// SPDX-License-Identifier: MIT OR Apache-2.0
pragma solidity >=0.6.11;

import "./Common.sol";
import "./Merkle.sol";
import "./Queue.sol";

contract Home is MerkleTreeManager, QueueManager, Common {
    using QueueLib for QueueLib.Queue;
    using MerkleLib for MerkleLib.Tree;

    mapping(uint32 => uint32) public sequences;

    uint256 constant BOND_SIZE = 50 ether;

    event Dispatch(
        uint32 indexed destination,
        uint32 indexed sequence,
        // the message is after this root. Some future update will contain it.
        bytes32 indexed current,
        bytes message
    );
    event ImproperUpdate();

    constructor(
        uint32 _originSLIP44,
        address _updater,
        bytes32 _current
    )
        payable
        MerkleTreeManager()
        QueueManager()
        Common(_originSLIP44, _updater, _current)
    {
        require(msg.value >= BOND_SIZE, "insufficient bond");
    }

    function fail() internal override {
        _setFailed();
        msg.sender.transfer(address(this).balance / 2);
    }

    function enqueue(
        uint32 destination,
        bytes32 recipient,
        bytes memory body
    ) external notFailed {
        uint32 sequence = sequences[destination] + 1;
        sequences[destination] = sequence;

        bytes32 _digest =
            Message.messageHash(
                originSLIP44,
                bytes32(uint256(uint160(msg.sender))),
                sequence,
                destination,
                recipient,
                body
            );

        tree.insert(_digest);
        queue.enqueue(root());
        emit Dispatch(destination, sequence, current, body);
    }

    function update(
        bytes32 _oldRoot,
        bytes32 _newRoot,
        bytes memory _signature
    ) external notFailed {
        if (improperUpdate(_newRoot, _oldRoot, _signature)) return;
        while (true) {
            bytes32 next = queue.dequeue();
            if (next == _newRoot) break;
        }
        emit Update(_oldRoot, _newRoot, _signature);
    }

    function improperUpdate(
        bytes32 _oldRoot,
        bytes32 _newRoot,
        bytes memory _signature
    ) public notFailed returns (bool) {
        require(Common.checkSig(_newRoot, _oldRoot, _signature), "bad sig");
        require(_oldRoot == current, "Not a current update");
        if (!queue.contains(_newRoot)) {
            fail();
            emit ImproperUpdate();
            return true;
        }
        return false;
    }

    function suggestUpdate() external view returns (bytes32, bytes32) {
        return (current, queue.lastItem());
    }
}