Alternative using timestamps to approximate teleport duration

blackhole/contracts/BlackHoleTimestamp.sol

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+pragma solidity ^0.4.22;
+
+import "openzeppelin-solidity/contracts/token/ERC20/ERC20.sol";
+
+/** @title BlackHole 
+ * 
+ * @dev Implementation of the BlackHole contract.
+ * It deadlocks ERC20 tockens and emit events on success.
+ */
+contract BlackHole {
+    event Opened();
+    event Teleport(uint amount, string note);
+    event Closed();
+
+    bool public closed = false;
+    ERC20 public erc20Contract;
+    uint public minimumAmount;
+    uint public startTime;
+    uint public eligibleCloseTime;
+
+    /** @dev Construction of the ETH BlackHole contract.
+     * @param _erc20Contract The address of the ERC20 contract to attract tockens from.
+     * @param _minDurationDays BlackHole can be closed after set days.
+     * @param _minimumAmount the smallest amount BlackHole can attract.
+     */
+    constructor(address _erc20Contract, uint _minDurationDays, uint _minimumAmount) public {
+        erc20Contract = ERC20(_erc20Contract);
+        minimumAmount = _minimumAmount;
+        startTime = block.timestamp; //start when contract is issued.
+        // Approximate. Does not account for leap seconds.
+        eligibleCloseTime = startTime + (_minDurationDays * 86400);
+        emit Opened();
+    }
+
+    /** @dev It closes the BlackHole if critical block has been reached.
+     */
+    function close() public {
+        require(!closed, "This BlackHole contract's active period has expired.");
+        require(block.timestamp >= eligibleCloseTime, "BlackHole hasn't reached the critical mass");
+        closed = true;
+        emit Closed();
+    }
+
+    /** @dev teleport attracts tokens and emit Teleport event
+     * @param note Teleport event note.
+     */
+    function teleport(string note) public {
+        uint amount = attract();
+        emit Teleport(amount, note);
+    }
+
+    function attract() private returns (uint amount){
+        require(!closed, "blackHole closed");
+        uint balance = erc20Contract.balanceOf(msg.sender);
+        uint allowed = erc20Contract.allowance(msg.sender, address(this));
+        require(allowed >= minimumAmount, "less than minimum amount");
+        require(balance == allowed, "blackHole must attract all your tokens");
+        require(erc20Contract.transferFrom(msg.sender, address(this), balance), "blackHole can't attract your tokens");
+        return balance;
+    }
+
+    // Approximate based on timestamp and 86400 epoch day
+    function daysLeft() constant returns (uint) {
+      return (eligibleCloseTime - block.timestamp) / 86400;
+    }
+
+}

blackhole/migrations/2_contract_ts_migration.js

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+const fs = require('fs');
+const check = require('../../utils/Check');
+
+var ERC20Token = artifacts.require("./ERC20Token.sol");
+var BlackHole = artifacts.require("./BlackHoleEosAccount.sol")
+
+module.exports = function (deployer) {
+  const configFile = "../config.json";
+  //check(fs.existsSync(configFile), "configuration file: " + configFile);
+  const config = JSON.parse(fs.readFileSync(configFile));
+  //console.log(config)
+  const name = "ERC20 Test";
+  const symbol = config.blackhole.symbol;
+  const decimals = config.blackhole.decimals;
+  const tokens = config.blackhole.tokens;
+  //const genesisBlock = config.blackhole.critic_block;
+  const duration = config.blackhole.minDuration;
+  const minimumAmount = config.blackhole.minimum_amount;
+
+  check(name, "ERC20 name: " + name);
+  check(symbol, "ERC20 symbol: " + symbol);
+  check(tokens, "ERC20 tokens: " + tokens);
+  check(decimals, "ERC20 decimals: " + decimals);
+  //check(genesisBlock, "BlackHole critical block: " + genesisBlock);
+  check(duration, "BlackHole duration: " + duration);
+  check(minimumAmount, "BlackHole minimum amount: " + minimumAmount);
+
+  deployer.deploy(ERC20Token, name, symbol, tokens, decimals).then(() => {
+    return deployer.deploy(BlackHole, ERC20Token.address, duration, minimumAmount);
+  })
+    .then(() => {
+      fs.writeFileSync('../erc20_address', ERC20Token.address);
+      fs.writeFileSync('../blackhole_address', BlackHole.address);
+    })
+};
+

config_ts.json

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+{
+    "blackhole": {
+        "websocket_provider": "ws://127.0.0.1:7545",
+        "minDuration": "30",
+        "minimum_amount": "100",
+        "symbol": "<ERC20TokenSymbol>",
+        "decimals": "4",
+        "tokens": "4"
+    },
+    "eosiotoken": {
+        "chain_id": "038f4b0fc8ff18a4f0842a8f0564611f6e96e8535901dd45e43ac8691a1c4dca",
+        "http_endpoint": "http://dev.cryptolions.io:38888",
+        "account": "<EOSTokenCreatorAccount",
+        "private_key": "<EOSTokenCreatorAccountPrivateKey"
+    }
+}