From 4b380c828b57190dd9156cc1dad01a9f2be9ea96 Mon Sep 17 00:00:00 2001
From: conduition <conduition@proton.me>
Date: Thu, 14 Mar 2024 17:22:15 +0000
Subject: [PATCH] implement Clone on TicketedDLC (with documented stipulations)

---
 src/contract/outcome.rs   |  1 +
 src/contract/split.rs     |  1 +
 src/lib.rs                | 18 ++++++++++++++++--
 src/spend_info/funding.rs |  1 +
 src/spend_info/outcome.rs |  1 +
 src/spend_info/split.rs   |  1 +
 6 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/src/contract/outcome.rs b/src/contract/outcome.rs
index 5b6ee60..aa04237 100644
--- a/src/contract/outcome.rs
+++ b/src/contract/outcome.rs
@@ -16,6 +16,7 @@ use crate::{
 /// Represents the output of building the set of outcome transactions.
 /// This contains cached data used for constructing further transactions,
 /// or signing the outcome transactions themselves.
+#[derive(Clone)]
 pub(crate) struct OutcomeTransactionBuildOutput {
     outcome_txs: BTreeMap<Outcome, Transaction>,
     outcome_spend_infos: BTreeMap<Outcome, OutcomeSpendInfo>,
diff --git a/src/contract/split.rs b/src/contract/split.rs
index c5af0e8..b478524 100644
--- a/src/contract/split.rs
+++ b/src/contract/split.rs
@@ -17,6 +17,7 @@ use std::collections::{BTreeMap, BTreeSet};
 /// Represents the output of building the set of split transactions.
 /// This contains cached data used for constructing further transactions,
 /// or signing the split transactions themselves.
+#[derive(Clone)]
 pub(crate) struct SplitTransactionBuildOutput {
     split_txs: BTreeMap<Outcome, Transaction>,
     split_spend_infos: BTreeMap<WinCondition, SplitSpendInfo>,
diff --git a/src/lib.rs b/src/lib.rs
index 785e7f0..6d6d179 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -33,6 +33,20 @@ pub use parties::{MarketMaker, Player};
 
 /// Represents the combined output of building all transactions and precomputing
 /// all necessary data for a ticketed DLC.
+///
+/// This type does not have any serialization methods or trait implementations, because
+/// each party in the DLC is expected to use the [`ContractParameters`] to independently
+/// construct the [`TicketedDLC`] transactions which they will sign. This reduces the
+/// amount of data each party must validate. Instead of minutely inspecting thousands of
+/// transactions, they should validate the properties of the [`ContractParameters`], and
+/// thus be assured that if others are using the same [`ContractParameters`], then they
+/// will be constructing and signing the same set of transactions.
+///
+/// [`TicketedDLC`] implements [`Clone`], but cloning should be done very sparingly, because
+/// in real-world environments a [`TicketedDLC`] could easily encapsulate many thousands of
+/// transactions involved, consuming megabytes of memory. Cloning it would be extremely
+/// inefficient and potentially dangerous.
+#[derive(Clone)]
 pub struct TicketedDLC {
     params: ContractParameters,
     funding_outpoint: OutPoint,
@@ -52,13 +66,13 @@ impl TicketedDLC {
         let outcome_tx_build = contract::outcome::build_outcome_txs(&params, funding_outpoint)?;
         let split_tx_build = contract::split::build_split_txs(&params, &outcome_tx_build)?;
 
-        let txs = TicketedDLC {
+        let dlc = TicketedDLC {
             params,
             funding_outpoint,
             outcome_tx_build,
             split_tx_build,
         };
-        Ok(txs)
+        Ok(dlc)
     }
 
     /// Returns the contract parameters used to construct the DLC.
diff --git a/src/spend_info/funding.rs b/src/spend_info/funding.rs
index 1c8b102..0770e35 100644
--- a/src/spend_info/funding.rs
+++ b/src/spend_info/funding.rs
@@ -10,6 +10,7 @@ use crate::{
     parties::{MarketMaker, Player},
 };
 
+#[derive(Clone)]
 pub(crate) struct FundingSpendInfo {
     key_agg_ctx: KeyAggContext,
     funding_value: Amount,
diff --git a/src/spend_info/outcome.rs b/src/spend_info/outcome.rs
index a286120..a4b8416 100644
--- a/src/spend_info/outcome.rs
+++ b/src/spend_info/outcome.rs
@@ -36,6 +36,7 @@ use std::{borrow::Borrow, collections::BTreeMap};
 /// Once PTLCs are available, we can instead sign the split transaction once
 /// and distribute adaptor-signatures to each player, encrypted under the
 /// player's ticket point.
+#[derive(Clone)]
 pub(crate) struct OutcomeSpendInfo {
     untweaked_ctx: KeyAggContext,
     tweaked_ctx: KeyAggContext,
diff --git a/src/spend_info/split.rs b/src/spend_info/split.rs
index bba4f42..a4c29e4 100644
--- a/src/spend_info/split.rs
+++ b/src/spend_info/split.rs
@@ -27,6 +27,7 @@ use crate::{
 ///
 /// 3. A hash-lock which pays to the market maker immediately if they learn the
 //     payout preimage from the player.
+#[derive(Clone)]
 pub(crate) struct SplitSpendInfo {
     tweaked_ctx: KeyAggContext,
     payout_value: Amount,