loomnetwork/ethfiddle

pragma solidity^0.5.1;

contract Courier {
enum PackageStatus {
inTransit,
received,
cancelled,
arrived,
booked
}

struct Package {
    uint id;
    uint weight;
    address sender;
    PackageStatus status;
    address receiver;
}
uint MULTIPLIER = 1;
mapping (uint => address payable) public packageCourierId;
mapping (address => uint) public pendingDeliveryCharge;
Package[] private _packages;
event PackageBooked(uint id, address sender, address receiver, uint weight);
event PackagePicked(uint id, address courier, address sender, address receiver);
event PackageArrived(uint id, address courier, address sender, address receiver);
event PackageReceived(uint id, address courier, address sender, address receiver);
event PackageCancelled(uint id, address courier, address sender, address receiver);

function addPackage(uint  _weight, address payable receiver) public payable returns (uint){
    // Multipler is the numerical factor converting weight to delivery charge
    // we are keeping it as 1 for now.  Value must be equal to
    // weight*MULTIPLIER

    require(msg.value == _weight*MULTIPLIER, "Incorrect amount");

    uint id = _packages.length;
    _packages.push(Package({
        id: id,
        weight: _weight,
        sender: msg.sender,
        status: PackageStatus.booked,
        receiver: receiver
    }));



    emit PackageBooked(id, msg.sender, receiver, _weight);
    pendingDeliveryCharge[msg.sender] += msg.value;

    return id;

}

function pickPackage(uint _id) public{
    // courier calls this function to indicate that he has picked up the package
    Package storage currentPackage = _packages[_id];
    require(currentPackage.status == PackageStatus.booked, "Package is already dispatched");
    currentPackage.status = PackageStatus.inTransit;

    packageCourierId[_id] = msg.sender;

    emit PackagePicked(_id, msg.sender, currentPackage.sender, currentPackage.receiver);

}

function arrivedPackage(uint _id) public{
    // this function will be called by the courier
    // to indicate to the receiver that he has arrived at his address

    Package storage currentPackage = _packages[_id];
    require(currentPackage.status == PackageStatus.inTransit, "Package was not in transit for it to arrive");
    currentPackage.status = PackageStatus.arrived;

    emit PackageArrived(_id, msg.sender, currentPackage.sender, currentPackage.receiver);
}

function receivedPackage(uint _id) public payable returns (bool){
    // this function will be called by the receiver
    // to indicate that he has received the package


    Package storage currentPackage = _packages[_id];

    require(currentPackage.receiver == msg.sender && currentPackage.status == PackageStatus.arrived, "Package arrived at wrong receiver");
    currentPackage.status = PackageStatus.received;
    uint deliveryCharge = currentPackage.weight*MULTIPLIER;
    address payable courier = packageCourierId[_id];


    if(courier.send(deliveryCharge)){
        pendingDeliveryCharge[currentPackage.sender] -= deliveryCharge;
        emit PackageReceived(_id, courier, currentPackage.sender, currentPackage.receiver);
        return true;
    }
    else {
        return false;
    }
}

function cancelPackage(uint _id) public returns (bool){
    // only sender of package has the right to cancel Package
    // Funds will be given to courier only if he has picked up the package
    Package storage currentPackage = _packages[_id];
    require(msg.sender == currentPackage.sender && (currentPackage.status == PackageStatus.inTransit || currentPackage.status == PackageStatus.booked), "You do not have authorization to cancel package"