pragma solidity ^0.4.4;

/**
 * @title Contract for object that have an owner
 */
contract Owned {
    /**
     * Contract owner address
     */
    address public owner;

    /**
     * @dev Delegate contract to another person
     * @param _owner New owner address 
     */
    function setOwner(address _owner) onlyOwner
    { owner = _owner; }

    /**
     * @dev Owner check modifier
     */
    modifier onlyOwner { if (msg.sender != owner) throw; _; }
}

/**
 * @title Common pattern for destroyable contracts 
 */
contract Destroyable {
    address public hammer;

    /**
     * @dev Hammer setter
     * @param _hammer New hammer address
     */
    function setHammer(address _hammer) onlyHammer
    { hammer = _hammer; }

    /**
     * @dev Destroy contract and scrub a data
     * @notice Only hammer can call it 
     */
    function destroy() onlyHammer
    { suicide(msg.sender); }

    /**
     * @dev Hammer check modifier
     */
    modifier onlyHammer { if (msg.sender != hammer) throw; _; }
}

/**
 * @title Generic owned destroyable contract
 */
contract Object is Owned, Destroyable {
    function Object() {
        owner  = msg.sender;
        hammer = msg.sender;
    }
}

// Standard token interface (ERC 20)
// https://github.com/ethereum/EIPs/issues/20
contract ERC20 
{
// Functions:
    /// @return total amount of tokens
    uint256 public totalSupply;

    /// @param _owner The address from which the balance will be retrieved
    /// @return The balance
    function balanceOf(address _owner) constant returns (uint256);

    /// @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) returns (bool);

    /// @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);

    /// @notice `msg.sender` approves `_addr` to spend `_value` tokens
    /// @param _spender The address of the account able to transfer the tokens
    /// @param _value The amount of wei to be approved for transfer
    /// @return Whether the approval was successful or not
    function approve(address _spender, uint256 _value) returns (bool);

    /// @param _owner The address of the account owning tokens
    /// @param _spender The address of the account able to transfer the tokens
    /// @return Amount of remaining tokens allowed to spent
    function allowance(address _owner, address _spender) constant returns (uint256);

// Events:
    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);
}

/**
 * @title Token contract represents any asset in digital economy
 */
contract Token is Object, ERC20 {
    /* Short description of token */
    string public name;
    string public symbol;

    /* Total count of tokens exist */
    uint public totalSupply;

    /* Fixed point position */
    uint8 public decimals;
    
    /* Token approvement system */
    mapping(address => uint) balances;
    mapping(address => mapping(address => uint)) allowances;
 
    /**
     * @dev Get balance of plain address
     * @param _owner is a target address
     * @return amount of tokens on balance
     */
    function balanceOf(address _owner) constant returns (uint256)
    { return balances[_owner]; }
 
    /**
     * @dev Take allowed tokens
     * @param _owner The address of the account owning tokens
     * @param _spender The address of the account able to transfer the tokens
     * @return Amount of remaining tokens allowed to spent
     */
    function allowance(address _owner, address _spender) constant returns (uint256)
    { return allowances[_owner][_spender]; }

    /* Token constructor */
    function Token(string _name, string _symbol, uint8 _decimals, uint _count) {
        name        = _name;
        symbol      = _symbol;
        decimals    = _decimals;
        totalSupply = _count;
        balances[msg.sender] = _count;
    }
 
    /**
     * @dev Transfer self tokens to given address
     * @param _to destination address
     * @param _value amount of token values to send
     * @notice `_value` tokens will be sended to `_to`
     * @return `true` when transfer done
     */
    function transfer(address _to, uint _value) returns (bool) {
        if (balances[msg.sender] >= _value) {
            balances[msg.sender] -= _value;
            balances[_to]        += _value;
            Transfer(msg.sender, _to, _value);
            return true;
        }
        return false;
    }

    /**
     * @dev Transfer with approvement mechainsm
     * @param _from source address, `_value` tokens shold be approved for `sender`
     * @param _to destination address
     * @param _value amount of token values to send 
     * @notice from `_from` will be sended `_value` tokens to `_to`
     * @return `true` when transfer is done
     */
    function transferFrom(address _from, address _to, uint256 _value) returns (bool) {
        var avail = allowances[_from][msg.sender]
                  > balances[_from] ? balances[_from]
                                    : allowances[_from][msg.sender];
        if (avail >= _value) {
            allowances[_from][msg.sender] -= _value;
            balances[_from] -= _value;
            balances[_to]   += _value;
            Transfer(_from, _to, _value);
            return true;
        }
        return false;
    }

    /**
     * @dev Give to target address ability for self token manipulation without sending
     * @param _spender target address (future requester)
     * @param _value amount of token values for approving
     */
    function approve(address _spender, uint256 _value) returns (bool) {
        allowances[msg.sender][_spender] += _value;
        Approval(msg.sender, _spender, _value);
        return true;
    }

    /**
     * @dev Reset count of tokens approved for given address
     * @param _spender target address (future requester)
     */
    function unapprove(address _spender)
    { allowances[msg.sender][_spender] = 0; }
}

contract TokenEmission is Token {
    function TokenEmission(string _name, string _symbol, uint8 _decimals,
                           uint _start_count)
             Token(_name, _symbol, _decimals, _start_count)
    {}

    /**
     * @dev Token emission
     * @param _value amount of token values to emit
     * @notice owner balance will be increased by `_value`
     */
    function emission(uint _value) onlyOwner {
        // Overflow check
        if (_value + totalSupply < totalSupply) throw;

        totalSupply     += _value;
        balances[owner] += _value;
    }
 
    /**
     * @dev Burn the token values from sender balance and from total
     * @param _value amount of token values for burn 
     * @notice sender balance will be decreased by `_value`
     */
    function burn(uint _value) {
        if (balances[msg.sender] >= _value) {
            balances[msg.sender] -= _value;
            totalSupply      -= _value;
        }
    }
}

/**
 * @title Asset recipient interface
 */
contract Recipient {
    /**
     * @dev On received ethers
     * @param sender Ether sender
     * @param amount Ether value
     */
    event ReceivedEther(address indexed sender,
                        uint256 indexed amount);

    /**
     * @dev On received custom ERC20 tokens
     * @param from Token sender
     * @param value Token value
     * @param token Token contract address
     * @param extraData Custom additional data
     */
    event ReceivedTokens(address indexed from,
                         uint256 indexed value,
                         address indexed token,
                         bytes extraData);

    /**
     * @dev Receive approved ERC20 tokens
     * @param _from Spender address
     * @param _value Transaction value
     * @param _token ERC20 token contract address
     * @param _extraData Custom additional data
     */
    function receiveApproval(address _from, uint256 _value,
                             ERC20 _token, bytes _extraData) {
        if (!_token.transferFrom(_from, this, _value)) throw;
        ReceivedTokens(_from, _value, _token, _extraData);
    }

    /**
     * @dev Catch sended to contract ethers
     */
    function () payable
    { ReceivedEther(msg.sender, msg.value); }
}

/**
 * @title Crowdfunding contract
 */
contract Crowdfunding is Object, Recipient {
    /**
     * @dev Target fund account address
     */
    address public fund;

    /**
     * @dev Bounty token address
     */
    TokenEmission public bounty;
    
    /**
     * @dev Distribution of donations
     */
    mapping(address => uint256) public donations;

    /**
     * @dev Total funded value
     */
    uint256 public totalFunded;

    /**
     * @dev Documentation reference
     */
    string public reference;

    /**
     * @dev Crowdfunding configuration
     */
    Params public config;

    struct Params {
        /* start/stop block stamps */
        uint256 startBlock;
        uint256 stopBlock;

        /* Minimal/maximal funded value */
        uint256 minValue;
        uint256 maxValue;
        
        /**
         * Bounty ratio equation:
         *   bountyValue = value * ratio / scale
         * where
         *   ratio = R - (block - B) / S * V
         *  R - start bounty ratio
         *  B - start block number
         *  S - bounty reduction step in blocks 
         *  V - bounty reduction value
         */
        uint256 bountyScale;
        uint256 startRatio;
        uint256 reductionStep;
        uint256 reductionValue;
    }

    /**
     * @dev Calculate bounty value by reduction equation
     * @param _value Input donation value
     * @param _block Input block number
     * @return Bounty value
     */
    function bountyValue(uint256 _value, uint256 _block) constant returns (uint256) {
        if (_block < config.startBlock || _block > config.stopBlock)
            return 0;

        var R = config.startRatio;
        var B = config.startBlock;
        var S = config.reductionStep;
        var V = config.reductionValue;
        uint256 ratio = R - (_block - B) / S * V; 
        return _value * ratio / config.bountyScale; 
    }

    /**
     * @dev Crowdfunding running checks
     */
    modifier onlyRunning {
        bool isRunning = totalFunded  < config.maxValue
                      && block.number > config.startBlock
                      && block.number < config.stopBlock;
        if (!isRunning) throw;
        _;
    }

    /**
     * @dev Crowdfundung failure checks
     */
    modifier onlyFailure {
        bool isFailure = totalFunded  < config.minValue
                      && block.number > config.stopBlock;
        if (!isFailure) throw;
        _;
    }

    /**
     * @dev Crowdfunding success checks
     */
    modifier onlySuccess {
        bool isSuccess = totalFunded >= config.minValue
                      && block.number > config.stopBlock;
        if (!isSuccess) throw;
        _;
    }

    /**
     * @dev Crowdfunding contract initial 
     * @param _fund Destination account address
     * @param _bounty Bounty token address
     * @param _reference Reference documentation link
     * @param _startBlock Funding start block number
     * @param _stopBlock Funding stop block nubmer
     * @param _minValue Minimal funded value in wei 
     * @param _maxValue Maximal funded value in wei
     * @param _scale Bounty scaling factor by funded value
     * @param _startRatio Initial bounty ratio
     * @param _reductionStep Bounty reduction step in blocks 
     * @param _reductionValue Bounty reduction value
     * @notice this contract should be owner of bounty token
     */
    function Crowdfunding(
        address _fund,
        address _bounty,
        string  _reference,
        uint256 _startBlock,
        uint256 _stopBlock,
        uint256 _minValue,
        uint256 _maxValue,
        uint256 _scale,
        uint256 _startRatio,
        uint256 _reductionStep,
        uint256 _reductionValue
    ) {
        fund      = _fund;
        bounty    = TokenEmission(_bounty);
        reference = _reference;

        config.startBlock     = _startBlock;
        config.stopBlock      = _stopBlock;
        config.minValue       = _minValue;
        config.maxValue       = _maxValue;
        config.bountyScale    = _scale;
        config.startRatio     = _startRatio;
        config.reductionStep  = _reductionStep;
        config.reductionValue = _reductionValue;
    }

    /**
     * @dev Receive Ether token and send bounty
     */
    function () payable onlyRunning {
        ReceivedEther(msg.sender, msg.value);

        totalFunded           += msg.value;
        donations[msg.sender] += msg.value;

        var bountyVal = bountyValue(msg.value, block.number);
        bounty.emission(bountyVal);
        bounty.transfer(msg.sender, bountyVal);
    }

    /**
     * @dev Withdrawal balance on successfull finish
     */
    function withdraw() onlySuccess
    { if (!fund.send(this.balance)) throw; }

    /**
     * @dev Refund donations when no minimal value achieved
     */
    function refund() onlyFailure {
        var donation = donations[msg.sender];
        donations[msg.sender] = 0;
        if (!msg.sender.send(donation)) throw;
    }

    /**
     * @dev Disable receive another tokens
     */
    function receiveApproval(address _from, uint256 _value,
                             ERC20 _token, bytes _extraData)
    { throw; }
}