uplift(beta): fix(ui): use selected account for manage folders (#11152)

legacy/ui/legacy/src/main/java/com/fsck/k9/activity/MessageHomeAccountSelector.kt

@@ -0,0 +1,18 @@
+package com.fsck.k9.activity
+
+import net.thunderbird.core.android.account.LegacyAccountDto
+import net.thunderbird.core.android.account.LegacyAccountDtoManager
+import net.thunderbird.feature.search.legacy.LocalMessageSearch
+
+internal fun LocalMessageSearch.resolveAccount(
+    currentAccount: LegacyAccountDto?,
+    accountManager: LegacyAccountDtoManager,
+): LegacyAccountDto? {
+    return if (searchAllAccounts()) {
+        null
+    } else {
+        accountUuids.singleOrNull()
+            ?.let { accountManager.getAccount(it) }
+            ?: currentAccount
+    }
+}

legacy/ui/legacy/src/main/java/com/fsck/k9/activity/MessageHomeActivity.kt

@@ -1420,20 +1420,8 @@ open class MessageHomeActivity :
         singleFolderMode = false
 
         val folderIds = search.folderIds
-        if (search.searchAllAccounts()) {
-            val accountUuids = search.accountUuids
-            if (accountUuids.size == 1) {
-                account = accountManager.getAccount(accountUuids.elementAt(0))
-                singleFolderMode = folderIds.size == 1
-            } else {
-                account = null
-            }
-        } else {
-            if (account == null && search.accountUuids.size == 1) {
-                account = accountManager.getAccount(search.accountUuids.elementAt(0))
-            }
-            singleFolderMode = folderIds.size == 1
-        }
+        account = search.resolveAccount(currentAccount = account, accountManager = accountManager)
+        singleFolderMode = !search.searchAllAccounts() && folderIds.size == 1
 
         configureDrawer()
     }

legacy/ui/legacy/src/test/java/com/fsck/k9/activity/MessageHomeAccountSelectorTest.kt

@@ -0,0 +1,57 @@
+package com.fsck.k9.activity
+
+import assertk.assertThat
+import assertk.assertions.isSameInstanceAs
+import kotlinx.coroutines.flow.Flow
+import net.thunderbird.core.android.account.AccountRemovedListener
+import net.thunderbird.core.android.account.AccountsChangeListener
+import net.thunderbird.core.android.account.LegacyAccountDto
+import net.thunderbird.core.android.account.LegacyAccountDtoManager
+import net.thunderbird.feature.search.legacy.LocalMessageSearch
+import org.junit.Test
+
+class MessageHomeAccountSelectorTest {
+    private val firstAccount = LegacyAccountDto("11111111-1111-1111-1111-111111111111")
+    private val secondAccount = LegacyAccountDto("22222222-2222-2222-2222-222222222222")
+    private val accountManager = FakeLegacyAccountDtoManager(firstAccount, secondAccount)
+
+    @Test
+    fun `single-account search should replace current account`() {
+        val search = LocalMessageSearch().apply {
+            addAccountUuid(secondAccount.uuid)
+        }
+
+        val account = search.resolveAccount(
+            currentAccount = firstAccount,
+            accountManager = accountManager,
+        )
+
+        assertThat(account).isSameInstanceAs(secondAccount)
+    }
+
+    private class FakeLegacyAccountDtoManager(
+        vararg accounts: LegacyAccountDto,
+    ) : LegacyAccountDtoManager {
+        private val accounts = accounts.associateBy { it.uuid }
+
+        override fun getAccounts(): List<LegacyAccountDto> = accounts.values.toList()
+
+        override fun getAccountsFlow(): Flow<List<LegacyAccountDto>> = error("Not implemented")
+
+        override fun getAccount(accountUuid: String): LegacyAccountDto? = accounts[accountUuid]
+
+        override fun getAccountFlow(accountUuid: String): Flow<LegacyAccountDto?> = error("Not implemented")
+
+        override fun addAccountRemovedListener(listener: AccountRemovedListener) = error("Not implemented")
+
+        override fun moveAccount(account: LegacyAccountDto, newPosition: Int) = error("Not implemented")
+
+        override fun addOnAccountsChangeListener(accountsChangeListener: AccountsChangeListener) =
+            error("Not implemented")
+
+        override fun removeOnAccountsChangeListener(accountsChangeListener: AccountsChangeListener) =
+            error("Not implemented")
+
+        override fun saveAccount(account: LegacyAccountDto) = error("Not implemented")
+    }
+}