api: implement Rpc.GetChatIdByContactId()

deltachat/rpc.go

@@ -682,7 +682,14 @@ func (self *Rpc) LookupContactIdByAddr(accountId AccountId, addr string) (option
 //                   chat
 // ---------------------------------------------
 
-// TODO: get_chat_id_by_contact_id
+// Returns the [`ChatId`] for the 1:1 chat with `contactId` if it exists.
+//
+// If it does not exist, zero is returned.
+func (self *Rpc) GetChatIdByContactId(accountId AccountId, contactId ContactId) (ChatId, error) {
+	var id ChatId
+	err := self.Transport.CallResult(self.Context, &id, "get_chat_id_by_contact_id", accountId, contactId)
+	return id, err
+}
 
 // Returns all message IDs of the given types in a chat.
 // Typically used to show a gallery.

deltachat/rpc_test.go

@@ -43,6 +43,17 @@ func TestRpc_SetChatVisibility(t *testing.T) {
 	})
 }
 
+func TestRpc_GetChatIdByContactId(t *testing.T) {
+	t.Parallel()
+	acfactory.WithOnlineAccount(func(rpc *Rpc, accId AccountId) {
+		contactId, err := rpc.CreateContact(accId, "[email protected]", "")
+		require.Nil(t, err)
+		chatId, err := rpc.GetChatIdByContactId(accId, contactId)
+		require.Nil(t, err)
+		require.NotEqual(t, chatId, 0)
+	})
+}
+
 func TestAccount_Select(t *testing.T) {
 	t.Parallel()
 	acfactory.WithRpc(func(rpc *Rpc) {