pragma solidity ^0.4.23;

contract shop {

    struct tovar {
        string name;
        uint256 cost;
        address seller;
    }

    struct user {
        uint256 balance;
        address ip;
        tovar[] history_b;
        tovar[] history_s;
    }

    user[] users;
    tovar[] tovars;

    function strConcat(string _a, string _b, string _c, string _d, string _e) private returns (string){
        bytes memory _ba = bytes(_a);
        bytes memory _bb = bytes(_b);
        bytes memory _bc = bytes(_c);
        bytes memory _bd = bytes(_d);
        bytes memory _be = bytes(_e);
        string memory abcde = new string(_ba.length + _bb.length + _bc.length + _bd.length + _be.length);
        bytes memory babcde = bytes(abcde);
        uint k = 0;
        for (uint i = 0; i < _ba.length; i++) babcde[k++] = _ba[i];
        for (i = 0; i < _bb.length; i++) babcde[k++] = _bb[i];
        for (i = 0; i < _bc.length; i++) babcde[k++] = _bc[i];
        for (i = 0; i < _bd.length; i++) babcde[k++] = _bd[i];
        for (i = 0; i < _be.length; i++) babcde[k++] = _be[i];
        return string(babcde);
    }

    function strConcat(string _a, string _b, string _c, string _d) private returns (string) {
        return strConcat(_a, _b, _c, _d, "");
    }

    function strConcat(string _a, string _b, string _c) private returns (string) {
        return strConcat(_a, _b, _c, "", "");
    }

    function strConcat(string _a, string _b) private returns (string) {
        return strConcat(_a, _b, "", "", "");
    }

    function check_costumer(address _ip) private returns(bool){
        bool flag = false;
        for (uint256 i = 0; i < users.length; i++) {
            if (users[i].ip == _ip) {
                flag = true;
            }
        }
        return flag;
    }

    function view_balance() public view returns(uint256) {
        address views = msg.sender;
        bool flag = check_costumer(views);
        if (flag) {
            uint256 i = 0;
            while (users[i].ip != views) {
                i++;
            }
            return users[i].balance;
        } else {
            throw;
        }
    }

    function view_hisrory_sell() public view returns(string) {
        address views = msg.sender;
        bool flag = check_costumer(views);
        if (flag) {
            uint256 i = 0;
            while (users[i].ip != views) {
                i++;
            }
            string ans;
            for (uint256 j = 0; j < users[i].history_s.length; j++) {
                ans = string(strConcat(ans, users[i].history_s[j].name, ","));
            }
        }  else {
            throw;
        }
    }

    function view_hisrory_buy() public view returns(string) {
        address views = msg.sender;
        bool flag = check_costumer(views);
        if (flag) {
            uint256 i = 0;
            while (users[i].ip != views) {
                i++;
            }
            string ans;
            for (uint256 j = 0; j < users[i].history_s.length; j++) {
                ans = string(strConcat(ans, users[i].history_b[j].name, ","));
            }
        } else {
            throw;
        }
    }

    function init_user() public {
        bool flag = check_costumer(msg.sender);
        if (!flag) {
            users.length = users.length + 1;
            users[users.length - 1].ip = msg.sender;
            users[users.length - 1].balance = 10000;
        } else {
            throw;
        }
    }

    function add_tovar(string _name, uint256 _cost) public {
        bool flag = check_costumer(msg.sender);
        if (flag) {
            tovars.length = tovars.length + 1;
            tovars[tovars.length - 1].name = _name;
            tovars[tovars.length - 1].cost = _cost;
            tovars[tovars.length - 1].seller = msg.sender;
        } else {
            throw;
        }
    }

    function bye_tovar(uint256 _id) public {
        _id--;
        bool flag = check_costumer(msg.sender);
        if (flag) {
            address buy = msg.sender;
            uint256 m_id = 0;
            while (users[m_id].ip != buy) {
                m_id++;
            }
            if (users[m_id].balance < tovars[_id].cost) {
                //недостаточно денег - обработать
            } else {
                users[m_id].balance -= tovars[_id].cost;
                address sell = tovars[_id].seller;
                uint256 s_id = 0;
                while (users[s_id].ip != sell) {
                    s_id++;
                }
                users[m_id].history_b.length++;
                users[m_id].history_b[users[m_id].history_b.length - 1] = tovars[_id];
                users[s_id].history_s.length++;
                users[s_id].history_s[users[s_id].history_s.length - 1] = tovars[_id];
                users[s_id].balance += tovars[_id].cost;
                for (uint256 i = _id + 1; i < tovars.length; i++) {
                    tovars[i - 1] = tovars[i];
                }
                delete tovars[tovars.length - 1];
                tovars.length--;
            }
        } else {
            throw;
        }
    }
}