pragma solidity ^0.8.13;

contract CapabilitySelectorMap {
    mapping(bytes32 => uint256) private entries;

    function register(bytes4 selector, address endpoint, uint32 ttl) external {
        bytes32 key = keccak256(abi.encodePacked(msg.sender, selector));
        uint256 packed;
        unchecked {
            packed = ((block.timestamp + ttl) << 160) | uint160(endpoint);
        }
        assembly {
            let alive := gt(ttl, 0)
            sstore(key, mul(packed, alive))
        }
    }

    function resolve(address agent, bytes4 selector) external view returns (address) {
        uint256 packed = entries[keccak256(abi.encodePacked(agent, selector))];
        uint256 expiration = packed >> 160;
        if (block.timestamp >= expiration) return address(0);
        return address(uint160(packed));
    }
}