[Feature] Heritable contract

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 payee, uint amount, uint balance);
+  event Received(address payer, uint amount, uint balance);
+
+
+  function SimpleSavingsWallet(uint _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, uint 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.
+  uint public heartbeatTimeout;
+
+  // Timestamp of the owner's death, as pronounced by the heir.
+  uint public timeOfDeath;
+
+
+  event HeirChanged(address indexed owner, address indexed newHeir);
+  event OwnerHeartbeated(address indexed owner);
+  event OwnerProclaimedDead(address indexed owner, address indexed heir, uint 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(uint _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(uint newHeartbeatTimeout) internal onlyOwner {
+    require(ownerLives());
+    heartbeatTimeout = newHeartbeatTimeout;
+  }
+
+  function ownerLives() internal view returns (bool) {
+    return timeOfDeath == 0;
+  }
+}

test/Heritable.js

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+'use strict'
+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.js

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+'use strict'
+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])))
+  })
+})