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//
// BitchatProtocol.swift
// bitchat
//
// This is free and unencumbered software released into the public domain.
// For more information, see <https://unlicense.org>
//
///
/// # BitchatProtocol
///
/// Defines the application-layer protocol for BitChat mesh networking, including
/// message types, packet structures, and encoding/decoding logic.
///
/// ## Overview
/// BitchatProtocol implements a binary protocol optimized for Bluetooth LE's
/// constrained bandwidth and MTU limitations. It provides:
/// - Efficient binary message encoding
/// - Message fragmentation for large payloads
/// - TTL-based routing for mesh networks
/// - Privacy features: message padding and randomized relay jitter
/// - Integration points for end-to-end encryption
///
/// ## Protocol Design
/// The protocol uses a compact binary format to minimize overhead:
/// - 1-byte message type identifier
/// - Variable-length fields with length prefixes
/// - Network byte order (big-endian) for multi-byte values
/// - PKCS#7-style padding for privacy
///
/// ## Message Flow
/// 1. **Creation**: Messages are created with type, content, and metadata
/// 2. **Encoding**: Converted to binary format with proper field ordering
/// 3. **Fragmentation**: Split if larger than BLE MTU (512 bytes)
/// 4. **Transmission**: Sent via BLEService
/// 5. **Routing**: Relayed by intermediate nodes (TTL decrements)
/// 6. **Reassembly**: Fragments collected and reassembled
/// 7. **Decoding**: Binary data parsed back to message objects
///
/// ## Security Considerations
/// - Message padding (to 256/512/1024/2048-byte blocks) obscures actual content length
/// - Randomized relay jitter reduces the traffic-analysis signal; there is no
/// cover traffic or per-message timing obfuscation
/// - Integration with Noise Protocol for E2E encryption
/// - No persistent identifiers in protocol headers
///
/// ## Message Types
/// - **Announce/Leave**: Peer presence notifications
/// - **Message**: Public chat messages
/// - **Fragment**: Multi-part message handling
/// - **NoiseHandshake/NoiseEncrypted**: Encrypted channel establishment and
/// all private payloads (messages, delivery acks, read receipts)
/// - **CourierEnvelope**: Sealed store-and-forward mail
/// - **RequestSync/FileTransfer**: Gossip history sync and media transfer
///
/// ## Future Extensions
/// The protocol is designed to be extensible:
/// - Reserved message type ranges for future use
/// - Version field for protocol evolution
/// - Optional fields for new features
///
import Foundation
import CoreBluetooth
import BitFoundation
// MARK: - Noise Payload Types
/// Types of payloads embedded within noiseEncrypted messages.
/// The first byte of decrypted Noise payload indicates the type.
/// This provides privacy - observers can't distinguish message types.
enum NoisePayloadType: UInt8 {
// Messages and status
case privateMessage = 0x01 // Private chat message
case readReceipt = 0x02 // Message was read
case delivered = 0x03 // Message was delivered
// Private groups (0x04/0x05 reserved by other features)
case groupInvite = 0x06 // Creator-signed group state (invite)
case groupKeyUpdate = 0x07 // Creator-signed group state (key rotation / roster update)
// Live voice (push-to-talk)
case voiceFrame = 0x08 // One live voice-burst packet (see VoiceBurstPacket)
// Verification (QR-based OOB binding)
case verifyChallenge = 0x10 // Verification challenge
case verifyResponse = 0x11 // Verification response
// Transitive verification (web of trust)
case vouch = 0x12 // Batch of vouch attestations
var description: String {
switch self {
case .privateMessage: return "privateMessage"
case .readReceipt: return "readReceipt"
case .delivered: return "delivered"
case .groupInvite: return "groupInvite"
case .groupKeyUpdate: return "groupKeyUpdate"
case .voiceFrame: return "voiceFrame"
case .verifyChallenge: return "verifyChallenge"
case .verifyResponse: return "verifyResponse"
case .vouch: return "vouch"
}
}
}
// MARK: - Handshake State
// Lazy handshake state tracking
enum LazyHandshakeState {
case none // No session, no handshake attempted
case handshakeQueued // User action requires handshake
case handshaking // Currently in handshake process
case established // Session ready for use
case failed(Error) // Handshake failed
}
// MARK: - Delegate Protocol
protocol BitchatDelegate: AnyObject {
func didReceiveMessage(_ message: BitchatMessage)
func didConnectToPeer(_ peerID: PeerID)
func didDisconnectFromPeer(_ peerID: PeerID)
func didUpdatePeerList(_ peers: [PeerID])
// Optional method to check if a fingerprint belongs to a favorite peer
func isFavorite(fingerprint: String) -> Bool
func didUpdateMessageDeliveryStatus(_ messageID: String, status: DeliveryStatus)
// Low-level events for better separation of concerns
func didReceiveNoisePayload(from peerID: PeerID, type: NoisePayloadType, payload: Data, timestamp: Date)
// Encrypted group broadcast (opaque envelope; decrypted by the group coordinator)
func didReceiveGroupMessage(payload: Data, timestamp: Date)
// Public live-voice burst packet (signature-verified by the transport)
func didReceivePublicVoiceFrame(from peerID: PeerID, nickname: String, payload: Data, timestamp: Date)
// Bluetooth state updates for user notifications
func didUpdateBluetoothState(_ state: CBManagerState)
func didReceivePublicMessage(from peerID: PeerID, nickname: String, content: String, timestamp: Date, messageID: String?)
}
// Provide default implementation to make it effectively optional
extension BitchatDelegate {
func isFavorite(fingerprint: String) -> Bool {
return false
}
func didUpdateMessageDeliveryStatus(_ messageID: String, status: DeliveryStatus) {
// Default empty implementation
}
func didReceiveNoisePayload(from peerID: PeerID, type: NoisePayloadType, payload: Data, timestamp: Date) {
// Default empty implementation
}
func didReceiveGroupMessage(payload: Data, timestamp: Date) {
// Default empty implementation
}
func didReceivePublicVoiceFrame(from peerID: PeerID, nickname: String, payload: Data, timestamp: Date) {
// Default empty implementation
}
func didReceivePublicMessage(from peerID: PeerID, nickname: String, content: String, timestamp: Date, messageID: String?) {
// Default empty implementation
}
}