pragma solidity ^0.4.11;
/**
* Eth Hodler (f.k.a. Hodl DAO) and ERC20 token
* Author: CurrencyTycoon on GitHub
* License: MIT
* Date: 2017
*
* Deploy with the following args:
* "Eth Hodler", 18, "EHDL"
*
*/
contract EthHodler {
    /* ERC20 Public variables of the token */
    string public constant version = 'HDAO 0.7';
    string public name;
    string public symbol;
    uint8 public decimals;
    uint256 public totalSupply;

    /* ERC20 This creates an array with all balances */
    mapping (address => uint256) public balanceOf;
    mapping (address => mapping (address => uint256)) public allowance;


    /* store the block number when a withdrawal has been requested*/
    mapping (address => withdrawalRequest) public withdrawalRequests;
    struct withdrawalRequest {
    uint sinceTime;
    uint256 amount;
    }

    /**
     * feePot collects fees from quick withdrawals. This gets re-distributed to slow-withdrawals
    */
    uint256 public feePot;

    uint public timeWait = 30 days;
    //uint public timeWait = 1 minutes; // uncomment for TestNet

    uint256 public constant initialSupply = 0;

    /**
     * ERC20 events these generate a public event on the blockchain that will notify clients
    */
    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);

    event WithdrawalQuick(address indexed by, uint256 amount, uint256 fee); // quick withdrawal done
    event IncorrectFee(address indexed by, uint256 feeRequired);  // incorrect fee paid for quick withdrawal
    event WithdrawalStarted(address indexed by, uint256 amount);
    event WithdrawalDone(address indexed by, uint256 amount, uint256 reward); // amount is the amount that was used to calculate reward
    event WithdrawalPremature(address indexed by, uint timeToWait); // Needs to wait timeToWait before withdrawal unlocked
    event Deposited(address indexed by, uint256 amount);

    /**
     * Initializes contract with initial supply tokens to the creator of the contract
     * In our case, there's no initial supply. Tokens will be created as ether is sent
     * to the fall-back function. Then tokens are burned when ether is withdrawn.
     */
    function EthHodler(
    string tokenName,
    uint8 decimalUnits,
    string tokenSymbol
    ) {

        balanceOf[msg.sender] = initialSupply;              // Give the creator all initial tokens (0 in this case)
        totalSupply = initialSupply;                        // Update total supply (0 in this case)
        name = tokenName;                                   // Set the name for display purposes
        symbol = tokenSymbol;                               // Set the symbol for display purposes
        decimals = decimalUnits;                            // Amount of decimals for display purposes
    }

    /**
     * notPendingWithdrawal modifier guards the function from executing when a
     * withdrawal has been requested and is currently pending
     */
    modifier notPendingWithdrawal {
        if (withdrawalRequests[msg.sender].sinceTime > 0) throw;
        _;
    }

    /** ERC20 - transfer sends tokens
     * @notice send `_value` token to `_to` from `msg.sender`
     * @param _to The address of the recipient
     * @param _value The amount of token to be transferred
     * @return Whether the transfer was successful or not
     */
    function transfer(address _to, uint256 _value) notPendingWithdrawal {
        if (balanceOf[msg.sender] < _value) throw;           // Check if the sender has enough
        if (balanceOf[_to] + _value < balanceOf[_to]) throw; // Check for overflows
        if (withdrawalRequests[_to].sinceTime > 0) throw;    // can't move tokens when _to is pending withdrawal
        balanceOf[msg.sender] -= _value;                     // Subtract from the sender
        balanceOf[_to] += _value;                            // Add the same to the recipient
        Transfer(msg.sender, _to, _value);                   // Notify anyone listening that this transfer took place
    }

    /** ERC20 approve allows another contract to spend some tokens in your behalf
     * @notice `msg.sender` approves `_spender` to spend `_value` tokens
     * @param _spender The address of the account able to transfer the tokens
     * @param _value The amount of tokens to be approved for transfer
     * @return Whether the approval was successful or not
     *
     *
     * Note, there are some edge-cases with the ERC-20 approve mechanism. In this case a 'bounds check'
     * was added to make sure Alice cant' approve Bob for more tokens than she has.
     * The assumptions are that these scenarios could still happen if not mitigated by Alice:
     *
     * Scenario 1:
     *
     * The following scenario could be the expected outcome by Alice, but if not, Alice would need to set
     * her approval to Bob to 0 before Alice purchases more tokens.
     *
     *  1. Alice has 100 tokens.
     *  2. Alice approves 50 tokens for Bob.
     *  3. Alice approves 100 tokens for Charles
     *  4. Bob calls transferFrom and receives his 50 tokens.
     *  5. Charles calls transferFrom and receives the remaining 50 tokens
     *  6. Charles still has an approval for 50 more tokens from Alice, even though she now owns 0 tokens.
     *  7. Alice purchases 50 more tokens
     *  8. Charles sees this, and immediately calls transferFrom and receives those 50 tokens.
     *
     * Scenario 2:
     *
     * This is a race condition. To mitigate this problem, Alice should set the allowance to 0 in step 2,
     * then wait until it's mined, then if Bob didn't take the 100 she can set to 50. (Otherwise Bob may
     * potentially get 150 tokens)
     *
     *
     *  1. Alice approves Bob for 100,
     *  2. Alice changes it to 50
     *  3. Bob sees the change in the mempool before it's mined, and sends a new transaction
     *     that will hopefully win the race and withdraw the 100 first, meanwhile the 50 will
     *     be mined after and allow Bob to withdraw another 50.
     *
     *
     */
    function approve(address _spender, uint256 _value) notPendingWithdrawal
    returns (bool success) {

        // The following line has been commented out after peer review #2
        // It may be possible that Alice can pre-approve the recipient in advance, before she has a balance.
        // eg. Alice may approve a total lifetime amount for her child to spend, but only fund her account monthly.
        // It also allows her to have multiple equal approvees

        //if (balanceOf[msg.sender] < _value) return false; // Don't allow more than they currently have (bounds check)

        // To change the approve amount you first have to reduce the addresses´
        //  allowance to zero by calling `approve(_spender,0)` if it is not
        //  already 0 to mitigate the race condition described here:
        //  https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
        if ((_value != 0) && (allowance[msg.sender][_spender] != 0)) throw;
        allowance[msg.sender][_spender] = _value;
        Approval(msg.sender, _spender, _value);
        return true;                                      // we must return a bool as part of the ERC20
    }


    /**
     * ERC-20 Approves and then calls the receiving contract
    */
    function approveAndCall(address _spender, uint256 _value, bytes _extraData) notPendingWithdrawal
    returns (bool success) {

        if (!approve(_spender, _value)) return false;

        //call the receiveApproval function on the contract you want to be notified. This crafts the function signature manually so one doesn't have to include a contract in here just for this.
        //receiveApproval(address _from, uint256 _value, address _tokenContract, bytes _extraData)
        //it is assumed that when does this that the call *should* succeed, otherwise one would use vanilla approve instead.
        if(!_spender.call(bytes4(bytes32(sha3("receiveApproval(address,uint256,address,bytes)"))), msg.sender, _value, this, _extraData)) {
            throw;
        }
        return true;
    }

    /**
     * ERC20 A contract attempts to get the coins. Note: We are not allowing a transfer if
     * either the from or to address is pending withdrawal
     * @notice send `_value` token to `_to` from `_from` on the condition it is approved by `_from`
     * @param _from The address of the sender
     * @param _to The address of the recipient
     * @param _value The amount of token to be transferred
     * @return Whether the transfer was successful or not
     */
    function transferFrom(address _from, address _to, uint256 _value)
    returns (bool success) {
        // note that we can't use notPendingWithdrawal modifier here since this function does a transfer
        // on the behalf of _from
        if (withdrawalRequests[_from].sinceTime > 0) throw;   // can't move tokens when _from is pending withdrawal
        if (withdrawalRequests[_to].sinceTime > 0) throw;     // can't move tokens when _to is pending withdrawal
        if (balanceOf[_from] < _value) throw;                 // Check if the sender has enough
        if (balanceOf[_to] + _value < balanceOf[_to]) throw;  // Check for overflows
        if (_value > allowance[_from][msg.sender]) throw;     // Check allowance
        balanceOf[_from] -= _value;                           // Subtract from the sender
        balanceOf[_to] += _value;                             // Add the same to the recipient
        allowance[_from][msg.sender] -= _value;
        Transfer(_from, _to, _value);
        return true;
    }

    /**
     * withdrawalInitiate initiates the withdrawal by going into a waiting period
     * It remembers the block number & amount held at the time of request.
     * Tokens cannot be moved out during the waiting period, locking the tokens until then.
     * After the waiting period finishes, the call withdrawalComplete
     *
     * Gas: 64490
     *
     */
    function withdrawalInitiate() notPendingWithdrawal {
        WithdrawalStarted(msg.sender, balanceOf[msg.sender]);
        withdrawalRequests[msg.sender] = withdrawalRequest(now, balanceOf[msg.sender]);
    }

    /**
     * withdrawalComplete is called after the waiting period. The ether will be
     * returned to the caller and the tokens will be burned.
     * A reward will be issued based on the current amount in the feePot, relative to the
     * amount that was requested for withdrawal when withdrawalInitiate() was called.
     *
     * Gas: 30946
     */
    function withdrawalComplete() returns (bool) {
        withdrawalRequest r = withdrawalRequests[msg.sender];
        if (r.sinceTime == 0) throw;
        if ((r.sinceTime + timeWait) > now) {
            // holder needs to wait some more blocks
            WithdrawalPremature(msg.sender, r.sinceTime + timeWait - now);
            return false;
        }
        uint256 amount = withdrawalRequests[msg.sender].amount;
        uint256 reward = calculateReward(r.amount);
        withdrawalRequests[msg.sender].sinceTime = 0;   // This will unlock the holders tokens
        withdrawalRequests[msg.sender].amount = 0;      // clear the amount that was requested

        if (reward > 0) {
            if (feePot - reward > feePot) {             // underflow check
                feePot = 0;
            } else {
                feePot -= reward;
            }
        }
        doWithdrawal(reward);                           // burn the tokens and send back the ether
        WithdrawalDone(msg.sender, amount, reward);
        return true;

    }

    /**
     * Reward is based on the amount held, relative to total supply of tokens.
     */
    function calculateReward(uint256 v) constant returns (uint256) {
        uint256 reward = 0;
        if (feePot > 0) {
            reward = feePot * v / totalSupply; // assuming that if feePot > 0 then also totalSupply > 0
        }
        return reward;
    }

    /** calculate the fee for quick withdrawal
     */
    function calculateFee(uint256 v) constant returns  (uint256) {
        uint256 feeRequired = v / 100; // 1%
        return feeRequired;
    }

    /**
     * Quick withdrawal, needs to send ether to this function for the fee.
     *
     * Gas use: ? (including call to processWithdrawal)
    */
    function quickWithdraw() payable notPendingWithdrawal returns (bool) {
        uint256 amount = balanceOf[msg.sender];
        if (amount == 0) throw;
        // calculate required fee
        uint256 feeRequired = calculateFee(amount);
        if (msg.value != feeRequired) {
            IncorrectFee(msg.sender, feeRequired);   // notify the exact fee that needs to be sent
            throw;
        }
        feePot += msg.value;                         // add fee to the feePot
        doWithdrawal(0);                             // withdraw, 0 reward
        WithdrawalDone(msg.sender, amount, 0);
        return true;
    }

    /**
     * do withdrawal
     */
    function doWithdrawal(uint256 extra) internal {
        uint256 amount = balanceOf[msg.sender];
        if (amount == 0) throw;                      // cannot withdraw
        if (amount + extra > this.balance) {
            throw;                                   // contract doesn't have enough balance
        }

        balanceOf[msg.sender] = 0;
        if (totalSupply < totalSupply - amount) {
            throw;                                   // don't let it underflow (should not happen since amount <= totalSupply)
        } else {
            totalSupply -= amount;                   // deflate the supply!
        }
        Transfer(msg.sender, 0, amount);             // burn baby burn
        if (!msg.sender.send(amount + extra)) throw; // return back the ether or rollback if failed
    }


    /**
     * Fallback function when sending ether to the contract
     * Gas use: 65051
    */
    function () payable notPendingWithdrawal {
        uint256 amount = msg.value;         // amount that was sent
        if (amount == 0) throw;             // need to send some ETH
        balanceOf[msg.sender] += amount;    // mint new tokens
        totalSupply += amount;              // track the supply
        Transfer(0, msg.sender, amount);    // notify of the event
        Deposited(msg.sender, amount);
    }
}