feat: add match cancellation fee to discourage abuse

contracts/escrow/src/lib.rs

@@ -125,6 +125,23 @@ impl EscrowContract {
         Ok(())
     }
 
+    /// Update the protocol configuration.
+    pub fn set_protocol_config(env: Env, config: ProtocolConfig) -> Result<(), Error> {
+        let admin: Address = env
+            .storage()
+            .instance()
+            .get(&DataKey::Admin)
+            .ok_or(Error::Unauthorized)?;
+        admin.require_auth();
+        env.storage().instance().set(&DataKey::ProtocolConfig, &config);
+        Ok(())
+    }
+
+    /// Get the current protocol configuration.
+    pub fn get_protocol_config(env: Env) -> Result<ProtocolConfig, Error> {
+        env.storage().instance().get(&DataKey::ProtocolConfig).ok_or(Error::NotInitialized)
+    }
+
     /// Add a token to the allowlist — admin only.
     pub fn add_allowed_token(env: Env, token: Address) -> Result<(), Error> {
         let admin: Address = env
@@ -861,6 +878,18 @@ impl EscrowContract {
 
         let is_multi_token = m.token_b.is_some() && m.conversion_rate > 0;
 
+        let config: ProtocolConfig = env.storage().instance().get(&DataKey::ProtocolConfig).unwrap_or(ProtocolConfig {
+            cancellation_fee_basis_points: 0,
+            treasury: env.current_contract_address(),
+        });
+
+        let fee_amount = if config.cancellation_fee_basis_points > 0 {
+            m.stake_amount.checked_mul(config.cancellation_fee_basis_points as i128).ok_or(Error::Overflow)? / 10_000
+        } else {
+            0
+        };
+        let refund_amount = m.stake_amount.checked_sub(fee_amount).ok_or(Error::Overflow)?;
+
         if m.player1_deposited {
             let client_a = token::Client::new(&env, &m.token);
             client_a.transfer(&env.current_contract_address(), &m.player1, &m.stake_amount);

contracts/escrow/src/tests/cancellation_fee.rs

@@ -0,0 +1,80 @@
+#![cfg(test)]
+extern crate std;
+
+use super::*;
+use soroban_sdk::testutils::Address as _;
+
+#[test]
+fn test_cancellation_fee_deduction() {
+    let (env, contract_id, _oracle, player1, player2, token, admin) = setup();
+    let client = EscrowContractClient::new(&env, &contract_id);
+    let token_client = token_client(&env, &token);
+
+    // Initial balances
+    assert_eq!(token_client.balance(&player1), 1000);
+
+    let match_id = helpers::create_default_match(&client, &env, &player1, &player2, &token, "test_fee_game");
+
+    // Player 1 deposits
+    client.deposit(&match_id, &player1);
+    assert_eq!(token_client.balance(&player1), 900);
+    assert_eq!(token_client.balance(&contract_id), 100);
+
+    // Default fee is 1%. Stake is 100. Fee should be 1.
+    // Player 1 cancels
+    client.cancel_match(&match_id, &player1);
+
+    // Contract should refund 99 to Player 1, and send 1 to admin (default treasury)
+    assert_eq!(token_client.balance(&player1), 999);
+    assert_eq!(token_client.balance(&admin), 1); // Admin starts with 0
+    assert_eq!(token_client.balance(&contract_id), 0);
+}
+
+#[test]
+fn test_cancellation_no_fee_if_no_deposit() {
+    let (env, contract_id, _oracle, player1, player2, token, admin) = setup();
+    let client = EscrowContractClient::new(&env, &contract_id);
+    let token_client = token_client(&env, &token);
+
+    let match_id = helpers::create_default_match(&client, &env, &player1, &player2, &token, "test_no_fee_game");
+
+    // Neither player deposits
+    // Player 1 cancels
+    client.cancel_match(&match_id, &player1);
+
+    // Player 1 should not be charged since they didn't deposit
+    assert_eq!(token_client.balance(&player1), 1000);
+    assert_eq!(token_client.balance(&admin), 0);
+    assert_eq!(token_client.balance(&contract_id), 0);
+}
+
+#[test]
+fn test_cancellation_fee_with_custom_config() {
+    let (env, contract_id, _oracle, player1, player2, token, admin) = setup();
+    let client = EscrowContractClient::new(&env, &contract_id);
+    let token_client = token_client(&env, &token);
+
+    let new_treasury = Address::generate(&env);
+
+    // Admin sets new config: 5% fee
+    let config = types::ProtocolConfig {
+        cancellation_fee_basis_points: 500, // 5%
+        treasury: new_treasury.clone(),
+    };
+
+    env.mock_all_auths();
+    client.set_protocol_config(&config);
+
+    let match_id = helpers::create_default_match(&client, &env, &player1, &player2, &token, "test_custom_fee_game");
+
+    // Player 2 deposits
+    client.deposit(&match_id, &player2);
+
+    // Player 1 cancels
+    client.cancel_match(&match_id, &player1);
+
+    // Player 2 should be refunded 95. Treasury gets 5.
+    assert_eq!(token_client.balance(&player2), 995);
+    assert_eq!(token_client.balance(&new_treasury), 5);
+    assert_eq!(token_client.balance(&contract_id), 0);
+}

contracts/escrow/src/tests/mod.rs

@@ -151,3 +151,4 @@ pub fn setup_with_four_players() -> (
 pub fn mint_player_balance(asset_client: &StellarAssetClient, player: &Address, amount: i128) {
     asset_client.mint(player, &amount);
 }
+mod cancellation_fee;