Merge pull request OpenZeppelin#680 from ajsantander/azavalla-feature/inheritable-contract

Azavalla feature/inheritable contract

Author: eternauta1337

contracts/examples/SimpleSavingsWallet.sol

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+pragma solidity ^0.4.11;
+
+import "../ownership/Heritable.sol";
+
+
+/**
+ * @title SimpleSavingsWallet
+ * @dev Simplest form of savings wallet whose ownership can be claimed by a heir
+ * if owner dies.
+ * In this example, we take a very simple savings wallet providing two operations
+ * (to send and receive funds) and extend its capabilities by making it Heritable.
+ * The account that creates the contract is set as owner, who has the authority to
+ * choose an heir account. Heir account can reclaim the contract ownership in the
+ * case that the owner dies.
+ */
+contract SimpleSavingsWallet is Heritable {
+
+  event Sent(address indexed payee, uint256 amount, uint256 balance);
+  event Received(address indexed payer, uint256 amount, uint256 balance);
+
+
+  function SimpleSavingsWallet(uint256 _heartbeatTimeout) Heritable(_heartbeatTimeout) public {}
+  
+  /**
+   * @dev wallet can receive funds.
+   */
+  function () public payable {
+    Received(msg.sender, msg.value, this.balance);
+  }
+
+  /**
+   * @dev wallet can send funds
+   */
+  function sendTo(address payee, uint256 amount) public onlyOwner {
+    require(payee != 0 && payee != address(this));
+    require(amount > 0);
+    payee.transfer(amount);
+    Sent(payee, amount, this.balance);
+  }
+}

contracts/ownership/Heritable.sol

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+pragma solidity ^0.4.11;
+
+
+import "./Ownable.sol";
+
+
+/**
+ * @title Heritable
+ * @dev The Heritable contract provides ownership transfer capabilities, in the
+ * case that the current owner stops "heartbeating". Only the heir can pronounce the
+ * owner's death.
+ */
+contract Heritable is Ownable {
+  address public heir;
+
+  // Time window the owner has to notify they are alive.
+  uint256 public heartbeatTimeout;
+
+  // Timestamp of the owner's death, as pronounced by the heir.
+  uint256 public timeOfDeath;
+
+  event HeirChanged(address indexed owner, address indexed newHeir);
+  event OwnerHeartbeated(address indexed owner);
+  event OwnerProclaimedDead(address indexed owner, address indexed heir, uint256 timeOfDeath);
+  event HeirOwnershipClaimed(address indexed previousOwner, address indexed newOwner);
+
+
+  /**
+   * @dev Throw an exception if called by any account other than the heir's.
+   */
+  modifier onlyHeir() {
+    require(msg.sender == heir);
+    _;
+  }
+
+
+  /**
+   * @notice Create a new Heritable Contract with heir address 0x0.
+   * @param _heartbeatTimeout time available for the owner to notify they are alive,
+   * before the heir can take ownership.
+   */
+  function Heritable(uint256 _heartbeatTimeout) public {
+    setHeartbeatTimeout(_heartbeatTimeout);
+  }
+
+  function setHeir(address newHeir) public onlyOwner {
+    require(newHeir != owner);
+    heartbeat();
+    HeirChanged(owner, newHeir);
+    heir = newHeir;
+  }
+
+  /**
+   * @dev set heir = 0x0
+   */
+  function removeHeir() public onlyOwner {
+    heartbeat();
+    heir = 0;
+  }
+
+  /**
+   * @dev Heir can pronounce the owners death. To claim the ownership, they will
+   * have to wait for `heartbeatTimeout` seconds.
+   */
+  function proclaimDeath() public onlyHeir {
+    require(ownerLives());
+    OwnerProclaimedDead(owner, heir, timeOfDeath);
+    timeOfDeath = now;
+  }
+
+  /**
+   * @dev Owner can send a heartbeat if they were mistakenly pronounced dead.
+   */
+  function heartbeat() public onlyOwner {
+    OwnerHeartbeated(owner);
+    timeOfDeath = 0;
+  }
+
+  /**
+   * @dev Allows heir to transfer ownership only if heartbeat has timed out.
+   */
+  function claimHeirOwnership() public onlyHeir {
+    require(!ownerLives());
+    require(now >= timeOfDeath + heartbeatTimeout);
+    OwnershipTransferred(owner, heir);
+    HeirOwnershipClaimed(owner, heir);
+    owner = heir;
+    timeOfDeath = 0;
+  }
+
+  function setHeartbeatTimeout(uint256 newHeartbeatTimeout) internal onlyOwner {
+    require(ownerLives());
+    heartbeatTimeout = newHeartbeatTimeout;
+  }
+
+  function ownerLives() internal view returns (bool) {
+    return timeOfDeath == 0;
+  }
+}

test/Heritable.test.js

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+import increaseTime from './helpers/increaseTime';
+import expectThrow from './helpers/expectThrow';
+
+const NULL_ADDRESS = '0x0000000000000000000000000000000000000000';
+
+const Heritable = artifacts.require('../contracts/ownership/Heritable.sol');
+
+contract('Heritable', function (accounts) {
+  let heritable;
+  let owner;
+
+  beforeEach(async function () {
+    heritable = await Heritable.new(4141);
+    owner = await heritable.owner();
+  });
+
+  it('should start off with an owner, but without heir', async function () {
+    const heir = await heritable.heir();
+
+    assert.equal(typeof (owner), 'string');
+    assert.equal(typeof (heir), 'string');
+    assert.notStrictEqual(
+      owner, NULL_ADDRESS,
+      'Owner shouldn\'t be the null address'
+    );
+    assert.isTrue(
+      heir === NULL_ADDRESS,
+      'Heir should be the null address'
+    );
+  });
+
+  it('only owner should set heir', async function () {
+    const newHeir = accounts[1];
+    const someRandomAddress = accounts[2];
+    assert.isTrue(owner !== someRandomAddress);
+
+    await heritable.setHeir(newHeir, { from: owner });
+    await expectThrow(heritable.setHeir(newHeir, { from: someRandomAddress }));
+  });
+
+  it('owner can remove heir', async function () {
+    const newHeir = accounts[1];
+    await heritable.setHeir(newHeir, { from: owner });
+    let heir = await heritable.heir();
+
+    assert.notStrictEqual(heir, NULL_ADDRESS);
+    await heritable.removeHeir();
+    heir = await heritable.heir();
+    assert.isTrue(heir === NULL_ADDRESS);
+  });
+
+  it('heir can claim ownership only if owner is dead and timeout was reached', async function () {
+    const heir = accounts[1];
+    await heritable.setHeir(heir, { from: owner });
+    await expectThrow(heritable.claimHeirOwnership({ from: heir }));
+
+    await heritable.proclaimDeath({ from: heir });
+    await increaseTime(1);
+    await expectThrow(heritable.claimHeirOwnership({ from: heir }));
+
+    await increaseTime(4141);
+    await heritable.claimHeirOwnership({ from: heir });
+    assert.isTrue(await heritable.heir() === heir);
+  });
+
+  it('heir can\'t claim ownership if owner heartbeats', async function () {
+    const heir = accounts[1];
+    await heritable.setHeir(heir, { from: owner });
+
+    await heritable.proclaimDeath({ from: heir });
+    await heritable.heartbeat({ from: owner });
+    await expectThrow(heritable.claimHeirOwnership({ from: heir }));
+
+    await heritable.proclaimDeath({ from: heir });
+    await increaseTime(4141);
+    await heritable.heartbeat({ from: owner });
+    await expectThrow(heritable.claimHeirOwnership({ from: heir }));
+  });
+
+  it('should log events appropriately', async function () {
+    const heir = accounts[1];
+
+    const setHeirLogs = (await heritable.setHeir(heir, { from: owner })).logs;
+    const setHeirEvent = setHeirLogs.find(e => e.event === 'HeirChanged');
+
+    assert.isTrue(setHeirEvent.args.owner === owner);
+    assert.isTrue(setHeirEvent.args.newHeir === heir);
+
+    const heartbeatLogs = (await heritable.heartbeat({ from: owner })).logs;
+    const heartbeatEvent = heartbeatLogs.find(e => e.event === 'OwnerHeartbeated');
+
+    assert.isTrue(heartbeatEvent.args.owner === owner);
+
+    const proclaimDeathLogs = (await heritable.proclaimDeath({ from: heir })).logs;
+    const ownerDeadEvent = proclaimDeathLogs.find(e => e.event === 'OwnerProclaimedDead');
+
+    assert.isTrue(ownerDeadEvent.args.owner === owner);
+    assert.isTrue(ownerDeadEvent.args.heir === heir);
+
+    await increaseTime(4141);
+    const claimHeirOwnershipLogs = (await heritable.claimHeirOwnership({ from: heir })).logs;
+    const ownershipTransferredEvent = claimHeirOwnershipLogs.find(e => e.event === 'OwnershipTransferred');
+    const heirOwnershipClaimedEvent = claimHeirOwnershipLogs.find(e => e.event === 'HeirOwnershipClaimed');
+
+    assert.isTrue(ownershipTransferredEvent.args.previousOwner === owner);
+    assert.isTrue(ownershipTransferredEvent.args.newOwner === heir);
+    assert.isTrue(heirOwnershipClaimedEvent.args.previousOwner === owner);
+    assert.isTrue(heirOwnershipClaimedEvent.args.newOwner === heir);
+  });
+});

test/SimpleSavingsWallet.test.js

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+
+import expectThrow from './helpers/expectThrow';
+
+const SimpleSavingsWallet = artifacts.require('../contracts/examples/SimpleSavingsWallet.sol');
+
+contract('SimpleSavingsWallet', function (accounts) {
+  let savingsWallet;
+  let owner;
+
+  const paymentAmount = 4242;
+ 
+  beforeEach(async function () {
+    savingsWallet = await SimpleSavingsWallet.new(4141);
+    owner = await savingsWallet.owner();
+  });
+
+  it('should receive funds', async function () {
+    await web3.eth.sendTransaction({ from: owner, to: savingsWallet.address, value: paymentAmount });
+    assert.isTrue((new web3.BigNumber(paymentAmount)).equals(web3.eth.getBalance(savingsWallet.address)));
+  });
+
+  it('owner can send funds', async function () {
+    // Receive payment so we have some money to spend.
+    await web3.eth.sendTransaction({ from: accounts[9], to: savingsWallet.address, value: 1000000 });
+    await expectThrow(savingsWallet.sendTo(0, paymentAmount, { from: owner }));
+    await expectThrow(savingsWallet.sendTo(savingsWallet.address, paymentAmount, { from: owner }));
+    await expectThrow(savingsWallet.sendTo(accounts[1], 0, { from: owner }));
+
+    const balance = web3.eth.getBalance(accounts[1]);
+    await savingsWallet.sendTo(accounts[1], paymentAmount, { from: owner });
+    assert.isTrue(balance.plus(paymentAmount).equals(web3.eth.getBalance(accounts[1])));
+  });
+});