# https://gist.github.com/dperconti/0c3ce81c1bea6593e0989ab58ee411f4
import datetime
from pprint import pprint
from statistics import mean

TRANSACTIONS = [{"transaction_id": "tx_78e3fa01b572", "transaction_date": "2023-01-01", "transaction_type": "Purchases", "amount": 5000, "description": "Online shopping"}, {"transaction_id": "tx_d2c0df115b8c", "transaction_date": "2023-01-01", "transaction_type": "Purchases", "amount": 5000, "description": "Electronics purchase"}, {"transaction_id": "tx_225a164814a3", "transaction_date": "2023-01-02", "transaction_type": "Reversals", "reversal_transaction_id": "tx_78e3fa01b572", "amount": -5000, "description": "Merchant reversal"}, {"transaction_id": "tx_9787650c8d88", "transaction_date": "2023-01-03", "transaction_type": "Purchases", "amount": 50000, "description": "Online shopping"}, {"transaction_id": "tx_26a6cf6f5c3b", "transaction_date": "2023-01-03", "transaction_type": "Purchases", "amount": 30000, "description": "Online shopping"}, {"transaction_id": "tx_4c3511be46d0", "transaction_date": "2023-01-03", "transaction_type": "Refunds", "amount": -1500, "description": "Product return"}, {"transaction_id": "tx_39b600979652", "transaction_date": "2023-01-04", "transaction_type": "Payments", "amount": -5000, "description": "Credit card payment"}, {"transaction_id": "tx_b97f4ae1960b", "transaction_date": "2023-01-05", "transaction_type": "Purchases", "amount": 75000, "description": "Grocery shopping"}, {"transaction_id": "tx_3442c1d8c5ad", "transaction_date": "2023-01-05", "transaction_type": "Purchases", "amount": 5000, "description": "Grocery shopping"}, {"transaction_id": "tx_47bf2bc1f339", "transaction_date": "2023-01-06", "transaction_type": "Reversals", "reversal_transaction_id": "", "amount": -5000, "description": "Canceled order"}, {"transaction_id": "tx_44c03c248872", "transaction_date": "2023-01-07", "transaction_type": "Payments", "amount": -8000, "description": "Monthly bill payment"}, {"transaction_id": "tx_ca724c1f4489", "transaction_date": "2023-01-08", "transaction_type": "Purchases", "amount": 3200, "description": "Electronics purchase"}, {"transaction_id": "tx_8de806648612", "transaction_date": "2023-01-09", "transaction_type": "Payments", "amount": -1500, "description": "Partial payment"}, {"transaction_id": "tx_b2da976e7b15", "transaction_date": "2023-01-10", "transaction_type": "Purchases", "amount": 10000, "description": "Flight booking"}, {"transaction_id": "tx_73ab9d775507", "transaction_date": "2023-01-13", "transaction_type": "Purchases", "amount": 2000, "description": "Clothing purchase"}, {"transaction_id": "tx_6e906b3ac60b", "transaction_date": "2023-01-15", "reversal_transaction_id": "tx_b2da976e7b15", "transaction_type": "Reversals", "amount": -1000, "description": "Refunded order"}, {"transaction_id": "tx_7500b7c3f436", "transaction_date": "2023-01-15", "transaction_type": "Purchases", "amount": 5000, "description": "Medical bill payment"}, {"transaction_id": "tx_58e9c4fbe73c", "transaction_date": "2023-01-16", "transaction_type": "Purchases", "amount": 15000, "description": "Restaurant bill"}, {"transaction_id": "tx_c67fcd8b7ca9", "transaction_date": "2023-01-18", "transaction_type": "Payments", "amount": 2000, "description": "Utility bill payment"}, {"transaction_id": "tx_35575c16717f", "transaction_date": "2023-01-18", "transaction_type": "Purchases", "amount": 6000, "description": "Home appliance purchase"}, {"transaction_id": "tx_fe9cdf650dba", "transaction_date": "2023-01-18", "transaction_type": "Refunds", "amount": -1000, "description": "Canceled subscription refund"}, {"transaction_id": "tx_87d993379c5f", "transaction_date": "2023-01-20", "transaction_type": "Purchases", "amount": 3500, "description": "Insurance premium payment"}, {"transaction_id": "tx_ac1e68c1cb15", "transaction_date": "2023-01-21", "transaction_type": "Purchases", "amount": 4500, "description": "Gadget purchase"}, {"transaction_id": "tx_ee1575994652", "transaction_date": "2023-01-23", "transaction_type": "Purchases", "amount": 1200, "description": "Loan installment payment"}, {"transaction_id": "tx_2d6bd63cef9f", "transaction_date": "2023-01-23", "transaction_type": "Purchases", "amount": 1800, "description": "Book purchase"}, {"transaction_id": "tx_90b40faf5710", "transaction_date": "2023-01-23", "transaction_type": "Reversals", "reversal_transaction_id": "tx_ac1e68c1cb15", "amount": -4500, "description": "Gadget Reversal"}, {"transaction_id": "tx_3d6c0567257d", "transaction_date": "2023-01-25", "transaction_type": "Payments", "amount": -9000, "description": "Random repayment"}, {"transaction_id": "tx_39f0d051637a", "transaction_date": "2023-01-26", "transaction_type": "Purchases", "amount": 2500, "description": "Gift purchase"}, {"transaction_id": "tx_d7d59bdc5876", "transaction_date": "2023-01-27", "transaction_type": "Purchases", "amount": 1800, "description": "Education loan payment"}, {"transaction_id": "tx_d2c0df115b8c", "transaction_date": "2023-01-28", "transaction_type": "Purchases", "amount": 4200, "description": "Electronics purchase"}, {"transaction_id": "tx_7254c3c1dc10", "transaction_date": "2023-01-29", "transaction_type": "Payments", "amount": -2500, "description": "Credit card bill payment"}, {"transaction_id": "tx_7254c3c1dc10", "transaction_date": "2023-01-29", "transaction_type": "Payments", "amount": -188700, "description": "Balance Payoff"}]
YMD = "%Y-%m-%d"


class Transactions:
    def __init__(self, transactions, interest):
        self.interest = interest / 100 # to percent
        self.transactions = transactions
        self.start_date = datetime.datetime.strptime("2023-01-01", YMD)
        self.last_date = self._find_last_date()
        self.statement_dates = self._statement_dates()
        self.interest_rate = interest
        self.statements = {}
        self.calculate_statements()

    def _find_last_date(self):
        dates = sorted(t["transaction_date"] for t in self.transactions)
        if dates:
            return datetime.datetime.strptime(dates[-1], YMD)
        return self.start_date

    def _statement_dates(self):
        length = 7
        current = self.start_date
        target = self.last_date

        step = datetime.timedelta(days=(length - 1))

        dates = []
        while current <= target:
            chunk = [
                current,
            ]
            current += step
            if current > target:
                current = target
            chunk.append(current)
            current += datetime.timedelta(days=1)
            dates.append(chunk)
        return list(map(tuple, dates))

    def balance(self, transactions=None):
        if not transactions:
            # Handle any set of transactions
            transactions = self.transactions
        if not transactions:
            return None
        return sum(t["amount"] for t in transactions)

    def average(self):
        if not self.transactions:
            return None
        return mean(
            t["amount"]
            for t in self.transactions
            if t["transaction_type"] == "Purchases"
        )

    def largest(self):
        if not self.transactions:
            return None
        return max(abs(t["amount"]) for t in self.transactions)  # Largest by Volume
        # return max(t["amount"] for t in self.transactions if t['amount'] > 0)  # Highest amount over zero

    def calculate_statements(self):
        cursor = 0
        statements = {}
        keys = self.statement_dates
        for k in keys:
            statements[k] = {"transactions": [], "total": 0}

        for txn in self.transactions:
            txn_date = datetime.datetime.strptime(txn["transaction_date"], YMD)
            if not (keys[cursor][0] <= txn_date <= keys[cursor][1]):
                cursor += 1
            statements[keys[cursor]]["transactions"].append(txn)

        self.statements = statements
        return statements

    def calculate_interest(self):
        running_balance = 0
        for dates, statement in self.statements.items():
            total = self.balance(statement["transactions"])
            running_balance += total
            statement["total"] = total
            if total > 0:
                statement["transactions"].append({
                  "transaction_id": "tx_InterestCalc",
                  "transaction_date": "2023-99-99",
                  "transaction_type": "Interest",
                  "amount": int(self.interest * total),
                  "description": "Interest Charge"
                })

    def statements_print_formatted(self):
        total = 0
        for start_stop, statement in self.statements.items():
            start = datetime.datetime.strftime(start_stop[0], YMD)
            stop = datetime.datetime.strftime(start_stop[1], YMD)
            out = f"Date Range: {start} -> {stop}\n"
            for txn in statement["transactions"]:
                total += txn["amount"]
                out += (
                    f"* {txn['transaction_date']}"
                    f": {txn['transaction_id']}"
                    f": {txn['transaction_type']: <9}"
                    f"\t{txn['amount']:.0f}"
                    f"\t{total}"
                    f"\t{txn['description']}"
                )
                out += "\n"
            out += f"------------- TOTAL:{total}\n"

            print(out)


def interview():
    txns = Transactions(TRANSACTIONS, interest=12.34)

    balance = txns.balance()
    average = txns.average()
    largest = txns.largest()

    pprint(locals())
    print()

    txns.calculate_interest()
    txns.statements_print_formatted()


# Press the green button in the gutter to run the script.
if __name__ == "__main__":
    interview()

# See PyCharm help at https://www.jetbrains.com/help/pycharm/