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use crate::types::{Entry, NodeId, PeerState};
use serde::{Deserialize, Serialize};
use std::collections::{BTreeMap, HashMap};
/// Atomic state operations - lowest level instructions that mutate CoreState
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum StateOp {
/// Set a KV entry (used for Put/Delete/Sync - all just set an entry)
Set(Entry),
/// Clear a key from storage (used for tombstone GC)
Clear(String),
/// Update peer_ack: peer tells us how far they've synced our logs
UpdatePeerAck {
peer_id: NodeId,
ack_seq: u64,
monotonic: bool,
},
/// Update local_ack: we've synced this peer's logs up to this sequence
UpdateLocalAck {
peer_id: NodeId,
ack_seq: u64,
monotonic: bool,
},
/// Add entry to peer's log
PushPeerLog {
peer_id: NodeId,
entry: Entry,
max_entries: usize,
},
/// Increment next_seq
IncrementSeq,
/// Set next_seq to a specific value (for bootstrap recovery)
SetNextSeq(u64),
/// Add a new peer to the cluster
AddPeer { peer_id: NodeId },
/// Remove a peer from the cluster
RemovePeer { peer_id: NodeId },
}
/// Core state: the minimal state that defines the database
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct CoreState {
/// KV storage using BTreeMap for prefix scanning support
data: BTreeMap<String, Entry>,
/// All nodes state (including self and peers)
/// Each PeerState contains: local_ack, peer_ack, and log entries
peers: HashMap<NodeId, PeerState>,
/// Sequence generator for this node's log IDs
next_seq: u64,
}
impl CoreState {
pub fn new(node_id: NodeId, peer_ids: Vec<NodeId>) -> Self {
let mut peers = HashMap::new();
peers.insert(node_id, PeerState::new());
for peer_id in peer_ids {
if peer_id != node_id {
peers.insert(peer_id, PeerState::new());
}
}
Self {
data: BTreeMap::new(),
peers,
next_seq: 1,
}
}
fn peer_mut(&mut self, peer_id: NodeId) -> &mut PeerState {
self.peers.entry(peer_id).or_default()
}
pub fn is_noop(&self, op: &StateOp) -> bool {
match op {
StateOp::Set(_) => false,
StateOp::Clear(key) => !self.data.contains_key(key),
StateOp::UpdatePeerAck {
peer_id,
ack_seq,
monotonic,
} => {
let Some(peer_state) = self.peers.get(peer_id) else {
return false;
};
let final_ack_seq = if *monotonic {
peer_state.peer_ack.max(*ack_seq)
} else {
*ack_seq
};
peer_state.peer_ack == final_ack_seq
}
StateOp::UpdateLocalAck {
peer_id,
ack_seq,
monotonic,
} => {
let Some(peer_state) = self.peers.get(peer_id) else {
return false;
};
let final_ack_seq = if *monotonic {
peer_state.local_ack.max(*ack_seq)
} else {
*ack_seq
};
peer_state.local_ack == final_ack_seq
}
StateOp::PushPeerLog {
peer_id,
entry,
max_entries: _,
} => {
let Some(peer_state) = self.peers.get(peer_id) else {
return false;
};
// Use local_ack for consistency with execute()
entry.meta.seq <= peer_state.local_ack
}
StateOp::IncrementSeq => false,
StateOp::SetNextSeq(seq) => self.next_seq == *seq,
StateOp::AddPeer { peer_id } => self.peers.contains_key(peer_id),
StateOp::RemovePeer { peer_id } => !self.peers.contains_key(peer_id),
}
}
/// Execute a state operation - the only way to mutate CoreState
pub fn execute(&mut self, op: StateOp) {
match op {
StateOp::Set(entry) => {
self.data.insert(entry.key.clone(), entry);
}
StateOp::Clear(key) => {
self.data.remove(&key);
}
StateOp::UpdatePeerAck {
peer_id,
ack_seq,
monotonic,
} => {
let peer_state = self.peer_mut(peer_id);
if monotonic {
peer_state.peer_ack = peer_state.peer_ack.max(ack_seq);
} else {
peer_state.peer_ack = ack_seq;
}
}
StateOp::UpdateLocalAck {
peer_id,
ack_seq,
monotonic,
} => {
let peer_state = self.peer_mut(peer_id);
if monotonic {
peer_state.local_ack = peer_state.local_ack.max(ack_seq);
} else {
peer_state.local_ack = ack_seq;
}
}
StateOp::PushPeerLog {
peer_id,
entry,
max_entries,
} => {
let peer_state = self.peer_mut(peer_id);
if entry.meta.seq <= peer_state.local_ack {
return;
}
peer_state.push(entry.clone(), max_entries);
peer_state.local_ack = peer_state.local_ack.max(entry.meta.seq);
}
StateOp::AddPeer { peer_id } => {
_ = self.peer_mut(peer_id);
}
StateOp::RemovePeer { peer_id } => {
self.peers.remove(&peer_id);
}
StateOp::IncrementSeq => {
self.next_seq += 1;
}
StateOp::SetNextSeq(seq) => {
self.next_seq = self.next_seq.max(seq);
}
}
}
pub fn peers(&self) -> &HashMap<NodeId, PeerState> {
&self.peers
}
pub fn data(&self) -> &BTreeMap<String, Entry> {
&self.data
}
pub fn next_seq(&self) -> u64 {
self.next_seq
}
}