Merge pull request #48 from comit-network/refund-timeout

daemon/src/model/cfd.rs

@@ -299,6 +299,20 @@ fn calculate_profit(
     Ok((Amount::ZERO, Usd::ZERO))
 }
 
+pub trait AsBlocks {
+    /// Calculates the duration in Bitcoin blocks.
+    ///
+    /// On Bitcoin there is a block every 10 minutes/600 seconds on average.
+    /// It's the caller's responsibility to round the resulting floating point number.
+    fn as_blocks(&self) -> f32;
+}
+
+impl AsBlocks for Duration {
+    fn as_blocks(&self) -> f32 {
+        self.as_secs_f32() / 60.0 / 10.0
+    }
+}
+
 /// Calculates the buyer's margin in BTC
 ///
 /// The margin is the initial margin and represents the collateral the buyer has to come up with to
@@ -510,6 +524,23 @@ mod tests {
             r#"{"type":"Error","payload":{"common":{"transition_timestamp":{"secs_since_epoch":0,"nanos_since_epoch":0}}}}"#
         );
     }
+
+    #[test]
+    fn test_secs_into_blocks() {
+        let error_margin = f32::EPSILON;
+
+        let duration = Duration::from_secs(600);
+        let blocks = duration.as_blocks();
+        assert!(blocks - error_margin < 1.0 && blocks + error_margin > 1.0);
+
+        let duration = Duration::from_secs(0);
+        let blocks = duration.as_blocks();
+        assert!(blocks - error_margin < 0.0 && blocks + error_margin > 0.0);
+
+        let duration = Duration::from_secs(60);
+        let blocks = duration.as_blocks();
+        assert!(blocks - error_margin < 0.1 && blocks + error_margin > 0.1);
+    }
 }
 
 /// Contains all data we've assembled about the CFD through the setup protocol.

daemon/src/taker_cfd_actor.rs

@@ -2,7 +2,9 @@ use crate::db::{
     insert_cfd, insert_cfd_offer, insert_new_cfd_state_by_offer_id, load_all_cfds,
     load_offer_by_id, OfferOrigin,
 };
-use crate::model::cfd::{Cfd, CfdOffer, CfdOfferId, CfdState, CfdStateCommon, FinalizedCfd};
+use crate::model::cfd::{
+    AsBlocks, Cfd, CfdOffer, CfdOfferId, CfdState, CfdStateCommon, FinalizedCfd,
+};
 use crate::model::Usd;
 use crate::wire;
 use crate::wire::{AdaptorSignature, Msg0, Msg1, SetupMsg};
@@ -21,6 +23,20 @@ use std::collections::HashMap;
 use std::time::SystemTime;
 use tokio::sync::{mpsc, watch};
 
+/// A factor to be added to the CFD offer term for calculating the refund timelock.
+///
+/// The refund timelock is important in case the oracle disappears or never publishes a signature.
+/// Ideally, both users collaboratively settle in the refund scenario. This factor is important if
+/// the users do not settle collaboratively.
+/// `1.5` times the term as defined in CFD offer should be safe in the extreme case where a user
+/// publishes the commit transaction right after the contract was initialized. In this case, the  
+/// oracle still has `1.0 * cfdoffer.term` time to attest and no one can publish the refund
+/// transaction.
+/// The downside is that if the oracle disappears: the users would only notice at the end
+/// of the cfd term. In this case the users has to wait for another `1.5` times of the
+/// term to get his funds back.
+pub const REFUND_THRESHOLD: f32 = 1.5;
+
 #[derive(Debug)]
 #[allow(clippy::large_enum_variant)]
 pub enum Command {
@@ -119,15 +135,17 @@ where
                             .build_party_params(bitcoin::Amount::ZERO, pk) // TODO: Load correct quantity from DB
                             .unwrap();
 
+                        let cfd = load_offer_by_id(offer_id, &mut conn).await.unwrap();
+
                         let (actor, inbox) = setup_contract(
                             {
                                 let inbox = out_msg_maker_inbox.clone();
-
                                 move |msg| inbox.send(wire::TakerToMaker::Protocol(msg)).unwrap()
                             },
                             taker_params,
                             sk,
                             oracle_pk,
+                            cfd,
                         );
 
                         tokio::spawn({
@@ -170,6 +188,7 @@ fn setup_contract(
     taker: PartyParams,
     sk: SecretKey,
     oracle_pk: schnorrsig::PublicKey,
+    offer: CfdOffer,
 ) -> (
     impl Future<Output = FinalizedCfd>,
     mpsc::UnboundedSender<SetupMsg>,
@@ -193,7 +212,7 @@ fn setup_contract(
             (maker.clone(), maker_punish),
             (taker.clone(), taker_punish),
             oracle_pk,
-            0, // TODO: Calculate refund timelock based on CFD term
+            offer.term.mul_f32(REFUND_THRESHOLD).as_blocks().ceil() as u32,
             vec![],
             sk,
         )