POP3: reversed message order support

app/src/main/java/eu/faircode/email/Core.java

@@ -2981,7 +2981,8 @@ class Core {
             List<TupleUidl> ids = db.message().getUidls(folder.id);
             int max = (account.max_messages == null
                     ? imessages.length
-                    : Math.min(imessages.length, account.max_messages));
+                    : Math.min(imessages.length, Math.abs(account.max_messages)));
+            boolean reversed = (account.max_messages != null && account.max_messages < 0);
 
             boolean sync = true;
             if (!hasUidl && sync_quick_pop && !force &&
@@ -3003,6 +3004,7 @@ class Core {
                     " device=" + ids.size() +
                     " server=" + imessages.length +
                     " max=" + max + "/" + account.max_messages +
+                    " reversed=" + reversed +
                     " last=" + folder.last_sync_count +
                     " sync=" + sync +
                     " uidl=" + hasUidl);
@@ -3075,7 +3077,7 @@ class Core {
                 }
 
                 boolean _new = true;
-                for (int i = imessages.length - 1; i >= imessages.length - max; i--) {
+                for (int i = reversed ? 0 : imessages.length - 1; reversed ? i < max : i >= imessages.length - max; i += reversed ? 1 : -1) {
                     state.ensureRunning("Sync/POP3");
 
                     Message imessage = imessages[i];
@@ -3392,8 +3394,8 @@ class Core {
             }
 
             if (account.max_messages != null && !account.leave_on_device) {
-                int hidden = db.message().setMessagesUiHide(folder.id, account.max_messages);
-                int deleted = db.message().deleteMessagesKeep(folder.id, account.max_messages + 100);
+                int hidden = db.message().setMessagesUiHide(folder.id, Math.abs(account.max_messages));
+                int deleted = db.message().deleteMessagesKeep(folder.id, Math.abs(account.max_messages) + 100);
                 EntityLog.log(context, account.name + " POP" +
                         " cleanup max=" + account.max_messages + "" +
                         " hidden=" + hidden + " deleted=" + deleted);

app/src/main/java/eu/faircode/email/EntityAccount.java

@@ -58,7 +58,6 @@ public class EntityAccount extends EntityOrder implements Serializable {
     // https://tools.ietf.org/html/rfc2177
     static final int DEFAULT_KEEP_ALIVE_INTERVAL = 15; // minutes
     static final int DEFAULT_POLL_INTERVAL = 15; // minutes
-    static final int DEFAULT_MAX_MESSAGES = 250; // POP3
 
     static final int QUOTA_WARNING = 95; // percent
 
@@ -120,7 +119,7 @@ public class EntityAccount extends EntityOrder implements Serializable {
     public Boolean leave_deleted = false;
     @NonNull
     public Boolean leave_on_device = false;
-    public Integer max_messages; // POP3
+    public Integer max_messages = null; // POP3
     @NonNull
     public Boolean auto_seen = true;
     @ColumnInfo(name = "separator")

app/src/main/java/eu/faircode/email/FragmentGmail.java

@@ -529,11 +529,9 @@ public class FragmentGmail extends FragmentBase {
                         account.synchronize = true;
                         account.primary = (primary == null);
 
-                        if (pop) {
-                            // https://support.google.com/mail/answer/7104828
+                        // https://support.google.com/mail/answer/7104828
+                        if (pop)
                             account.leave_on_device = true;
-                            account.max_messages = EntityAccount.DEFAULT_MAX_MESSAGES;
-                        }
 
                         account.created = new Date().getTime();
                         account.last_connected = account.created;

app/src/main/java/eu/faircode/email/FragmentOAuth.java

@@ -891,9 +891,6 @@ public class FragmentOAuth extends FragmentBase {
                         account.partial_fetch = provider.partial;
                         account.raw_fetch = provider.raw;
 
-                        if (pop)
-                            account.max_messages = EntityAccount.DEFAULT_MAX_MESSAGES;
-
                         account.created = new Date().getTime();
                         account.last_connected = account.created;
 

app/src/main/java/eu/faircode/email/FragmentPop.java

@@ -445,6 +445,8 @@ public class FragmentPop extends FragmentBase {
                 if (TextUtils.isEmpty(interval))
                     interval = Integer.toString(EntityAccount.DEFAULT_POLL_INTERVAL);
                 Integer max_messages = (TextUtils.isEmpty(max) ? null : Integer.parseInt(max));
+                if (max_messages != null && max_messages == 0)
+                    max_messages = null;
                 int poll_interval = Math.max(1, Integer.parseInt(interval));
 
                 if (TextUtils.isEmpty(name))
@@ -793,11 +795,10 @@ public class FragmentPop extends FragmentBase {
                     cbLeaveDeleted.setChecked(account == null ? true : account.leave_deleted);
                     cbLeaveDevice.setChecked(account == null ? false : account.leave_on_device);
 
-                    if (account != null && account.max_messages == null)
-                        etMax.setText(null);
+                    if (account != null && account.max_messages != null)
+                        etMax.setText(Integer.toString(account.max_messages));
                     else
-                        etMax.setText(Integer.toString(account == null
-                                ? EntityAccount.DEFAULT_MAX_MESSAGES : account.max_messages));
+                        etMax.setText(null);
 
                     etInterval.setText(account == null ? "" : Long.toString(account.poll_interval));
                     cbUnmetered.setChecked(jcondition.optBoolean("unmetered"));

app/src/main/res/layout/fragment_pop.xml

@@ -469,12 +469,22 @@
             android:id="@+id/etMax"
             android:layout_width="match_parent"
             android:layout_height="wrap_content"
-            android:inputType="number"
+            android:inputType="numberSigned"
             android:maxLength="9"
             android:textAppearance="@style/TextAppearance.AppCompat.Medium"
             app:layout_constraintStart_toStartOf="parent"
             app:layout_constraintTop_toBottomOf="@id/tvMax" />
 
+        <TextView
+            android:id="@+id/tvMaxRemark"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:text="@string/title_max_messages_remark"
+            android:textAppearance="@style/TextAppearance.AppCompat.Small"
+            android:textStyle="italic"
+            app:layout_constraintStart_toStartOf="parent"
+            app:layout_constraintTop_toBottomOf="@id/etMax" />
+
         <!-- keep alive -->
 
         <TextView
@@ -485,7 +495,7 @@
             android:text="@string/title_keep_poll_interval"
             android:textAppearance="@style/TextAppearance.AppCompat.Small"
             app:layout_constraintStart_toStartOf="parent"
-            app:layout_constraintTop_toBottomOf="@id/etMax" />
+            app:layout_constraintTop_toBottomOf="@id/tvMaxRemark" />
 
         <eu.faircode.email.EditTextPlain
             android:id="@+id/etInterval"

app/src/main/res/values/strings.xml

@@ -1112,6 +1112,10 @@
     <string name="title_leave_deleted">Leave deleted messages on server</string>
     <string name="title_leave_on_device">Leave messages on device</string>
     <string name="title_max_messages">Maximum number of messages to download (blank for all)</string>
+    <string name="title_max_messages_remark">
+        Enter a positive number to download the messages at the end (most common)
+        and a negative number to download the messages at the beginning (least common)
+    </string>
     <string name="title_keep_poll_interval">Poll interval (minutes)</string>
     <string name="title_keep_alive_interval">Keep-alive interval (minutes)</string>
     <string name="title_keep_alive_noop">Restart IMAP IDLE periodically</string>