From c5fab40535c9345e5c72749db01a83ba9f95b274 Mon Sep 17 00:00:00 2001
From: Mark Spanbroek <mark@spanbroek.net>
Date: Tue, 15 Feb 2022 17:01:54 +0100
Subject: [PATCH] Account locking

---
 contracts/AccountLocks.sol     |  65 +++++++++++++
 contracts/TestAccountLocks.sol |  23 +++++
 test/AccountLocks.js           | 165 +++++++++++++++++++++++++++++++++
 test/examples.js               |  10 +-
 test/time.js                   |   6 ++
 5 files changed, 267 insertions(+), 2 deletions(-)
 create mode 100644 contracts/AccountLocks.sol
 create mode 100644 contracts/TestAccountLocks.sol
 create mode 100644 test/AccountLocks.js
 create mode 100644 test/time.js

diff --git a/contracts/AccountLocks.sol b/contracts/AccountLocks.sol
new file mode 100644
index 0000000..9417fad
--- /dev/null
+++ b/contracts/AccountLocks.sol
@@ -0,0 +1,65 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.0;
+
+contract AccountLocks {
+  uint256 public constant MAX_LOCKS_PER_ACCOUNT = 128;
+
+  mapping(bytes32 => Lock) private locks;
+  mapping(address => Account) private accounts;
+
+  function _createLock(bytes32 id, uint256 expiry) internal {
+    require(locks[id].owner == address(0), "Lock already exists");
+    locks[id] = Lock(msg.sender, expiry, false);
+  }
+
+  function _lock(address account, bytes32 lockId) internal {
+    require(locks[lockId].owner != address(0), "Lock does not exist");
+    bytes32[] storage accountLocks = accounts[account].locks;
+    removeInactiveLocks(accountLocks);
+    require(accountLocks.length < MAX_LOCKS_PER_ACCOUNT, "Max locks reached");
+    accountLocks.push(lockId);
+  }
+
+  function _unlock(bytes32 lockId) internal {
+    Lock storage lock = locks[lockId];
+    require(lock.owner != address(0), "Lock does not exist");
+    require(lock.owner == msg.sender, "Only lock creator can unlock");
+    lock.unlocked = true;
+  }
+
+  function _unlockAccount() internal {
+    bytes32[] storage accountLocks = accounts[msg.sender].locks;
+    removeInactiveLocks(accountLocks);
+    require(accountLocks.length == 0, "Account locked");
+  }
+
+  function removeInactiveLocks(bytes32[] storage lockIds) private {
+    uint256 index = 0;
+    while (true) {
+      if (index >= lockIds.length) {
+        return;
+      }
+      if (isInactive(locks[lockIds[index]])) {
+        lockIds[index] = lockIds[lockIds.length - 1];
+        lockIds.pop();
+      } else {
+        index++;
+      }
+    }
+  }
+
+  function isInactive(Lock storage lock) private view returns (bool) {
+    // solhint-disable-next-line not-rely-on-time
+    return lock.unlocked || lock.expiry <= block.timestamp;
+  }
+
+  struct Lock {
+    address owner;
+    uint256 expiry;
+    bool unlocked;
+  }
+
+  struct Account {
+    bytes32[] locks;
+  }
+}
diff --git a/contracts/TestAccountLocks.sol b/contracts/TestAccountLocks.sol
new file mode 100644
index 0000000..cf54020
--- /dev/null
+++ b/contracts/TestAccountLocks.sol
@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.0;
+
+import "./AccountLocks.sol";
+
+// exposes internal functions for testing
+contract TestAccountLocks is AccountLocks {
+  function createLock(bytes32 id, uint256 expiry) public {
+    _createLock(id, expiry);
+  }
+
+  function lock(address account, bytes32 id) public {
+    _lock(account, id);
+  }
+
+  function unlock(bytes32 id) public {
+    _unlock(id);
+  }
+
+  function unlockAccount() public {
+    _unlockAccount();
+  }
+}
diff --git a/test/AccountLocks.js b/test/AccountLocks.js
new file mode 100644
index 0000000..2cff736
--- /dev/null
+++ b/test/AccountLocks.js
@@ -0,0 +1,165 @@
+const { ethers } = require("hardhat")
+const { expect } = require("chai")
+const { exampleLock } = require("./examples")
+const { now } = require("./time")
+
+describe("Account Locks", function () {
+  let locks
+
+  beforeEach(async function () {
+    let AccountLocks = await ethers.getContractFactory("TestAccountLocks")
+    locks = await AccountLocks.deploy()
+  })
+
+  describe("creating a lock", function () {
+    it("allows creation of a lock with an expiry time", async function () {
+      let { id, expiry } = exampleLock()
+      await locks.createLock(id, expiry)
+    })
+
+    it("fails to create a lock with an existing id", async function () {
+      let { id, expiry } = exampleLock()
+      await locks.createLock(id, expiry)
+      await expect(locks.createLock(id, expiry + 1)).to.be.revertedWith(
+        "Lock already exists"
+      )
+    })
+  })
+
+  describe("locking an account", function () {
+    let lock
+
+    beforeEach(async function () {
+      lock = exampleLock()
+      await locks.createLock(lock.id, lock.expiry)
+    })
+
+    it("locks an account", async function () {
+      let [account] = await ethers.getSigners()
+      await locks.lock(account.address, lock.id)
+    })
+
+    it("fails to lock account when lock does not exist", async function () {
+      let [account] = await ethers.getSigners()
+      let nonexistent = exampleLock().id
+      await expect(locks.lock(account.address, nonexistent)).to.be.revertedWith(
+        "Lock does not exist"
+      )
+    })
+  })
+
+  describe("unlocking a lock", function () {
+    let lock
+
+    beforeEach(async function () {
+      lock = exampleLock()
+      await locks.createLock(lock.id, lock.expiry)
+    })
+
+    it("unlocks a lock", async function () {
+      await locks.unlock(lock.id)
+    })
+
+    it("fails to unlock a lock that does not exist", async function () {
+      let nonexistent = exampleLock().id
+      await expect(locks.unlock(nonexistent)).to.be.revertedWith(
+        "Lock does not exist"
+      )
+    })
+
+    it("fails to unlock by someone other than the creator", async function () {
+      let [_, other] = await ethers.getSigners()
+      await expect(locks.connect(other).unlock(lock.id)).to.be.revertedWith(
+        "Only lock creator can unlock"
+      )
+    })
+  })
+
+  describe("unlocking an account", function () {
+    it("unlocks an account that has not been locked", async function () {
+      await locks.unlockAccount()
+    })
+
+    it("unlocks an account whose locks have been unlocked", async function () {
+      let [account] = await ethers.getSigners()
+      let lock = exampleLock()
+      await locks.createLock(lock.id, lock.expiry)
+      await locks.lock(account.address, lock.id)
+      await locks.unlock(lock.id)
+      await locks.unlockAccount()
+    })
+
+    it("unlocks an account whose locks have expired", async function () {
+      let [account] = await ethers.getSigners()
+      let lock = { ...exampleLock(), expiry: now() }
+      await locks.createLock(lock.id, lock.expiry)
+      await locks.lock(account.address, lock.id)
+      await locks.unlockAccount()
+    })
+
+    it("unlocks multiple accounts tied to the same lock", async function () {
+      let [account0, account1] = await ethers.getSigners()
+      let lock = exampleLock()
+      await locks.createLock(lock.id, lock.expiry)
+      await locks.lock(account0.address, lock.id)
+      await locks.lock(account1.address, lock.id)
+      await locks.unlock(lock.id)
+      await locks.connect(account0).unlockAccount()
+      await locks.connect(account1).unlockAccount()
+    })
+
+    it("fails to unlock when some locks are still locked", async function () {
+      let [account] = await ethers.getSigners()
+      let [lock1, lock2] = [exampleLock(), exampleLock()]
+      await locks.createLock(lock1.id, lock1.expiry)
+      await locks.createLock(lock2.id, lock2.expiry)
+      await locks.lock(account.address, lock1.id)
+      await locks.lock(account.address, lock2.id)
+      await locks.unlock(lock1.id)
+      await expect(locks.unlockAccount()).to.be.revertedWith("Account locked")
+    })
+  })
+
+  describe("limits", function () {
+    let maxlocks
+    let account
+
+    beforeEach(async function () {
+      maxlocks = await locks.MAX_LOCKS_PER_ACCOUNT()
+      ;[account] = await ethers.getSigners()
+    })
+
+    async function addLock() {
+      let { id, expiry } = exampleLock()
+      await locks.createLock(id, expiry)
+      await locks.lock(account.address, id)
+      return id
+    }
+
+    it("supports a limited amount of locks per account", async function () {
+      for (let i = 0; i < maxlocks; i++) {
+        await addLock()
+      }
+      await expect(addLock()).to.be.revertedWith("Max locks reached")
+    })
+
+    it("doesn't count unlocked locks towards the limit", async function () {
+      for (let i = 0; i < maxlocks; i++) {
+        let id = await addLock()
+        await locks.unlock(id)
+      }
+      await expect(addLock()).not.to.be.reverted
+    })
+
+    it("handles maximum amount of locks within gas limit", async function () {
+      let ids = []
+      for (let i = 0; i < maxlocks; i++) {
+        ids.push(await addLock())
+      }
+      for (let id of ids) {
+        await locks.unlock(id)
+      }
+      await locks.unlockAccount()
+    })
+  })
+})
diff --git a/test/examples.js b/test/examples.js
index cf1a8ba..9ec4da6 100644
--- a/test/examples.js
+++ b/test/examples.js
@@ -1,4 +1,5 @@
 const { ethers } = require("hardhat")
+const { now, hours } = require("./time")
 
 const exampleRequest = () => ({
   duration: 150, // 150 blocks ≈ half an hour
@@ -11,7 +12,12 @@ const exampleRequest = () => ({
 
 const exampleBid = () => ({
   price: 42,
-  bidExpiry: Math.round(Date.now() / 1000) + 60 * 60, // 1 hour from now
+  bidExpiry: now() + hours(1),
 })
 
-module.exports = { exampleRequest, exampleBid }
+const exampleLock = () => ({
+  id: ethers.utils.randomBytes(32),
+  expiry: now() + hours(1),
+})
+
+module.exports = { exampleRequest, exampleBid, exampleLock }
diff --git a/test/time.js b/test/time.js
new file mode 100644
index 0000000..6144f12
--- /dev/null
+++ b/test/time.js
@@ -0,0 +1,6 @@
+const now = () => Math.round(Date.now() / 1000)
+const hours = (amount) => amount * minutes(60)
+const minutes = (amount) => amount * seconds(60)
+const seconds = (amount) => amount
+
+module.exports = { now, hours, minutes, seconds }