Rahul Surya

package raft

import "sync"

type State int
const (
    Follower State = iota
    Candidate
    Leader
)

type LogEntry struct {
    Term    int
    Command string
}

type Raft struct {
    mu        sync.Mutex
    id        int
    peers     []int
    state     State
    
    // Persistent consensus state
    currentTerm int
    votedFor    int
    log         []LogEntry
    commitIndex int
}

// AppendEntries RPC handles log replication & heartbeats
func (rf *Raft) AppendEntries(args *AppendEntriesArgs, reply *AppendEntriesReply) {
    rf.mu.Lock()
    defer rf.mu.Unlock()
    
    // Reject outdated leader terms
    if args.Term < rf.currentTerm {
        reply.Success = false
        return
    }
    
    // Reset election timer
    rf.heartbeatCh <- true
    
    // Truncate logs if conflict exists & append new entries
    if len(args.Entries) > 0 {
        rf.log = append(rf.log[:args.PrevLogIndex+1], args.Entries...)
    }
    
    // Commit and apply to state machine
    if args.LeaderCommit > rf.commitIndex {
        rf.commitIndex = min(args.LeaderCommit, len(rf.log)-1)
    }
    reply.Success = true
}