Project 1: Expense Tracker CLI

uv run expense add 250 "দুপুরের খাবার" --category food
uv run expense add 60 "রিকশা" --category transport --date 2026-10-28
uv run expense list --month 2026-10
uv run expense report --month 2026-10
uv run expense delete 3
uv run expense export --month 2026-10 --out october.csv

$ uv run expense report --month 2026-10

অক্টোবর ২০২৬ এর খরচ
-----------------------------
food          ৳ 4,250.00   (৪৮%)
transport     ৳ 1,860.00   (২১%)
bills         ৳ 2,700.00   (৩১%)
-----------------------------
মোট           ৳ 8,810.00
সবচেয়ে বড় খরচ: বিদ্যুৎ বিল (৳ 1,450.00)

expense-tracker/
├── pyproject.toml
├── README.md
├── src/expense_tracker/
│   ├── __init__.py
│   ├── models.py        ← Expense, Category (dataclass/enum), Money format
│   ├── errors.py        ← ExpenseError পরিবার
│   ├── storage.py       ← JsonStorage: load, save (atomic)
│   ├── service.py       ← ExpenseService: add, list, delete, report (logic)
│   ├── export.py        ← CSV
│   └── cli.py           ← argparse, output সাজানো, error ধরা
└── tests/
    ├── conftest.py
    ├── test_models.py
    ├── test_service.py
    └── test_storage.py

# models.py
from dataclasses import dataclass
from datetime import date
from enum import StrEnum


class Category(StrEnum):
    FOOD = "food"
    TRANSPORT = "transport"
    BILLS = "bills"
    SHOPPING = "shopping"
    HEALTH = "health"
    OTHER = "other"


@dataclass
class Expense:
    id: int
    amount: int            # পয়সায়
    title: str
    category: Category
    spent_on: date


def format_taka(paisa: int) -> str:
    return f"৳ {paisa / 100:,.2f}"


def parse_taka(text: str) -> int:
    """'250' বা '250.50' কে পয়সায় বদলায়।"""
    ...   # তুমি লেখো: Decimal ব্যবহার করো, ঋণাত্মক বা শূন্য হলে InvalidAmountError

# errors.py
class ExpenseError(Exception):
    """সব expense error এর মূল। cli এটা ধরে সুন্দর message দেখাবে।"""

class InvalidAmountError(ExpenseError): ...
class ExpenseNotFoundError(ExpenseError): ...
class StorageError(ExpenseError): ...

# storage.py
from pathlib import Path
from typing import Protocol


class Storage(Protocol):
    def load(self) -> list[Expense]: ...
    def save(self, expenses: list[Expense]) -> None: ...


class JsonStorage:
    def __init__(self, path: Path) -> None:
        self.path = path

    def load(self) -> list[Expense]:
        # file না থাকলে খালি list
        # JSON ভাঙা থাকলে StorageError (from e)
        ...

    def save(self, expenses: list[Expense]) -> None:
        # atomic save: .tmp এ লিখে os.replace
        ...

# service.py
class ExpenseService:
    def __init__(self, storage: Storage) -> None:
        self.storage = storage

    def add(self, amount: int, title: str, category: Category, spent_on: date) -> Expense: ...
    def list_month(self, year: int, month: int) -> list[Expense]: ...
    def delete(self, expense_id: int) -> None: ...      # না পেলে ExpenseNotFoundError
    def report(self, year: int, month: int) -> "MonthlyReport": ...

# cli.py
import argparse
import sys


def build_parser() -> argparse.ArgumentParser:
    parser = argparse.ArgumentParser(prog="expense", description="দৈনিক খরচের হিসাব")
    sub = parser.add_subparsers(dest="command", required=True)

    add = sub.add_parser("add", help="নতুন খরচ")
    add.add_argument("amount")
    add.add_argument("title")
    add.add_argument("--category", default="other", choices=[c.value for c in Category])
    add.add_argument("--date", type=date.fromisoformat, default=date.today())

    lst = sub.add_parser("list", help="মাসের খরচ")
    lst.add_argument("--month", required=True, help="যেমন 2026-10")

    # report, delete, export তুমি যোগ করো
    return parser


def main(argv: list[str] | None = None) -> int:
    args = build_parser().parse_args(argv)
    service = ExpenseService(JsonStorage(default_path()))
    try:
        match args.command:
            case "add":
                exp = service.add(parse_taka(args.amount), args.title, Category(args.category), args.date)
                print(f"যোগ হলো #{exp.id}: {exp.title} {format_taka(exp.amount)}")
            case "list":
                ...
    except ExpenseError as e:
        print(f"সমস্যা: {e}", file=sys.stderr)
        return 1
    return 0

[project.scripts]
expense = "expense_tracker.cli:main"

# tests/conftest.py
import pytest
from expense_tracker.storage import JsonStorage
from expense_tracker.service import ExpenseService


@pytest.fixture
def service(tmp_path):
    return ExpenseService(JsonStorage(tmp_path / "data.json"))