vortex-sim 0.1.0

//! Simulated network with configurable latency, drops, partitions, and reordering.
//!
//! Every message delivery is deterministic given the same seed. The network
//! supports symmetric/asymmetric partitions, jitter, duplication, and more.

use std::collections::{HashMap, HashSet, VecDeque};
use vortex_core::{DetRng, NodeId};

/// Configuration for a simulated network link between two nodes.
#[derive(Debug, Clone)]
pub struct LinkConfig {
    /// One-way latency in simulated ticks.
    pub latency_ticks: u64,
    /// Drop probability (0.0 = never, 1.0 = always).
    pub drop_probability: f64,
    /// Jitter in ticks: delivery = latency ± rand(0..jitter).
    pub jitter_ticks: u64,
    /// If true, messages may be reordered due to jitter.
    pub reorder: bool,
    /// Probability that a message is delivered twice.
    pub duplicate_probability: f64,
    /// Probability that a message is corrupted (random byte flip).
    pub corrupt_probability: f64,
    /// Maximum messages per tick on this link (0 = unlimited).
    pub bandwidth_limit: u64,
}

impl Default for LinkConfig {
    fn default() -> Self {
        Self {
            latency_ticks: 1,
            drop_probability: 0.0,
            jitter_ticks: 0,
            reorder: false,
            duplicate_probability: 0.0,
            corrupt_probability: 0.0,
            bandwidth_limit: 0,
        }
    }
}

/// A message in-flight in the simulated network.
#[derive(Debug, Clone)]
pub struct InFlightMessage {
    /// Source node.
    pub from: NodeId,
    /// Destination node.
    pub to: NodeId,
    /// Message payload.
    pub payload: Vec<u8>,
    /// Tick at which this message should be delivered.
    pub deliver_at: u64,
}

/// Simulated network that intercepts all inter-node communication.
///
/// Fully deterministic given the same seed. Supports partitions, drops,
/// latency, jitter, reordering, and message duplication.
pub struct SimNetwork {
    current_tick: u64,
    in_flight: VecDeque<InFlightMessage>,
    link_configs: HashMap<(NodeId, NodeId), LinkConfig>,
    partitions: HashSet<(NodeId, NodeId)>,
    delivered: HashMap<NodeId, VecDeque<(NodeId, Vec<u8>)>>,
    rng: DetRng,
    total_sent: u64,
    total_dropped: u64,
    total_delivered: u64,
    total_corrupted: u64,
    total_throttled: u64,
    /// Messages delivered per link per tick (for bandwidth limiting).
    tick_delivery_counts: HashMap<(NodeId, NodeId), u64>,
}

impl SimNetwork {
    /// Create a new simulated network with the given random seed.
    pub fn new(seed: u64) -> Self {
        Self {
            current_tick: 0,
            in_flight: VecDeque::new(),
            link_configs: HashMap::new(),
            partitions: HashSet::new(),
            delivered: HashMap::new(),
            rng: DetRng::derive(seed, "network"),
            total_sent: 0,
            total_dropped: 0,
            total_delivered: 0,
            total_corrupted: 0,
            total_throttled: 0,
            tick_delivery_counts: HashMap::new(),
        }
    }

    /// Set the link configuration between two nodes.
    pub fn set_link_config(&mut self, from: NodeId, to: NodeId, config: LinkConfig) {
        self.link_configs.insert((from, to), config);
    }

    /// Configure all links between the given nodes symmetrically.
    pub fn set_all_links(&mut self, nodes: &[NodeId], config: LinkConfig) {
        for &a in nodes {
            for &b in nodes {
                if a != b {
                    self.link_configs.insert((a, b), config.clone());
                }
            }
        }
    }

    /// Inject a symmetric partition: all messages between a and b are dropped.
    pub fn inject_partition(&mut self, a: NodeId, b: NodeId) {
        self.partitions.insert((a, b));
        self.partitions.insert((b, a));
    }

    /// Heal a symmetric partition.
    pub fn heal_partition(&mut self, a: NodeId, b: NodeId) {
        self.partitions.remove(&(a, b));
        self.partitions.remove(&(b, a));
    }

    /// Inject a one-way partition: from→to dropped, to→from delivered.
    pub fn inject_one_way_partition(&mut self, from: NodeId, to: NodeId) {
        self.partitions.insert((from, to));
    }

    /// Heal a one-way partition.
    pub fn heal_one_way_partition(&mut self, from: NodeId, to: NodeId) {
        self.partitions.remove(&(from, to));
    }

    /// Heal all partitions.
    pub fn heal_all_partitions(&mut self) {
        self.partitions.clear();
    }

    /// Submit a message into the network.
    pub fn send(&mut self, from: NodeId, to: NodeId, payload: Vec<u8>) {
        self.total_sent += 1;

        // Check partition
        if self.partitions.contains(&(from, to)) {
            self.total_dropped += 1;
            return;
        }

        // Get link config
        let config = self
            .link_configs
            .get(&(from, to))
            .cloned()
            .unwrap_or_default();

        // Random drop
        if config.drop_probability > 0.0 && self.rng.next_f64() < config.drop_probability {
            self.total_dropped += 1;
            return;
        }

        // Calculate delivery time with jitter
        let base_latency = config.latency_ticks as i64;
        let jitter = if config.jitter_ticks > 0 {
            let j = config.jitter_ticks as i64;
            let range = 2 * j + 1;
            (self.rng.next_f64() * range as f64) as i64 - j
        } else {
            0
        };
        let effective_latency = (base_latency + jitter).max(1) as u64;
        let deliver_at = self.current_tick + effective_latency;

        // Check for duplication
        let should_duplicate = config.duplicate_probability > 0.0
            && self.rng.next_f64() < config.duplicate_probability;

        self.in_flight.push_back(InFlightMessage {
            from,
            to,
            payload: payload.clone(),
            deliver_at,
        });

        if should_duplicate {
            let dup_delay = (self.rng.next_f64() * 5.0) as u64 + 1;
            self.in_flight.push_back(InFlightMessage {
                from,
                to,
                payload,
                deliver_at: deliver_at + dup_delay,
            });
        }
    }

    /// Advance by one tick, delivering any due messages.
    pub fn tick(&mut self) {
        self.current_tick += 1;
        self.tick_delivery_counts.clear();

        let mut still_in_flight = VecDeque::new();
        while let Some(msg) = self.in_flight.pop_front() {
            if msg.deliver_at <= self.current_tick {
                // Check partition at delivery time
                if self.partitions.contains(&(msg.from, msg.to)) {
                    self.total_dropped += 1;
                    continue;
                }

                // Check bandwidth limit
                let config = self
                    .link_configs
                    .get(&(msg.from, msg.to))
                    .cloned()
                    .unwrap_or_default();
                if config.bandwidth_limit > 0 {
                    let count = self
                        .tick_delivery_counts
                        .entry((msg.from, msg.to))
                        .or_insert(0);
                    if *count >= config.bandwidth_limit {
                        // Re-queue for next tick
                        still_in_flight.push_back(InFlightMessage {
                            deliver_at: self.current_tick + 1,
                            ..msg
                        });
                        self.total_throttled += 1;
                        continue;
                    }
                    *count += 1;
                }

                // Apply corruption
                let payload = if config.corrupt_probability > 0.0
                    && self.rng.next_f64() < config.corrupt_probability
                {
                    let mut corrupted = msg.payload;
                    if !corrupted.is_empty() {
                        let idx = self.rng.next_u64_below(corrupted.len() as u64) as usize;
                        corrupted[idx] ^= 1u8 << (self.rng.next_u64_below(8) as u8);
                    }
                    self.total_corrupted += 1;
                    corrupted
                } else {
                    msg.payload
                };

                self.delivered
                    .entry(msg.to)
                    .or_default()
                    .push_back((msg.from, payload));
                self.total_delivered += 1;
            } else {
                still_in_flight.push_back(msg);
            }
        }
        self.in_flight = still_in_flight;
    }

    /// Drain delivered messages for a specific node.
    pub fn drain(&mut self, node_id: NodeId) -> Vec<(NodeId, Vec<u8>)> {
        self.delivered
            .get_mut(&node_id)
            .map(|q| q.drain(..).collect())
            .unwrap_or_default()
    }

    /// Current simulation tick.
    pub fn current_tick(&self) -> u64 {
        self.current_tick
    }

    /// Number of messages currently in-flight.
    pub fn in_flight_count(&self) -> usize {
        self.in_flight.len()
    }

    /// Stats: total messages sent.
    pub fn total_sent(&self) -> u64 {
        self.total_sent
    }

    /// Stats: total messages dropped.
    pub fn total_dropped(&self) -> u64 {
        self.total_dropped
    }

    /// Stats: total messages delivered.
    pub fn total_delivered(&self) -> u64 {
        self.total_delivered
    }

    /// Stats: total messages corrupted.
    pub fn total_corrupted(&self) -> u64 {
        self.total_corrupted
    }

    /// Stats: total messages throttled (delayed due to bandwidth limit).
    pub fn total_throttled(&self) -> u64 {
        self.total_throttled
    }

    /// Get all active partition pairs.
    pub fn partition_pairs(&self) -> Vec<(NodeId, NodeId)> {
        self.partitions.iter().copied().collect()
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_basic_delivery() {
        let mut net = SimNetwork::new(42);
        net.send(1, 2, b"hello".to_vec());
        assert!(net.drain(2).is_empty()); // Not yet delivered
        net.tick();
        let msgs = net.drain(2);
        assert_eq!(msgs.len(), 1);
        assert_eq!(msgs[0].0, 1);
        assert_eq!(msgs[0].1, b"hello");
    }

    #[test]
    fn test_partition() {
        let mut net = SimNetwork::new(42);
        net.inject_partition(1, 2);
        net.send(1, 2, b"lost".to_vec());
        net.tick();
        assert!(net.drain(2).is_empty());

        net.heal_partition(1, 2);
        net.send(1, 2, b"found".to_vec());
        net.tick();
        assert_eq!(net.drain(2).len(), 1);
    }

    #[test]
    fn test_one_way_partition() {
        let mut net = SimNetwork::new(42);
        net.inject_one_way_partition(1, 2);
        net.send(1, 2, b"blocked".to_vec());
        net.send(2, 1, b"ok".to_vec());
        net.tick();
        assert!(net.drain(2).is_empty());
        assert_eq!(net.drain(1).len(), 1);
    }

    #[test]
    fn test_latency() {
        let mut net = SimNetwork::new(42);
        net.set_link_config(
            1,
            2,
            LinkConfig {
                latency_ticks: 5,
                ..Default::default()
            },
        );
        net.send(1, 2, b"delayed".to_vec());
        for _ in 0..4 {
            net.tick();
            assert!(net.drain(2).is_empty());
        }
        net.tick();
        assert_eq!(net.drain(2).len(), 1);
    }

    #[test]
    fn test_deterministic() {
        let mut net1 = SimNetwork::new(100);
        let mut net2 = SimNetwork::new(100);
        let config = LinkConfig {
            drop_probability: 0.5,
            ..Default::default()
        };
        for net in [&mut net1, &mut net2] {
            net.set_link_config(1, 2, config.clone());
            for i in 0..10 {
                net.send(1, 2, vec![i]);
            }
            net.tick();
        }
        assert_eq!(net1.drain(2).len(), net2.drain(2).len());
    }

    #[test]
    fn test_jitter_varies_delivery() {
        let mut net = SimNetwork::new(42);
        net.set_link_config(
            1,
            2,
            LinkConfig {
                latency_ticks: 10,
                jitter_ticks: 5,
                reorder: true,
                ..Default::default()
            },
        );
        for i in 0..20u8 {
            net.send(1, 2, vec![i]);
        }
        let mut delivery_ticks = Vec::new();
        for tick in 1..=20 {
            net.tick();
            let count = net.drain(2).len();
            for _ in 0..count {
                delivery_ticks.push(tick);
            }
        }
        assert_eq!(delivery_ticks.len(), 20);
        let first = delivery_ticks[0];
        assert!(
            delivery_ticks.iter().any(|&t| t != first),
            "jitter should vary delivery"
        );
    }

    #[test]
    fn test_duplication() {
        let mut net = SimNetwork::new(42);
        net.set_link_config(
            1,
            2,
            LinkConfig {
                duplicate_probability: 1.0,
                ..Default::default()
            },
        );
        net.send(1, 2, b"hello".to_vec());
        for _ in 0..10 {
            net.tick();
        }
        assert_eq!(net.drain(2).len(), 2);
    }

    #[test]
    fn test_corruption() {
        let mut net = SimNetwork::new(42);
        net.set_link_config(
            1,
            2,
            LinkConfig {
                corrupt_probability: 1.0,
                ..Default::default()
            },
        );
        net.send(1, 2, b"hello".to_vec());
        net.tick();
        let msgs = net.drain(2);
        assert_eq!(msgs.len(), 1);
        // Message should be corrupted (bit flipped)
        assert_ne!(msgs[0].1, b"hello");
        assert_eq!(net.total_corrupted(), 1);
    }

    #[test]
    fn test_bandwidth_limit() {
        let mut net = SimNetwork::new(42);
        net.set_link_config(
            1,
            2,
            LinkConfig {
                bandwidth_limit: 2,
                ..Default::default()
            },
        );
        // Send 5 messages
        for i in 0..5u8 {
            net.send(1, 2, vec![i]);
        }
        // First tick: only 2 delivered due to bandwidth limit
        net.tick();
        assert_eq!(net.drain(2).len(), 2);
        // Second tick: 2 more
        net.tick();
        assert_eq!(net.drain(2).len(), 2);
        // Third tick: last 1
        net.tick();
        assert_eq!(net.drain(2).len(), 1);
        assert!(net.total_throttled() >= 3);
    }

    #[test]
    fn test_stats() {
        let mut net = SimNetwork::new(42);
        net.inject_partition(1, 2);
        net.send(1, 2, b"dropped".to_vec()); // dropped (1→2 partitioned)
        net.send(2, 1, b"also_dropped".to_vec()); // dropped (symmetric: 2→1 also partitioned)
        net.send(3, 1, b"ok".to_vec()); // delivered
        net.tick();
        assert_eq!(net.total_sent(), 3);
        assert_eq!(net.total_dropped(), 2);
        assert_eq!(net.total_delivered(), 1);
    }
}