From 5481bd0014ff09ccaa4cd52c60581b279389fd38 Mon Sep 17 00:00:00 2001
From: Pete Schwamb <pete@schwamb.net>
Date: Mon, 14 Apr 2025 12:47:02 -0500
Subject: [PATCH] Fix calibration decoding, and lagged backfill processing

---
 .../G7CGMManager/G7BackfillMessage.swift      |  7 ++++---
 G7SensorKit/G7CGMManager/G7Sensor.swift       | 20 +++++++++++++------
 G7SensorKitTests/G7GlucoseMessageTests.swift  | 17 ++++++++++++++++
 3 files changed, 35 insertions(+), 9 deletions(-)

diff --git a/G7SensorKit/G7CGMManager/G7BackfillMessage.swift b/G7SensorKit/G7CGMManager/G7BackfillMessage.swift
index 2658cb4..90cc3eb 100644
--- a/G7SensorKit/G7CGMManager/G7BackfillMessage.swift
+++ b/G7SensorKit/G7CGMManager/G7BackfillMessage.swift
@@ -32,18 +32,19 @@ public struct G7BackfillMessage: Equatable {
             return nil
         }
 
-        timestamp = data[0..<4].toInt()
+        
+        timestamp = data[0..<3].toInt()
 
         let glucoseBytes = data[4..<6].to(UInt16.self)
 
         if glucoseBytes != 0xffff {
             glucose = glucoseBytes & 0xfff
-            glucoseIsDisplayOnly = (glucoseBytes & 0xf000) > 0
         } else {
             glucose = nil
-            glucoseIsDisplayOnly = false
         }
 
+        glucoseIsDisplayOnly = data[7] & 0x10 != 0
+
         algorithmState = AlgorithmState(rawValue: data[6])
 
         if data[8] == 0x7f {
diff --git a/G7SensorKit/G7CGMManager/G7Sensor.swift b/G7SensorKit/G7CGMManager/G7Sensor.swift
index ea215d1..aa88883 100644
--- a/G7SensorKit/G7CGMManager/G7Sensor.swift
+++ b/G7SensorKit/G7CGMManager/G7Sensor.swift
@@ -195,6 +195,9 @@ public final class G7Sensor: G7BluetoothManagerDelegate {
     func peripheralDidDisconnect(_ manager: G7BluetoothManager, peripheralManager: G7PeripheralManager, wasRemoteDisconnect: Bool) {
         if let sensorID = sensorID, sensorID == peripheralManager.peripheral.name {
 
+            // Sometimes we do not receive the backfillFinished message before disconnect
+            flushBackfillBuffer()
+
             let suspectedEndOfSession: Bool
 
             self.log.info("Sensor disconnected: wasRemoteDisconnect:%{public}@", String(describing: wasRemoteDisconnect))
@@ -249,18 +252,23 @@ public final class G7Sensor: G7BluetoothManagerDelegate {
                 }
             }
         case .backfillFinished:
-            if backfillBuffer.count > 0 {
-                delegateQueue.async {
-                    self.delegate?.sensor(self, didReadBackfill: self.backfillBuffer)
-                    self.backfillBuffer = []
-                }
-            }
+            flushBackfillBuffer()
         default:
             self.delegate?.sensor(self, logComms: response.hexadecimalString)
             break
         }
     }
 
+    func flushBackfillBuffer() {
+        if backfillBuffer.count > 0 {
+            let backfill = backfillBuffer
+            self.backfillBuffer = []
+            delegateQueue.async {
+                self.delegate?.sensor(self, didReadBackfill: backfill)
+            }
+        }
+    }
+
     func bluetoothManager(_ manager: G7BluetoothManager, didReceiveBackfillResponse response: Data) {
 
         log.debug("Received backfill response: %{public}@", response.hexadecimalString)
diff --git a/G7SensorKitTests/G7GlucoseMessageTests.swift b/G7SensorKitTests/G7GlucoseMessageTests.swift
index 739f7e0..5d61445 100644
--- a/G7SensorKitTests/G7GlucoseMessageTests.swift
+++ b/G7SensorKitTests/G7GlucoseMessageTests.swift
@@ -131,6 +131,23 @@ final class G7GlucoseMessageTests: XCTestCase {
         let data = Data(hexadecimalString: "cf5802008f00060f10")!
         let message = G7BackfillMessage(data: data)!
         XCTAssertEqual(153807, message.timestamp)
+        XCTAssertEqual(143, message.glucose)
+        XCTAssertEqual(.known(.ok), message.algorithmState)
+        XCTAssertNil(message.condition)
+        XCTAssertEqual(false, message.glucoseIsDisplayOnly)
+        XCTAssertEqual(true, message.hasReliableGlucose)
+    }
+
+    func testBackfillTimestampWithHighByte() {
+        let data = Data(hexadecimalString: "f20e0d00ba00060ffb")!
+        let message = G7BackfillMessage(data: data)!
+        XCTAssertEqual(855794, message.timestamp)
+    }
+
+    func testBackfillCalibration() {
+        let data = Data(hexadecimalString: "f63d00008500061efe")!
+        let message = G7BackfillMessage(data: data)!
+        XCTAssertEqual(true, message.glucoseIsDisplayOnly)
     }
 
 }