pragma solidity ^0.4.23;


/**
* @title ERC20Basic
* @dev Simpler version of ERC20 interface
*/
contract ERC20Basic {
function totalSupply() public view returns (uint256);
function balanceOf(address who) public view returns (uint256);
function transfer(address to, uint256 value) public returns (bool);
event Transfer(address indexed from, address indexed to, uint256 value);
}



/**
* @title SafeMath
* @dev Math operations with safety checks that throw on error
*/
library SafeMath {

/**
* @dev Multiplies two numbers, throws on overflow.
*/
function mul(uint256 a, uint256 b) internal pure returns (uint256 c) {
// Gas optimization: this is cheaper than asserting 'a' not being zero, but the
// benefit is lost if 'b' is also tested.

if (a == 0) {
return 0;
}

c = a * b;
assert(c / a == b);
return c;
}

/**
* @dev Integer division of two numbers, truncating the quotient.
*/
function div(uint256 a, uint256 b) internal pure returns (uint256) {
// assert(b > 0); // Solidity automatically throws when dividing by 0
// uint256 c = a / b;
// assert(a == b * c + a % b); // There is no case in which this doesn't hold
return a / b;
}

/**
* @dev Subtracts two numbers, throws on overflow (i.e. if subtrahend is greater than minuend).
*/
function sub(uint256 a, uint256 b) internal pure returns (uint256) {
assert(b <= a);
return a - b;
}

/**
* @dev Adds two numbers, throws on overflow.
*/
function add(uint256 a, uint256 b) internal pure returns (uint256 c) {
c = a + b;
assert(c >= a);
return c;
}
}



/**
* @title Basic token
* @dev Basic version of StandardToken, with no allowances.
*/
contract BasicToken is ERC20Basic {
using SafeMath for uint256;

mapping(address => uint256) balances;

uint256 totalSupply_;

/**
* @dev total number of tokens in existence
*/
function totalSupply() public view returns (uint256) {
return totalSupply_;
}

/**
* @dev transfer token for a specified address
* @param _to The address to transfer to.
* @param _value The amount to be transferred.
*/
function transfer(address _to, uint256 _value) public returns (bool) {
require(_to != address(0));
require(_value <= balances[msg.sender]);

balances[msg.sender] = balances[msg.sender].sub(_value);
balances[_to] = balances[_to].add(_value);
emit Transfer(msg.sender, _to, _value);
return true;
}

/**
* @dev Gets the balance of the specified address.
* @param _owner The address to query the the balance of.
* @return An uint256 representing the amount owned by the passed address.
*/
function balanceOf(address _owner) public view returns (uint256) {
return balances[_owner];
}

}


/**
* @title ERC20 interface
*/
contract ERC20 is ERC20Basic {
function allowance(address owner, address spender)
public view returns (uint256);

function transferFrom(address from, address to, uint256 value)
public returns (bool);

function approve(address spender, uint256 value) public returns (bool);
event Approval(
address indexed owner,
address indexed spender,
uint256 value
);
}


/**
* @title Standard ERC20 token
*
* @dev Implementation of the basic standard token.
* @dev https://github.com/ethereum/EIPs/issues/20
* @dev Based on code by FirstBlood: https://github.com/Firstbloodio/token/blob/master/smart_contract/FirstBloodToken.sol
*/
contract StandardToken is ERC20, BasicToken {

mapping (address => mapping (address => uint256)) internal allowed;


/**
* @dev Transfer tokens from one address to another
* @param _from address The address which you want to send tokens from
* @param _to address The address which you want to transfer to
* @param _value uint256 the amount of tokens to be transferred
*/
function transferFrom(
address _from,
address _to,
uint256 _value
)
public
returns (bool)
{
require(_to != address(0));
require(_value <= balances[_from]);
require(_value <= allowed[_from][msg.sender]);

balances[_from] = balances[_from].sub(_value);
balances[_to] = balances[_to].add(_value);
allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
emit Transfer(_from, _to, _value);
return true;
}

/**
* @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
* @param _spender The address which will spend the funds.
* @param _value The amount of tokens to be spent.
*/
function approve(address _spender, uint256 _value) public returns (bool) {
allowed[msg.sender][_spender] = _value;
emit Approval(msg.sender, _spender, _value);
return true;
}

/**
* @dev Function to check the amount of tokens that an owner allowed to a spender.
* @param _owner address The address which owns the funds.
* @param _spender address The address which will spend the funds.
* @return A uint256 specifying the amount of tokens still available for the spender.
*/
function allowance(
address _owner,
address _spender
)
public
view
returns (uint256)
{
return allowed[_owner][_spender];
}

/**
* @dev Increase the amount of tokens that an owner allowed to a spender.
*
* approve should be called when allowed[_spender] == 0. To increment
* allowed value is better to use this function to avoid 2 calls (and wait until
* the first transaction is mined)
* From MonolithDAO Token.sol
* @param _spender The address which will spend the funds.
* @param _addedValue The amount of tokens to increase the allowance by.
*/
function increaseApproval(
address _spender,
uint _addedValue
)
public
returns (bool)
{
allowed[msg.sender][_spender] = (
allowed[msg.sender][_spender].add(_addedValue));
emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
return true;
}

/**
* @dev Decrease the amount of tokens that an owner allowed to a spender.
*
* approve should be called when allowed[_spender] == 0. To decrement
* allowed value is better to use this function to avoid 2 calls (and wait until
* the first transaction is mined)
* From MonolithDAO Token.sol
* @param _spender The address which will spend the funds.
* @param _subtractedValue The amount of tokens to decrease the allowance by.
*/
function decreaseApproval(
address _spender,
uint _subtractedValue
)
public
returns (bool)
{
uint oldValue = allowed[msg.sender][_spender];
if (_subtractedValue > oldValue) {
allowed[msg.sender][_spender] = 0;
} else {
allowed[msg.sender][_spender] = oldValue.sub(_subtractedValue);
}
emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
return true;
}

}



/**
* @title Ownable
* @dev The Ownable contract has an owner address, and provides basic authorization control
* functions, this simplifies the implementation of "user permissions".
*/
contract Ownable {
address public owner;


event OwnershipRenounced(address indexed previousOwner);
event OwnershipTransferred(
address indexed previousOwner,
address indexed newOwner
);


/**
* @dev The Ownable constructor sets the original `owner` of the contract to the sender
* account.
*/
constructor() public {
owner = msg.sender;
}

/**
* @dev Throws if called by any account other than the owner.
*/
modifier onlyOwner() {
require(msg.sender == owner);
_;
}

/**
* @dev Allows the current owner to relinquish control of the contract.
*/
function renounceOwnership() public onlyOwner {
emit OwnershipRenounced(owner);
owner = address(0);
}

/**
* @dev Allows the current owner to transfer control of the contract to a newOwner.
* @param _newOwner The address to transfer ownership to.
*/
function transferOwnership(address _newOwner) public onlyOwner {
_transferOwnership(_newOwner);
}

/**
* @dev Transfers control of the contract to a newOwner.
* @param _newOwner The address to transfer ownership to.
*/
function _transferOwnership(address _newOwner) internal {
require(_newOwner != address(0));
emit OwnershipTransferred(owner, _newOwner);
owner = _newOwner;
}
}


/**
* @title Mintable token
*/
contract MintableToken is StandardToken, Ownable {
event Mint(address indexed to, uint256 amount);
event MintFinished();

bool public mintingFinished = false;


modifier canMint() {
require(!mintingFinished);
_;
}

modifier hasMintPermission() {
require(msg.sender == owner);
_;
}

/**
* @dev Function to mint tokens
* @param _to The address that will receive the minted tokens.
* @param _amount The amount of tokens to mint.
* @return A boolean that indicates if the operation was successful.
*/
function mint(
address _to,
uint256 _amount
)
hasMintPermission
canMint
public
returns (bool)
{
totalSupply_ = totalSupply_.add(_amount);
balances[_to] = balances[_to].add(_amount);
emit Mint(_to, _amount);
emit Transfer(address(0), _to, _amount);
return true;
}

/**
* @dev Function to stop minting new tokens.
* @return True if the operation was successful.
*/
function finishMinting() onlyOwner canMint public returns (bool) {
mintingFinished = true;
emit MintFinished();
return true;
}
}


contract FreezableToken is StandardToken {
// freezing chains
mapping (bytes32 => uint64) internal chains;
// freezing amounts for each chain
mapping (bytes32 => uint) internal freezings;
// total freezing balance per address
mapping (address => uint) internal freezingBalance;

event Freezed(address indexed to, uint64 release, uint amount);
event Released(address indexed owner, uint amount);

/**
* @dev Gets the balance of the specified address include freezing tokens.
* @param _owner The address to query the the balance of.
* @return An uint256 representing the amount owned by the passed address.
*/
function balanceOf(address _owner) public view returns (uint256 balance) {
return super.balanceOf(_owner) + freezingBalance[_owner];
}

/**
* @dev Gets the balance of the specified address without freezing tokens.
* @param _owner The address to query the the balance of.
* @return An uint256 representing the amount owned by the passed address.
*/
function actualBalanceOf(address _owner) public view returns (uint256 balance) {
return super.balanceOf(_owner);
}

function freezingBalanceOf(address _owner) public view returns (uint256 balance) {
return freezingBalance[_owner];
}

/**
* @dev gets freezing count
* @param _addr Address of freeze tokens owner.
*/
function freezingCount(address _addr) public view returns (uint count) {
uint64 release = chains[toKey(_addr, 0)];
while (release != 0) {
count++;
release = chains[toKey(_addr, release)];
}
}

/**
* @dev gets freezing end date and freezing balance for the freezing portion specified by index.
* @param _addr Address of freeze tokens owner.
* @param _index Freezing portion index. It ordered by release date descending.
*/
function getFreezing(address _addr, uint _index) public view returns (uint64 _release, uint _balance) {
for (uint i = 0; i < _index + 1; i++) {
_release = chains[toKey(_addr, _release)];
if (_release == 0) {
return;
}
}
_balance = freezings[toKey(_addr, _release)];
}

/**
* @dev freeze your tokens to the specified address.
* Be careful, gas usage is not deterministic,
* and depends on how many freezes _to address already has.
* @param _to Address to which token will be freeze.
* @param _amount Amount of token to freeze.
* @param _until Release date, must be in future.
*/
function freezeTo(address _to, uint _amount, uint64 _until) public {
require(_to != address(0));
require(_amount <= balances[msg.sender]);

balances[msg.sender] = balances[msg.sender].sub(_amount);

bytes32 currentKey = toKey(_to, _until);
freezings[currentKey] = freezings[currentKey].add(_amount);
freezingBalance[_to] = freezingBalance[_to].add(_amount);

freeze(_to, _until);
emit Transfer(msg.sender, _to, _amount);
emit Freezed(_to, _until, _amount);
}

/**
* @dev release first available freezing tokens.
*/
function releaseOnce() public {
bytes32 headKey = toKey(msg.sender, 0);
uint64 head = chains[headKey];
require(head != 0);
require(uint64(block.timestamp) > head);
bytes32 currentKey = toKey(msg.sender, head);

uint64 next = chains[currentKey];

uint amount = freezings[currentKey];
delete freezings[currentKey];

balances[msg.sender] = balances[msg.sender].add(amount);
freezingBalance[msg.sender] = freezingBalance[msg.sender].sub(amount);

if (next == 0) {
delete chains[headKey];
} else {
chains[headKey] = next;
delete chains[currentKey];
}
emit Released(msg.sender, amount);
}

/**
* @dev release all available for release freezing tokens. Gas usage is not deterministic!
* @return how many tokens was released
*/
function releaseAll() public returns (uint tokens) {
uint release;
uint balance;
(release, balance) = getFreezing(msg.sender, 0);
while (release != 0 && block.timestamp > release) {
releaseOnce();
tokens += balance;
(release, balance) = getFreezing(msg.sender, 0);
}
}

function toKey(address _addr, uint _release) internal pure returns (bytes32 result) {
// WISH masc to increase entropy
result = 0x5749534800000000000000000000000000000000000000000000000000000000;
assembly {
result := or(result, mul(_addr, 0x10000000000000000))
result := or(result, _release)
}
}

function freeze(address _to, uint64 _until) internal {
require(_until > block.timestamp);
bytes32 key = toKey(_to, _until);
bytes32 parentKey = toKey(_to, uint64(0));
uint64 next = chains[parentKey];

if (next == 0) {
chains[parentKey] = _until;
return;
}

bytes32 nextKey = toKey(_to, next);
uint parent;

while (next != 0 && _until > next) {
parent = next;
parentKey = nextKey;

next = chains[nextKey];
nextKey = toKey(_to, next);
}

if (_until == next) {
return;
}

if (next != 0) {
chains[key] = next;
}

chains[parentKey] = _until;
}
}


/**
* @title Burnable Token
* @dev Token that can be irreversibly burned (destroyed).
*/
contract BurnableToken is BasicToken {

event Burn(address indexed burner, uint256 value);

/**
* @dev Burns a specific amount of tokens.
* @param _value The amount of token to be burned.
*/
function burn(uint256 _value) public {
_burn(msg.sender, _value);
}

function _burn(address _who, uint256 _value) internal {
require(_value <= balances[_who]);
// no need to require value <= totalSupply, since that would imply the
// sender's balance is greater than the totalSupply, which *should* be an assertion failure

balances[_who] = balances[_who].sub(_value);
totalSupply_ = totalSupply_.sub(_value);
emit Burn(_who, _value);
emit Transfer(_who, address(0), _value);
}
}



/**
* @title Pausable
* @dev Base contract which allows children to implement an emergency stop mechanism.
*/
contract Pausable is Ownable {
event Pause();
event Unpause();

bool public paused = false;


/**
* @dev Modifier to make a function callable only when the contract is not paused.
*/
modifier whenNotPaused() {
require(!paused);
_;
}

/**
* @dev Modifier to make a function callable only when the contract is paused.
*/
modifier whenPaused() {
require(paused);
_;
}

/**
* @dev called by the owner to pause, triggers stopped state
*/
function pause() onlyOwner whenNotPaused public {
paused = true;
emit Pause();
}

/**
* @dev called by the owner to unpause, returns to normal state
*/
function unpause() onlyOwner whenPaused public {
paused = false;
emit Unpause();
}
}


contract FreezableMintableToken is FreezableToken, MintableToken {
/**
* @dev Mint the specified amount of token to the specified address and freeze it until the specified date.
* Be careful, gas usage is not deterministic,
* and depends on how many freezes _to address already has.
* @param _to Address to which token will be freeze.
* @param _amount Amount of token to mint and freeze.
* @param _until Release date, must be in future.
* @return A boolean that indicates if the operation was successful.
*/
function mintAndFreeze(address _to, uint _amount, uint64 _until) public onlyOwner canMint returns (bool) {
totalSupply_ = totalSupply_.add(_amount);

bytes32 currentKey = toKey(_to, _until);
freezings[currentKey] = freezings[currentKey].add(_amount);
freezingBalance[_to] = freezingBalance[_to].add(_amount);

freeze(_to, _until);
emit Mint(_to, _amount);
emit Freezed(_to, _until, _amount);
emit Transfer(msg.sender, _to, _amount);
return true;
}
}



contract Consts {
uint public constant TOKEN_DECIMALS = 18;
uint8 public constant TOKEN_DECIMALS_UINT8 = 18;
uint public constant TOKEN_DECIMAL_MULTIPLIER = 10 ** TOKEN_DECIMALS;

string public constant TOKEN_NAME = 'EduCoin';
string public constant TOKEN_SYMBOL = "EDC";
bool public constant PAUSED = false;
address public constant TARGET_USER = 0x0f53f511fBbC795f4e8F7b1516159638fb2D409B;

bool public constant CONTINUE_MINTING = true;
}




contract EduCoin is Consts, FreezableMintableToken, BurnableToken, Pausable

{

event Initialized();
bool public initialized = false;

constructor() public {
init();
transferOwnership(TARGET_USER);
}


function name() public pure returns (string _name) {
return TOKEN_NAME;
}

function symbol() public pure returns (string _symbol) {
return TOKEN_SYMBOL;
}

function decimals() public pure returns (uint8 _decimals) {
return TOKEN_DECIMALS_UINT8;
}

function transferFrom(address _from, address _to, uint256 _value) public returns (bool _success) {
require(!paused);
return super.transferFrom(_from, _to, _value);
}

function transfer(address _to, uint256 _value) public returns (bool _success) {
require(!paused);
return super.transfer(_to, _value);
}


function init() private {
require(!initialized);
initialized = true;

if (PAUSED) {
pause();
}


address[1] memory addresses = [address(0x0f53f511fBbC795f4e8F7b1516159638fb2D409B)];
uint[1] memory amounts = [uint(2000000000000000000000000000)];
uint64[1] memory freezes = [uint64(0)];

for (uint i = 0; i < addresses.length; i++) {
if (freezes[i] == 0) {
mint(addresses[i], amounts[i]);
} else {
mintAndFreeze(addresses[i], amounts[i], freezes[i]);
}
}


if (!CONTINUE_MINTING) {
finishMinting();
}

emit Initialized();
}

}