Use 0 value for "delete_server_after" default.

Now 0 means "never delete", 1 means "delete at once" and other values
indicate the number of seconds after which them message should be
deleted from the server.

Configuration value interpretation is moved into
Context.get_config_delete_server_after() function.

src/config.rs

@@ -68,9 +68,12 @@ pub enum Config {
     /// Timer in seconds after which the message is deleted from the
     /// server.
     ///
-    /// Equals to -1 by default, which means the message is never
+    /// Equals to 0 by default, which means the message is never
     /// deleted.
-    #[strum(props(default = "-1"))]
+    ///
+    /// Value 1 is treated as "delete at once": messages are deleted
+    /// immediately, without moving to DeltaChat folder.
+    #[strum(props(default = "0"))]
     DeleteServerAfter,
 
     SaveMimeHeaders,
@@ -136,6 +139,18 @@ impl Context {
         self.get_config_int(key) != 0
     }
 
+    /// Gets configured "delete_server_after" value.
+    ///
+    /// `None` means never delete the message, `Some(0)` means delete
+    /// at once, `Some(x)` means delete after `x` seconds.
+    pub fn get_config_delete_server_after(&self) -> Option<i64> {
+        match self.get_config_int(Config::DeleteServerAfter) {
+            0 => None,
+            1 => Some(0),
+            x => Some(x as i64),
+        }
+    }
+
     /// Set the given config key.
     /// If `None` is passed as a value the value is cleared and set to the default if there is one.
     pub fn set_config(&self, key: Config, value: Option<&str>) -> crate::sql::Result<()> {

src/dc_receive_imf.rs

@@ -204,14 +204,14 @@ pub fn dc_receive_imf(
         }
     } else {
         // Get user-configured server deletion
-        let delete_server_after = context.get_config_int(Config::DeleteServerAfter);
+        let delete_server_after = context.get_config_delete_server_after();
 
-        if delete_server_after != 0 {
+        if delete_server_after != Some(0) {
             // Move message if we don't delete it immediately.
             context.do_heuristics_moves(server_folder.as_ref(), insert_msg_id);
         }
 
-        if delete_server_after >= 0 {
+        if let Some(delete_server_after) = delete_server_after {
             info!(
                 context,
                 "Scheduling message deletion in {} seconds", delete_server_after

src/imap/mod.rs

@@ -1308,9 +1308,9 @@ fn precheck_imf(context: &Context, rfc724_mid: &str, server_folder: &str, server
         if old_server_folder.is_empty() && old_server_uid == 0 {
             info!(context, "[move] detected bcc-self {}", rfc724_mid,);
 
-            let delete_server_after = context.get_config_int(Config::DeleteServerAfter);
+            let delete_server_after = context.get_config_delete_server_after();
 
-            if delete_server_after != 0 {
+            if delete_server_after != Some(0) {
                 context.do_heuristics_moves(server_folder.as_ref(), msg_id);
                 job_add(
                     context,
@@ -1321,7 +1321,7 @@ fn precheck_imf(context: &Context, rfc724_mid: &str, server_folder: &str, server
                 );
             }
 
-            if delete_server_after >= 0 {
+            if let Some(delete_server_after) = delete_server_after {
                 info!(
                     context,
                     "Scheduling BCC-self deletion in {} seconds", delete_server_after

src/job.rs

@@ -859,8 +859,11 @@ pub fn job_send_msg(context: &Context, msg_id: MsgId) -> Result<()> {
         .get_config(Config::ConfiguredAddr)
         .unwrap_or_default();
     let lowercase_from = from.to_lowercase();
+
+    // Send BCC to self if it is enabled and we are not going to
+    // delete it immediately.
     if context.get_config_bool(Config::BccSelf)
-        && context.get_config_int(Config::DeleteServerAfter) != 0
+        && context.get_config_delete_server_after() != Some(0)
         && !recipients
             .iter()
             .any(|x| x.to_lowercase() == lowercase_from)