Add refunds

contracts/common.sol

@@ -11,7 +11,7 @@ struct Ticket {
     /// The amount of funds to send.
     uint256 value;
     /// The timestamp when the ticket was registered
-    uint256 timestamp;
+    uint256 createdAt;
 }
 
 struct TicketsWithIndex {

contracts/l2.sol

@@ -16,12 +16,10 @@ struct L2Deposit {
 }
 
 // Authorized: all tickets in this batch are authorized but not claimed
-// Claimed: all tickets in this batch are claimed
-// Refunded: all tickets in this batch have been refunded, due to inactivity or provable fraud.
+// Withdrawn: all tickets in this batch are withdrawn (either claimed or refunded)
 enum BatchStatus {
     Authorized,
-    Claimed,
-    Refunded
+    Withdrawn
 }
 
 struct Batch {
@@ -37,10 +35,10 @@ uint256 constant safetyDelay = 60;
 
 contract L2 is SignatureChecker {
     Ticket[] public tickets;
-    // `batches` is used to record the fact that tickets with nonce between startingNonce and startingNonce + numTickets-1 are authorized, claimed or refunded.
+    // `batches` is used to record the fact that tickets with nonce between startingNonce and startingNonce + numTickets-1 are authorized or withdrawn.
     // Indexed by nonce
     mapping(uint256 => Batch) batches;
-    uint256 nextNonceToAuthorize = 0;
+    uint256 nextBatchStart = 0;
 
     function depositOnL2(L2Deposit calldata deposit) public payable {
         uint256 amountAvailable = deposit.trustedAmount;
@@ -64,7 +62,7 @@ contract L2 is SignatureChecker {
         Ticket memory ticket = Ticket({
             l1Recipient: deposit.l1Recipient,
             value: deposit.depositAmount,
-            timestamp: block.timestamp
+            createdAt: block.timestamp
         });
 
         // ticket's nonce is now its index in `tickets`
@@ -81,9 +79,9 @@ contract L2 is SignatureChecker {
             TicketsWithIndex memory ticketsWithIndex
         ) = createBatch(first, last);
         bytes32 message = keccak256(abi.encode(ticketsWithIndex));
-        uint256 earliestTimestamp = tickets[first].timestamp;
+        uint256 earliestTimestamp = tickets[first].createdAt;
 
-        require(nextNonceToAuthorize == first, "Batches must be gapless");
+        require(nextBatchStart == first, "Batches must be gapless");
         require(
             recoverSigner(message, signature) == lpAddress,
             "Must be signed by liquidity provider"
@@ -95,7 +93,7 @@ contract L2 is SignatureChecker {
         );
 
         batches[first] = batch;
-        nextNonceToAuthorize = last + 1;
+        nextBatchStart = last + 1;
     }
 
     function createBatch(uint256 first, uint256 last)
@@ -131,7 +129,7 @@ contract L2 is SignatureChecker {
             "safetyDelay must have passed since authorization timestamp"
         );
 
-        batch.status = BatchStatus.Claimed;
+        batch.status = BatchStatus.Withdrawn;
         batches[first] = batch;
         (bool sent, ) = lpAddress.call{value: batch.total}("");
         require(sent, "Failed to send Ether");
@@ -187,6 +185,31 @@ contract L2 is SignatureChecker {
             require(sent, "Failed to send Ether");
         }
 
-        batches[honestStartNonce].status = BatchStatus.Refunded;
+        batches[honestStartNonce].status = BatchStatus.Withdrawn;
+    }
+
+    /**
+     * @notice Refund all tickets with nonce >= nextBatchStart and nonce <= lastNonce
+     * @param lastNonce Nonce of the "expired" ticket aka a ticket that is past AuthorizationWindow
+     */
+    function refund(uint256 lastNonce) public {
+        require(
+            block.timestamp > tickets[lastNonce].createdAt + maxAuthDelay,
+            "maxAuthDelay must have passed since deposit"
+        );
+
+        require(
+            nextBatchStart <= lastNonce,
+            "The nonce must not be a part of a batch"
+        );
+        (Batch memory batch, ) = createBatch(nextBatchStart, lastNonce);
+        batches[nextBatchStart] = batch;
+        batch.status = BatchStatus.Withdrawn;
+        nextBatchStart = lastNonce + 1;
+
+        (bool sent, ) = tickets[lastNonce].l1Recipient.call{
+            value: tickets[lastNonce].value
+        }("");
+        require(sent, "Failed to send Ether");
     }
 }

src/constants.ts

@@ -1,5 +1,5 @@
 export const SIGNED_SWAPS_ABI_TYPE = [
-  "tuple(uint256 startIndex, tuple(address l1Recipient, uint256 value, uint256 timestamp)[]) ",
+  "tuple(uint256 startIndex, tuple(address l1Recipient, uint256 value, uint256 createdAt)[]) ",
 ];
 
 export const USE_ERC20 = process.env.USE_ERC20 === "true";

test/safe.test.ts

@@ -192,3 +192,21 @@ it("Handles a fraud proofs", async () => {
     ),
   );
 });
+
+it("Able to get a ticket refunded", async () => {
+  await deposit(0, 10);
+  await expect(customerL2.refund(0, { gasLimit })).to.be.rejectedWith(
+    "maxAuthDelay must have passed since deposit",
+  );
+  await ethers.provider.send("evm_increaseTime", [61]);
+  await waitForTx(customerL2.refund(0, { gasLimit }));
+  await waitForTx(customerL2.refund(1, { gasLimit }));
+  await expect(customerL2.refund(1, { gasLimit })).to.be.rejectedWith(
+    "The nonce must not be a part of a batch",
+  );
+
+  await deposit(2, 8);
+  await ethers.provider.send("evm_increaseTime", [61]);
+  // Refund 3rd and 4th deposit
+  await waitForTx(customerL2.refund(2, { gasLimit }));
+});