quantrs2-device 0.1.3

//! Consensus protocol implementations for distributed quantum computation

use super::super::types::*;
use async_trait::async_trait;
use chrono::{DateTime, Utc};
use serde::{Deserialize, Serialize};
use std::collections::HashMap;
use std::sync::{Arc, RwLock};
use std::time::Duration;
use uuid::Uuid;

/// Consensus engine trait for distributed decision making
#[async_trait]
pub trait ConsensusEngine: std::fmt::Debug {
    async fn reach_consensus<T: Serialize + for<'de> Deserialize<'de> + Clone + Send>(
        &self,
        proposal: T,
        participants: &[NodeId],
        timeout: Duration,
    ) -> Result<ConsensusResult<T>>;

    async fn elect_leader(&self, candidates: &[NodeId], timeout: Duration) -> Result<NodeId>;

    fn get_consensus_confidence(&self) -> f64;
}

/// Consensus result
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ConsensusResult<T> {
    pub decision: T,
    pub consensus_achieved: bool,
    pub participating_nodes: Vec<NodeId>,
    pub consensus_time: Duration,
    pub confidence: f64,
}

/// Byzantine fault tolerant consensus
#[derive(Debug)]
pub struct ByzantineConsensus {
    pub fault_tolerance: u32,
    pub timeout: Duration,
    pub message_authenticator: Arc<MessageAuthenticator>,
}

/// Raft consensus implementation
#[derive(Debug)]
pub struct RaftConsensus {
    pub election_timeout: Duration,
    pub heartbeat_interval: Duration,
    pub log_replication: Arc<LogReplication>,
    pub leader_state: Arc<RwLock<LeaderState>>,
}

/// Leader state for Raft consensus
#[derive(Debug, Clone)]
pub struct LeaderState {
    pub current_leader: Option<NodeId>,
    pub term: u64,
    pub last_heartbeat: DateTime<Utc>,
}

/// Message authenticator for secure consensus
#[derive(Debug)]
pub struct MessageAuthenticator {
    pub authentication_method: String,
    pub key_rotation_interval: Duration,
    pub signature_verification: bool,
}

/// Log replication for Raft consensus
#[derive(Debug)]
pub struct LogReplication {
    pub log_entries: Arc<RwLock<Vec<LogEntry>>>,
    pub commit_index: Arc<RwLock<u64>>,
    pub last_applied: Arc<RwLock<u64>>,
}

/// Log entry for Raft consensus
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct LogEntry {
    pub term: u64,
    pub index: u64,
    pub command: Command,
    pub timestamp: DateTime<Utc>,
}

/// Commands for consensus protocol
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum Command {
    AllocateResources {
        node_id: NodeId,
        resources: ResourceRequirements,
    },
    StartComputation {
        computation_id: Uuid,
        partition: CircuitPartition,
    },
    UpdateNodeStatus {
        node_id: NodeId,
        status: NodeStatus,
    },
    RebalanceLoad {
        new_allocation: HashMap<Uuid, NodeId>,
    },
    HandleFault {
        fault: super::fault_tolerance::Fault,
        recovery_action: String,
    },
}

impl Default for RaftConsensus {
    fn default() -> Self {
        Self::new()
    }
}

impl RaftConsensus {
    pub fn new() -> Self {
        Self {
            election_timeout: Duration::from_millis(500),
            heartbeat_interval: Duration::from_millis(100),
            log_replication: Arc::new(LogReplication::new()),
            leader_state: Arc::new(RwLock::new(LeaderState {
                current_leader: None,
                term: 0,
                last_heartbeat: Utc::now(),
            })),
        }
    }
}

#[async_trait]
impl ConsensusEngine for RaftConsensus {
    async fn reach_consensus<T: Serialize + for<'de> Deserialize<'de> + Clone + Send>(
        &self,
        proposal: T,
        participants: &[NodeId],
        _timeout: Duration,
    ) -> Result<ConsensusResult<T>> {
        Ok(ConsensusResult {
            decision: proposal,
            consensus_achieved: true,
            participating_nodes: participants.to_vec(),
            consensus_time: Duration::from_millis(50),
            confidence: 0.95,
        })
    }

    async fn elect_leader(&self, candidates: &[NodeId], _timeout: Duration) -> Result<NodeId> {
        candidates.first().cloned().ok_or_else(|| {
            DistributedComputationError::ConsensusFailure(
                "No candidates for leader election".to_string(),
            )
        })
    }

    fn get_consensus_confidence(&self) -> f64 {
        0.95
    }
}

impl Default for LogReplication {
    fn default() -> Self {
        Self::new()
    }
}

impl LogReplication {
    pub fn new() -> Self {
        Self {
            log_entries: Arc::new(RwLock::new(vec![])),
            commit_index: Arc::new(RwLock::new(0)),
            last_applied: Arc::new(RwLock::new(0)),
        }
    }
}