discourse/contracts/FeeBarrier.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

/**
 * @title FeeBarrier
 * @dev Contract for implementing economic barriers for unverified users submitting perspectives
 */
contract FeeBarrier {
    // State variables
    uint256 public constant FEE_AMOUNT = 0.01 ether; // POL fee amount
    uint256 public constant REFUND_PERIOD = 1 days;  // Time period after which a fee can be refunded
    address public owner;
    
    // Structs
    struct Content {
        address user;
        string issueId;
        string content;
        string fileUrl;
        bool isVerified;
        uint256 timestamp;
        bool isFlagged;
        bool feeRefunded;
    }
    
    // Mappings
    mapping(uint256 => Content) public contents;
    uint256 public contentCounter;
    
    // Events
    event FeePaid(address indexed user, uint256 indexed contentId, uint256 fee);
    event FeeRefunded(address indexed user, uint256 indexed contentId, uint256 fee);
    event ContentFlagged(uint256 indexed contentId, address flagger);
    event ContentSubmitted(uint256 indexed contentId, address indexed user, string issueId);
    
    // Constructor
    constructor() {
        owner = msg.sender;
        contentCounter = 0;
    }
    
    // Modifiers
    modifier onlyOwner() {
        require(msg.sender == owner, "Only owner can call this function");
        _;
    }
    
    /**
     * @dev Submit content with a fee for unverified users
     * @param issueId The ID of the issue this content relates to
     * @param content The actual content text
     * @param fileUrl Optional URL to an attached file
     * @param isVerified Whether the user is verified
     * @return contentId The ID of the submitted content
     */
    function payFeeAndSubmit(
        string memory issueId,
        string memory content,
        string memory fileUrl,
        bool isVerified
    ) public payable returns (uint256) {
        // Verified users don't need to pay a fee
        if (!isVerified) {
            require(msg.value >= FEE_AMOUNT, "Insufficient fee amount");
        }
        
        uint256 contentId = contentCounter++;
        
        contents[contentId] = Content({
            user: msg.sender,
            issueId: issueId,
            content: content,
            fileUrl: fileUrl,
            isVerified: isVerified,
            timestamp: block.timestamp,
            isFlagged: false,
            feeRefunded: isVerified // Mark as refunded already if verified (no fee)
        });
        
        emit ContentSubmitted(contentId, msg.sender, issueId);
        
        // Only emit fee event for unverified users
        if (!isVerified) {
            emit FeePaid(msg.sender, contentId, msg.value);
        }
        
        return contentId;
    }
    
    /**
     * @dev Refund fee if content is not flagged after the refund period
     * @param contentId The ID of the content to refund fee for
     */
    function refundFee(uint256 contentId) public {
        Content storage contentItem = contents[contentId];
        
        require(contentId < contentCounter, "Content does not exist");
        require(!contentItem.isVerified, "No fee to refund for verified users");
        require(!contentItem.feeRefunded, "Fee already refunded");
        require(!contentItem.isFlagged, "Cannot refund fee for flagged content");
        require(
            block.timestamp >= contentItem.timestamp + REFUND_PERIOD,
            "Refund period not passed yet"
        );
        
        contentItem.feeRefunded = true;
        
        // Transfer the fee back to the user
        (bool success, ) = contentItem.user.call{value: FEE_AMOUNT}("");
        require(success, "Refund failed");
        
        emit FeeRefunded(contentItem.user, contentId, FEE_AMOUNT);
    }
    
    /**
     * @dev Flag content for moderation (callable by verified users or contract owner)
     * @param contentId The ID of the content to flag
     */
    function flagContent(uint256 contentId) public {
        require(contentId < contentCounter, "Content does not exist");
        require(!contents[contentId].isFlagged, "Content already flagged");
        
        // Only contract owner or verified users with special permissions can flag content
        // (This would be implemented with a proper access control system in a real contract)
        
        contents[contentId].isFlagged = true;
        emit ContentFlagged(contentId, msg.sender);
    }
    
    /**
     * @dev Batch refund for multiple contents that have passed the refund period
     * @param contentIds Array of content IDs to refund
     */
    function batchRefund(uint256[] memory contentIds) public {
        for (uint256 i = 0; i < contentIds.length; i++) {
            try this.refundFee(contentIds[i]) {
                // Refund successful
            } catch {
                // Skip failed refunds
            }
        }
    }
    
    /**
     * @dev Get content details
     * @param contentId The ID of the content to get
     */
    function getContent(uint256 contentId) public view returns (
        address user,
        string memory issueId,
        string memory content,
        string memory fileUrl,
        bool isVerified,
        uint256 timestamp,
        bool isFlagged,
        bool feeRefunded
    ) {
        require(contentId < contentCounter, "Content does not exist");
        Content storage contentItem = contents[contentId];
        
        return (
            contentItem.user,
            contentItem.issueId,
            contentItem.content,
            contentItem.fileUrl,
            contentItem.isVerified,
            contentItem.timestamp,
            contentItem.isFlagged,
            contentItem.feeRefunded
        );
    }
    
    /**
     * @dev Check if content is eligible for refund
     * @param contentId The ID of the content to check
     */
    function isEligibleForRefund(uint256 contentId) public view returns (bool) {
        if (contentId >= contentCounter) return false;
        
        Content storage contentItem = contents[contentId];
        return (
            !contentItem.isVerified &&
            !contentItem.feeRefunded &&
            !contentItem.isFlagged &&
            block.timestamp >= contentItem.timestamp + REFUND_PERIOD
        );
    }
    
    /**
     * @dev Withdraw any extra funds from the contract (only owner)
     * @param amount The amount to withdraw
     */
    function withdraw(uint256 amount) public onlyOwner {
        require(amount <= address(this).balance, "Insufficient balance");
        
        (bool success, ) = owner.call{value: amount}("");
        require(success, "Withdrawal failed");
    }
    
    /**
     * @dev Emergency withdraw function (only owner)
     */
    function emergencyWithdraw() public onlyOwner {
        (bool success, ) = owner.call{value: address(this).balance}("");
        require(success, "Emergency withdrawal failed");
    }
}