Added some crazy AI generated ideas, as a brainstorming exercise.

examples/cross_chain_relay.rs

@@ -0,0 +1,310 @@
+use serde::{Deserialize, Serialize};
+use std::collections::{HashMap, HashSet};
+use std::time::{SystemTime, UNIX_EPOCH};
+
+/// Represents a blockchain identifier
+#[derive(Debug, Clone, Hash, Eq, PartialEq, Serialize, Deserialize)]
+pub struct ChainId(pub String);
+
+/// A message being relayed between chains
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct CrossChainMessage {
+    /// Unique identifier for this message
+    pub id: String,
+    /// Source blockchain
+    pub source_chain: ChainId,
+    /// Destination blockchain
+    pub dest_chain: ChainId,
+    /// Block height on source chain when message was created
+    pub source_block: u64,
+    /// Nonce for ordering messages from same block
+    pub nonce: u64,
+    /// The actual message payload
+    pub payload: Vec<u8>,
+    /// Timestamp when message was created
+    pub timestamp: u64,
+    /// Signatures from source chain validators
+    pub validator_signatures: Vec<ValidatorSignature>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct ValidatorSignature {
+    pub validator_id: String,
+    pub signature: Vec<u8>,
+}
+
+/// CRDT structure for accumulating cross-chain messages
+#[derive(Debug, Clone)]
+pub struct CrossChainRelayCRDT {
+    /// All messages seen by this node
+    messages: HashMap<String, CrossChainMessage>,
+    /// Track which messages have been delivered to which chains
+    deliveries: HashMap<ChainId, HashSet<String>>,
+    /// Byzantine fault detection - track conflicting messages
+    conflicts: HashMap<String, Vec<CrossChainMessage>>,
+}
+
+impl CrossChainRelayCRDT {
+    pub fn new() -> Self {
+        Self {
+            messages: HashMap::new(),
+            deliveries: HashMap::new(),
+            conflicts: HashMap::new(),
+        }
+    }
+
+    /// Add a new message to the CRDT
+    pub fn add_message(&mut self, message: CrossChainMessage) -> Result<(), String> {
+        // Verify the message has enough validator signatures
+        if !self.verify_signatures(&message) {
+            return Err("Insufficient valid signatures".to_string());
+        }
+
+        // Check for Byzantine behavior - same ID but different content
+        if let Some(existing) = self.messages.get(&message.id) {
+            if !self.messages_equal(existing, &message) {
+                self.conflicts
+                    .entry(message.id.clone())
+                    .or_insert_with(Vec::new)
+                    .push(message.clone());
+                return Err("Conflicting message detected".to_string());
+            }
+        }
+
+        // Add the message
+        self.messages.insert(message.id.clone(), message);
+        Ok(())
+    }
+
+    /// Merge another CRDT instance into this one
+    pub fn merge(&mut self, other: &CrossChainRelayCRDT) {
+        // Merge messages
+        for (id, message) in &other.messages {
+            if !self.messages.contains_key(id) {
+                let _ = self.add_message(message.clone());
+            }
+        }
+
+        // Merge delivery tracking
+        for (chain, delivered) in &other.deliveries {
+            self.deliveries
+                .entry(chain.clone())
+                .or_insert_with(HashSet::new)
+                .extend(delivered.clone());
+        }
+
+        // Merge conflict tracking
+        for (id, conflicts) in &other.conflicts {
+            self.conflicts
+                .entry(id.clone())
+                .or_insert_with(Vec::new)
+                .extend(conflicts.clone());
+        }
+    }
+
+    /// Get all messages destined for a specific chain that haven't been delivered yet
+    pub fn get_pending_messages(&self, dest_chain: &ChainId) -> Vec<&CrossChainMessage> {
+        let delivered = self.deliveries.get(dest_chain).cloned().unwrap_or_default();
+
+        let mut pending: Vec<&CrossChainMessage> = self
+            .messages
+            .values()
+            .filter(|msg| msg.dest_chain == *dest_chain && !delivered.contains(&msg.id))
+            .collect();
+
+        // Sort by source block height, then nonce for deterministic ordering
+        pending.sort_by(|a, b| {
+            a.source_block
+                .cmp(&b.source_block)
+                .then(a.nonce.cmp(&b.nonce))
+        });
+
+        pending
+    }
+
+    /// Mark messages as delivered to a chain
+    pub fn mark_delivered(&mut self, chain: &ChainId, message_ids: Vec<String>) {
+        let delivered = self
+            .deliveries
+            .entry(chain.clone())
+            .or_insert_with(HashSet::new);
+        delivered.extend(message_ids);
+    }
+
+    /// Get messages within a time window (for oracle-like use cases)
+    pub fn get_messages_in_window(
+        &self,
+        chain: &ChainId,
+        start_time: u64,
+        end_time: u64,
+    ) -> Vec<&CrossChainMessage> {
+        self.messages
+            .values()
+            .filter(|msg| {
+                msg.dest_chain == *chain && msg.timestamp >= start_time && msg.timestamp <= end_time
+            })
+            .collect()
+    }
+
+    /// Verify validator signatures (simplified - real implementation would check against validator set)
+    fn verify_signatures(&self, message: &CrossChainMessage) -> bool {
+        // In real implementation:
+        // 1. Get validator set for source chain at source block height
+        // 2. Verify each signature
+        // 3. Check if we have enough stake represented
+
+        // For now, just check we have at least 2 signatures
+        message.validator_signatures.len() >= 2
+    }
+
+    fn messages_equal(&self, a: &CrossChainMessage, b: &CrossChainMessage) -> bool {
+        a.source_chain == b.source_chain
+            && a.dest_chain == b.dest_chain
+            && a.source_block == b.source_block
+            && a.nonce == b.nonce
+            && a.payload == b.payload
+    }
+}
+
+/// Example: Oracle price aggregation use case
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct PriceOracleMessage {
+    pub oracle_id: String,
+    pub asset_pair: String,
+    pub price: u128,
+    pub confidence: u8,
+}
+
+impl CrossChainRelayCRDT {
+    /// Aggregate oracle prices from messages in a time window
+    pub fn aggregate_oracle_prices(
+        &self,
+        dest_chain: &ChainId,
+        asset_pair: &str,
+        time_window: u64,
+    ) -> Option<u128> {
+        let now = SystemTime::now()
+            .duration_since(UNIX_EPOCH)
+            .unwrap()
+            .as_secs();
+        let messages = self.get_messages_in_window(dest_chain, now - time_window, now);
+
+        let mut prices = Vec::new();
+
+        for msg in messages {
+            if let Ok(oracle_msg) = serde_json::from_slice::<PriceOracleMessage>(&msg.payload) {
+                if oracle_msg.asset_pair == asset_pair {
+                    prices.push(oracle_msg.price);
+                }
+            }
+        }
+
+        if prices.is_empty() {
+            return None;
+        }
+
+        // Calculate median price
+        prices.sort();
+        Some(prices[prices.len() / 2])
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_cross_chain_relay() {
+        let mut relay1 = CrossChainRelayCRDT::new();
+        let mut relay2 = CrossChainRelayCRDT::new();
+
+        let ethereum = ChainId("ethereum".to_string());
+        let polygon = ChainId("polygon".to_string());
+
+        // Create a message from Ethereum to Polygon
+        let message = CrossChainMessage {
+            id: "msg1".to_string(),
+            source_chain: ethereum.clone(),
+            dest_chain: polygon.clone(),
+            source_block: 1000,
+            nonce: 1,
+            payload: b"transfer:100:USDC:0x123...".to_vec(),
+            timestamp: 1234567890,
+            validator_signatures: vec![
+                ValidatorSignature {
+                    validator_id: "val1".to_string(),
+                    signature: vec![1, 2, 3],
+                },
+                ValidatorSignature {
+                    validator_id: "val2".to_string(),
+                    signature: vec![4, 5, 6],
+                },
+            ],
+        };
+
+        // Add to first relay
+        relay1.add_message(message.clone()).unwrap();
+
+        // Get pending messages for Polygon
+        let pending = relay1.get_pending_messages(&polygon);
+        assert_eq!(pending.len(), 1);
+
+        // Merge relay1 into relay2
+        relay2.merge(&relay1);
+
+        // Both should now have the same message
+        assert_eq!(relay2.get_pending_messages(&polygon).len(), 1);
+
+        // Mark as delivered
+        relay2.mark_delivered(&polygon, vec!["msg1".to_string()]);
+        assert_eq!(relay2.get_pending_messages(&polygon).len(), 0);
+    }
+
+    #[test]
+    fn test_oracle_aggregation() {
+        let mut relay = CrossChainRelayCRDT::new();
+        let ethereum = ChainId("ethereum".to_string());
+        let now = SystemTime::now()
+            .duration_since(UNIX_EPOCH)
+            .unwrap()
+            .as_secs();
+
+        // Add price submissions from multiple oracles
+        for i in 0..5 {
+            let price_msg = PriceOracleMessage {
+                oracle_id: format!("oracle{}", i),
+                asset_pair: "ETH/USD".to_string(),
+                price: 2000 + (i as u128 * 10), // Prices: 2000, 2010, 2020, 2030, 2040
+                confidence: 95,
+            };
+
+            let message = CrossChainMessage {
+                id: format!("price{}", i),
+                source_chain: ChainId(format!("oracle{}", i)),
+                dest_chain: ethereum.clone(),
+                source_block: 1000,
+                nonce: i as u64,
+                payload: serde_json::to_vec(&price_msg).unwrap(),
+                timestamp: now - 30, // 30 seconds ago
+                validator_signatures: vec![
+                    ValidatorSignature {
+                        validator_id: "val1".to_string(),
+                        signature: vec![1, 2, 3],
+                    },
+                    ValidatorSignature {
+                        validator_id: "val2".to_string(),
+                        signature: vec![4, 5, 6],
+                    },
+                ],
+            };
+
+            relay.add_message(message).unwrap();
+        }
+
+        // Aggregate prices from last minute
+        let median_price = relay
+            .aggregate_oracle_prices(&ethereum, "ETH/USD", 60)
+            .unwrap();
+        assert_eq!(median_price, 2020); // Median of 2000, 2010, 2020, 2030, 2040
+    }
+}