Refactor: Extract types from BitchatProtocol (#611)

* Extract BitchatMessage into a separate file

* Convert `fromBinaryPayload` to `convenience init?`

* Extract message dedup into an extension

* Remove dead `formatMessageContent`

* Minor refactor of timestamp and username formatting

* Remove dead `getSenderColor`

* Extract MessagePadding into a separate file

* Extract BitchatPacket into a separate file

* Extract ReadReceipt into a separate file

* Extract NoisePayload into a separate file

* Remove unnecessary import

bitchat/Models/BitchatPacket.swift

@@ -0,0 +1,91 @@
+//
+// BitchatPacket.swift
+// bitchat
+//
+// This is free and unencumbered software released into the public domain.
+// For more information, see <https://unlicense.org>
+//
+
+import Foundation
+
+/// The core packet structure for all BitChat protocol messages.
+/// Encapsulates all data needed for routing through the mesh network,
+/// including TTL for hop limiting and optional encryption.
+/// - Note: Packets larger than BLE MTU (512 bytes) are automatically fragmented
+struct BitchatPacket: Codable {
+    let version: UInt8
+    let type: UInt8
+    let senderID: Data
+    let recipientID: Data?
+    let timestamp: UInt64
+    let payload: Data
+    var signature: Data?
+    var ttl: UInt8
+    
+    init(type: UInt8, senderID: Data, recipientID: Data?, timestamp: UInt64, payload: Data, signature: Data?, ttl: UInt8) {
+        self.version = 1
+        self.type = type
+        self.senderID = senderID
+        self.recipientID = recipientID
+        self.timestamp = timestamp
+        self.payload = payload
+        self.signature = signature
+        self.ttl = ttl
+    }
+    
+    // Convenience initializer for new binary format
+    init(type: UInt8, ttl: UInt8, senderID: String, payload: Data) {
+        self.version = 1
+        self.type = type
+        // Convert hex string peer ID to binary data (8 bytes)
+        var senderData = Data()
+        var tempID = senderID
+        while tempID.count >= 2 {
+            let hexByte = String(tempID.prefix(2))
+            if let byte = UInt8(hexByte, radix: 16) {
+                senderData.append(byte)
+            }
+            tempID = String(tempID.dropFirst(2))
+        }
+        self.senderID = senderData
+        self.recipientID = nil
+        self.timestamp = UInt64(Date().timeIntervalSince1970 * 1000) // milliseconds
+        self.payload = payload
+        self.signature = nil
+        self.ttl = ttl
+    }
+    
+    var data: Data? {
+        BinaryProtocol.encode(self)
+    }
+    
+    func toBinaryData(padding: Bool = true) -> Data? {
+        BinaryProtocol.encode(self, padding: padding)
+    }
+
+    // Backward-compatible helper (defaults to padded encoding)
+    func toBinaryData() -> Data? {
+        toBinaryData(padding: true)
+    }
+    
+    /// Create binary representation for signing (without signature and TTL fields)
+    /// TTL is excluded because it changes during packet relay operations
+    func toBinaryDataForSigning() -> Data? {
+        // Create a copy without signature and with fixed TTL for signing
+        // TTL must be excluded because it changes during relay
+        let unsignedPacket = BitchatPacket(
+            type: type,
+            senderID: senderID,
+            recipientID: recipientID,
+            timestamp: timestamp,
+            payload: payload,
+            signature: nil, // Remove signature for signing
+            ttl: 0 // Use fixed TTL=0 for signing to ensure relay compatibility
+        )
+        return BinaryProtocol.encode(unsignedPacket)
+    }
+    
+    static func from(_ data: Data) -> BitchatPacket? {
+        BinaryProtocol.decode(data)
+    }
+}

bitchat/Models/MessagePadding.swift

@@ -0,0 +1,61 @@
+//
+// MessagePadding.swift
+// bitchat
+//
+// This is free and unencumbered software released into the public domain.
+// For more information, see <https://unlicense.org>
+//
+
+import Foundation
+
+/// Provides privacy-preserving message padding to obscure actual content length.
+/// Uses PKCS#7-style padding with random bytes to prevent traffic analysis.
+struct MessagePadding {
+    // Standard block sizes for padding
+    static let blockSizes = [256, 512, 1024, 2048]
+    
+    // Add PKCS#7-style padding to reach target size
+    static func pad(_ data: Data, toSize targetSize: Int) -> Data {
+        guard data.count < targetSize else { return data }
+        
+        let paddingNeeded = targetSize - data.count
+        // Constrain to 255 to fit a single-byte pad length marker
+        guard paddingNeeded > 0 && paddingNeeded <= 255 else { return data }
+        
+        var padded = data
+        // PKCS#7: All pad bytes are equal to the pad length
+        padded.append(contentsOf: Array(repeating: UInt8(paddingNeeded), count: paddingNeeded))
+        return padded
+    }
+    
+    // Remove padding from data
+    static func unpad(_ data: Data) -> Data {
+        guard !data.isEmpty else { return data }
+        let last = data.last!
+        let paddingLength = Int(last)
+        // Must have at least 1 pad byte and not exceed data length
+        guard paddingLength > 0 && paddingLength <= data.count else { return data }
+        // Verify PKCS#7: all last N bytes equal to pad length
+        let start = data.count - paddingLength
+        let tail = data[start...]
+        for b in tail { if b != last { return data } }
+        return Data(data[..<start])
+    }
+    
+    // Find optimal block size for data
+    static func optimalBlockSize(for dataSize: Int) -> Int {
+        // Account for encryption overhead (~16 bytes for AES-GCM tag)
+        let totalSize = dataSize + 16
+        
+        // Find smallest block that fits
+        for blockSize in blockSizes {
+            if totalSize <= blockSize {
+                return blockSize
+            }
+        }
+        
+        // For very large messages, just use the original size
+        // (will be fragmented anyway)
+        return dataSize
+    }
+}

bitchat/Models/NoisePayload.swift

@@ -0,0 +1,41 @@
+//
+// NoisePayload.swift
+// bitchat
+//
+// This is free and unencumbered software released into the public domain.
+// For more information, see <https://unlicense.org>
+//
+
+import Foundation
+
+/// Helper to create typed Noise payloads
+struct NoisePayload {
+    let type: NoisePayloadType
+    let data: Data
+    
+    /// Encode payload with type prefix
+    func encode() -> Data {
+        var encoded = Data()
+        encoded.append(type.rawValue)
+        encoded.append(data)
+        return encoded
+    }
+    
+    /// Decode payload from data
+    static func decode(_ data: Data) -> NoisePayload? {
+        // Ensure we have at least 1 byte for the type
+        guard !data.isEmpty else {
+            return nil
+        }
+        
+        // Safely get the first byte
+        let firstByte = data[data.startIndex]
+        guard let type = NoisePayloadType(rawValue: firstByte) else {
+            return nil
+        }
+        
+        // Create a proper Data copy (not a subsequence) for thread safety
+        let payloadData = data.count > 1 ? Data(data.dropFirst()) : Data()
+        return NoisePayload(type: type, data: payloadData)
+    }
+}

bitchat/Models/ReadReceipt.swift

@@ -0,0 +1,95 @@
+//
+// ReadReceipt.swift
+// bitchat
+//
+// This is free and unencumbered software released into the public domain.
+// For more information, see <https://unlicense.org>
+//
+
+import Foundation
+
+struct ReadReceipt: Codable {
+    let originalMessageID: String
+    let receiptID: String
+    var readerID: String  // Who read it
+    let readerNickname: String
+    let timestamp: Date
+    
+    init(originalMessageID: String, readerID: String, readerNickname: String) {
+        self.originalMessageID = originalMessageID
+        self.receiptID = UUID().uuidString
+        self.readerID = readerID
+        self.readerNickname = readerNickname
+        self.timestamp = Date()
+    }
+    
+    // For binary decoding
+    private init(originalMessageID: String, receiptID: String, readerID: String, readerNickname: String, timestamp: Date) {
+        self.originalMessageID = originalMessageID
+        self.receiptID = receiptID
+        self.readerID = readerID
+        self.readerNickname = readerNickname
+        self.timestamp = timestamp
+    }
+    
+    func encode() -> Data? {
+        try? JSONEncoder().encode(self)
+    }
+    
+    static func decode(from data: Data) -> ReadReceipt? {
+        try? JSONDecoder().decode(ReadReceipt.self, from: data)
+    }
+    
+    // MARK: - Binary Encoding
+    
+    func toBinaryData() -> Data {
+        var data = Data()
+        data.appendUUID(originalMessageID)
+        data.appendUUID(receiptID)
+        // ReaderID as 8-byte hex string
+        var readerData = Data()
+        var tempID = readerID
+        while tempID.count >= 2 && readerData.count < 8 {
+            let hexByte = String(tempID.prefix(2))
+            if let byte = UInt8(hexByte, radix: 16) {
+                readerData.append(byte)
+            }
+            tempID = String(tempID.dropFirst(2))
+        }
+        while readerData.count < 8 {
+            readerData.append(0)
+        }
+        data.append(readerData)
+        data.appendDate(timestamp)
+        data.appendString(readerNickname)
+        return data
+    }
+    
+    static func fromBinaryData(_ data: Data) -> ReadReceipt? {
+        // Create defensive copy
+        let dataCopy = Data(data)
+        
+        // Minimum size: 2 UUIDs (32) + readerID (8) + timestamp (8) + min nickname
+        guard dataCopy.count >= 49 else { return nil }
+        
+        var offset = 0
+        
+        guard let originalMessageID = dataCopy.readUUID(at: &offset),
+              let receiptID = dataCopy.readUUID(at: &offset) else { return nil }
+        
+        guard let readerIDData = dataCopy.readFixedBytes(at: &offset, count: 8) else { return nil }
+        let readerID = readerIDData.hexEncodedString()
+        guard InputValidator.validatePeerID(readerID) else { return nil }
+        
+        guard let timestamp = dataCopy.readDate(at: &offset),
+              InputValidator.validateTimestamp(timestamp),
+              let readerNicknameRaw = dataCopy.readString(at: &offset),
+              let readerNickname = InputValidator.validateNickname(readerNicknameRaw) else { return nil }
+        
+        return ReadReceipt(originalMessageID: originalMessageID,
+                          receiptID: receiptID,
+                          readerID: readerID,
+                          readerNickname: readerNickname,
+                          timestamp: timestamp)
+    }
+}