diff --git a/.gitignore b/.gitignore
index ea8c4bf..9649e79 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
 /target
+.vimrc
diff --git a/src/bayou.rs b/src/bayou.rs
index 8fc711e..1ea8395 100644
--- a/src/bayou.rs
+++ b/src/bayou.rs
@@ -62,18 +62,29 @@ impl<S: BayouState> Bayou<S> {
         })
     }
 
+    /// Re-reads the state from persistent storage backend
     pub async fn sync(&mut self) -> Result<()> {
         // 1. List checkpoints
-        // 2. Load last checkpoint
+        // 2. Load last checkpoint if different from currently used one
         // 3. List all operations starting from checkpoint
         // 4. Check that first operation has same timestamp as checkpoint (if not zero)
         // 5. Apply all operations in order
         unimplemented!()
     }
 
-    pub fn state(&self) -> &S {
+    /// Applies a new operation on the state. Once this function returns,
+    /// the option has been safely persisted to storage backend
+    pub async fn push(&mut self, op: S::Op) -> Result<()> {
         unimplemented!()
     }
+
+    pub fn state(&self) -> &S {
+        if let Some(last) = self.history.last() {
+            last.2.as_ref().unwrap()
+        } else {
+            &self.checkpoint.1
+        }
+    }
 }
 
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
diff --git a/src/main.rs b/src/main.rs
index 2b17e4c..81cf220 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -8,9 +8,9 @@ mod cryptoblob;
 mod time;
 mod uidindex;
 
-use bayou::Bayou;
+use bayou::*;
 use cryptoblob::Key;
-use uidindex::{UidIndex, UidIndexOp};
+use uidindex::*;
 
 #[tokio::main]
 async fn main() {
@@ -43,5 +43,10 @@ async fn do_stuff() -> Result<()> {
 
     mail_index.sync().await?;
 
+    let add_mail_op = mail_index
+        .state()
+        .op_mail_add(MailUuid([0xFFu8; 24]), vec!["\\Unseen".into()]);
+    mail_index.push(add_mail_op).await?;
+
     Ok(())
 }
diff --git a/src/uidindex.rs b/src/uidindex.rs
index 7c5500f..600cf6a 100644
--- a/src/uidindex.rs
+++ b/src/uidindex.rs
@@ -28,6 +28,30 @@ pub struct UidIndex {
 pub enum UidIndexOp {
     MailAdd(MailUuid, ImapUid, Vec<String>),
     MailDel(MailUuid),
+    FlagAdd(MailUuid, Vec<String>),
+    FlagDel(MailUuid, Vec<String>),
+}
+
+impl UidIndex {
+    #[must_use]
+    pub fn op_mail_add(&self, uuid: MailUuid, flags: Vec<String>) -> UidIndexOp {
+        UidIndexOp::MailAdd(uuid, self.internalseq, flags)
+    }
+
+    #[must_use]
+    pub fn op_mail_del(&self, uuid: MailUuid) -> UidIndexOp {
+        UidIndexOp::MailDel(uuid)
+    }
+
+    #[must_use]
+    pub fn op_flag_add(&self, uuid: MailUuid, flags: Vec<String>) -> UidIndexOp {
+        UidIndexOp::FlagAdd(uuid, flags)
+    }
+
+    #[must_use]
+    pub fn op_flag_del(&self, uuid: MailUuid, flags: Vec<String>) -> UidIndexOp {
+        UidIndexOp::FlagDel(uuid, flags)
+    }
 }
 
 impl Default for UidIndex {
@@ -74,6 +98,19 @@ impl BayouState for UidIndex {
                 }
                 new.internalseq += 1;
             }
+            UidIndexOp::FlagAdd(uuid, new_flags) => {
+                let mail_flags = new.mail_flags.entry(*uuid).or_insert(vec![]);
+                for flag in new_flags {
+                    if !mail_flags.contains(flag) {
+                        mail_flags.push(flag.to_string());
+                    }
+                }
+            }
+            UidIndexOp::FlagDel(uuid, rm_flags) => {
+                if let Some(mail_flags) = new.mail_flags.get_mut(uuid) {
+                    mail_flags.retain(|x| !rm_flags.contains(x));
+                }
+            }
         }
         new
     }