api: add ContactId.set_name()

This API allows to explicitly set
a name of the contact
instead of trying to create a new contact
with the same address.

Not all contacts are identified
by the email address
and we are going to introduce
contacts identified by their keys.

deltachat-jsonrpc/src/api.rs

@@ -1537,6 +1537,7 @@ impl CommandApi {
         Ok(())
     }
 
+    /// Sets display name for existing contact.
     async fn change_contact_name(
         &self,
         account_id: u32,
@@ -1545,9 +1546,7 @@ impl CommandApi {
     ) -> Result<()> {
         let ctx = self.get_context(account_id).await?;
         let contact_id = ContactId::new(contact_id);
-        let contact = Contact::get_by_id(&ctx, contact_id).await?;
-        let addr = contact.get_addr();
-        Contact::create(&ctx, &name, addr).await?;
+        contact_id.set_name(&ctx, &name).await?;
         Ok(())
     }
 

src/contact.rs

@@ -95,6 +95,29 @@ impl ContactId {
         self.0
     }
 
+    /// Sets display name for existing contact.
+    ///
+    /// Display name may be an empty string,
+    /// in which case the name displayed in the UI
+    /// for this contact will switch to the
+    /// contact's authorized name.
+    pub async fn set_name(self, context: &Context, name: &str) -> Result<()> {
+        context
+            .sql
+            .transaction(|transaction| {
+                let is_changed = transaction.execute(
+                    "UPDATE contacts SET name=?1 WHERE id=?2 AND name!=?1",
+                    (name, self),
+                )? > 0;
+                if is_changed {
+                    update_chat_names(context, transaction, self)?;
+                }
+                Ok(())
+            })
+            .await?;
+        Ok(())
+    }
+
     /// Mark contact as bot.
     pub(crate) async fn mark_bot(&self, context: &Context, is_bot: bool) -> Result<()> {
         context
@@ -909,7 +932,7 @@ impl Contact {
 
                         if update_name || update_authname {
                             let contact_id = ContactId::new(row_id);
-                            update_chat_names(context, &transaction, contact_id)?;
+                            update_chat_names(context, transaction, contact_id)?;
                         }
                         sth_modified = Modifier::Modified;
                     }