fix: Only suggest upgrading to a version F-Droid has built (#717)

The F-Droid API can return a `suggestedVersionCode` that F-Droid has not
successfully built (e.g., there was a network issue preventing F-Droid
from fetching the source code at the time of the last build).

This meant users were being prompted to update when there was not a
built package to update to.

Fix this by verifying that `suggestedVersionCode` appears in the list of
packages. If it doesn't then fall back to the highest version code in
the list of packages.

Fixes #684

app/src/fdroid/kotlin/app/pachli/updatecheck/UpdateCheck.kt

@@ -34,6 +34,19 @@ class UpdateCheck @Inject constructor(
     }
 
     override suspend fun remoteFetchLatestVersionCode(): Int? {
-        return fdroidService.getPackage(BuildConfig.APPLICATION_ID).getOrNull()?.suggestedVersionCode
+        val fdroidPackage = fdroidService.getPackage(BuildConfig.APPLICATION_ID).getOrNull() ?: return null
+
+        // `packages` is a list of all packages that have been built and are available.
+        //
+        // The package with `suggestedVersionCode` might not have been built yet (see
+        // https://github.com/pachli/pachli-android/issues/684).
+        //
+        // Check that `suggestedVersionCode` appears in the list of packages. If it
+        // does, use that.
+        val suggestedVersionCode = fdroidPackage.suggestedVersionCode
+        if (fdroidPackage.packages.any { it.versionCode == suggestedVersionCode }) return suggestedVersionCode
+
+        // Otherwise, use the highest version code in `packages`.
+        return fdroidPackage.packages.maxByOrNull { it.versionCode }?.versionCode
     }
 }

app/src/testFdroid/kotlin/app/pachli/updatecheck/UpdateCheckTest.kt

@@ -0,0 +1,98 @@
+/*
+ * Copyright 2024 Pachli Association
+ *
+ * This file is a part of Pachli.
+ *
+ * This program is free software; you can redistribute it and/or modify it under the terms of the
+ * GNU General Public License as published by the Free Software Foundation; either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * Pachli is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even
+ * the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
+ * Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with Pachli; if not,
+ * see <http://www.gnu.org/licenses>.
+ */
+
+package app.pachli.updatecheck
+
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import app.pachli.core.preferences.SharedPreferencesRepository
+import app.pachli.core.testing.fakes.InMemorySharedPreferences
+import at.connyduck.calladapter.networkresult.NetworkResult
+import com.google.common.truth.Truth.assertThat
+import kotlinx.coroutines.test.TestScope
+import kotlinx.coroutines.test.runTest
+import org.junit.Before
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.mockito.kotlin.any
+import org.mockito.kotlin.doReturn
+import org.mockito.kotlin.mock
+import org.mockito.kotlin.reset
+import org.mockito.kotlin.stub
+
+@RunWith(AndroidJUnit4::class)
+class UpdateCheckTest {
+    private val fdroidService: FdroidService = mock()
+    private lateinit var updateCheck: UpdateCheck
+
+    @Before
+    fun setup() {
+        reset(fdroidService)
+        updateCheck = UpdateCheck(
+            SharedPreferencesRepository(InMemorySharedPreferences(), TestScope()),
+            fdroidService,
+        )
+    }
+
+    @Test
+    fun `remoteFetchLatestVersionCode returns null on network error`() = runTest {
+        fdroidService.stub {
+            onBlocking { getPackage(any()) } doReturn NetworkResult.failure(Exception())
+        }
+
+        assertThat(updateCheck.remoteFetchLatestVersionCode()).isNull()
+    }
+
+    @Test
+    fun `remoteFetchLatestVersionCode returns suggestedVersionCode if in packages`() = runTest {
+        fdroidService.stub {
+            onBlocking { getPackage(any()) } doReturn NetworkResult.success(
+                FdroidPackage(
+                    packageName = "app.pachli",
+                    suggestedVersionCode = 3,
+                    packages = listOf(
+                        FdroidPackageVersion(versionName = "3.0", versionCode = 3),
+                        FdroidPackageVersion(versionName = "2.0", versionCode = 2),
+                        FdroidPackageVersion(versionName = "1.0", versionCode = 1),
+                    ),
+                ),
+            )
+        }
+
+        // "3" is the `suggestedVersionCode`, and is in `packages`, so should be returned.
+        assertThat(updateCheck.remoteFetchLatestVersionCode()).isEqualTo(3)
+    }
+
+    @Test
+    fun `remoteFetchLatestVersionCode returns greatest code if suggestedVersionCode is missing`() = runTest {
+        fdroidService.stub {
+            onBlocking { getPackage(any()) } doReturn NetworkResult.success(
+                FdroidPackage(
+                    packageName = "app.pachli",
+                    suggestedVersionCode = 3,
+                    packages = listOf(
+                        FdroidPackageVersion(versionName = "2.0", versionCode = 2),
+                        FdroidPackageVersion(versionName = "1.0", versionCode = 1),
+                    ),
+                ),
+            )
+        }
+
+        // "3" is the `suggestedVersionCode`, but is not in `packages`, so the greatest
+        // `versionCode` in `packages` should be returned.
+        assertThat(updateCheck.remoteFetchLatestVersionCode()).isEqualTo(2)
+    }
+}