Add `saturation` parameter

Add a parameter, `saturation` to the network-level configuration, under `SlotReservationConfig`. This parameter represents the percentage of total time before expiry that all addresses are eligible to reserve a slot. Total time is the duration between request creation and expiry. Valid range is [0, 99].

Note, this parameter is not yet used anywhere.

contracts/Configuration.sol

@@ -6,6 +6,7 @@ import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
 struct MarketplaceConfig {
   CollateralConfig collateral;
   ProofConfig proofs;
+  SlotReservationsConfig reservations;
 }
 
 struct CollateralConfig {
@@ -29,3 +30,10 @@ struct ProofConfig {
   // blocks. Should be a prime number to ensure there are no cycles.
   uint8 downtimeProduct;
 }
+
+struct SlotReservationsConfig {
+  // Percentage of total time before expiry that all addresses are eligible to
+  // reserve a slot. Total time is the duration between request creation and
+  // expiry. Valid range is [0, 99].
+  uint8 saturation;
+}

contracts/FuzzMarketplace.sol

@@ -10,7 +10,8 @@ contract FuzzMarketplace is Marketplace {
     Marketplace(
       MarketplaceConfig(
         CollateralConfig(10, 5, 3, 10),
-        ProofConfig(10, 5, 64, "", 67)
+        ProofConfig(10, 5, 64, "", 67),
+        SlotReservationsConfig(20)
       ),
       new TestToken(),
       new TestVerifier()

contracts/Marketplace.sol

@@ -59,7 +59,10 @@ contract Marketplace is SlotReservations, Proofs, StateRetrieval, Endian {
     MarketplaceConfig memory configuration,
     IERC20 token_,
     IGroth16Verifier verifier
-  ) Proofs(configuration.proofs, verifier) {
+  )
+    SlotReservations(configuration.reservations)
+    Proofs(configuration.proofs, verifier)
+  {
     _token = token_;
 
     require(

contracts/Requests.sol

@@ -10,7 +10,10 @@ struct Request {
   Content content;
   uint256 expiry; // amount of seconds since start of the request at which this request expires
   bytes32 nonce; // random nonce to differentiate between similar requests
-  uint8 expansion; // Percentage of addresses eligible to reserve a slot halfway between request creation and when all network addresses are eligible to participate. [1-100].
+  // Percentage of addresses eligible to reserve a slot halfway between request
+  // creation and when all network addresses are eligible to participate
+  // (saturation). Acceptable range is [1-100].
+  uint8 expansion;
 }
 
 struct Ask {

contracts/SlotReservations.sol

@@ -2,15 +2,22 @@
 pragma solidity 0.8.23;
 
 import "@openzeppelin/contracts/utils/structs/EnumerableSet.sol";
+import "./Configuration.sol";
 import "./Requests.sol";
 
 contract SlotReservations {
   using EnumerableSet for EnumerableSet.AddressSet;
 
   mapping(SlotId => EnumerableSet.AddressSet) internal _reservations;
+  SlotReservationsConfig private _config;
 
   uint8 private constant _MAX_RESERVATIONS = 3;
 
+  constructor(SlotReservationsConfig memory config) {
+    require(config.saturation <= 100, "saturation must be [0, 100]");
+    _config = config;
+  }
+
   function reserveSlot(SlotId slotId) public {
     address host = msg.sender;
     require(canReserveSlot(slotId), "Reservation not allowed");

contracts/TestSlotReservations.sol

@@ -6,6 +6,9 @@ import "./SlotReservations.sol";
 contract TestSlotReservations is SlotReservations {
   using EnumerableSet for EnumerableSet.AddressSet;
 
+  // solhint-disable-next-line no-empty-blocks
+  constructor(SlotReservationsConfig memory config) SlotReservations(config) {}
+
   function contains(SlotId slotId, address host) public view returns (bool) {
     return _reservations[slotId].contains(host);
   }

deploy/marketplace.js

@@ -14,7 +14,10 @@ const CONFIGURATION = {
     // `downtime` needs to be larger than `period` when running hardhat
     // in automine mode, because it can produce a block every second
     downtime: 64,
-    downtimeProduct: 67
+    downtimeProduct: 67,
+    // saturate addresses eligible to reserve slots 20% of the total time before
+    // expiry
+    saturation: 20
   },
 }
 

test/SlotReservations.test.js

@@ -4,6 +4,7 @@ const { exampleRequest } = require("./examples")
 const { requestId, slotId } = require("./ids")
 
 describe("SlotReservations", function () {
+  const saturation = 20
   let reservations
   let provider, address1, address2, address3
   let request
@@ -14,7 +15,7 @@ describe("SlotReservations", function () {
     let SlotReservations = await ethers.getContractFactory(
       "TestSlotReservations"
     )
-    reservations = await SlotReservations.deploy()
+    reservations = await SlotReservations.deploy({ saturation })
     ;[provider, address1, address2, address3] = await ethers.getSigners()
 
     request = await exampleRequest()

test/examples.js

@@ -16,6 +16,9 @@ const exampleConfiguration = () => ({
     zkeyHash: "",
     downtimeProduct: 67,
   },
+  reservations: {
+    saturation: 20,
+  },
 })
 
 const exampleRequest = async () => {

test/ids.js

@@ -2,7 +2,8 @@ const { ethers } = require("hardhat")
 const { keccak256, defaultAbiCoder } = ethers.utils
 
 function requestId(request) {
-  const Ask = "tuple(int64, uint256, uint256, uint256, uint256, uint256, uint64)"
+  const Ask =
+    "tuple(int64, uint256, uint256, uint256, uint256, uint256, uint64)"
   const Content = "tuple(string, bytes32)"
   const Request =
     "tuple(address, " + Ask + ", " + Content + ", uint256, bytes32, uint8)"
@@ -33,7 +34,7 @@ function requestToArray(request) {
       contentToArray(request.content),
       request.expiry,
       request.nonce,
-      request.expansion
+      request.expansion,
     ],
   ]
 }