// archy-messh Phase 1 — tri-protocol RX scanner + trippy acid display
// ---------------------------------------------------------------------------
// Target: Heltec WiFi LoRa 32 V3 (ESP32-S3 + single SX1262 + 128x64 SSD1306).
//
// The radio rotates through the Reticulum / meshTastic / meshCore PHY presets
// (RTC), listening in each dwell window and logging every raw packet it
// demodulates. The OLED shows all three networks live — R T C — behind an
// animated acid-house smiley, with per-network activity blips. Received
// Meshtastic packets are decoded on-chip (AES-128-CTR + protobuf).
//
// HONEST HARDWARE NOTE: the single onboard SX1262 can only be tuned to ONE
// PHY at a time (ARCHITECTURE.md §2), so "all three active" is fast time-
// slicing, not literal simultaneity. True concurrent reception needs added
// radios (Phase 2 / Option B). The UI presents all three as armed; the scan
// cycles between them faster than a human notices.
//
// This increment still does NOT decode/bridge/transmit — that is the next
// roadmap step (firmware/README.md). It proves RX + the device UX.
// ---------------------------------------------------------------------------

#include <Arduino.h>
#include <RadioLib.h>
#include <U8g2lib.h>
#include <Wire.h>
#include <math.h>
#include "mbedtls/aes.h"
#include "esp_mac.h"
#include "esp_random.h"
#include <AES.h>           // rweather/Crypto — AES-128-ECB for MeshCore DM cipher
#include <SHA256.h>        // rweather/Crypto — HMAC-SHA256 for MeshCore packet MAC
#include <Preferences.h>   // NVS-backed persistent identity seed
extern "C" {
#include "ed_25519.h"      // orlp/ed25519 (vendored, lib/ed25519) — identity, sign, ECDH
}

// --- Heltec V3 SX1262 pin map (from the Heltec V3 schematic) ----------------
static const int PIN_LORA_NSS  = 8;
static const int PIN_LORA_DIO1 = 14;
static const int PIN_LORA_NRST = 12;
static const int PIN_LORA_BUSY = 13;
static const int PIN_LORA_SCK  = 9;
static const int PIN_LORA_MISO = 11;
static const int PIN_LORA_MOSI = 10;
static const float  TCXO_VOLTAGE = 1.8f;
static const int8_t RX_TX_POWER  = 10;

// --- Heltec V3 OLED + power ------------------------------------------------
static const int PIN_OLED_SDA = 17;
static const int PIN_OLED_SCL = 18;
static const int PIN_OLED_RST = 21;
static const int PIN_VEXT     = 36;  // drives Vext rail; LOW = ON (powers OLED)

SX1262 radio = new Module(PIN_LORA_NSS, PIN_LORA_DIO1, PIN_LORA_NRST, PIN_LORA_BUSY);
U8G2_SSD1306_128X64_NONAME_F_HW_I2C oled(U8G2_R0, PIN_OLED_RST, PIN_OLED_SCL, PIN_OLED_SDA);

// --- The three PHY presets (RTC) -------------------------------------------
// Values from docs/ARCHITECTURE.md §1. Items flagged are open questions the
// scan is meant to test against reality.
struct PhyConfig {
  const char* name;
  char        letter;   // R / T / C  for the display
  float       freqMHz;
  float       bwKHz;
  uint8_t     sf;
  uint8_t     cr;       // 4/cr
  uint8_t     syncWord;
  uint16_t    preamble;
};

static const PhyConfig CONFIGS[] = {
  // meshTastic EU868 "LongFast" — confirmed correct (received live packets).
  { "meshtastic", 'T', 869.525f, 250.0f, 11, 5, 0x2b, 16 },
  // MeshCore narrowband — read live from the "HP Pro Desk" node's SELF_INFO
  // (companion serial protocol, 2026-07-01): 869.618 MHz / 62.5 kHz / SF8 / CR5.
  { "meshcore",   'C', 869.618f, 62.5f, 8, 5, 0x12, 16 },
  // Reticulum has no fixed preset; PLACEHOLDER — set to your RNS RNode config.
  { "reticulum",  'R', 867.200f, 125.0f,  8, 5, 0x12, 16 },
};
static const size_t NUM_CONFIGS = sizeof(CONFIGS) / sizeof(CONFIGS[0]);
static const uint32_t DWELL_MS = 3000;   // camp long enough to sit through a
                                         // flood-rebroadcast burst on each PHY;
                                         // tune vs. how "live" C/R need to feel

// Device identity — this single name is what the bridge will present on ALL
// three networks once the participation/TX layer lands, so a message addressed
// to "Reticutasticore" on Meshtastic, MeshCore or Reticulum reaches this device:
//   - Meshtastic: User.long_name = DEVICE_NAME, short_name = DEVICE_SHORT (<=4)
//   - MeshCore:   advertised contact name = DEVICE_NAME
//   - Reticulum:  LXMF delivery display_name = DEVICE_NAME
// (RX-only today; the constants exist now so TX inherits them with no churn.)
static const char* DEVICE_NAME  = "Reticutasticore";
static const char* DEVICE_SHORT = "RTC";

// --- Runtime stats ----------------------------------------------------------
struct NetStat {
  uint32_t pkts = 0;
  int16_t  lastRssi = 0;
  bool     seen = false;
  uint32_t lastRxMs = 0;   // for the RX activity blip
};
static NetStat  stats[NUM_CONFIGS];
static int      activeIdx = 0;
static uint32_t totalPkts = 0;
static uint32_t dwellStart = 0;
static uint32_t frame = 0;

// Outbound message queued from the serial console ("T:hello", or bare "hello"
// == all nets). Flushed on the matching PHY window so the radio is tuned right.
static char     txText[200] = {0};
static bool     txPending = false;
static char     txNets[4]  = {0};   // subset of "TCR"; empty == all

// Last decoded human-readable event, shown along the bottom of the display.
static char     lastMsg[40] = {0};
static char     lastMsgNet = ' ';
static uint32_t lastMsgMs = 0;

// Meshtastic node identity (this device's presence on the mesh).
static uint32_t nodeNum = 0;
static char     nodeId[12] = {0};        // "!xxxxxxxx"
static uint32_t lastAnnounceMs = 0;
static const uint32_t ANNOUNCE_INTERVAL_MS = 60000;  // re-announce every 60s

// Message modal: on an inbound text we play an intro animation (upside-down
// spinning striped smiley + lightning bolts) then a Meshtastic-style modal
// stating the network, sender and text. Network-agnostic — any protocol that
// decodes a message drives it.
static bool     msgModalActive = false;
static uint32_t msgModalStart = 0;
static char     modalNet[14] = {0};
static char     modalSender[20] = {0};
static char     modalText[80] = {0};
static const uint32_t MODAL_INTRO_MS = 1400;
static const uint32_t MODAL_TOTAL_MS = 6500;

static void triggerMessageModal(const char* net, const char* sender, const char* text) {
  strncpy(modalNet, net, sizeof(modalNet) - 1);       modalNet[sizeof(modalNet) - 1] = 0;
  strncpy(modalSender, sender, sizeof(modalSender) - 1); modalSender[sizeof(modalSender) - 1] = 0;
  strncpy(modalText, text, sizeof(modalText) - 1);    modalText[sizeof(modalText) - 1] = 0;
  msgModalActive = true; msgModalStart = millis();
}

// --- RX interrupt -----------------------------------------------------------
static volatile bool rxFlag = false;
ICACHE_RAM_ATTR static void onDio1() { rxFlag = true; }

static bool applyConfig(const PhyConfig& c) {
  radio.standby();
  bool ok = true;
  ok &= radio.setFrequency(c.freqMHz)       == RADIOLIB_ERR_NONE;
  ok &= radio.setBandwidth(c.bwKHz)         == RADIOLIB_ERR_NONE;
  ok &= radio.setSpreadingFactor(c.sf)      == RADIOLIB_ERR_NONE;
  ok &= radio.setCodingRate(c.cr)           == RADIOLIB_ERR_NONE;
  ok &= radio.setSyncWord(c.syncWord)       == RADIOLIB_ERR_NONE;
  ok &= radio.setPreambleLength(c.preamble) == RADIOLIB_ERR_NONE;
  if (!ok) return false;
  return radio.startReceive() == RADIOLIB_ERR_NONE;
}

// --- On-chip Meshtastic decode ---------------------------------------------
// Default-channel ("LongFast") packets use AES-128-CTR with a PUBLIC key.
// Validated offline against real captured packets (firmware/tools/
// meshtastic_decode.py). Wire format: 16-byte header + encrypted Data protobuf.
static const uint8_t MT_KEY[16] = {
  0xd4, 0xf1, 0xbb, 0x3a, 0x20, 0x29, 0x07, 0x59,
  0xf0, 0xbc, 0xff, 0xab, 0xcf, 0x4e, 0x69, 0x01};

static uint32_t readVarint(const uint8_t* b, size_t len, size_t& i) {
  uint32_t v = 0; int shift = 0;
  while (i < len) {
    uint8_t c = b[i++];
    v |= (uint32_t)(c & 0x7f) << shift; shift += 7;
    if (!(c & 0x80)) break;
  }
  return v;
}

// Decode a Meshtastic packet into a short human string (text, or node name for
// NodeInfo). Returns false if not decodable / not an interesting type.
static bool decodeMeshtastic(const uint8_t* pkt, size_t len, char* out, size_t outsz,
                             bool* isText, uint32_t* senderOut) {
  if (len <= 16) return false;
  uint32_t sender, pid;
  memcpy(&sender, pkt + 4, 4);
  memcpy(&pid, pkt + 8, 4);
  if (senderOut) *senderOut = sender;
  if (isText) *isText = false;

  // CTR nonce = packetId (8 LE, high 4 zero) + fromNode (4 LE) + extraNonce (4 = 0)
  uint8_t nonce[16]; memset(nonce, 0, 16);
  memcpy(nonce + 0, &pid, 4);
  memcpy(nonce + 8, &sender, 4);

  size_t plen = len - 16;
  if (plen > 240) return false;
  uint8_t plain[240];
  mbedtls_aes_context aes; mbedtls_aes_init(&aes);
  mbedtls_aes_setkey_enc(&aes, MT_KEY, 128);
  size_t nc_off = 0; uint8_t stream[16]; memset(stream, 0, 16);
  mbedtls_aes_crypt_ctr(&aes, plen, &nc_off, nonce, stream, pkt + 16, plain);
  mbedtls_aes_free(&aes);

  // Data protobuf: field 1 = portnum (varint), field 2 = payload (bytes)
  size_t i = 0; uint8_t port = 0; const uint8_t* payload = nullptr; size_t payLen = 0;
  while (i < plen) {
    uint8_t tag = plain[i++]; uint8_t field = tag >> 3, wt = tag & 7;
    if (wt == 0) { uint32_t v = readVarint(plain, plen, i); if (field == 1) port = (uint8_t)v; }
    else if (wt == 2) { uint32_t l = readVarint(plain, plen, i);
                        if (field == 2) { payload = plain + i; payLen = l; } i += l; }
    else break;
  }
  if (!payload) return false;

  if (port == 1) {  // TEXT_MESSAGE_APP
    size_t n = payLen < outsz - 1 ? payLen : outsz - 1;
    memcpy(out, payload, n); out[n] = 0;
    if (isText) *isText = true;
    return true;
  }
  if (port == 4) {  // NODEINFO_APP -> User protobuf; field 3 = shortName
    size_t j = 0; const uint8_t* sn = nullptr; size_t snl = 0;
    while (j < payLen) {
      uint8_t tag = payload[j++]; uint8_t f = tag >> 3, w = tag & 7;
      if (w == 2) { uint32_t l = readVarint(payload, payLen, j);
                    if (f == 3) { sn = payload + j; snl = l; } j += l; }
      else if (w == 0) { readVarint(payload, payLen, j); }
      else break;
    }
    if (sn) { size_t n = snl < outsz - 1 ? snl : outsz - 1;
              memcpy(out, sn, n); out[n] = 0; return true; }
  }
  return false;
}

// AES-128-CTR (symmetric, so same call encrypts) with the Meshtastic default key.
static void mtCryptCtr(uint32_t sender, uint32_t pid, const uint8_t* in, uint8_t* out, size_t n) {
  uint8_t nonce[16]; memset(nonce, 0, 16);
  memcpy(nonce + 0, &pid, 4);
  memcpy(nonce + 8, &sender, 4);
  mbedtls_aes_context aes; mbedtls_aes_init(&aes);
  mbedtls_aes_setkey_enc(&aes, MT_KEY, 128);
  size_t nc_off = 0; uint8_t stream[16]; memset(stream, 0, 16);
  mbedtls_aes_crypt_ctr(&aes, n, &nc_off, nonce, stream, in, out);
  mbedtls_aes_free(&aes);
}

// Announce this device as a Meshtastic node named DEVICE_NAME. Broadcasts a
// NodeInfo (User protobuf) on the LongFast primary channel (hash 0x08) so it
// appears in other Meshtastic clients — and, because we advertise no public
// key, DMs to us fall back to channel encryption, which we can already decode.
static void announceMeshtastic() {
  // User protobuf: field1 id, field2 long_name, field3 short_name
  uint8_t user[64]; size_t u = 0;
  size_t idl = strlen(nodeId), lnl = strlen(DEVICE_NAME), snl = strlen(DEVICE_SHORT);
  user[u++] = 0x0a; user[u++] = idl; memcpy(user + u, nodeId, idl);      u += idl;
  user[u++] = 0x12; user[u++] = lnl; memcpy(user + u, DEVICE_NAME, lnl); u += lnl;
  user[u++] = 0x1a; user[u++] = snl; memcpy(user + u, DEVICE_SHORT, snl); u += snl;

  // Data protobuf: portnum=4 (NODEINFO_APP), payload=User
  uint8_t data[96]; size_t d = 0;
  data[d++] = 0x08; data[d++] = 0x04;             // portnum = 4
  data[d++] = 0x12; data[d++] = (uint8_t)u; memcpy(data + d, user, u); d += u;

  uint32_t pid = esp_random();
  uint8_t enc[96];
  mtCryptCtr(nodeNum, pid, data, enc, d);

  // 16-byte header + ciphertext
  uint8_t pkt[128]; uint32_t dest = 0xffffffff;
  memcpy(pkt + 0, &dest, 4);
  memcpy(pkt + 4, &nodeNum, 4);
  memcpy(pkt + 8, &pid, 4);
  pkt[12] = 0x63;  // flags: hop_limit=3, hop_start=3
  pkt[13] = 0x08;  // channel hash (LongFast primary)
  pkt[14] = 0x00;  // next_hop
  pkt[15] = 0x00;  // relay_node
  memcpy(pkt + 16, enc, d);

  radio.standby();
  int st = radio.transmit(pkt, 16 + d);
  Serial.printf("  [T] announce '%s' (%s) id=0x%08x -> tx=%d : ",
                DEVICE_NAME, nodeId, pid, st);
  for (size_t i = 0; i < 16 + d; i++) Serial.printf("%02x", pkt[i]);   // TX hex for self-verify
  Serial.println();
  radio.startReceive();
}

// Send a text message on the Meshtastic LongFast primary channel. Same wire
// format as announceMeshtastic() but portnum=1 (TEXT_MESSAGE_APP), payload =
// the raw UTF-8 text. Assumes the radio is already tuned to the 'T' PHY.
static void sendMeshtasticText(const char* text) {
  size_t tl = strlen(text);
  if (tl > 200) tl = 200;

  // Data protobuf: field1 portnum=1 (varint), field2 payload=text (bytes)
  uint8_t data[224]; size_t d = 0;
  data[d++] = 0x08; data[d++] = 0x01;                 // portnum = 1
  data[d++] = 0x12; data[d++] = (uint8_t)tl;          // payload, len-delimited
  memcpy(data + d, text, tl); d += tl;

  uint32_t pid = esp_random();
  uint8_t enc[224];
  mtCryptCtr(nodeNum, pid, data, enc, d);

  uint8_t pkt[240]; uint32_t dest = 0xffffffff;
  memcpy(pkt + 0, &dest, 4);
  memcpy(pkt + 4, &nodeNum, 4);
  memcpy(pkt + 8, &pid, 4);
  pkt[12] = 0x63;  // flags: hop_limit=3, hop_start=3
  pkt[13] = 0x08;  // channel hash (LongFast primary)
  pkt[14] = 0x00;  // next_hop
  pkt[15] = 0x00;  // relay_node
  memcpy(pkt + 16, enc, d);

  radio.standby();
  int st = radio.transmit(pkt, 16 + d);
  Serial.printf("  [T] TX text id=0x%08x -> tx=%d : \"%s\"\n", pid, st, text);
  radio.startReceive();
}

// --- MeshCore identity + advert TX -----------------------------------------
// MeshCore nodes prove identity with an Ed25519 keypair. To appear as a contact
// in other clients we broadcast a signed ADVERT (PAYLOAD_TYPE_ADVERT = 0x04):
//   on-air: [header 0x12][path_len 0x00][pub_key 32][timestamp 4 LE][sig 64][app_data]
//   signed message = pub_key || timestamp || app_data   (verified in MeshCore
//   Mesh.cpp onRecvPacket PAYLOAD_TYPE_ADVERT). app_data = flags(0x81 = chat
//   node + has-name) followed by the UTF-8 name.
static uint8_t  mcSeed[32];       // persistent 32-byte identity seed (NVS)
static uint8_t  mcPrv[64];        // orlp expanded private key, derived from seed
static uint8_t  mcPub[32];        // Ed25519 public key = MeshCore identity
static uint32_t lastMcAdvertMs = 0;
static const uint32_t MC_ADVERT_INTERVAL_MS = 30000;
// Build-time epoch base (2026-07-01 UTC) + uptime — advert timestamps just need
// to be fresh/monotonic; the node has no RTC.
static const uint32_t MC_EPOCH_BASE = 1782864000UL;
static uint32_t mcNow() { return MC_EPOCH_BASE + millis() / 1000; }

static void initMeshCoreIdentity() {
  Preferences prefs;
  prefs.begin("meshcore", false);
  // NVS key "prv" holds the 32-byte seed (unchanged from the first identity so
  // peers that already added us keep recognising the same public key).
  if (prefs.getBytes("prv", mcSeed, 32) != 32) {
    for (int i = 0; i < 32; i++) mcSeed[i] = (uint8_t)esp_random();  // HW CSPRNG
    prefs.putBytes("prv", mcSeed, 32);
    Serial.println("MeshCore: generated new Ed25519 identity");
  }
  prefs.end();
  ed25519_create_keypair(mcPub, mcPrv, mcSeed);   // seed -> (pub, expanded prv)
  Serial.print("MeshCore identity pub: ");
  for (int i = 0; i < 32; i++) Serial.printf("%02x", mcPub[i]);
  Serial.println();
}

static void sendMeshCoreAdvert() {
  uint8_t app_data[40]; size_t ad = 0;
  app_data[ad++] = 0x81;                       // flags: chat node + has name
  size_t nl = strlen(DEVICE_NAME); if (nl > 32) nl = 32;
  memcpy(app_data + ad, DEVICE_NAME, nl); ad += nl;

  uint32_t ts = mcNow();
  uint8_t message[32 + 4 + 40]; size_t ml = 0;
  memcpy(message + ml, mcPub, 32);  ml += 32;
  memcpy(message + ml, &ts, 4);     ml += 4;
  memcpy(message + ml, app_data, ad); ml += ad;

  uint8_t sig[64];
  ed25519_sign(sig, message, ml, mcPub, mcPrv);

  uint8_t pkt[2 + 32 + 4 + 64 + 40]; size_t p = 0;
  pkt[p++] = 0x12;                             // route=flood(2) | type=advert(4)
  pkt[p++] = 0x00;                             // path_len = 0 (direct/flood)
  memcpy(pkt + p, mcPub, 32); p += 32;
  memcpy(pkt + p, &ts, 4);    p += 4;
  memcpy(pkt + p, sig, 64);   p += 64;
  memcpy(pkt + p, app_data, ad); p += ad;

  radio.standby();
  int st = radio.transmit(pkt, p);
  Serial.printf("  [C] advert '%s' ts=%u -> tx=%d (%u bytes) : ",
                DEVICE_NAME, ts, st, (unsigned)p);
  for (size_t i = 0; i < p; i++) Serial.printf("%02x", pkt[i]);   // TX hex for self-verify
  Serial.println();
  radio.startReceive();
}

// Send an encrypted MeshCore direct message to a contact (Ed25519 pubkey).
// Mirror of the RX path: plaintext = timestamp(4) + flags(1) + text, then
// encryptThenMAC = HMAC-SHA256(2) prefix + AES-128-ECB(zero-padded plaintext),
// wrapped as [header][path_len 0][dest_hash][src_hash][cipher].
static void sendMeshCoreText(const uint8_t* dest_pub, const char* text) {
  uint32_t ts = mcNow();
  uint8_t plain[176]; size_t pl = 0;
  memcpy(plain + pl, &ts, 4); pl += 4;
  plain[pl++] = 0x00;                          // flags: attempt 0, TXT_TYPE_PLAIN
  size_t tl = strlen(text); if (tl > 140) tl = 140;
  memcpy(plain + pl, text, tl); pl += tl;

  uint8_t secret[32];
  ed25519_key_exchange(secret, dest_pub, mcPrv);   // ECDH shared secret

  // AES-128-ECB over the plaintext, zero-padded to a 16-byte boundary.
  uint8_t cipher[2 + 176 + 16]; uint8_t* enc = cipher + 2; size_t el = 0;
  AES128 aes; aes.setKey(secret, 16);
  size_t off = 0;
  while (pl - off >= 16) { aes.encryptBlock(enc + el, plain + off); el += 16; off += 16; }
  if (pl - off > 0) {
    uint8_t tmp[16]; memset(tmp, 0, 16); memcpy(tmp, plain + off, pl - off);
    aes.encryptBlock(enc + el, tmp); el += 16;
  }
  // 2-byte truncated HMAC-SHA256 over the ciphertext (key = 32-byte secret).
  SHA256 sha; sha.resetHMAC(secret, 32); sha.update(enc, el);
  sha.finalizeHMAC(secret, 32, cipher, 2);
  size_t clen = 2 + el;

  uint8_t pkt[4 + sizeof(cipher)]; size_t p = 0;
  pkt[p++] = 0x0A;                             // route=flood(2) | type=TXT_MSG(2)
  pkt[p++] = 0x00;                             // path_len = 0
  pkt[p++] = dest_pub[0];                      // dest_hash
  pkt[p++] = mcPub[0];                         // src_hash
  memcpy(pkt + p, cipher, clen); p += clen;

  radio.standby();
  int st = radio.transmit(pkt, p);
  Serial.printf("  [C] TX dm -> tx=%d (%u bytes) : \"%s\"\n", st, (unsigned)p, text);
  radio.startReceive();
}

// --- MeshCore contacts (heard adverts) + DM receive ------------------------
// To decrypt a direct message we need the SENDER's full public key. MeshCore
// packets only carry a 1-byte src_hash (pubkey prefix), so we remember pubkeys
// from the adverts we hear and match on that hash.
struct McContact { uint8_t pub[32]; char name[24]; bool used; };
static const int MC_MAX_CONTACTS = 8;
static McContact mcContacts[MC_MAX_CONTACTS];
static int mcContactRR = 0;   // round-robin eviction cursor

static void mcStoreContact(const uint8_t* pub, const char* name) {
  for (int i = 0; i < MC_MAX_CONTACTS; i++)               // update existing
    if (mcContacts[i].used && memcmp(mcContacts[i].pub, pub, 32) == 0) {
      strncpy(mcContacts[i].name, name, sizeof(mcContacts[i].name) - 1);
      return;
    }
  for (int i = 0; i < MC_MAX_CONTACTS; i++)               // fill a free slot
    if (!mcContacts[i].used) {
      mcContacts[i].used = true; memcpy(mcContacts[i].pub, pub, 32);
      strncpy(mcContacts[i].name, name, sizeof(mcContacts[i].name) - 1);
      return;
    }
  int i = mcContactRR; mcContactRR = (mcContactRR + 1) % MC_MAX_CONTACTS;  // evict
  memcpy(mcContacts[i].pub, pub, 32);
  strncpy(mcContacts[i].name, name, sizeof(mcContacts[i].name) - 1);
  mcContacts[i].name[sizeof(mcContacts[i].name) - 1] = 0;
}

// MeshCore Utils::MACThenDecrypt — verify a 2-byte truncated HMAC-SHA256 over
// the ciphertext (key = 32-byte shared secret), then AES-128-ECB decrypt (key =
// first 16 bytes). Returns plaintext length (multiple of 16) or 0 on bad MAC.
static int mcMACThenDecrypt(const uint8_t* secret, uint8_t* dest,
                            const uint8_t* src, int src_len) {
  if (src_len <= 2 || (src_len - 2) % 16 != 0) return 0;
  uint8_t hmac[2];
  SHA256 sha;
  sha.resetHMAC(secret, 32);
  sha.update(src + 2, src_len - 2);
  sha.finalizeHMAC(secret, 32, hmac, 2);
  if (memcmp(hmac, src, 2) != 0) return 0;               // MAC mismatch
  AES128 aes; aes.setKey(secret, 16);
  int n = src_len - 2; const uint8_t* sp = src + 2; uint8_t* dp = dest;
  for (int o = 0; o < n; o += 16) { aes.decryptBlock(dp, sp); dp += 16; sp += 16; }
  return n;
}

// Parse a received MeshCore packet: store adverts, decrypt DMs addressed to us.
static void handleMeshCorePacket(const uint8_t* buf, size_t len) {
  if (len < 2) return;
  uint8_t header = buf[0];
  uint8_t route = header & 0x03;
  uint8_t ptype = (header >> 2) & 0x0F;
  size_t i = 1;
  if (route == 0x00 || route == 0x03) i += 4;            // transport codes
  if (i >= len) return;
  uint8_t plb = buf[i++];
  uint8_t hsize = (plb >> 6) + 1, hcount = plb & 0x3F;
  i += (size_t)hsize * hcount;                            // skip path hashes
  if (i >= len) return;
  const uint8_t* payload = buf + i;
  int payload_len = (int)len - (int)i;

  if (ptype == 0x04) {                                    // ADVERT
    if (payload_len < 32 + 4 + 64 + 1) return;
    char name[24] = {0};
    const uint8_t* app = payload + 32 + 4 + 64;
    int app_len = payload_len - (32 + 4 + 64);
    if (app_len > 1) { int nl = app_len - 1; if (nl > 23) nl = 23; memcpy(name, app + 1, nl); }
    mcStoreContact(payload, name);
    strncpy(lastMsg, name[0] ? name : "advert", sizeof(lastMsg) - 1);
    lastMsg[sizeof(lastMsg) - 1] = 0; lastMsgNet = 'C'; lastMsgMs = millis();
    Serial.printf("      decoded[C](advert): %s\n", name);
    return;
  }
  if (ptype == 0x02) {                                    // TXT_MSG (direct message)
    if (payload_len < 2 + 2 + 16) return;
    uint8_t dest_hash = payload[0], src_hash = payload[1];
    if (dest_hash != mcPub[0]) return;                    // not addressed to us
    const uint8_t* macData = payload + 2;
    int macLen = payload_len - 2;
    for (int c = 0; c < MC_MAX_CONTACTS; c++) {
      if (!mcContacts[c].used || mcContacts[c].pub[0] != src_hash) continue;
      uint8_t secret[32];
      ed25519_key_exchange(secret, mcContacts[c].pub, mcPrv);   // ECDH
      uint8_t plain[192];
      int n = mcMACThenDecrypt(secret, plain, macData, macLen);
      if (n > 5) {
        plain[n < (int)sizeof(plain) ? n : (int)sizeof(plain) - 1] = 0;
        uint8_t txt_type = plain[4] & 0x03;
        const char* text = (const char*)&plain[5];
        if (txt_type == 0) {                              // TXT_TYPE_PLAIN
          strncpy(lastMsg, text, sizeof(lastMsg) - 1); lastMsg[sizeof(lastMsg) - 1] = 0;
          lastMsgNet = 'C'; lastMsgMs = millis();
          Serial.printf("      decoded[C](dm from %s): %s\n", mcContacts[c].name, text);
          triggerMessageModal("meshCore", mcContacts[c].name, text);
        }
        return;
      }
    }
    Serial.printf("      [C] DM for us but no matching contact (src_hash=%02x)\n", src_hash);
  }
}

static void drainPacket() {
  size_t len = radio.getPacketLength();
  uint8_t buf[256];
  if (len > sizeof(buf)) len = sizeof(buf);
  int state = radio.readData(buf, len);
  if (state != RADIOLIB_ERR_NONE) {
    Serial.printf("  [%s] RX error state=%d\n", CONFIGS[activeIdx].name, state);
    return;
  }
  NetStat& s = stats[activeIdx];
  s.pkts++; s.seen = true; s.lastRssi = (int16_t)radio.getRSSI(); s.lastRxMs = millis();
  totalPkts++;
  Serial.printf("  [%s] PACKET len=%u rssi=%ddBm snr=%.1fdB : ",
                CONFIGS[activeIdx].name, (unsigned)len, s.lastRssi, radio.getSNR());
  for (size_t i = 0; i < len; i++) Serial.printf("%02x", buf[i]);
  Serial.println();

  // meshTastic packets we can decode on-chip today.
  if (CONFIGS[activeIdx].letter == 'T') {
    char msg[64]; bool isText = false; uint32_t snd = 0;
    if (decodeMeshtastic(buf, len, msg, sizeof(msg), &isText, &snd)) {
      strncpy(lastMsg, msg, sizeof(lastMsg) - 1); lastMsg[sizeof(lastMsg) - 1] = 0;
      lastMsgNet = 'T'; lastMsgMs = millis();
      Serial.printf("      decoded[T]%s: %s\n", isText ? "(text)" : "(info)", msg);
      if (isText) {
        char sid[16]; snprintf(sid, sizeof(sid), "!%08x", snd);
        triggerMessageModal("meshTastic", sid, msg);
      }
    }
  }

  // MeshCore: store heard adverts, decrypt direct messages addressed to us.
  if (CONFIGS[activeIdx].letter == 'C') {
    handleMeshCorePacket(buf, len);
  }
}

// --- The trippy acid display ------------------------------------------------
// Left: an acid-house smiley wobbling inside expanding psychedelic rings.
// Right: "RMC" and the three network rows with live counts + RX blips.
static void drawAcidSmiley(int cx, int cy) {
  // expanding ripple rings (the trip)
  for (int k = 0; k < 3; k++) {
    int r = (int)((frame * 2 + k * 13) % 42);
    if (r > 3) oled.drawCircle(cx, cy, r, U8G2_DRAW_ALL);
  }
  // face: filled disc, eyes + smile cut back out in background colour
  oled.setDrawColor(1);
  oled.drawDisc(cx, cy, 18, U8G2_DRAW_ALL);
  oled.setDrawColor(0);
  oled.drawBox(cx - 8, cy - 8, 3, 7);   // left eye
  oled.drawBox(cx + 5, cy - 8, 3, 7);   // right eye
  for (int dx = -10; dx <= 10; dx++) {   // grinning acid smile
    int dy = 4 + (100 - dx * dx) / 22;   // corners up, dips in the middle
    oled.drawPixel(cx + dx, cy + dy);
    oled.drawPixel(cx + dx, cy + dy + 1);
  }
  oled.setDrawColor(1);
}

// Periodic freak-out: the face becomes a spinning striped ball with wide-open
// googly eyes and a gaping mouth.
static void drawAcidSmileyFreaky(int cx, int cy) {
  const int R = 18;
  oled.setDrawColor(1);
  oled.drawDisc(cx, cy, R, U8G2_DRAW_ALL);
  // rotating stripes carved into the ball (the spin)
  float th = frame * 0.35f;
  float c = cosf(th), s = sinf(th);
  oled.setDrawColor(0);
  for (int off = -R; off <= R; off += 4) {
    float px = cx - s * off, py = cy + c * off;
    oled.drawLine((int)(px - c * R), (int)(py - s * R),
                  (int)(px + c * R), (int)(py + s * R));
  }
  oled.setDrawColor(1);
  oled.drawCircle(cx, cy, R, U8G2_DRAW_ALL);   // crisp rim
  // wide-open googly eyes: white halo -> dark iris -> white pupil highlight,
  // so they read against the striped ball (a plain white disc would vanish)
  for (int sgn = -1; sgn <= 1; sgn += 2) {
    int ex = cx + sgn * 7;
    oled.setDrawColor(1); oled.drawDisc(ex, cy - 6, 4, U8G2_DRAW_ALL);  // halo
    oled.setDrawColor(0); oled.drawDisc(ex, cy - 6, 3, U8G2_DRAW_ALL);  // iris
    oled.setDrawColor(1); oled.drawDisc(ex, cy - 6, 1, U8G2_DRAW_ALL);  // pupil
  }
  // gaping mouth: white ring around a dark O
  oled.setDrawColor(1); oled.drawDisc(cx, cy + 7, 5, U8G2_DRAW_ALL);
  oled.setDrawColor(0); oled.drawDisc(cx, cy + 7, 3, U8G2_DRAW_ALL);
  oled.setDrawColor(1);
}

static void drawMarchingBorder() {
  for (int x = 0; x < 128; x++) {
    if (((x + frame) & 3) == 0) { oled.drawPixel(x, 0); oled.drawPixel(x, 63); }
  }
  for (int y = 0; y < 64; y++) {
    if (((y + frame) & 3) == 0) { oled.drawPixel(0, y); oled.drawPixel(127, y); }
  }
}

static const PhyConfig* configByLetter(char L) {
  for (size_t i = 0; i < NUM_CONFIGS; i++) if (CONFIGS[i].letter == L) return &CONFIGS[i];
  return nullptr;
}
static int indexByLetter(char L) {
  for (size_t i = 0; i < NUM_CONFIGS; i++) if (CONFIGS[i].letter == L) return (int)i;
  return -1;
}

// --- Message-received animation + modal ------------------------------------
static void drawBolt(int x, int y, int h) {
  oled.drawLine(x, y, x - 3, y + h / 2);
  oled.drawLine(x - 3, y + h / 2, x + 3, y + h / 2);
  oled.drawLine(x + 3, y + h / 2, x - 1, y + h);
}

// Greedy word-wrap for a fixed-width font (6px/char here).
static void drawWrapped(const char* text, int x, int y0, int cpl, int lineh, int maxlines) {
  int n = strlen(text), i = 0, line = 0;
  while (i < n && line < maxlines) {
    int end = i + cpl;
    if (end < n) { int b = end; while (b > i && text[b] != ' ') b--; if (b > i) end = b; }
    else end = n;
    char buf[40]; int len = end - i; if (len > 39) len = 39;
    memcpy(buf, text + i, len); buf[len] = 0;
    oled.drawStr(x, y0 + line * lineh, buf);
    i = end; while (i < n && text[i] == ' ') i++;
    line++;
  }
}

// Intro: the striped smiley spins UPSIDE DOWN (eyes below, mouth above) while
// lightning bolts flash — a beat before the modal, à la Meshtastic.
static void drawMsgIntro() {
  oled.clearBuffer();
  int cx = 64, cy = 30; const int R = 22;
  oled.setDrawColor(1); oled.drawDisc(cx, cy, R, U8G2_DRAW_ALL);
  float th = -frame * 0.5f;                 // reversed spin
  float c = cosf(th), s = sinf(th);
  oled.setDrawColor(0);
  for (int off = -R; off <= R; off += 4) {
    float px = cx - s * off, py = cy + c * off;
    oled.drawLine((int)(px - c * R), (int)(py - s * R), (int)(px + c * R), (int)(py + s * R));
  }
  oled.setDrawColor(1); oled.drawCircle(cx, cy, R, U8G2_DRAW_ALL);
  for (int sgn = -1; sgn <= 1; sgn += 2) {  // eyes BELOW centre (upside down)
    int ex = cx + sgn * 8;
    oled.setDrawColor(1); oled.drawDisc(ex, cy + 8, 4, U8G2_DRAW_ALL);
    oled.setDrawColor(0); oled.drawDisc(ex, cy + 8, 3, U8G2_DRAW_ALL);
    oled.setDrawColor(1); oled.drawDisc(ex, cy + 8, 1, U8G2_DRAW_ALL);
  }
  oled.setDrawColor(1); oled.drawDisc(cx, cy - 9, 5, U8G2_DRAW_ALL);  // mouth ABOVE
  oled.setDrawColor(0); oled.drawDisc(cx, cy - 9, 3, U8G2_DRAW_ALL);
  oled.setDrawColor(1);
  if ((frame / 2) & 1) { drawBolt(22, 5, 22); drawBolt(106, 5, 22); }
  else                 { drawBolt(14, 12, 20); drawBolt(114, 10, 22); }
  oled.setFont(u8g2_font_5x8_tf);
  const char* t = "INCOMING";
  oled.drawStr((128 - oled.getStrWidth(t)) / 2, 62, t);
  oled.sendBuffer();
}

// Modal: network banner + sender + wrapped message text.
static void drawMsgModal() {
  oled.clearBuffer();
  oled.drawRFrame(1, 1, 126, 62, 3);
  oled.drawBox(1, 1, 126, 13);              // header bar
  oled.setDrawColor(0);
  oled.setFont(u8g2_font_6x10_tf);
  oled.drawStr((128 - oled.getStrWidth(modalNet)) / 2, 11, modalNet);
  oled.setDrawColor(1);
  oled.setFont(u8g2_font_5x8_tf);
  char sl[28]; snprintf(sl, sizeof(sl), "from %s", modalSender);
  oled.drawStr(6, 24, sl);
  oled.setFont(u8g2_font_6x10_tf);
  drawWrapped(modalText, 6, 36, 19, 11, 3);
  oled.sendBuffer();
}

static void drawUI() {
  if (msgModalActive) {
    uint32_t e = millis() - msgModalStart;
    if (e < MODAL_INTRO_MS) { drawMsgIntro(); return; }
    if (e < MODAL_TOTAL_MS) { drawMsgModal(); return; }
    msgModalActive = false;
  }
  oled.clearBuffer();

  // Every ~9s the smiley freaks out (spins, stripes, eyes + mouth open) for ~2.5s.
  bool freaky = (millis() % 9000) < 2500;
  if (freaky) drawAcidSmileyFreaky(31, 33);
  else        drawAcidSmiley(31, 33);
  drawMarchingBorder();

  // "RTC" punk header on the right
  oled.setFont(u8g2_font_bubble_tr);
  const char* rtc = "RTC";
  int rw = oled.getStrWidth(rtc);
  int rx = 64 + (64 - rw) / 2;
  if ((frame / 10) & 1) {                 // strobe invert
    oled.drawBox(64, 0, 64, 22);
    oled.setDrawColor(0); oled.drawStr(rx, 19, rtc); oled.setDrawColor(1);
  } else {
    oled.drawStr(rx, 19, rtc);
  }

  // three network rows, in R T C order
  const char order[3] = {'R', 'T', 'C'};
  oled.setFont(u8g2_font_6x10_tf);
  uint32_t now = millis();
  for (int r = 0; r < 3; r++) {
    int idx = indexByLetter(order[r]);
    if (idx < 0) continue;
    const NetStat& s = stats[idx];
    int y = 32 + r * 11;                   // baseline (below the taller header)
    bool active = (idx == activeIdx);
    if (active) oled.drawFrame(64, y - 9, 64, 11);
    char line[24];
    if (s.seen) snprintf(line, sizeof(line), "%c %4lu", order[r], (unsigned long)s.pkts);
    else        snprintf(line, sizeof(line), "%c   --", order[r]);
    oled.drawStr(67, y, line);
    // RX activity blip (filled when a packet landed in the last 400ms)
    bool blip = s.seen && (now - s.lastRxMs < 400);
    if (blip) oled.drawDisc(121, y - 4, 3, U8G2_DRAW_ALL);
    else      oled.drawCircle(121, y - 4, 3, U8G2_DRAW_ALL);
  }

  // last decoded event along the bottom of the right column
  if (lastMsg[0]) {
    oled.setFont(u8g2_font_4x6_tf);
    char line[24];
    snprintf(line, sizeof(line), "%c:%s", lastMsgNet, lastMsg);
    line[15] = 0;  // truncate to fit the ~60px column
    oled.drawStr(66, 62, line);
  }

  oled.sendBuffer();
}

void setup() {
  Serial.begin(115200);
  uint32_t t0 = millis();
  while (!Serial && millis() - t0 < 2000) { }

  Serial.println("\n=== archy-messh Phase 1 — RTC scanner + acid display ===");

  // Power the OLED rail, then reset the panel, then bring up U8g2.
  pinMode(PIN_VEXT, OUTPUT); digitalWrite(PIN_VEXT, LOW); delay(60);
  pinMode(PIN_OLED_RST, OUTPUT);
  digitalWrite(PIN_OLED_RST, LOW);  delay(20);
  digitalWrite(PIN_OLED_RST, HIGH); delay(20);
  oled.begin();
  oled.setBusClock(400000);

  // Boot splash: the device identity, shared across all three networks.
  oled.clearBuffer();
  drawAcidSmiley(64, 24);
  oled.setFont(u8g2_font_6x10_tf);
  int nw = oled.getStrWidth(DEVICE_NAME);
  oled.drawStr((128 - nw) / 2, 52, DEVICE_NAME);
  oled.setFont(u8g2_font_5x8_tf);
  const char* sub = "R T C  bridge";
  int sw = oled.getStrWidth(sub);
  oled.drawStr((128 - sw) / 2, 62, sub);
  oled.sendBuffer();
  Serial.printf("Device identity (all networks): %s / %s\n", DEVICE_NAME, DEVICE_SHORT);
  delay(2200);

  SPI.begin(PIN_LORA_SCK, PIN_LORA_MISO, PIN_LORA_MOSI, PIN_LORA_NSS);
  const PhyConfig& first = CONFIGS[0];
  int state = radio.begin(first.freqMHz, first.bwKHz, first.sf, first.cr,
                          first.syncWord, RX_TX_POWER, first.preamble, TCXO_VOLTAGE);
  Serial.printf("radio.begin -> %d %s\n", state, state == RADIOLIB_ERR_NONE ? "(OK)" : "(ERR)");
  if (state != RADIOLIB_ERR_NONE) {
    Serial.println("!! SX1262 init failed — check wiring/TCXO. Halting.");
    while (true) { drawUI(); frame++; delay(60); }  // still show the trip
  }
  radio.setDio2AsRfSwitch(true);
  radio.setDio1Action(onDio1);
  radio.setOutputPower(14);   // EU868-safe TX power for announces

  // Derive this device's Meshtastic NodeNum from the last 4 bytes of the MAC.
  uint8_t mac[6]; esp_read_mac(mac, ESP_MAC_WIFI_STA);
  nodeNum = ((uint32_t)mac[2] << 24) | ((uint32_t)mac[3] << 16) |
            ((uint32_t)mac[4] << 8) | mac[5];
  snprintf(nodeId, sizeof(nodeId), "!%08x", nodeNum);
  Serial.printf("Meshtastic node: %s (%s)\n", DEVICE_NAME, nodeId);

  initMeshCoreIdentity();

  activeIdx = 0;
  applyConfig(CONFIGS[0]);
  dwellStart = millis();
}

// Read a line from the serial console into the TX queue. Syntax:
//   "hello"      -> send "hello" on all networks
//   "T:hello"    -> send only on Meshtastic  (T / C / R prefix, case-insensitive)
static void pollSerialTx() {
  static char buf[210]; static size_t n = 0;
  while (Serial.available()) {
    char c = Serial.read();
    if (c == '\r') continue;
    if (c == '\n') {
      buf[n] = 0;
      if (n > 0) {
        const char* msg = buf;
        strcpy(txNets, "TCR");            // default: all networks
        if (n >= 2 && buf[1] == ':') {
          char L = toupper(buf[0]);
          if (L == 'T' || L == 'C' || L == 'R') { txNets[0] = L; txNets[1] = 0; msg = buf + 2; }
        }
        strncpy(txText, msg, sizeof(txText) - 1); txText[sizeof(txText) - 1] = 0;
        txPending = true;
        Serial.printf("  [tx] queued for %s: \"%s\"\n", txNets, txText);
      }
      n = 0;
    } else if (n < sizeof(buf) - 1) {
      buf[n++] = c;
    }
  }
}

// If a message is queued for the currently-tuned network, send it now.
static void flushTxOnWindow() {
  if (!txPending) return;
  char L = CONFIGS[activeIdx].letter;
  char* p = strchr(txNets, L);
  if (!p) return;                          // not queued for this network

  if (L == 'T') {
    sendMeshtasticText(txText);
  } else if (L == 'C') {
    // DM the text to every MeshCore contact we've heard an advert from.
    int sent = 0;
    for (int c = 0; c < MC_MAX_CONTACTS; c++)
      if (mcContacts[c].used) { sendMeshCoreText(mcContacts[c].pub, txText); sent++; }
    if (sent == 0) Serial.printf("  [C] no known contacts yet — nobody to DM\n");
  } else {
    // Reticulum TX not built yet — acknowledge, don't fake it.
    Serial.printf("  [%c] TX not implemented yet (msg: \"%s\")\n", L, txText);
  }

  // Remove this network from the pending set; done when none remain.
  memmove(p, p + 1, strlen(p));            // includes the NUL terminator
  if (txNets[0] == 0) txPending = false;
}

void loop() {
  pollSerialTx();

  // Non-blocking scan: rotate the radio when the dwell window elapses, so the
  // display keeps animating smoothly the whole time.
  if (millis() - dwellStart >= DWELL_MS) {
    activeIdx = (activeIdx + 1) % NUM_CONFIGS;
    applyConfig(CONFIGS[activeIdx]);
    dwellStart = millis();
  }
  flushTxOnWindow();
  if (rxFlag) {
    rxFlag = false;
    drainPacket();
    radio.startReceive();
  }
  // Announce ourselves as a Meshtastic node while tuned to that PHY.
  if (CONFIGS[activeIdx].letter == 'T' &&
      (lastAnnounceMs == 0 || millis() - lastAnnounceMs > ANNOUNCE_INTERVAL_MS)) {
    announceMeshtastic();
    lastAnnounceMs = millis();
  }
  // Advertise ourselves as a MeshCore chat node while tuned to that PHY, so we
  // show up as a contact in other MeshCore clients.
  if (CONFIGS[activeIdx].letter == 'C' &&
      (lastMcAdvertMs == 0 || millis() - lastMcAdvertMs > MC_ADVERT_INTERVAL_MS)) {
    sendMeshCoreAdvert();
    lastMcAdvertMs = millis();
  }
  drawUI();
  frame++;
  delay(45);   // ~20 fps
}