Add support for UIDVALIDITY to ImapFolder

mail/protocols/imap/src/main/java/com/fsck/k9/mail/store/imap/ImapFolder.java

@@ -67,6 +67,7 @@ public class ImapFolder {
     private volatile boolean exists;
     private boolean inSearch = false;
     private boolean canCreateKeywords = false;
+    private Long uidValidity = null;
 
 
     public ImapFolder(ImapStore store, String name) {
@@ -88,6 +89,14 @@ public class ImapFolder {
         this.type = type;
     }
 
+    public Long getUidValidity() {
+        if (!isOpen()) {
+            throw new IllegalStateException("ImapFolder needs to be open");
+        }
+
+        return uidValidity;
+    }
+
     private String getPrefixedName() throws MessagingException {
         String prefixedName = "";
 
@@ -164,6 +173,7 @@ public class ImapFolder {
             this.mode = mode;
 
             for (ImapResponse response : responses) {
+                extractUidValidity(response);
                 handlePermanentFlags(response);
             }
 
@@ -180,6 +190,13 @@ public class ImapFolder {
         }
     }
 
+    private void extractUidValidity(ImapResponse response) {
+        UidValidityResponse uidValidityResponse = UidValidityResponse.parse(response);
+        if (uidValidityResponse != null) {
+            uidValidity = uidValidityResponse.getUidValidity();
+        }
+    }
+
     private void handlePermanentFlags(ImapResponse response) {
         PermanentFlagsResponse permanentFlagsResponse = PermanentFlagsResponse.parse(response);
         if (permanentFlagsResponse == null) {

mail/protocols/imap/src/main/java/com/fsck/k9/mail/store/imap/ImapList.java

@@ -42,6 +42,24 @@ class ImapList extends ArrayList<Object> {
         return inRange(index) && get(index) instanceof String;
     }
 
+    public boolean isLong(int index) {
+        if (!inRange(index)) {
+            return false;
+        }
+
+        Object value = get(index);
+        if (!(value instanceof String)) {
+            return false;
+        }
+
+        try {
+            Long.parseLong((String) value);
+            return true;
+        } catch (NumberFormatException e) {
+            return false;
+        }
+    }
+
     public long getLong(int index) {
         return Long.parseLong(getString(index));
     }

mail/protocols/imap/src/main/java/com/fsck/k9/mail/store/imap/Responses.java

@@ -16,4 +16,5 @@ class Responses {
     public static final String PERMANENTFLAGS = "PERMANENTFLAGS";
     public static final String COPYUID = "COPYUID";
     public static final String SEARCH = "SEARCH";
+    public static final String UIDVALIDITY = "UIDVALIDITY";
 }

mail/protocols/imap/src/main/java/com/fsck/k9/mail/store/imap/UidValidityResponse.kt

@@ -0,0 +1,21 @@
+package com.fsck.k9.mail.store.imap
+
+import com.fsck.k9.mail.store.imap.ImapResponseParser.equalsIgnoreCase
+
+internal class UidValidityResponse private constructor(val uidValidity: Long) {
+    companion object {
+        @JvmStatic
+        fun parse(response: ImapResponse): UidValidityResponse? {
+            if (response.isTagged || !equalsIgnoreCase(response[0], Responses.OK) || !response.isList(1)) return null
+
+            val responseTextList = response.getList(1)
+            if (responseTextList.size < 2 || !equalsIgnoreCase(responseTextList[0], Responses.UIDVALIDITY) ||
+                !responseTextList.isLong(1)) return null
+
+            val uidValidity = responseTextList.getLong(1)
+            if (uidValidity !in 0L..0xFFFFFFFFL) return null
+
+            return UidValidityResponse(uidValidity)
+        }
+    }
+}

mail/protocols/imap/src/test/java/com/fsck/k9/mail/store/imap/UidValidityResponseTest.kt

@@ -0,0 +1,63 @@
+package com.fsck.k9.mail.store.imap
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNotNull
+import org.junit.Assert.assertNull
+import org.junit.Test
+
+class UidValidityResponseTest {
+    @Test
+    fun validResponseWithText() {
+        val response = ImapResponseHelper.createImapResponse("* OK [UIDVALIDITY 23] UIDs valid")
+
+        val result = UidValidityResponse.parse(response)
+
+        assertNotNull(result)
+        assertEquals(23, result!!.uidValidity)
+    }
+
+    @Test
+    fun validResponseWithoutText() {
+        val response = ImapResponseHelper.createImapResponse("* OK [UIDVALIDITY 42]")
+
+        val result = UidValidityResponse.parse(response)
+
+        assertNotNull(result)
+        assertEquals(42, result!!.uidValidity)
+    }
+
+    @Test
+    fun taggedResponse_shouldReturnNull() {
+        assertNotValid("99 OK [UIDVALIDITY 42]")
+    }
+
+    @Test
+    fun noResponse_shouldReturnNull() {
+        assertNotValid("* NO [UIDVALIDITY 42]")
+    }
+
+    @Test
+    fun responseTextWithOnlyOneItem_shouldReturnNull() {
+        assertNotValid("* OK [UIDVALIDITY]")
+    }
+
+    @Test
+    fun uidValidityIsNotANumber_shouldReturnNull() {
+        assertNotValid("* OK [UIDVALIDITY fourtytwo]")
+    }
+
+    @Test
+    fun negativeUidValidity_shouldReturnNull() {
+        assertNotValid("* OK [UIDVALIDITY -1]")
+    }
+
+    @Test
+    fun uidValidityOutsideRange_shouldReturnNull() {
+        assertNotValid("* OK [UIDVALIDITY 4294967296]")
+    }
+
+    private fun assertNotValid(response: String) {
+        val result = UidValidityResponse.parse(ImapResponseHelper.createImapResponse(response))
+        assertNull(result)
+    }
+}