Initial project commit

lib/nightscout/com/eveningoutpost/dexdrip/G5Model/DexSyncKeeper.java

@@ -0,0 +1,84 @@
+package com.eveningoutpost.dexdrip.G5Model;
+
+// jamorham
+
+import com.eveningoutpost.dexdrip.Models.JoH;
+import com.eveningoutpost.dexdrip.Models.UserError;
+import com.eveningoutpost.dexdrip.UtilityModels.Constants;
+import com.eveningoutpost.dexdrip.UtilityModels.PersistentStore;
+
+import static com.eveningoutpost.dexdrip.UtilityModels.BgGraphBuilder.DEXCOM_PERIOD;
+
+public class DexSyncKeeper {
+
+    private static final String TAG = DexTimeKeeper.class.getSimpleName();
+    private static final String DEX_SYNC_STORE = "DEX_SYNC_STORE-";
+    private static final long OLDEST_POSSIBLE = 1533839836123L;
+    private static final long GRACE_TIME = 5000;
+    private static final long VALIDITY_PERIOD = Constants.DAY_IN_MS;
+
+
+    // store sync time as now
+    public static void store(final String transmitterId) {
+        store(transmitterId, JoH.tsl());
+    }
+
+    // store sync time
+    public static void store(final String transmitterId, final long when) {
+
+        if ((transmitterId == null) || (transmitterId.length() != 6)) {
+            UserError.Log.e(TAG, "Invalid dex transmitter in store: " + transmitterId);
+            return;
+        }
+
+        if (when < OLDEST_POSSIBLE) {
+            UserError.Log.wtf(TAG, "Invalid timestamp to store: " + JoH.dateTimeText(when));
+            return;
+        }
+
+        PersistentStore.setLong(DEX_SYNC_STORE + transmitterId, when);
+        UserError.Log.d(TAG, "Sync time updated to: " + JoH.dateTimeText(when));
+    }
+
+    // anticpiate next wake up from now
+    public static long anticipate(final String transmitterId) {
+        return anticipate(transmitterId, JoH.tsl());
+    }
+
+    // anticipate next wake up from time
+    // -1 means we don't know anything
+    static long anticipate(final String transmitterId, final long now) {
+        final long last = PersistentStore.getLong(DEX_SYNC_STORE + transmitterId);
+        if (last < OLDEST_POSSIBLE) {
+            return -1;
+        }
+        if (last > now) {
+            UserError.Log.e(TAG, "Anticipation time in the future! cannot use: " + JoH.dateTimeText(last));
+            return -1; // can't be in the future
+        }
+
+        if (now - last > VALIDITY_PERIOD) {
+            UserError.Log.e(TAG, "Anticipation time too old to use: " + JoH.dateTimeText(last));
+            return -1;
+        }
+
+        final long modulo = (now - last) % DEXCOM_PERIOD;
+        if ((modulo < GRACE_TIME) && ((now - last) > GRACE_TIME)) return now;
+        final long next = now + (DEXCOM_PERIOD - modulo);
+        return next;
+    }
+
+    public static boolean isReady(final String transmitterId) {
+        return anticipate(transmitterId, JoH.tsl()) != -1;
+    }
+
+    // are we outside connection window?
+    // TODO also handle waking up before window PRE_GRACE_TIME = 20seconds?
+    public static boolean outsideWindow(final String transmitterId) {
+        final long now = JoH.tsl();
+        final long next = anticipate(transmitterId, now);
+        return next != now;
+    }
+
+}
+