marketplace: re-instate currentCollateral()

So that a storage provider can know how much collateral is
returned when it calls freeSlot()

Author: markspanbroek

contracts/Marketplace.sol

@@ -67,9 +67,10 @@ contract Marketplace is SlotReservations, Proofs, StateRetrieval, Endian {
   }
 
   struct Slot {
-    SlotState state;
     RequestId requestId;
     uint64 slotIndex;
+    uint128 currentCollateral;
+    SlotState state;
     address host;
   }
 
@@ -100,6 +101,10 @@ contract Marketplace is SlotReservations, Proofs, StateRetrieval, Endian {
     return _vault;
   }
 
+  function currentCollateral(SlotId slotId) public view returns (uint128) {
+    return _slots[slotId].currentCollateral;
+  }
+
   function requestStorage(Request calldata request) public {
     RequestId id = request.id();
 
@@ -216,6 +221,8 @@ contract Marketplace is SlotReservations, Proofs, StateRetrieval, Endian {
     _vault.designate(fund, hostAccount, designated);
     _vault.flow(fund, clientAccount, hostAccount, rate);
 
+    slot.currentCollateral = collateral;
+
     _addToMySlots(slot.host, slotId);
 
     slot.state = SlotState.Filled;
@@ -323,6 +330,7 @@ contract Marketplace is SlotReservations, Proofs, StateRetrieval, Endian {
     _vault.designate(fund, validatorAccount, validatorReward);
     _vault.burnDesignated(fund, hostAccount, slashedAmount - validatorReward);
 
+    slot.currentCollateral -= slashedAmount;
     if (missingProofs(slotId) >= _config.collateral.maxNumberOfSlashes) {
       // When the number of slashings is at or above the allowed amount,
       // free the slot.
@@ -352,6 +360,7 @@ contract Marketplace is SlotReservations, Proofs, StateRetrieval, Endian {
     _removeFromMySlots(slot.host, slotId);
     _reservations[slotId].clear(); // We purge all the reservations for the slot
     slot.state = SlotState.Repair;
+    slot.currentCollateral = 0;
     slot.host = address(0);
     context.slotsFilled -= 1;
     emit SlotFreed(requestId, slot.slotIndex);
@@ -377,6 +386,7 @@ contract Marketplace is SlotReservations, Proofs, StateRetrieval, Endian {
     Request storage request = _requests[requestId];
     context.state = RequestState.Finished;
     Slot storage slot = _slots[slotId];
+    slot.currentCollateral = 0;
 
     _removeFromMyRequests(request.client, requestId);
     _removeFromMySlots(slot.host, slotId);
@@ -398,6 +408,7 @@ contract Marketplace is SlotReservations, Proofs, StateRetrieval, Endian {
     SlotId slotId
   ) private requestIsKnown(requestId) {
     Slot storage slot = _slots[slotId];
+    slot.currentCollateral = 0;
     _removeFromMySlots(slot.host, slotId);
     FundId fund = requestId.asFundId();
     AccountId account = _vault.hostAccount(slot.host, slot.slotIndex);

test/Marketplace.test.js

@@ -327,6 +327,13 @@ describe("Marketplace", function () {
       })
     })
 
+    it("updates the slot's current collateral", async function () {
+      await marketplace.reserveSlot(slot.request, slot.index)
+      await marketplace.fillSlot(slot.request, slot.index, proof)
+      const collateral = await marketplace.currentCollateral(slotId(slot))
+      expect(collateral).to.equal(collateralPerSlot(request))
+    })
+
     it("fails to retrieve a request of an empty slot", async function () {
       expect(marketplace.getActiveSlot(slotId(slot))).to.be.revertedWith(
         "Marketplace_SlotIsFree"
@@ -583,6 +590,12 @@ describe("Marketplace", function () {
       await token.approve(marketplace.address, collateral)
       await marketplace.fillSlot(slot.request, slot.index, proof)
     })
+
+    it("updates the slot's current collateral", async function () {
+      await waitUntilStarted(marketplace, request, proof, token)
+      await marketplace.freeSlot(id)
+      expect(await marketplace.currentCollateral(id)).to.equal(0)
+    })
   })
 
   describe("paying out a slot", function () {
@@ -637,6 +650,21 @@ describe("Marketplace", function () {
       expect(endBalance - startBalance).to.be.equal(expectedPartialPayout)
     })
 
+    it("updates the collateral when freeing a finished slot", async function () {
+      await waitUntilStarted(marketplace, request, proof, token)
+      await waitUntilFinished(marketplace, requestId(request))
+      await marketplace.freeSlot(slotId(slot))
+      expect(await marketplace.currentCollateral(slotId(slot))).to.equal(0)
+    })
+
+    it("updates the collateral when freeing a cancelled slot", async function () {
+      await marketplace.reserveSlot(slot.request, slot.index)
+      await marketplace.fillSlot(slot.request, slot.index, proof)
+      await waitUntilCancelled(marketplace, request)
+      await marketplace.freeSlot(slotId(slot))
+      expect(await marketplace.currentCollateral(slotId(slot))).to.equal(0)
+    })
+
     it("does not pay when the contract hasn't ended", async function () {
       await marketplace.reserveSlot(slot.request, slot.index)
       await marketplace.fillSlot(slot.request, slot.index, proof)
@@ -1191,7 +1219,13 @@ describe("Marketplace", function () {
         await marketplace.markProofAsMissing(id, missedPeriod)
         const endBalance = await marketplace.getSlotBalance(id)
         expect(endBalance).to.equal(startBalance - slashAmount)
+      })
 
+      it("updates the slot's current collateral", async function () {
+        await setNextBlockTimestamp(await currentTime())
+        await marketplace.markProofAsMissing(id, missedPeriod)
+        const currentCollateral = await marketplace.currentCollateral(id)
+        expect(currentCollateral).to.equal(collateral - slashAmount)
       })
 
       it("rewards validator when marking proof as missing", async function () {
@@ -1234,6 +1268,11 @@ describe("Marketplace", function () {
         expect(await marketplace.getSlotBalance(slotId(slot))).to.equal(0)
       })
 
+      it("updates the slot's current collateral", async function () {
+        const collateral = await marketplace.currentCollateral(slotId(slot))
+        expect(collateral).to.equal(0)
+      })
+
       it("resets missed proof counter", async function () {
         expect(await marketplace.missingProofs(slotId(slot))).to.equal(0)
       })