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#!/usr/bin/env python3
"""expenses.py — a command-line expense tracker."""

import argparse
import json
from datetime import date
from pathlib import Path

FILE = Path("expenses.json")

# ---------- persistence ----------

def load():
"""Load expenses from JSON. Return empty list if file missing."""
if not FILE.exists():
return []
try:
with FILE.open() as f:
return json.load(f)
except json.JSONDecodeError:
print(f"Warning: {FILE} is corrupt. Starting fresh.")
return []

def save(expenses):
"""Write expenses to JSON."""
with FILE.open("w") as f:
json.dump(expenses, f, indent=2)

# ---------- commands ----------

def add_expense(amount, description, category="general"):
"""Add an expense and save."""
expenses = load()
expenses.append({
"date": date.today().isoformat(),
"amount": amount,
"description": description,
"category": category,
})
save(expenses)
print(f"Added: `${amount:.2f} — {description} ({category})")

def list_expenses():
"""Print all expenses."""
expenses = load()
if not expenses:
print("No expenses yet. Use 'add' to create one.")
return
print(f"{'Date':12} {'Amount':>10} {'Category':12} Description")
print("-" * 70)
for e in expenses:
print(f"{e['date']:12} $`{e['amount']:>9.2f} {e['category']:12} {e['description']}")

def summary():
"""Print total, count, and per-category breakdown."""
expenses = load()
if not expenses:
print("No expenses to summarize.")
return

total = sum(e["amount"] for e in expenses)
print(f"Total spent: `${total:.2f} across {len(expenses)} expenses")
print()

by_category = {}
for e in expenses:
cat = e["category"]
by_category[cat] = by_category.get(cat, 0) + e["amount"]

print("By category:")
for cat, amt in sorted(by_category.items(), key=lambda kv: kv[1], reverse=True):
pct = (amt / total) * 100
print(f" {cat:15} $`{amt:>8.2f} ({pct:.0f}%)")

# ---------- CLI ----------

def main():
parser = argparse.ArgumentParser(description="Track your expenses from the command line.")
sub = parser.add_subparsers(dest="command", required=True)

add = sub.add_parser("add", help="Add an expense")
add.add_argument("amount", type=float, help="Amount in dollars")
add.add_argument("description", help="Description")
add.add_argument("--category", default="general", help="Category (default: general)")

sub.add_parser("list", help="List all expenses")
sub.add_parser("summary", help="Show summary")

args = parser.parse_args()

if args.command == "add":
add_expense(args.amount, args.description, args.category)
elif args.command == "list":
list_expenses()
elif args.command == "summary":
summary()

if name == "main":
main()

# Add three expenses
python expenses.py add 12.50 "Coffee" --category food
python expenses.py add 45.00 "Gas" --category transport
python expenses.py add 8.99 "Streaming" --category entertainment

# List them
python expenses.py list
Date Amount Category Description
----------------------------------------------------------------------
2026-10-23 $ 12.50 food Coffee</span> <span class="out">2026-10-23 $ 45.00 transport Gas
2026-10-23 `$ 8.99 entertainment Streaming

# Summarize
python expenses.py summary
Total spent:  45.00 (68%)
 food  8.99 (14%)

# See the auto-generated help
python expenses.py --help
python expenses.py add --help