app.py

from flask import Flask, Response, render_template, request, url_for, make_response, flash, redirect
from flask_sqlalchemy import SQLAlchemy
from datetime import datetime, date as Date
from sqlalchemy import func



app = Flask(__name__)

app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///expenses.db'
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
app.config['SECRET_KEY'] = 'my-secret-key'
db = SQLAlchemy(app)

class Expense(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    description = db.Column(db.String(120), nullable=False)
    amount = db.Column(db.Float, nullable=False)
    category = db.Column(db.String(50), nullable=False)
    date = db.Column(db.Date, nullable=False, default=Date.today)

    def __init__(self, description, amount, category, expense_date):
        self.description = description
        self.amount = amount
        self.category = category
        self.date = expense_date




with app.app_context():
    db.create_all()


CATEGORIES = ["Food", "Transport", "Rent", "Utilities", "Health", "Work"]


def parse_date_or_not(s: str):
    if not s:
        return None
    try:
        return datetime.strptime(s, "%Y-%m-%d").date()
    except ValueError:
        return None


@app.route("/")
def index():


    start_str = (request.args.get("start") or "").strip()
    end_str = (request.args.get("end") or "").strip()
    selected_category = (request.args.get("category") or "").strip()


    start_date = parse_date_or_not(start_str)
    end_date = parse_date_or_not(end_str)

    if start_date and end_date and end_date < start_date:
        flash("End date cannot be before start date.", "error")
        start_date = end_date = None
        start_str = end_str = ""


    q = Expense.query
    expense_date = getattr(Expense, "date")

    if start_date:
        q = q.filter(expense_date >= start_date)
    if end_date:
        q = q.filter(expense_date <= end_date)

    if selected_category:
        q = q.filter(Expense.category == selected_category)

    expenses = q.order_by(expense_date.desc(), Expense.id.desc()).all()
    total = round(sum(e.amount for e in expenses), 2)


    cat_q = db.session.query(Expense.category, func.sum(Expense.amount))

    if start_date:
        cat_q = cat_q.filter(expense_date >= start_date)
    if end_date:
        cat_q = cat_q.filter(expense_date <= end_date)
    if selected_category:
        cat_q = cat_q.filter(Expense.category == selected_category)

    cat_rows = cat_q.group_by(Expense.category).all()

    cat_labels = [c for c, _ in cat_rows]
    cat_values = [round(float(s or 0), 2) for _, s in cat_rows]





    day_q = db.session.query(Expense.date, func.sum(Expense.amount))

    if start_date:
        day_q = day_q.filter(expense_date >= start_date)
    if end_date:
        day_q = day_q.filter(expense_date <= end_date)
    if selected_category:
        day_q = day_q.filter(Expense.category == selected_category)

    day_rows = (
        day_q
        .group_by(Expense.date)
        .order_by(Expense.date)
        .all()
        )

    day_labels = [d.isoformat() for d, _ in day_rows]
    day_values = [round(float(s or 0), 2) for _, s in day_rows]










    return render_template(
        "index.html", 
        expenses=expenses,
        categories=CATEGORIES,
        today=Date.today().isoformat(),
        total=total,
        start_str=start_str,
        end_str=end_str,
        selected_category=selected_category,
        cat_labels=cat_labels,
        cat_values=cat_values,
        day_labels=day_labels,
        day_values=day_values
        
        )


@app.route("/add", methods=['POST'])
def add():

    description = (request.form.get("description") or "").strip()
    amount_str = (request.form.get("amount") or "").strip()
    category = (request.form.get("category") or "").strip()
    date_str = (request.form.get("date") or "").strip()

    if not description or not amount_str or not category:
        flash("Please fill description, amount, and category", "error")
        return redirect(url_for("index"))


    try:
        amount = float(amount_str)
        if amount <= 0:
            raise ValueError

    except ValueError:
        flash("Amount must be a positive number", "error")
        return redirect(url_for("index"))
    

    try:
        d = datetime.strptime(date_str, "%Y-%m-%d").date() if date_str else Date.today()
    except ValueError:
        d = Date.today()

    e = Expense(description, amount, category, d)
    db.session.add(e)
    db.session.commit() 

    flash("Expense added successfully", "success")
    return redirect(url_for("index"))


@app.route('/delete/<int:expense_id>', methods=['POST'])
def delete(expense_id):
    e = Expense.query.get_or_404(expense_id)
    db.session.delete(e)
    db.session.commit()

    flash("Expense deleted successfully", "success")
    return redirect(url_for("index"))



@app.route('/edit/<int:expense_id>', methods=['GET'])
def edit(expense_id):
    e = Expense.query.get_or_404(expense_id)

    return render_template(
        "edit.html",
        expense=e,
        categories=CATEGORIES, 
        today=Date.today().isoformat()
    )

@app.route('/edit/<int:expense_id>', methods=['POST'])
def edit_post(expense_id):
    e = Expense.query.get_or_404(expense_id)

    description = (request.form.get("description") or "").strip()
    amount_str = (request.form.get("amount") or "").strip()
    category = (request.form.get("category") or "").strip()
    date_str = (request.form.get("date") or "").strip()

    if not description or not amount_str or not category:
        flash("Please fill description, amount, and category", "error")
        return redirect(url_for("edit", expense_id=expense_id))
    
    try:
        amount = float(amount_str)
        if amount <= 0:
            raise ValueError
    except ValueError:
        flash("Amount must be a positive number", "error")
        return redirect(url_for("edit", expense_id=expense_id))

    try:
        d = datetime.strptime(date_str, "%Y-%m-%d").date() if date_str else Date.today()
    except ValueError:  
        d = Date.today()

    e.description = description
    e.amount = amount
    e.category = category
    e.date = d

    db.session.commit()
    flash("Expense updated successfully", "success")
    return redirect(url_for("index"))


    return render_template(
        "edit.html",
        expense=e,
        categories=CATEGORIES, 
        today=Date.today().isoformat()
    )



@app.route("/export.csv")
def export_csv():

    start_str = (request.args.get("start") or "").strip()
    end_str = (request.args.get("end") or "").strip()
    selected_category = (request.args.get("category") or "").strip()


    start_date = parse_date_or_not(start_str)
    end_date = parse_date_or_not(end_str)

    q = Expense.query
    expense_date = getattr(Expense, "date")

    if start_date:
        q = q.filter(expense_date >= start_date)
    if end_date:
        q = q.filter(expense_date <= end_date)

    if selected_category:
        q = q.filter(Expense.category == selected_category)


    expenses = q.order_by(expense_date, Expense.id).all()

    lines = ["date,description,amount,category"]

    for e in expenses:
        lines.append(
            f"{e.date.isoformat()},{e.description},{e.amount:.2f},{e.category}"
            )
    csv_data = "\n".join(lines)



    fname_start = start_str or "all"
    fname_end = end_str or "all"
    filename = f"expenses_{fname_start}_to_{fname_end}.csv"




    return Response (
        csv_data,
        headers = {
            "Content-Type": "text/csv",
            "Content-Disposition": f"attachment; filename={filename}"
        }
    )

    







if __name__ == "__main__":
    app.run(debug=True, port=5000)