private void calculateDebts()
{
//We are iterating over the debtors list and the creditors list.
//For each debtor we pay as much as we can to each creditor, until our balance is 0. Then we move to the next
//debtor. If the creditor's balance reaches 0, we move to the next creditor.
int debtorsIndex = 0;
int creditorsIndex = 0;
while (debtorsIndex < debtors.Count && creditorsIndex < creditors.Count)
{
UserSubTotal currDebtor = debtors[debtorsIndex];
UserSubTotal currCreditor = creditors[creditorsIndex];
decimal currentPaid = 0;
if (currDebtor.balance > currCreditor.balance)
{
//in this case the current debtor has a larger balance than the current creditor balance.
//the current debtor will pay the entire balance of the current creditor.
//we reduce the balance of the current debtor by the balance of the current creditor.
//we move to the next creditor that needs to be payed.
currentPaid = currCreditor.balance;
currDebtor.balance -= currCreditor.balance;
currCreditor.balance = 0;
creditorsIndex += 1;
}
else if (currDebtor.balance < currCreditor.balance)
{
//in this case the current creditor has a larger balance than the current debtor's balance.
//the current debtor will pay their entire balance to the current creditor.
//we reduce the balance of the current creditor by the balance of the current debtor.
//we move to the next debtor that owes money.
currentPaid = currDebtor.balance;
currCreditor.balance -= currDebtor.balance;
currDebtor.balance = 0;
debtorsIndex += 1;
}
else
{
//In this case the current creditor has an equal balance as the current debtor.
//The debtor will pay off the creditors balance.
//We move to the next creditor and debtor.
currentPaid = currDebtor.balance;
currCreditor.balance = 0;
currDebtor.balance = 0;
debtorsIndex += 1;
creditorsIndex += 1;
}
//We add an object to keep track of who payed who, and how much.
Debt newDebt = new Debt()
{
debtor = currDebtor.name, creditor = currCreditor.name, amount = currentPaid
};
debts.Add(newDebt);
}
}
private void calculateTotalCostAndSubTotals(List <Booking> bookings)
{
decimal total = 0;
List <UserSubTotal> subTotals = new List <UserSubTotal>();
//For each booking, we go through each expense to populate the total cost of the trip, and the subtotal for each
//booking a.k.a user
foreach (Booking b in bookings)
{
UserSubTotal newSubTotal = new UserSubTotal {
name = b.User.UserName, subtotal = 0, balance = 0
};
foreach (Expense e in b.Expenses)
{
total += e.Cost;
newSubTotal.subtotal += e.Cost;
}
subTotals.Add(newSubTotal);
}
//This is the equally divided cost of the trip for each user.
decimal costForEach = subTotals.Count == 0 ? 0 : total / subTotals.Count;
//For each user subtotal, we are seeing if they spent more or less than the costForEach.
//We add them to the creditors list or debtors list.
foreach (UserSubTotal st in subTotals)
{
decimal difference = st.subtotal - costForEach;
if (difference < 0)
{
//In this case, the user spent less than the costForEach. So they have an owing balance, and they are
//added to the debtors list.
st.balance = Math.Abs(difference);
debtors.Add(st);
}
else
{
st.balance = difference;
creditors.Add(st);
}
}
this.SubTotals = subTotals;
this.TotalCost = total;
}