tree_in_solidity.sol

pragma solidity ^0.4.24;

contract Tree {
    struct Node {
        bytes32 name;
        bytes32 parent;
        bytes32 data;
        bytes32[] nodes;
    }

    mapping(bytes32 => Node) nodes;

    function() public {
        revert();
    }

    function get(bytes32 _name, bytes32 _parent) public view returns (bytes32, bytes32, bytes32, bytes32[]) {
        Node storage node = nodes[keccak256(_parent, _name)];
        return (node.name, node.parent, node.data, node.nodes);
    }

    function add(bytes32 _name, bytes32 _parent, string _data) public {
        require(_name.length > 0);
        
        bytes32 path = keccak256(_parent, _name);
        Node storage node = nodes[path];
        require(node.name == 0x0);
        
        nodes[path] = Node({
            name: _name, 
            parent: _parent, 
            data: _data, 
            nodes: new bytes32[](0)
        });
        nodes[_parent].nodes.push(path);
    }

    function update(bytes32 _name, bytes32 _parent, bytes32 _data) public {
        bytes32 path = keccak256(_parent, _name);
        Node storage node = nodes[path];
        require(node.name.length > 0);
        
        node.data = _data;
    }

    function remove(bytes32 _name, bytes32 _parent) public {
        bytes32 path = keccak256(_parent, _name);
        require(nodes[path].nodes.length == 0);     // allow to remove leaves (node without linked nodes)
        
        delete nodes[path];                         // removes from nodes
        
        // removes from parent list of nodes
        bytes32[] storage childs = nodes[_parent].nodes;
        for (uint256 i = getIndex(childs, path); i < childs.length - 1; i++) {
            childs[i] = childs[i + 1];
        }
        delete childs[childs.length - 1];
        childs.length--;
    }

    function getIndex(bytes32[] childs, bytes32 _path) pure internal returns (uint256) {
        for (uint256 i = 0; i < childs.length; i++) {
            if (_path == childs[i]) {
                return i;
            }
        }
        return childs.length - 1;
    }
}