A smart contract that helps people HODL

hodl.sol

pragma solidity ^0.4.19;

// Copyright (c) 2017 Christian Calderon
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

contract HODL{
  struct Deposit {
    uint balance;
    uint maturity_date;
  }
  event newDeposit(address indexed withdrawer, uint indexed hodl_time, uint indexed amount);
  event Withdrawal(address indexed withdrawer, uint indexed amount);
  mapping(address => Deposit[]) deposits;

  function hodl(address owner, uint time_to_hodl) public payable {
    assert(msg.value > 0);
    assert(time_to_hodl > 0);
    assert(time_to_hodl <= 31557600); // one year
    Deposit memory d = Deposit(msg.value, block.timestamp + time_to_hodl);
    deposits[owner].push(d);
    newDeposit(owner, time_to_hodl, msg.value);
  }

  function withdraw() public {
    Deposit[] storage d = deposits[msg.sender];
    require(d.length > 0);
    uint amount_to_send = 0;
    for(uint i = 0; i < d.length; i++){
      Deposit storage d_i = d[i];
      if((d_i.balance > 0) && (d_i.maturity_date < block.timestamp)){
        amount_to_send += d_i.balance;
        d_i.balance = 0;
        d_i.maturity_date = 0;
      }
    }
    require(amount_to_send > 0);
    msg.sender.transfer(amount_to_send);
    Withdrawal(msg.sender, amount_to_send);
  }
}