BLE LTK: define all the steps

omnipod-dash/src/main/java/info/nightscout/androidaps/plugins/pump/omnipod/dash/driver/comm/ltk/LTKExchanger.kt

@@ -6,8 +6,10 @@ import info.nightscout.androidaps.logging.LTag
 import info.nightscout.androidaps.plugins.pump.omnipod.dash.driver.comm.Id
 import info.nightscout.androidaps.plugins.pump.omnipod.dash.driver.comm.OmnipodDashBleManagerImpl
 import info.nightscout.androidaps.plugins.pump.omnipod.dash.driver.comm.message.MessageIO
+import info.nightscout.androidaps.plugins.pump.omnipod.dash.driver.comm.message.MessagePacket
 import info.nightscout.androidaps.plugins.pump.omnipod.dash.driver.comm.message.StringLengthPrefixEncoding
 import info.nightscout.androidaps.utils.extensions.hexStringToByteArray
+import info.nightscout.androidaps.utils.extensions.toHex
 import java.security.SecureRandom
 
 internal class LTKExchanger(private val aapsLogger: AAPSLogger, private val msgIO: MessageIO) {
@@ -17,6 +19,8 @@ internal class LTKExchanger(private val aapsLogger: AAPSLogger, private val msgI
     private val controllerId = Id.fromInt(OmnipodDashBleManagerImpl.CONTROLLER_ID)
     val nodeId = controllerId.increment()
     private var seq: Byte = 1
+    private var ltk = ByteArray(0)
+    private var noncePrefix = ByteArray(0)
 
     init {
         val random = SecureRandom()
@@ -36,28 +40,36 @@ internal class LTKExchanger(private val aapsLogger: AAPSLogger, private val msgI
         // read SPS1
         val podSps1 = msgIO.receiveMessage()
         aapsLogger.info(LTag.PUMPBTCOMM, "Received message: %s", podSps1)
-/*
+        processSps1FromPod(podSps1)
+
+        seq++
+
         // send SPS2
-        var sps2 = PairMessage()
+        val sps2 = sps2()
         msgIO.sendMesssage(sps2.messagePacket)
         // read SPS2
+
         val podSps2 = msgIO.receiveMessage()
+        validatePodSps2(podSps2)
 
         // send SP0GP0
-        msgIO.sendMesssage(sps2.messagePacket)
+        msgIO.sendMesssage(sp0gp0().messagePacket)
         // read P0
+
+        //TODO: if we fail to read or validate p0 will lead to undefined state
+        // it could be that:
+        // - the pod answered with p0 and we did not receive/could not process the answer
+        // - the pod answered with some sort of error
         val p0 = msgIO.receiveMessage()
-*/
+        validateP0(p0)
-        return null
+
+        return LTK(
+            ltk = ltk,
+            noncePrefix = noncePrefix,
+        )
     }
 
-    private fun sp2(): ByteArray {
+    private fun sp1sp2(sp1: ByteArray, sp2: ByteArray): PairMessage {
-        // This is GetPodStatus command, with page 0 parameter.
-        // We could replace that in the future with the serialized GetPodStatus()
-        return GET_POD_STATUS_HEX_COMMAND.hexStringToByteArray()
-    }
-
-    fun sp1sp2(sp1: ByteArray, sp2: ByteArray): PairMessage {
         val payload = StringLengthPrefixEncoding.formatKeys(
             arrayOf("SP1=", ",SP2="),
             arrayOf(sp1, sp2),
@@ -70,7 +82,7 @@ internal class LTKExchanger(private val aapsLogger: AAPSLogger, private val msgI
         )
     }
 
-    fun sps1(): PairMessage {
+    private fun sps1(): PairMessage {
         val publicKey = X25519.publicFromPrivate(privateKey)
         val payload = StringLengthPrefixEncoding.formatKeys(
             arrayOf("SPS1="),
@@ -84,6 +96,34 @@ internal class LTKExchanger(private val aapsLogger: AAPSLogger, private val msgI
         )
     }
 
+    private fun processSps1FromPod(msg: MessagePacket) {
+        aapsLogger.debug(LTag.PUMPBTCOMM, "Received SPS1 from pod: ${msg.payload.toHex()}")
+
+    }
+
+    private fun sps2(): PairMessage {
+        TODO("implement")
+    }
+
+    private fun validatePodSps2(podSps2: MessagePacket) {
+        TODO("implement")
+
+    }
+
+    private fun sp2(): ByteArray {
+        // This is GetPodStatus command, with page 0 parameter.
+        // We could replace that in the future with the serialized GetPodStatus()
+        return GET_POD_STATUS_HEX_COMMAND.hexStringToByteArray()
+    }
+
+    private fun sp0gp0(): PairMessage {
+        TODO("implement")
+    }
+
+    private fun validateP0(p0: MessagePacket) {
+        TODO("implement")
+
+    }
     companion object {
 
         private val GET_POD_STATUS_HEX_COMMAND = "ffc32dbd08030e0100008a" // TODO for now we are assuming this command is build out of constant parameters, use a proper command builder for that.