app-unpriv: Downgrade minSDK to 28 (P)

This is probably the lowest version we can reasonably support with
OMAPI.

app-common/build.gradle.kts

@@ -8,7 +8,7 @@ android {
     compileSdk = 34
 
     defaultConfig {
-        minSdk = 30
+        minSdk = 28
 
         testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
     }

app-common/src/main/java/im/angry/openeuicc/core/EuiccChannelManager.kt

@@ -35,7 +35,7 @@ open class EuiccChannelManager(protected val context: Context) {
     private val handler = Handler(HandlerThread("BaseEuiccChannelManager").also { it.start() }.looper)
 
     protected open val uiccCards: Collection<UiccCardInfoCompat>
-        get() = (0..<tm.activeModemCount).map { FakeUiccCardInfoCompat(it) }
+        get() = (0..<tm.activeModemCountCompat).map { FakeUiccCardInfoCompat(it) }
 
     private suspend fun connectSEService(): SEService = suspendCoroutine { cont ->
         handler.post {

app-common/src/main/java/im/angry/openeuicc/core/OmapiApduInterface.kt

@@ -3,7 +3,7 @@ package im.angry.openeuicc.core
 import android.se.omapi.Channel
 import android.se.omapi.SEService
 import android.se.omapi.Session
-import im.angry.openeuicc.util.UiccPortInfoCompat
+import im.angry.openeuicc.util.*
 import net.typeblog.lpac_jni.ApduInterface
 import net.typeblog.lpac_jni.LocalProfileAssistant
 import net.typeblog.lpac_jni.impl.HttpInterfaceImpl
@@ -17,7 +17,7 @@ class OmapiApduInterface(
     private lateinit var lastChannel: Channel
 
     override fun connect() {
-        session = service.getUiccReader(port.logicalSlotIndex + 1).openSession()
+        session = service.getUiccReaderCompat(port.logicalSlotIndex + 1).openSession()
     }
 
     override fun disconnect() {

app-common/src/main/java/im/angry/openeuicc/util/TelephonyCompat.kt

@@ -1,5 +1,25 @@
 package im.angry.openeuicc.util
 
+import android.os.Build
+import android.se.omapi.Reader
+import android.se.omapi.SEService
+import android.telephony.TelephonyManager
+
+val TelephonyManager.activeModemCountCompat: Int
+    get() = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
+        activeModemCount
+    } else {
+        phoneCount
+    }
+
+fun SEService.getUiccReaderCompat(slotNumber: Int): Reader {
+    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
+        return getUiccReader(slotNumber)
+    } else {
+        return readers.first { it.name == "SIM${slotNumber}" || (slotNumber == 1 && it.name == "SIM") }
+    }
+}
+
 /*
  * In the privileged version, the EuiccChannelManager should work
  * based on real Uicc{Card,Port}Info reported by TelephonyManager.

app-unpriv/build.gradle.kts

@@ -21,7 +21,7 @@ android {
 
     defaultConfig {
         applicationId = "im.angry.easyeuicc"
-        minSdk = 30
+        minSdk = 28
         targetSdk = 34
     }