbeatTimer = Timer.scheduledTimer(withTimeInterval: interval, repeats: false) { [weak self] _ in
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Task { @MainActor [weak self] in
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self?.performHeartbeat()
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}
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}
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}
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private func performHeartbeat() {
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// Always schedule next loop first ensures continuity even if this one fails/skips
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defer { scheduleNextHeartbeat() }
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// 1. Check preconditions
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guard TorManager.shared.isReady else {
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SecureLogger.debug("Presence: skipping heartbeat (Tor not ready)", category: .session)
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return
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}
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// App must be active (or at least we shouldn't broadcast if in background, usually)
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if !TorManager.shared.isForeground() {
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return
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}
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// 2. Get channels
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let channels = LocationStateManager.shared.availableChannels
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guard !channels.isEmpty else { return }
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// 3. Filter and broadcast
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// We use Task + sleep for decorrelation to allow the main runloop to proceed
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for channel in channels {
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// Check privacy restriction
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if !self.allowedPrecisions.contains(channel.geohash.count) {
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continue
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}
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// Launch independent task for each channel's delay
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Task { @MainActor in
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// Random delay for decorrelation
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let delay = TimeInterval.random(in: self.burstMinDelay...self.burstMaxDelay)
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let nanoseconds = UInt64(delay * 1_000_000_000)
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try? await Task.sleep(nanoseconds: nanoseconds)
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self.broadcastPresence(for: channel.geohash)
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}
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}
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}
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private func broadcastPresence(for geohash: String) {
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do {
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guard let identity = try? idBridge.deriveIdentity(forGeohash: geohash) else {
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return
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}
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let event = try NostrProtocol.createGeohashPresenceEvent(
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geohash: geohash,
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senderIdentity: identity
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)
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// Send via RelayManager
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let targetRelays = GeoRelayDirectory.shared.closestRelays(
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toGeohash: geohash,
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count: TransportConfig.nostrGeoRelayCount
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)
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if !targetRelays.isEmpty {
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NostrRelayManager.shared.sendEvent(event, to: targetRelays)
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SecureLogger.debug("Presence: sent heartbeat for \(geohash) (pub=\(identity.publicKeyHex.prefix(6))...)", category: .session)
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}
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} catch {
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SecureLogger.error("Presence: failed to create event for \(geohash): \(error)", category: .session)
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}
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}
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}
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@@ -56,7 +56,8 @@ extension ChatViewModel {
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}
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func subscribeNostrEvent(_ event: NostrEvent) {
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guard event.kind == NostrProtocol.EventKind.ephemeralEvent.rawValue,
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guard (event.kind == NostrProtocol.EventKind.ephemeralEvent.rawValue ||
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event.kind == NostrProtocol.EventKind.geohashPresence.rawValue),
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!deduplicationService.hasProcessedNostrEvent(event.id)
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else {
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return
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@@ -86,6 +87,11 @@ extension ChatViewModel {
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// Update participants last-seen for this pubkey
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participantTracker.recordParticipant(pubkeyHex: event.pubkey)
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// If presence heartbeat (Kind 20001), stop here - no content to display
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if event.kind == NostrProtocol.EventKind.geohashPresence.rawValue {
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return
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}
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// Track teleported tag (only our format ["t","teleport"]) for icon state
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let hasTeleportTag = event.tags.contains(where: { tag in
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tag.count >= 2 && tag[0].lowercased() == "t" && tag[1].lowercased() == "teleport"
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@@ -239,8 +245,9 @@ extension ChatViewModel {
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}
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func handleNostrEvent(_ event: NostrEvent) {
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// Only handle ephemeral kind 20000 with matching tag
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guard event.kind == NostrProtocol.EventKind.ephemeralEvent.rawValue else { return }
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// Only handle ephemeral kind 20000 or presence kind 20001 with matching tag
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guard (event.kind == NostrProtocol.EventKind.ephemeralEvent.rawValue ||
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event.kind == NostrProtocol.EventKind.geohashPresence.rawValue) else { return }
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// Deduplicate
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if deduplicationService.hasProcessedNostrEvent(event.id) { return }
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@@ -299,6 +306,11 @@ extension ChatViewModel {
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// Update participants last-seen for this pubkey
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participantTracker.recordParticipant(pubkeyHex: event.pubkey)
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// If presence heartbeat (Kind 20001), stop here - no content to display
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if event.kind == NostrProtocol.EventKind.geohashPresence.rawValue {
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return
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}
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let senderName = displayNameForNostrPubkey(event.pubkey)
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let content = event.content
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@@ -464,7 +476,8 @@ extension ChatViewModel {
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}
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func subscribeNostrEvent(_ event: NostrEvent, gh: String) {
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guard event.kind == NostrProtocol.EventKind.ephemeralEvent.rawValue else { return }
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guard (event.kind == NostrProtocol.EventKind.ephemeralEvent.rawValue ||
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event.kind == NostrProtocol.EventKind.geohashPresence.rawValue) else { return }
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// Compute current participant count (5-minute window) BEFORE updating with this event
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let existingCount = participantTracker.participantCount(for: gh)
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@@ -40,10 +40,31 @@ struct LocationChannelsSheet: View {
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}
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static func levelTitle(for level: GeohashChannelLevel, count: Int) -> String {
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// High-precision uncertainty: if count is 0 for high-precision levels,
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// show "?" because presence broadcasting is disabled for privacy.
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let isHighPrecision = (level == .neighborhood || level == .block || level == .building)
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if isHighPrecision && count == 0 {
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return String(
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format: String(localized: "location_channels.row_title_unknown", defaultValue: "%@ [? people]"),
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locale: .current,
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level.displayName
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)
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}
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return rowTitle(label: level.displayName, count: count)
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}
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static func bookmarkTitle(geohash: String, count: Int) -> String {
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// Check precision for bookmarks too
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let len = geohash.count
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// Neighborhood=6, Block=7, Building=8+
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let isHighPrecision = (len >= 6)
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if isHighPrecision && count == 0 {
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return String(
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format: String(localized: "location_channels.row_title_unknown", defaultValue: "%@ [? people]"),
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locale: .current,
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"#\(geohash)"
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)
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}
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return rowTitle(label: "#\(geohash)", count: count)
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}
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@@ -0,0 +1,96 @@
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# Geohash Presence Specification
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## Overview
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The Geohash Presence feature provides a mechanism to track online participants in geohash-based location channels. It uses a dedicated ephemeral Nostr event kind to broadcast "heartbeats," ensuring accurate and privacy-preserving online counts.
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## Nostr Protocol
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### Event Kind
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A new ephemeral event kind is defined for presence heartbeats:
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- **Kind:** `20001` (`GEOHASH_PRESENCE`)
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- **Type:** Ephemeral (not stored by relays long-term)
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### Event Structure
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The presence event mimics the structure of a geohash chat message (Kind 20000) but without content or nickname metadata, to minimize overhead and focus purely on "liveness".
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```json
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{
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"kind": 20001,
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"created_at": <timestamp>,
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"tags": [
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["g", "<geohash>"]
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],
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"content": "",
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"pubkey": "<geohash_derived_pubkey>",
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"id": "<event_id>",
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"sig": "<signature>"
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}
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```
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* **`content`**: Must be empty string.
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* **`tags`**: Must include `["g", "<geohash>"]`. Should NOT include `["n", "<nickname>"]`.
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* **`pubkey`**: The ephemeral identity derived specifically for this geohash (same as used for chat messages).
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## Client Behavior
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### 1. Broadcasting Presence
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Clients MUST broadcast a Kind 20001 presence event globally when the app is open, regardless of which screen the user is viewing.
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* **Global Heartbeat:**
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* **Trigger:** Application start / initialization, or whenever location (available geohashes) changes.
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* **Frequency:** Randomized loop interval between **40s and 80s** (average 60s).
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* **Scope:** Sent to *all* geohash channels corresponding to the device's *current physical location*.
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* **Privacy Restriction:** Presence MUST ONLY be broadcast to low-precision geohash levels to protect user privacy. Specifically:
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* **Allowed:** `REGION` (precision 2), `PROVINCE` (precision 4), `CITY` (precision 5).
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* **Denied:** `NEIGHBORHOOD` (precision 6), `BLOCK` (precision 7), `BUILDING` (precision 8+).
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* **Decorrelation:** Individual broadcasts within a heartbeat loop must be separated by random delays (e.g., 2-5 seconds) to prevent temporal correlation of public keys across different geohash levels. The main loop delay is adjusted to maintain the target average cadence.
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### 2. Subscribing to Presence
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Clients must update their Nostr filters to listen for both chat and presence events on geohash channels.
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* **Filter:**
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* `kinds`: `[20000, 20001]`
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* `#g`: `["<geohash>"]`
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### 3. Participant Counting
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The "online participants" count shown in the UI aggregates unique public keys from both presence heartbeats and active chat messages.
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* **Logic:**
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* Maintain a map of `pubkey -> last_seen_timestamp` for each geohash.
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* Update `last_seen_timestamp` upon receiving a valid **Kind 20001 (Presence)** OR **Kind 20000 (Chat)** event.
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* A participant is considered "online" if their `last_seen_timestamp` is within the last **5 minutes**.
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### 4. UI Presentation
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The presentation of the participant count depends on the geohash precision level and data availability.
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* **Standard Display:** For channels where presence is broadcast (Region, Province, City) OR any channel where at least one participant has been detected, show the exact count: `[N people]`.
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* **High-Precision Uncertainty:** For high-precision channels (Neighborhood, Block, Building) where:
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* Presence broadcasting is disabled (privacy restriction).
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* **AND** the detected participant count is `0`.
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* **Display:** `[? people]`
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* **Reasoning:** Since clients don't announce themselves in these channels, a count of "0" is misleading (people could be lurking).
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### 5. Implementation Details (Android Reference)
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* **`NostrKind.GEOHASH_PRESENCE`**: Added constant `20001`.
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* **`NostrProtocol.createGeohashPresenceEvent`**: Helper to generate the event.
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* **`GeohashViewModel`**:
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* `startGlobalPresenceHeartbeat()`: Coroutine that `collectLatest` on `LocationChannelManager.availableChannels`.
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* Implements randomized loop logic (40-80s) and per-broadcast random delays (2-5s).
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* Filters channels by `precision <= 5` before broadcasting.
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* **`GeohashMessageHandler`**:
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* Refactored `onEvent` to update participant counts for both Kind 20000 and 20001.
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* **`LocationChannelsSheet`**:
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* Implements the `[? people]` display logic for high-precision, zero-count channels.
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## Benefits
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* **Accuracy:** Counts reflect both active listeners (via heartbeats) and active speakers (via messages).
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* **Privacy:** High-precision location presence is NOT broadcast. Temporal correlation between different levels is obfuscated via random delays.
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* **Consistency:** "Online" status is maintained globally while the app is open.
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* **Transparency:** The UI correctly reflects uncertainty (`?`) when privacy rules prevent accurate passive counting.
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