Keep in-flight batch until ACK

src/main.cpp

@@ -62,6 +62,9 @@ static uint16_t g_batch_id = 1;
 static uint16_t g_last_sent_batch_id = 0;
 static uint8_t g_batch_retry_count = 0;
 static bool g_batch_ack_pending = false;
+static MeterData g_inflight_samples[METER_BATCH_MAX_SAMPLES];
+static size_t g_inflight_count = 0;
+static uint16_t g_inflight_batch_id = 0;
 
 static uint16_t g_last_batch_id_rx[NUM_SENDERS] = {};
 
@@ -207,7 +210,7 @@ static bool inject_batch_meta(String &json, int16_t rssi_dbm, float snr_db, uint
   return serializeJson(doc, json) > 0;
 }
 
-static bool send_batch_payload(const uint8_t *data, size_t len, uint32_t ts_for_display) {
+static bool send_batch_payload(const uint8_t *data, size_t len, uint32_t ts_for_display, uint16_t batch_id) {
   if (!data || len == 0 || len > BATCH_MAX_COMPRESSED) {
     return false;
   }
@@ -231,7 +234,7 @@ static bool send_batch_payload(const uint8_t *data, size_t len, uint32_t ts_for_
     pkt.payload_len = chunk_len + BATCH_HEADER_SIZE;
 
     uint8_t *payload = pkt.payload;
-    write_u16_le(&payload[0], g_batch_id);
+    write_u16_le(&payload[0], batch_id);
     payload[2] = i;
     payload[3] = chunk_count;
     write_u16_le(&payload[4], static_cast<uint16_t>(len));
@@ -247,9 +250,6 @@ static bool send_batch_payload(const uint8_t *data, size_t len, uint32_t ts_for_
     delay(10);
   }
 
-  if (all_ok) {
-    g_batch_id++;
-  }
   display_set_last_tx(all_ok, ts_for_display);
   return all_ok;
 }
@@ -272,8 +272,16 @@ static bool send_meter_batch(uint32_t ts_for_display) {
     return false;
   }
 
+  for (size_t i = 0; i < count; ++i) {
+    g_inflight_samples[i] = ordered[i];
+  }
+  g_inflight_count = count;
+  g_inflight_batch_id = g_batch_id;
+
   String json;
-  if (!meterBatchToJson(ordered, count, g_batch_id, json, &g_sender_faults, g_sender_last_error)) {
+  if (!meterBatchToJson(g_inflight_samples, g_inflight_count, g_inflight_batch_id, json, &g_sender_faults, g_sender_last_error)) {
+    g_inflight_count = 0;
+    g_inflight_batch_id = 0;
     return false;
   }
 
@@ -283,11 +291,39 @@ static bool send_meter_batch(uint32_t ts_for_display) {
     return false;
   }
 
-  bool ok = send_batch_payload(compressed, compressed_len, ts_for_display);
+  bool ok = send_batch_payload(compressed, compressed_len, ts_for_display, g_inflight_batch_id);
   g_last_batch_send_ms = millis();
   if (ok) {
-    g_last_sent_batch_id = static_cast<uint16_t>(g_batch_id - 1);
+    g_last_sent_batch_id = g_inflight_batch_id;
     g_batch_ack_pending = true;
+    g_batch_id++;
+  } else {
+    g_inflight_count = 0;
+    g_inflight_batch_id = 0;
+  }
+  return ok;
+}
+
+static bool resend_inflight_batch(uint32_t ts_for_display) {
+  if (!g_batch_ack_pending || g_inflight_count == 0) {
+    return false;
+  }
+  String json;
+  if (!meterBatchToJson(g_inflight_samples, g_inflight_count, g_inflight_batch_id, json, &g_sender_faults, g_sender_last_error)) {
+    return false;
+  }
+
+  static uint8_t compressed[BATCH_MAX_COMPRESSED];
+  size_t compressed_len = 0;
+  if (!compressBuffer(reinterpret_cast<const uint8_t *>(json.c_str()), json.length(), compressed, sizeof(compressed), compressed_len)) {
+    g_inflight_count = 0;
+    g_inflight_batch_id = 0;
+    return false;
+  }
+
+  bool ok = send_batch_payload(compressed, compressed_len, ts_for_display, g_inflight_batch_id);
+  if (ok) {
+    g_last_batch_send_ms = millis();
   }
   return ok;
 }
@@ -461,8 +497,13 @@ static void sender_loop() {
       if (g_batch_ack_pending && ack_id == g_last_sent_batch_id) {
         g_batch_ack_pending = false;
         g_batch_retry_count = 0;
-        g_meter_sample_count = 0;
+        if (g_inflight_count >= g_meter_sample_count) {
-        g_meter_sample_head = 0;
+          g_meter_sample_count = 0;
+        } else {
+          g_meter_sample_count -= static_cast<uint8_t>(g_inflight_count);
+        }
+        g_inflight_count = 0;
+        g_inflight_batch_id = 0;
       }
     }
   }
@@ -470,12 +511,17 @@ static void sender_loop() {
   if (g_batch_ack_pending && (now_ms - g_last_batch_send_ms >= BATCH_ACK_TIMEOUT_MS)) {
     if (g_batch_retry_count < BATCH_MAX_RETRIES) {
       g_batch_retry_count++;
-      send_meter_batch(last_sample_ts());
+      resend_inflight_batch(last_sample_ts());
     } else {
       g_batch_ack_pending = false;
       g_batch_retry_count = 0;
-      g_meter_sample_count = 0;
+      if (g_inflight_count >= g_meter_sample_count) {
-      g_meter_sample_head = 0;
+        g_meter_sample_count = 0;
+      } else {
+        g_meter_sample_count -= static_cast<uint8_t>(g_inflight_count);
+      }
+      g_inflight_count = 0;
+      g_inflight_batch_id = 0;
       note_fault(g_sender_faults, g_sender_last_error, g_sender_last_error_utc, g_sender_last_error_ms, FaultType::LoraTx);
       display_set_last_error(g_sender_last_error, g_sender_last_error_utc, g_sender_last_error_ms);
     }