投资练习

// SPDX-License-Identifier: GPL-3.0

pragma solidity >=0.7.0 <0.9.0;

contract CrowdFundingStorage{
    
    struct Campaign {
        address payable receiver;
        uint numFunders;
        uint fundingGoal;
        uint totalAmount;
    }

    struct Funder{
        address addr;
        uint amount;
    }

    uint public numCompagins;
    mapping (uint => Campaign) campanies;
    mapping (uint => Funder[]) funders;
    mapping (uint => mapping(address => bool)) public isPatticipate;
}


contract CrowdFunding is CrowdFundingStorage{

    address immutable owner;

    constructor (){
        owner = msg.sender;
    }
 
    modifier judgeParticipate(uint campaignID){
        require(isPatticipate[campaignID][msg.sender]==false);
        _;
    }

    modifier judgeOwner(){
        require(msg.sender == owner);
        _;
    }

    function newCampaign(address payable receiver, uint goal) external returns(uint campaignID){
        campaignID = numCompagins++;
        Campaign storage c = campanies[campaignID];
        c.receiver = receiver;
        c.fundingGoal = goal;
    }

    function bid(uint campaignID) external payable judgeParticipate(campaignID){
        Campaign storage c = campanies[campaignID];
        c.totalAmount += msg.value;
        c.numFunders += 1;
        funders[campaignID].push(Funder({
            addr: msg.sender,
            amount: msg.value
        }));
        isPatticipate[campaignID][msg.sender] = true;
    }

    function withdraw(uint campaignID) external returns (bool){
        Campaign storage c = campanies[campaignID];
        if(c.totalAmount < c.fundingGoal){
            return false;
        }
        uint amount = c.totalAmount;
        c.totalAmount = 0;
        c.receiver.transfer(amount);
        return true;
    }
}