// SPDX-License-Identifier: MIT
pragma solidity ^0.8.30;

/// Public links only. The board does not fetch, endorse or verify destinations.
contract FractoraBoard {
    struct Link { address author; string url; string title; uint64 createdAt; bool active; }
    Link[] private links;
    mapping(address => mapping(bytes32 => bool)) public activeUrl;
    event LinkPublished(uint256 indexed id, address indexed author, string url, string title);
    event LinkRemoved(uint256 indexed id, address indexed author);
    error InvalidUrl(); error InvalidTitle(); error Duplicate(); error NotAuthor(); error Missing();

    function publish(string calldata url, string calldata title) external returns (uint256 id) {
        bytes memory u = bytes(url); bytes memory t = bytes(title);
        if (u.length < 9 || u.length > 256 || u[0] != 'h' || u[1] != 't' || u[2] != 't' || u[3] != 'p' || u[4] != 's' || u[5] != ':' || u[6] != '/' || u[7] != '/') revert InvalidUrl();
        // A prefix check is not a full URL validator or a safety guarantee.
        for (uint256 i; i < u.length; ++i) if (uint8(u[i]) <= 32 || uint8(u[i]) == 127) revert InvalidUrl();
        if (t.length == 0 || t.length > 80) revert InvalidTitle();
        bytes32 key = keccak256(u);
        if (activeUrl[msg.sender][key]) revert Duplicate();
        activeUrl[msg.sender][key] = true; id = links.length;
        links.push(Link(msg.sender, url, title, uint64(block.timestamp), true));
        emit LinkPublished(id, msg.sender, url, title);
    }
    function remove(uint256 id) external {
        if (id >= links.length || !links[id].active) revert Missing();
        Link storage link = links[id];
        if (link.author != msg.sender) revert NotAuthor();
        link.active = false; activeUrl[msg.sender][keccak256(bytes(link.url))] = false;
        emit LinkRemoved(id, msg.sender);
    }
    function count() external view returns (uint256) { return links.length; }
    function get(uint256 id) external view returns (Link memory) {
        if (id >= links.length) revert Missing(); return links[id];
    }
}