pragma solidity ^0.4.24;

contract SafeMath {
  function safeMul(uint a, uint b) internal returns (uint) {
    uint c = a * b;
    assert(a == 0 || c / a == b);
    return c;
  }

  function safeSub(uint a, uint b) internal returns (uint) {
    assert(b <= a);
    return a - b;
  }

  function safeAdd(uint a, uint b) internal returns (uint) {
    uint c = a + b;
    assert(c>=a && c>=b);
    return c;
  }
}

contract Token {
    bytes32 public standard;
    bytes32 public name;
    bytes32 public symbol;
    uint256 public totalSupply;
    uint8 public decimals;
    bool public allowTransactions;
    mapping (address => uint256) public balanceOf;
    mapping (address => mapping (address => uint256)) public allowance;
    function transfer(address _to, uint256 _value) returns (bool success);
    function approveAndCall(address _spender, uint256 _value, bytes _extraData) returns (bool success);
    function approve(address _spender, uint256 _value) returns (bool success);
    function transferFrom(address _from, address _to, uint256 _value) returns (bool success);
}

contract GaintDex is SafeMath {
  address public admin; //the admin address
  address public feeAccount; //the account that will receive fees
  uint public feeMake; //percentage times (1 ether)
  uint public feeTake; //percentage times (1 ether)
  mapping (address => mapping (address => uint)) public tokens; //mapping of token addresses to mapping of account balances (token=0 means Ether)
  mapping (address => mapping (bytes32 => bool)) public orders; //mapping of user accounts to mapping of order hashes to booleans (true = submitted by user, equivalent to offchain signature)
  mapping (address => mapping (bytes32 => uint)) public orderFills; //mapping of user accounts to mapping of order hashes to uints (amount of order that has been filled)

  event Order(address tokenGet, uint amountGet, address tokenGive, uint amountGive, uint expires, uint nonce, address user);
  event Cancel(address tokenGet, uint amountGet, address tokenGive, uint amountGive, uint expires, uint nonce, address user, uint8 v, bytes32 r, bytes32 s);
  event Trade(address tokenGet, uint amountGet, address tokenGive, uint amountGive, address get, address give);
  event Deposit(address token, address user, uint amount, uint balance);
  event Withdraw(address token, address user, uint amount, uint balance);

  constructor() {
    admin = msg.sender;
    feeAccount = msg.sender;
    feeMake = 700000000000000;
    feeTake = 700000000000000;
  }

  function changeAdmin(address admin_) {
    require(msg.sender == admin);
    admin = admin_;
  }

  function changeFeeAccount(address feeAccount_) {
    require(msg.sender == admin);
    feeAccount = feeAccount_;
  }

  function changeFeeMake(uint feeMake_) {
    require(msg.sender == admin);
    feeMake = feeMake_;
  }

  function changeFeeTake(uint feeTake_) {
    require(msg.sender == admin);
    feeTake = feeTake_;
  }

  function deposit() payable {
    tokens[0][msg.sender] = safeAdd(tokens[0][msg.sender], msg.value);
    Deposit(0, msg.sender, msg.value, tokens[0][msg.sender]);
  }

  function withdraw(uint amount) {
    require(tokens[0][msg.sender] >= amount);
    tokens[0][msg.sender] = safeSub(tokens[0][msg.sender], amount);
    require(msg.sender.call.value(amount)());
    Withdraw(0, msg.sender, amount, tokens[0][msg.sender]);
  }

  function depositToken(address token, uint amount) {
    //remember to call Token(address).approve(this, amount) or this contract will not be able to do the transfer on your behalf.
    require(token != 0);
    require(Token(token).transferFrom(msg.sender, this, amount));
    tokens[token][msg.sender] = safeAdd(tokens[token][msg.sender], amount);
    Deposit(token, msg.sender, amount, tokens[token][msg.sender]);
  }

  function withdrawToken(address token, uint amount) {
    require(token !=0 );
    require(tokens[token][msg.sender] >= amount);
    tokens[token][msg.sender] = safeSub(tokens[token][msg.sender], amount);
    require(Token(token).transfer(msg.sender, amount));
    Withdraw(token, msg.sender, amount, tokens[token][msg.sender]);
  }

  function balanceOf(address token, address user) constant returns (uint) {
    return tokens[token][user];
  }

  function trade(address tokenGet, uint amountGet, address tokenGive, uint amountGive, uint expires, uint nonce, address user, uint8 v, bytes32 r, bytes32 s, uint amount) {
    //amount is in amountGet terms
    bytes32 hash = keccak256(this, tokenGet, amountGet, tokenGive, amountGive, expires, nonce);
    require((ecrecover(keccak256("\x19Ethereum Signed Message:\n32", hash),v,r,s) == user) &&
       block.number <= expires && safeAdd(orderFills[user][hash], amount) <= amountGet);
    tradeBalances(tokenGet, amountGet, tokenGive, amountGive, user, amount);
    orderFills[user][hash] = safeAdd(orderFills[user][hash], amount);
    Trade(tokenGet, amount, tokenGive, amountGive * amount / amountGet, user, msg.sender);
  }

  function tradeBalances(address tokenGet, uint amountGet, address tokenGive, uint amountGive, address user, uint amount) private {
    uint feeMakeXfer = safeMul(amount, feeMake) / (1 ether);
    uint feeTakeXfer = safeMul(amount, feeTake) / (1 ether);
    
    tokens[tokenGet][msg.sender] = safeSub(tokens[tokenGet][msg.sender], safeAdd(amount, feeTakeXfer));
    tokens[tokenGet][user] = safeAdd(tokens[tokenGet][user], safeSub(amount, feeMakeXfer));
    tokens[tokenGet][feeAccount] = safeAdd(tokens[tokenGet][feeAccount], safeAdd(feeMakeXfer, feeTakeXfer));
    tokens[tokenGive][user] = safeSub(tokens[tokenGive][user], safeMul(amountGive, amount) / amountGet);
    tokens[tokenGive][msg.sender] = safeAdd(tokens[tokenGive][msg.sender], safeMul(amountGive, amount) / amountGet);
  }

  function testTrade(address tokenGet, uint amountGet, address tokenGive, uint amountGive, uint expires, uint nonce, address user, uint8 v, bytes32 r, bytes32 s, uint amount, address sender) constant returns(bool) {
    if (!(
      tokens[tokenGet][sender] >= amount &&
      availableVolume(tokenGet, amountGet, tokenGive, amountGive, expires, nonce, user, v, r, s) >= amount
    )) return false;
    return true;
  }

  function availableVolume(address tokenGet, uint amountGet, address tokenGive, uint amountGive, uint expires, uint nonce, address user, uint8 v, bytes32 r, bytes32 s) constant returns(uint) {
    bytes32 hash = keccak256(this, tokenGet, amountGet, tokenGive, amountGive, expires, nonce);
    if (!(
      (ecrecover(keccak256("\x19Ethereum Signed Message:\n32", hash),v,r,s) == user) &&
      block.number <= expires
    )) return 0;
    uint available1 = safeSub(amountGet, orderFills[user][hash]);
    uint available2 = safeMul(tokens[tokenGive][user], amountGet) / amountGive;
    if (available1<available2) return available1;
    return available2;
  }

  function amountFilled(address tokenGet, uint amountGet, address tokenGive, uint amountGive, uint expires, uint nonce, address user, uint8 v, bytes32 r, bytes32 s) constant returns(uint) {
    bytes32 hash = keccak256(this, tokenGet, amountGet, tokenGive, amountGive, expires, nonce);
    return orderFills[user][hash];
  }
}