challenge_py.py

import uuid

OMISE_FEE    = 0.0365
THAILAND_VAT = 0.07

class Transaction:
    def __init__(self, balance, direction, amount, description):
        self.balance     = balance
        self.direction   = direction
        self.amount      = amount
        self.description = description

    def match(self, balance, direction):
        return self.balance == balance and self.direction == direction

    def __str__(self):
        return "[ {:>11s} ] {:<6s} {:>7,.2f} - {}".format(
            self.balance,
            self.direction,
            self.amount,
            self.description,
        )

class Charge:
    def __init__(self, merchant, customer, amount):
        self.id       = 'chrg_' + uuid.uuid4().hex[-6:]
        self.merchant = merchant
        self.customer = customer
        self.amount   = amount

    def bookkeep(self):
        total   = self.amount
        fee     = round(total * OMISE_FEE, 2)
        fee_vat = round(fee * THAILAND_VAT, 2)
        net     = total - fee - fee_vat

        return [
            Transaction(self.customer, 'credit', total,   'customer charge'),
            Transaction(self.id,       'debit',  total,   'customer charge'),
            Transaction(self.id,       'credit', fee,     'processing fee'),
            Transaction('Omise',       'debit',  fee,     'processing fee'),
            Transaction(self.id,       'credit', fee_vat, 'VAT on processing fee'),
            Transaction('Omise',       'debit',  fee_vat, 'VAT on processing fee'),
            Transaction(self.id,       'credit', net,     'merchant net'),
            Transaction(self.merchant, 'debit',  net,     'merchant net'),
        ]
    
    def __str__(self):
        return '[{}] {} - {} {:>7,.2f}'.format(
            self.merchant,
            self.id,
            self.customer,
            self.amount,
        )


charges = [
    Charge('Burger King', 'John', 199.88),
    Charge('Burger King', 'John',  99.89),
    Charge('Burger King', 'John', 259.99),
]

transactions = []
for chrg in charges:
    transactions.extend(chrg.bookkeep())

debits  = sum(tx.amount for tx in transactions if tx.match('John', 'debit'))
credits = sum(tx.amount for tx in transactions if tx.match('John', 'credit'))
john_total = debits - credits

debits  = sum(tx.amount for tx in transactions if tx.match('Omise', 'debit'))
credits = sum(tx.amount for tx in transactions if tx.match('Omise', 'credit'))
omise_total = debits - credits

debits  = sum(tx.amount for tx in transactions if tx.match('Burger King', 'debit'))
credits = sum(tx.amount for tx in transactions if tx.match('Burger King', 'credit'))
bking_total = debits - credits

print("John has %.2f in balance" % (john_total))
print("Omise has %.2f in balance" % (omise_total))
print("Burger King has %.2f in balance" % (bking_total))

print("\nCharges:")
for charge in charges:
    print(charge)

print("\nTransactions:")
for tx in transactions:
    print(tx)