address review: probe the active source so media falls back too

An existing token-auth source with an already-synced library would fail playback before
any API call ran: stream and cover-art URLs are built by uri() and fetched by
ExoPlayer/Coil, outside stream(). Probe the active source once when it uses token auth so
the 41 flips and persists before any URL is built.

Also base the retry on the flag the request actually used (concurrent requests no longer
lose their retry), report the fallback from ping() so Add Source flips the toggle instead
of reporting success and saving token auth on, and make the callback non-null.

app/src/test/kotlin/com/subtracks/data/repo/SourceRepositoryTest.kt

@@ -7,11 +7,18 @@ import androidx.test.core.app.ApplicationProvider
 import androidx.test.ext.junit.runners.AndroidJUnit4
 import com.subtracks.data.db.SubtracksDatabase
 import com.subtracks.data.prefs.fakeUserPreferences
+import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.runBlocking
 import kotlinx.coroutines.test.runTest
+import kotlinx.coroutines.withTimeout
 import okhttp3.OkHttpClient
+import okhttp3.mockwebserver.MockResponse
+import okhttp3.mockwebserver.MockWebServer
 import org.junit.After
 import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertTrue
 import org.junit.Before
 import org.junit.Test
 import org.junit.runner.RunWith
@@ -20,6 +27,7 @@ import org.junit.runner.RunWith
 class SourceRepositoryTest {
     private lateinit var db: SubtracksDatabase
     private lateinit var repository: SourceRepository
+    private val messages = ArrayList<String>()
 
     @Before
     fun setUp() {
@@ -29,7 +37,7 @@ class SourceRepositoryTest {
                 .inMemoryDatabaseBuilder(context, SubtracksDatabase::class.java)
                 .setDriver(BundledSQLiteDriver())
                 .build()
-        repository = SourceRepository(db, OkHttpClient(), fakeUserPreferences())
+        repository = SourceRepository(db, OkHttpClient(), fakeUserPreferences(), showMessage = { messages += it })
     }
 
     @After
@@ -57,4 +65,49 @@ class SourceRepositoryTest {
                     .address,
             )
         }
+
+    @Test
+    fun aTokenAuthSourceIsProbedAndSwitchedToPassword() =
+        runBlocking {
+            withServer { server ->
+                server.enqueue(MockResponse().setBody(failed(41)))
+                server.enqueue(MockResponse().setBody(OK))
+
+                repository.addSource("nav", server.url("/").toString(), "u", "s3cret", true)
+
+                val config = withTimeout(5_000) { repository.activeConfig().first { it != null && !it.useTokenAuth } }
+                assertFalse(config!!.useTokenAuth)
+                withTimeout(5_000) { while (messages.isEmpty()) delay(10) }
+                assertEquals(1, messages.size)
+            }
+        }
+
+    @Test
+    fun pingReportsWhetherItFellBackToThePassword() =
+        runBlocking {
+            withServer { server ->
+                server.enqueue(MockResponse().setBody(failed(41)))
+                server.enqueue(MockResponse().setBody(OK))
+                server.enqueue(MockResponse().setBody(OK))
+
+                assertTrue(repository.ping(server.url("/").toString(), "u", "s3cret", true).getOrThrow())
+                assertFalse(repository.ping(server.url("/").toString(), "u", "s3cret", false).getOrThrow())
+            }
+        }
+
+    private suspend fun withServer(block: suspend (MockWebServer) -> Unit) {
+        val server = MockWebServer()
+        server.start()
+        try {
+            block(server)
+        } finally {
+            server.shutdown()
+        }
+    }
+
+    private fun failed(code: Int) = "<subsonic-response status=\"failed\"><error code=\"$code\" message=\"nope\"/></subsonic-response>"
+
+    private companion object {
+        const val OK = "<subsonic-response status=\"ok\" version=\"1.16.1\"/>"
+    }
 }

app/src/test/kotlin/com/subtracks/data/source/subsonic/SubsonicClientTest.kt

@@ -27,7 +27,7 @@ class SubsonicClientTest {
 
     private fun client(
         tokenAuth: Boolean,
-        onTokenAuthUnsupported: (() -> Unit)? = null,
+        onTokenAuthUnsupported: () -> Unit = {},
     ) = SubsonicClient(
         baseUrl = server.url("/"),
         username = "guest",