// SPDX-License-Identifier: Unlicense
pragma solidity ^0.8.24;

import "./core/DAO.sol";
import "./interfaces/IAcceptAvailability.sol";

contract Availability is IAcceptAvailability, DAOContract {
    struct AvailabilityStake {
        address worker;
        uint256 amount;
        uint endTime;
        bool assigned;
    }

    mapping(uint => AvailabilityStake) public stakes;
    uint public stakeCount;

    event AvailabilityStaked(uint stakeIndex);

    constructor(DAO dao) DAOContract(dao) {}

    /// Accept availability stakes as reputation token transfer
    function acceptAvailability(
        address sender,
        uint256 amount,
        uint duration
    ) external {
        require(
            msg.sender == address(dao),
            "acceptAvailability must only be called by DAO contract"
        );
        require(amount > 0, "No stake provided");
        uint stakeIndex = stakeCount++;
        AvailabilityStake storage stake = stakes[stakeIndex];
        stake.worker = sender;
        stake.amount = amount;
        stake.endTime = block.timestamp + duration;
        emit AvailabilityStaked(stakeIndex);
    }

    function extendAvailability(uint stakeIndex, uint duration) external {
        AvailabilityStake storage stake = stakes[stakeIndex];
        require(
            msg.sender == stake.worker,
            "Worker can only extend their own availability stake"
        );
        require(!stake.assigned, "Stake has already been assigned work");
        if (block.timestamp > stake.endTime) {
            stake.endTime = block.timestamp + duration;
        } else {
            stake.endTime = stake.endTime + duration;
        }
        emit AvailabilityStaked(stakeIndex);
    }

    /// Select a worker randomly from among the available workers, weighted by amount staked
    function randomWeightedSelection() internal view returns (uint stakeIndex) {
        uint totalStakes;
        for (uint i = 0; i < stakeCount; i++) {
            if (stakes[i].assigned) continue;
            if (block.timestamp > stakes[i].endTime) continue;
            totalStakes += stakes[i].amount;
        }
        require(totalStakes > 0, "No available worker stakes");
        uint select = block.prevrandao % totalStakes;
        uint acc;
        for (uint i = 0; i < stakeCount; i++) {
            if (stakes[i].assigned) continue;
            if (block.timestamp > stakes[i].endTime) continue;
            acc += stakes[i].amount;
            if (acc > select) {
                stakeIndex = i;
                break;
            }
        }
    }

    /// Assign a random available worker
    function assignWork() internal returns (uint stakeIndex) {
        stakeIndex = randomWeightedSelection();
        AvailabilityStake storage stake = stakes[stakeIndex];
        stake.assigned = true;
    }
}