//
//                                          |\,'\
//          ___                             | '  \
//     ___  \ /  ___         ,'\_           | .-. \        /|
//     \ /  | |,'__ \  ,'\_  |   \          | | | |      ,' |_   /|
//   _ | |  | |\/  \ \ |   \ | |\_|    _    | |_| |   _ '-. .-',' |_   _
//  // | |  | |____| | | |\_|| |__    //    |     | ,'_`. | | '-. .-',' `. ,'\_
//  \\_| |_,' .-, _  | | |   | |\ \  //    .| |\_/ | / \ || |   | | / |\  \|   \
//   `-. .-'| |/ / | | | |   | | \ \//     |  |    | | | || |   | | | |_\ || |\_|
//     | |  | || \_| | | |   /_\  \ /      | |`    | | | || |   | | | .---'| |
//     | |  | |\___,_\ /_\ _      //       | |     | \_/ || |   | | | |  /\| |
//     /_\  | |           //_____//       .||`  _   `._,' | |   | | \ `-' /| |
//          /_\           `------'        \ |  /-\ND _     `.\  | |  `._,' /_\
//                                         \|        |HE         `.\
//                                                                                                                                      
//        ,--.  ,--. ,-----. ,------.  ,-----.,------. ,--. ,--.,--.   ,--.    
//        |  '--'  |'  .-.  '|  .--. ''  .--./|  .--. '|  | |  | \  `.'  /    
//        |  .--.  ||  | |  ||  '--'.'|  |    |  '--'.'|  | |  |  .'    \      
//        |  |  |  |'  '-'  '|  |\  \ '  '--'\|  |\  \ '  '-'  ' /  .'.  \    
//        `--'  `--' `-----' `--' '--' `-----'`--' '--' `-----' '--'   '--'    
//  
//     The              ,--------. ,-----. ,--. ,--.,------.,--.  ,--. ,---.   
//      0xDiary        '--.  .--''  .-.  '|  .'   /|  .---'|  ,'.|  |'   .-'
//        Token           |  |   |  | |  ||  .   ' |  `--, |  |' '  |`.  `-.  
//                        |  |   '  '-'  '|  |\   \|  `---.|  | `   |.-'    | 
//                        `--'    `-----' `--' '--'`------'`--'  `--'`-----'
//   
//                  A Mineable ERC-20 / ERC-918 Token/Smart Contract
//                     
//                    
// ----------------------------------------------------------------------------
// 
//  0xDiary Basics:
//
//  	Symbol                     : 0xDIARY
//  	Name                       : The 0xDiary Token
//   	Total supply               : 1,000,000
//  	Decimals                   : 8
//   	First Miner Era Reward     : 4 0xDIARY
//  	Number of Eras             : 3
//  	Target Diff. Readjustment  : 250 Blocks
//  	Target Block Time          : 2 Minutes

//
// ----------------------------------------------------------------------------
//
//   Website: https://0xhorcrux.github.io
//
// ----------------------------------------------------------------------------
//
//   ERC-20 / ERC-918 Token Fundamentals:
//
//   	- Autonomous decentralized currency
//
//   	- SoliditySHA3 proof of work algorithm
// 
//   	- Automatic difficulty adjustment
// 
//   	- Connectable with other Ethereum Smart Contracts
//
//-----------------------------------------------------------------------------
//
//   The Spellbook:
//    
//    - Use a computers processing power to destroy a piece of an 0xHorcrux.
//
//    - Download a solo miner or join a pool to participate.
//
//    - Miners are rewarded with a piece of a 0xHorcrux when they find a block.
//
//    - There is a limited supply of token pieces for each 0xHorcrux.
//
//    - Mining difficulty increases over time making them harder to acquire.
//
//    - More at https://0xhorcrux.github.io
//
//-----------------------------------------------------------------------------
pragma solidity ^0.4.18;
// ----------------------------------------------------------------------------

// '0xDiary Token' contract

// Mineable ERC20 Token using Proof Of Work

// Symbol      : 0xDIARY

// Name        : The 0xDiary Token

// Total supply: 1,000,000 pieces

// Decimals    : 8

// ----------------------------------------------------------------------------
// Safe maths
// ----------------------------------------------------------------------------

library SafeMath {

    function add(uint a, uint b) internal pure returns (uint c) {

        c = a + b;

        require(c >= a);

    }

    function sub(uint a, uint b) internal pure returns (uint c) {

        require(b <= a);

        c = a - b;

    }

    function mul(uint a, uint b) internal pure returns (uint c) {

        c = a * b;

        require(a == 0 || c / a == b);

    }

    function div(uint a, uint b) internal pure returns (uint c) {

        require(b > 0);

        c = a / b;

    }

}

library ExtendedMath {

    //return the smaller of the two inputs (a or b)
    function limitLessThan(uint a, uint b) internal pure returns (uint c) {

        if(a > b) return b;

        return a;

    }
}

// ----------------------------------------------------------------------------
// ERC Token Standard #20 Interface
// https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20-token-standard.md
// ----------------------------------------------------------------------------

contract ERC20Interface {

    function totalSupply() public constant returns (uint);

    function balanceOf(address tokenOwner) public constant returns (uint balance);

    function allowance(address tokenOwner, address spender) public constant returns (uint remaining);

    function transfer(address to, uint tokens) public returns (bool success);

    function approve(address spender, uint tokens) public returns (bool success);

    function transferFrom(address from, address to, uint tokens) public returns (bool success);

    event Transfer(address indexed from, address indexed to, uint tokens);

    event Approval(address indexed tokenOwner, address indexed spender, uint tokens);

}

// ----------------------------------------------------------------------------
// Contract function to receive approval and execute function in one call
// ----------------------------------------------------------------------------

contract ApproveAndCallFallBack {

    function receiveApproval(address from, uint256 tokens, address token, bytes data) public;

}

// ----------------------------------------------------------------------------
// Owned contract
// ----------------------------------------------------------------------------

contract Owned {

    address public owner;

    address public newOwner;

    event OwnershipTransferred(address indexed _from, address indexed _to);

    function Owned() public {

        owner = msg.sender;

    }

    modifier onlyOwner {

        require(msg.sender == owner);

        _;

    }

    function transferOwnership(address _newOwner) public onlyOwner {

        newOwner = _newOwner;

    }

    function acceptOwnership() public {

        require(msg.sender == newOwner);

        OwnershipTransferred(owner, newOwner);

        owner = newOwner;

        newOwner = address(0);

    }

}

// ----------------------------------------------------------------------------
// ERC20 Token, with the addition of symbol, name and decimals and an
// initial fixed supply
// ----------------------------------------------------------------------------

contract _0xDiaryToken is ERC20Interface, Owned {

    using SafeMath for uint;
    using ExtendedMath for uint;

    string public symbol;

    string public  name;

    uint8 public decimals;

    uint public _totalSupply;

    uint public latestDifficultyPeriodStarted;

    uint public epochCount;//number of 'blocks' mined

    uint public _BLOCKS_PER_READJUSTMENT = 250;

    //a little number
    uint public  _MINIMUM_TARGET = 2**16;

      //a big number is easier ; just find a solution that is smaller
    //uint public  _MAXIMUM_TARGET = 2**224;  bitcoin uses 224
    uint public  _MAXIMUM_TARGET = 2**234;

    uint public miningTarget;

    bytes32 public challengeNumber;   //generate a new one when a new reward is minted

    uint public rewardEra;
    uint public maxSupplyForEra;

    address public lastRewardTo;
    uint public lastRewardAmount;
    uint public lastRewardEthBlockNumber;

    bool locked = false;

    mapping(bytes32 => bytes32) solutionForChallenge;

    uint public tokensMinted;

    mapping(address => uint) balances;

    mapping(address => mapping(address => uint)) allowed;

    event Mint(address indexed from, uint reward_amount, uint epochCount, bytes32 newChallengeNumber);

    // ------------------------------------------------------------------------
    // Constructor
    // ------------------------------------------------------------------------

    function _0xDiaryToken() public onlyOwner{


        symbol = "0xDIARY";

        name = "The 0xDiary Token";

        decimals = 8;

        _totalSupply = 1000000 * 10**uint(decimals);

        if(locked) revert();
        locked = true;

        tokensMinted = 0;

        rewardEra = 0;
        maxSupplyForEra = _totalSupply.div(2);

        miningTarget = _MAXIMUM_TARGET;

        latestDifficultyPeriodStarted = block.number;

        _startNewMiningEpoch();

        //The owner gets nothing! You must mine this ERC20 token
        //balances[owner] = _totalSupply;
        //Transfer(address(0), owner, _totalSupply);

    }

        function mint(uint256 nonce, bytes32 challenge_digest) public returns (bool success) {

            //the PoW must contain work that includes a recent ethereum block hash (challenge number) and the msg.sender's address to prevent MITM attacks
            bytes32 digest =  keccak256(challengeNumber, msg.sender, nonce );

            //the challenge digest must match the expected
            if (digest != challenge_digest) revert();

            //the digest must be smaller than the target
            if(uint256(digest) > miningTarget) revert();

            //only allow one reward for each challenge
             bytes32 solution = solutionForChallenge[challengeNumber];
             solutionForChallenge[challengeNumber] = digest;
             if(solution != 0x0) revert();  //prevent the same answer from awarding twice

            uint reward_amount = getMiningReward();

            balances[msg.sender] = balances[msg.sender].add(reward_amount);

            tokensMinted = tokensMinted.add(reward_amount);

            //Cannot mint more tokens than there are
            assert(tokensMinted <= maxSupplyForEra);

            //set readonly diagnostics data
            lastRewardTo = msg.sender;
            lastRewardAmount = reward_amount;
            lastRewardEthBlockNumber = block.number;

             _startNewMiningEpoch();

              Mint(msg.sender, reward_amount, epochCount, challengeNumber );

           return true;

        }

    //a new 'block' to be mined
    function _startNewMiningEpoch() internal {

      //if max supply for the era will be exceeded next reward round then enter the new era before that happens

      //3 is the final reward era, almost all tokens minted
      //once the final era is reached, more tokens will not be given out because the assert function
      if( tokensMinted.add(getMiningReward()) > maxSupplyForEra && rewardEra < 2)
      {
        rewardEra = rewardEra + 1;
      }

      //set the next minted supply at which the era will change
      // total supply is 10000000000000000  because of 10 decimal places
      maxSupplyForEra = _totalSupply - _totalSupply.div( 2**(rewardEra + 1));

      epochCount = epochCount.add(1);

      //every so often, readjust difficulty. Dont readjust when deploying
      if(epochCount % _BLOCKS_PER_READJUSTMENT == 0)
      {
        _reAdjustDifficulty();
      }

      //make the latest ethereum block hash a part of the next challenge for PoW to prevent pre-mining future blocks
      //do this last since this is a protection mechanism in the mint() function
      challengeNumber = block.blockhash(block.number - 1);

    }

    //https://en.bitcoin.it/wiki/Difficulty#What_is_the_formula_for_difficulty.3F
    //as of 2017 the bitcoin difficulty was up to 17 zeroes, it was only 8 in the early days

    //readjust the target by 5 percent
    function _reAdjustDifficulty() internal {

        uint ethBlocksSinceLastDifficultyPeriod = block.number - latestDifficultyPeriodStarted;
        //assume 360 ethereum blocks per hour

        //we want miners to spend 2 minutes to mine each 'block', about 12 ethereum blocks = one 0xdiary epoch
                      uint epochsMined = _BLOCKS_PER_READJUSTMENT; //256

       
        uint targetEthBlocksPerDiffPeriod = epochsMined * 12; //should be 12 times slower than ethereum

        //if there were less eth blocks passed in time than expected
        if( ethBlocksSinceLastDifficultyPeriod < targetEthBlocksPerDiffPeriod )
        {
          uint excess_block_pct = (targetEthBlocksPerDiffPeriod.mul(100)).div( ethBlocksSinceLastDifficultyPeriod );

          uint excess_block_pct_extra = excess_block_pct.sub(100).limitLessThan(1000);
          // If there were 5% more blocks mined than expected then this is 5.  If there were 100% more blocks mined than expected then this is 100.

          //make it harder
          miningTarget = miningTarget.sub(miningTarget.div(2000).mul(excess_block_pct_extra));   //by up to 50 %
        }else{
          uint shortage_block_pct = (ethBlocksSinceLastDifficultyPeriod.mul(100)).div( targetEthBlocksPerDiffPeriod );

          uint shortage_block_pct_extra = shortage_block_pct.sub(100).limitLessThan(1000); //always between 0 and 1000

          //make it easier
          miningTarget = miningTarget.add(miningTarget.div(2000).mul(shortage_block_pct_extra));   //by up to 50 %
        }

        latestDifficultyPeriodStarted = block.number;

        if(miningTarget < _MINIMUM_TARGET) //very difficult
        {
          miningTarget = _MINIMUM_TARGET;
        }

        if(miningTarget > _MAXIMUM_TARGET) //very easy
        {
          miningTarget = _MAXIMUM_TARGET;
        }
    }

    //this is a recent ethereum block hash, used to prevent pre-mining future blocks
    function getChallengeNumber() public constant returns (bytes32) {
        return challengeNumber;
    }

    //the number of zeroes the digest of the PoW solution requires.  Auto adjusts
     function getMiningDifficulty() public constant returns (uint) {
        return _MAXIMUM_TARGET.div(miningTarget);
    }

    function getMiningTarget() public constant returns (uint) {
       return miningTarget;
   }

    //1m pieces total
    //reward begins at 4 and is cut in half every reward era (as tokens are mined)
    function getMiningReward() public constant returns (uint) {
        //once we get half way thru the coins, only get 2 per block

         //every reward era, the reward amount halves.

         return (4 * 10**uint(decimals) ).div( 2**rewardEra ) ;

    }

    //help debug mining software
    function getMintDigest(uint256 nonce, bytes32 challenge_digest, bytes32 challenge_number) public view returns (bytes32 digesttest) {

        bytes32 digest = keccak256(challenge_number,msg.sender,nonce);

        return digest;

      }

        //help debug mining software
      function checkMintSolution(uint256 nonce, bytes32 challenge_digest, bytes32 challenge_number, uint testTarget) public view returns (bool success) {

          bytes32 digest = keccak256(challenge_number,msg.sender,nonce);

          if(uint256(digest) > testTarget) revert();

          return (digest == challenge_digest);

        }

    // ------------------------------------------------------------------------
    // Total supply
    // ------------------------------------------------------------------------

    function totalSupply() public constant returns (uint) {

        return _totalSupply  - balances[address(0)];

    }

    // ------------------------------------------------------------------------
    // Get the token balance for account `tokenOwner`
    // ------------------------------------------------------------------------

    function balanceOf(address tokenOwner) public constant returns (uint balance) {

        return balances[tokenOwner];

    }

    // ------------------------------------------------------------------------
    // Transfer the balance from token owner's account to `to` account
    // - Owner's account must have sufficient balance to transfer
    // - 0 value transfers are allowed
    // ------------------------------------------------------------------------

    function transfer(address to, uint tokens) public returns (bool success) {

        balances[msg.sender] = balances[msg.sender].sub(tokens);

        balances[to] = balances[to].add(tokens);

        Transfer(msg.sender, to, tokens);

        return true;

    }

    // ------------------------------------------------------------------------
    // Token owner can approve for `spender` to transferFrom(...) `tokens`
    // from the token owner's account
    //
    // https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20-token-standard.md
    // recommends that there are no checks for the approval double-spend attack
    // as this should be implemented in user interfaces
    // ------------------------------------------------------------------------

    function approve(address spender, uint tokens) public returns (bool success) {

        allowed[msg.sender][spender] = tokens;

        Approval(msg.sender, spender, tokens);

        return true;

    }

    // ------------------------------------------------------------------------
    // Transfer `tokens` from the `from` account to the `to` account
    //
    // The calling account must already have sufficient tokens approve(...)-d
    // for spending from the `from` account and
    // - From account must have sufficient balance to transfer
    // - Spender must have sufficient allowance to transfer
    // - 0 value transfers are allowed
    // ------------------------------------------------------------------------

    function transferFrom(address from, address to, uint tokens) public returns (bool success) {

        balances[from] = balances[from].sub(tokens);

        allowed[from][msg.sender] = allowed[from][msg.sender].sub(tokens);

        balances[to] = balances[to].add(tokens);

        Transfer(from, to, tokens);

        return true;

    }

    // ------------------------------------------------------------------------
    // Returns the amount of tokens approved by the owner that can be
    // transferred to the spender's account
    // ------------------------------------------------------------------------

    function allowance(address tokenOwner, address spender) public constant returns (uint remaining) {

        return allowed[tokenOwner][spender];

    }

    // ------------------------------------------------------------------------
    // Token owner can approve for `spender` to transferFrom(...) `tokens`
    // from the token owner's account. The `spender` contract function
    // `receiveApproval(...)` is then executed
    // ------------------------------------------------------------------------

    function approveAndCall(address spender, uint tokens, bytes data) public returns (bool success) {

        allowed[msg.sender][spender] = tokens;

        Approval(msg.sender, spender, tokens);

        ApproveAndCallFallBack(spender).receiveApproval(msg.sender, tokens, this, data);

        return true;

    }

    // ------------------------------------------------------------------------
    // Don't accept ETH
    // ------------------------------------------------------------------------

    function () public payable {

        revert();

    }

    // ------------------------------------------------------------------------
    // Owner can transfer out any accidentally sent ERC20 tokens
    // ------------------------------------------------------------------------

    function transferAnyERC20Token(address tokenAddress, uint tokens) public onlyOwner returns (bool success) {

        return ERC20Interface(tokenAddress).transfer(owner, tokens);

    }

}

// ----------------------------------------------------------------------------
//
//                                          |\,'\
//          ___                             | '  \
//     ___  \ /  ___         ,'\_           | .-. \        /|
//     \ /  | |,'__ \  ,'\_  |   \          | | | |      ,' |_   /|
//   _ | |  | |\/  \ \ |   \ | |\_|    _    | |_| |   _ '-. .-',' |_   _
//  // | |  | |____| | | |\_|| |__    //    |     | ,'_`. | | '-. .-',' `. ,'\_
//  \\_| |_,' .-, _  | | |   | |\ \  //    .| |\_/ | / \ || |   | | / |\  \|   \
//   `-. .-'| |/ / | | | |   | | \ \//     |  |    | | | || |   | | | |_\ || |\_|
//     | |  | || \_| | | |   /_\  \ /      | |`    | | | || |   | | | .---'| |
//     | |  | |\___,_\ /_\ _      //       | |     | \_/ || |   | | | |  /\| |
//     /_\  | |           //_____//       .||`  _   `._,' | |   | | \ `-' /| |
//          /_\           `------'        \ |  /-\ND _     `.\  | |  `._,' /_\
//                                         \|        |HE         `.\
//                                                                                                                                      
//        ,--.  ,--. ,-----. ,------.  ,-----.,------. ,--. ,--.,--.   ,--.    
//        |  '--'  |'  .-.  '|  .--. ''  .--./|  .--. '|  | |  | \  `.'  /    
//        |  .--.  ||  | |  ||  '--'.'|  |    |  '--'.'|  | |  |  .'    \      
//        |  |  |  |'  '-'  '|  |\  \ '  '--'\|  |\  \ '  '-'  ' /  .'.  \    
//        `--'  `--' `-----' `--' '--' `-----'`--' '--' `-----' '--'   '--'    
//  
//     The              ,--------. ,-----. ,--. ,--.,------.,--.  ,--. ,---.   
//      0xDiary        '--.  .--''  .-.  '|  .'   /|  .---'|  ,'.|  |'   .-'
//        Token           |  |   |  | |  ||  .   ' |  `--, |  |' '  |`.  `-.  
//                        |  |   '  '-'  '|  |\   \|  `---.|  | `   |.-'    | 
//                        `--'    `-----' `--' '--'`------'`--'  `--'`-----'
//
//
//          0xDiary   0xRing   0xLocket   0xCup   0xDiadem   0xHP   0xSnake
//