wip mesh graph

app/src/main/java/com/bitchat/android/services/meshgraph/GossipTLV.kt

@@ -0,0 +1,76 @@
+package com.bitchat.android.services.meshgraph
+
+import android.util.Log
+
+/**
+ * Gossip TLV helpers for embedding direct neighbor peer IDs in ANNOUNCE payloads.
+ * Uses compact TLV: [type=0x04][len=1 byte][value=N*8 bytes of peerIDs]
+ */
+object GossipTLV {
+    // TLV type for a compact list of direct neighbor peerIDs (each 8 bytes)
+    const val DIRECT_NEIGHBORS_TYPE: UByte = 0x04u
+
+    /**
+     * Encode up to 10 unique peerIDs (hex string up to 16 chars) as TLV value.
+     */
+    fun encodeNeighbors(peerIDs: List<String>): ByteArray {
+        val unique = peerIDs.distinct().take(10)
+        val valueBytes = unique.flatMap { id -> hexStringPeerIdTo8Bytes(id).toList() }.toByteArray()
+        if (valueBytes.size > 255) {
+            // Safety check, though 10*8 = 80 bytes, so well under 255
+            Log.w("GossipTLV", "Neighbors value exceeds 255, truncating")
+        }
+        return byteArrayOf(DIRECT_NEIGHBORS_TYPE.toByte(), valueBytes.size.toByte()) + valueBytes
+    }
+
+    /**
+     * Scan a TLV-encoded announce payload and extract neighbor peerIDs if present.
+     */
+    fun decodeNeighborsFromAnnouncementPayload(payload: ByteArray): List<String> {
+        val result = mutableListOf<String>()
+        var offset = 0
+        while (offset + 2 <= payload.size) {
+            val type = payload[offset].toUByte()
+            val len = payload[offset + 1].toUByte().toInt()
+            offset += 2
+            if (offset + len > payload.size) break
+            val value = payload.sliceArray(offset until offset + len)
+            offset += len
+
+            if (type == DIRECT_NEIGHBORS_TYPE) {
+                // Value is N*8 bytes of peer IDs
+                var pos = 0
+                while (pos + 8 <= value.size) {
+                    val idBytes = value.sliceArray(pos until pos + 8)
+                    result.add(bytesToPeerIdHex(idBytes))
+                    pos += 8
+                }
+                break // only one neighbors TLV expected
+            }
+        }
+        return result
+    }
+
+    private fun hexStringPeerIdTo8Bytes(hexString: String): ByteArray {
+        val clean = hexString.lowercase().take(16)
+        val result = ByteArray(8) { 0 }
+        var idx = 0
+        var out = 0
+        while (idx + 1 < clean.length && out < 8) {
+            val byteStr = clean.substring(idx, idx + 2)
+            val b = byteStr.toIntOrNull(16)?.toByte() ?: 0
+            result[out++] = b
+            idx += 2
+        }
+        return result
+    }
+
+    private fun bytesToPeerIdHex(bytes: ByteArray): String {
+        val sb = StringBuilder()
+        for (b in bytes.take(8)) {
+            sb.append(String.format("%02x", b))
+        }
+        return sb.toString()
+    }
+}
+

app/src/main/java/com/bitchat/android/services/meshgraph/MeshGraphService.kt

@@ -0,0 +1,96 @@
+package com.bitchat.android.services.meshgraph
+
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.asStateFlow
+import java.util.concurrent.ConcurrentHashMap
+
+/**
+ * Maintains an internal undirected graph of the mesh based on gossip.
+ * Nodes are peers (peerID), edges are direct connections.
+ */
+class MeshGraphService private constructor() {
+    data class GraphNode(val peerID: String, val nickname: String?)
+    data class GraphEdge(val a: String, val b: String)
+    data class GraphSnapshot(val nodes: List<GraphNode>, val edges: List<GraphEdge>)
+
+    // Map peerID -> nickname (may be null if unknown)
+    private val nicknames = ConcurrentHashMap<String, String?>()
+    // Adjacency (undirected): peerID -> set of neighbor peerIDs
+    private val adjacency = ConcurrentHashMap<String, MutableSet<String>>()
+    // Latest announcement timestamp per peer (ULong from packet)
+    private val lastUpdate = ConcurrentHashMap<String, ULong>()
+
+    private val _graphState = MutableStateFlow(GraphSnapshot(emptyList(), emptyList()))
+    val graphState: StateFlow<GraphSnapshot> = _graphState.asStateFlow()
+
+    /**
+     * Update graph from a verified announcement.
+     * Replaces previous neighbors for origin if this is newer (by timestamp).
+     */
+    fun updateFromAnnouncement(originPeerID: String, originNickname: String?, neighbors: List<String>, timestamp: ULong) {
+        // Newer-only replacement per origin
+        val prevTs = lastUpdate[originPeerID]
+        if (prevTs != null && prevTs >= timestamp) return
+        lastUpdate[originPeerID] = timestamp
+
+        synchronized(this) {
+            // Update nickname
+            if (originNickname != null) nicknames[originPeerID] = originNickname
+
+            // Remove old symmetric edges contributed by this origin
+            val prevNeighbors = adjacency[originPeerID]?.toSet().orEmpty()
+            prevNeighbors.forEach { n ->
+                adjacency[n]?.remove(originPeerID)
+            }
+
+            // Replace origin's adjacency with new set
+            val newSet = neighbors.distinct().take(10).filter { it != originPeerID }.toMutableSet()
+            adjacency[originPeerID] = newSet
+            // Ensure nodes exist for neighbors
+            newSet.forEach { n ->
+                adjacency.putIfAbsent(n, mutableSetOf())
+                // Add symmetric edge for undirected graph visualization
+                adjacency[n]?.add(originPeerID)
+            }
+
+            // Compute snapshot
+            publishSnapshot()
+        }
+    }
+
+    fun updateNickname(peerID: String, nickname: String?) {
+        if (nickname == null) return
+        nicknames[peerID] = nickname
+        publishSnapshot()
+    }
+
+    private fun publishSnapshot() {
+        val nodes = mutableSetOf<String>()
+        adjacency.forEach { (a, neighbors) ->
+            nodes.add(a)
+            nodes.addAll(neighbors)
+        }
+        // Merge in nicknames-only nodes
+        nodes.addAll(nicknames.keys)
+
+        val nodeList = nodes.map { GraphNode(it, nicknames[it]) }.sortedBy { it.peerID }
+        val edgeSet = mutableSetOf<Pair<String, String>>()
+        adjacency.forEach { (a, ns) ->
+            ns.forEach { b ->
+                val (x, y) = if (a <= b) a to b else b to a
+                edgeSet.add(x to y)
+            }
+        }
+        val edges = edgeSet.map { GraphEdge(it.first, it.second) }.sortedWith(compareBy({ it.a }, { it.b }))
+        _graphState.value = GraphSnapshot(nodeList, edges)
+    }
+
+    companion object {
+        @Volatile private var INSTANCE: MeshGraphService? = null
+        fun getInstance(): MeshGraphService = INSTANCE ?: synchronized(this) {
+            INSTANCE ?: MeshGraphService().also { INSTANCE = it }
+        }
+    }
+}
+