Personal Finance App w. adapted currencies

import tkinter as tk
from tkinter import ttk
from datetime import datetime
from datetime import timedelta
import json
import os
import requests
from matplotlib.figure import Figure
from matplotlib.backends.backend_tkagg import FigureCanvasTkAgg


root = tk.Tk()
root.title("Personal Finance Tracker")
root.geometry("700x500")

transactions = []
currencies = ["USD", "EUR", "CAD", "JPY", "CNY", "GBP"]
exchange_rates = {}
BASE_CURRENCY = "USD"


# --- Functions ---
def fetch_exchange_rates(base=BASE_CURRENCY):
    url = f"https://api.frankfurter.app/latest?from={base}"
    try:
        response = requests.get(url)
        data = response.json()
        return data["rates"]
    except Exception as e:
        print("Failed to fetch exchange rates:", e)
        return {}

exchange_rates.update(fetch_exchange_rates("USD"))

def save_transactions():
    with open("transactions.json", "w") as f:
        json.dump(transactions, f, indent=4)

def load_transactions():
    if os.path.exists("transactions.json"):
        with open("transactions.json", "r") as f:
            loaded = json.load(f)
            transactions.extend(loaded)
            filter_and_display()


def add_transactions():
    description = desc_entry.get()
    amount = amount_entry.get()
    type = type_var.get()
    category = category_var.get()
    currency = currency_var.get()
    date = datetime.now().strftime("%Y-%m-%d") # %d-%m-%Y

    try:
        amount = float(amount)
    except ValueError:
        result_label.config(text="Amount must be a number!", fg="red")
        return

    if not description or not category or type not in ["Income", "Expense"]:
        result_label.config(text="Please fill all the fields.", fg="red")
        return

    # Store transaction and update table
    transactions.append([date, description, category, f"{amount:.2f}", currency, type])

    # tree.insert("", "end", values=(date, description, category, f"{amount:.2f}", currency, type))
    # update_summary()
    filter_and_display()

    clear_fields()
    save_transactions()
    result_label.config(text="Transaction added!", fg="green")

def update_summary():
    target_currency = default_currency_var.get()
    rates = exchange_rates

    income = 0
    expense = 0

    displayed = [tree.item(i, "values") for i in tree.get_children()]
    for t in displayed:
        amount = float(t[3])
        currency = t[4]

        rate_currency = 1.0 if currency == BASE_CURRENCY else rates.get(currency)
        rate_target = 1.0 if target_currency == BASE_CURRENCY else rates.get(target_currency)

        if rate_currency is None or rate_target is None:
            continue

        converted = amount / rate_currency * rate_target

        if t[5] == "Income":
            income += converted
        else:
            expense += converted

    balance = income - expense
    summary_label.config(
        text=f"Income: {target_currency} {income:.2f}    "
             f"Expense: {target_currency} {expense:.2f}    "
             f"Balance: {target_currency} {balance:.2f}"
    )

def convert_currency(amount, from_cur, to_cur, rates, base):
    if from_cur == to_cur:
        return float(amount)

    # rate relative to base; 1 base -> r units of cur
    def rate_vs_base(cur):
        if cur == base:
            return 1.0
        r = rates.get(cur)
        if r is None:
            raise ValueError(f"Missing FX rate for {cur} relative to {base}")
        return float(r)

    # A -> base
    if from_cur == base:
        amt_in_base = float(amount)
    else:
        r_from = rate_vs_base(from_cur)
        amt_in_base = float(amount) / r_from  # because r_from = units of 'from_cur' per 1 base

    # base -> B
    if to_cur == base:
        return amt_in_base
    r_to = rate_vs_base(to_cur)
    return amt_in_base * r_to

def compute_category_totals(transactions_list, selected_currency, rates, base):
    totals = {}
    for row in transactions_list:
        try:
            t_date, _desc, category, amount_str, from_cur, t_type = row
        except Exception:
            continue

        if str(t_type).lower() != "expense":
            continue

        try:
            amt = float(amount_str)
        except (TypeError, ValueError):
            continue

        try:
            amt_conv = convert_currency(amt, from_cur, selected_currency, rates, base)
        except Exception as e:
            print(f"[FX WARN] {e}; skipping row: {row}")
            continue

        totals[category] = totals.get(category, 0.0) + amt_conv
    return totals

def update_charts():
    # clear charts
    pie_ax.clear()
    bar_ax.clear()

    # get displayed transactions straight from the table
    displayed = [tree.item(i, "values") for i in tree.get_children()]

    # convert expenses to the currently selected summary currency
    target_currency = default_currency_var.get()
    category_totals = compute_category_totals(displayed, target_currency, exchange_rates, BASE_CURRENCY)

    if not category_totals:
        pie_ax.text(0.5, 0.5, 'No expenses', ha='center', va='center', fontsize=12)
        bar_ax.text(0.5, 0.5, 'No expenses', ha='center', va='center', fontsize=12)
    else:
        # pie chart
        pie_ax.pie(category_totals.values(), labels=category_totals.keys(), autopct="%1.1f%%")
        pie_ax.set_title(f"Expenses by Category ({target_currency})")

        # bar chart
        bar_ax.bar(category_totals.keys(), category_totals.values(), color="skyblue")
        bar_ax.set_ylabel(f"Amount ({target_currency})")
        bar_ax.set_xlabel("Expenses by Category")
        bar_ax.tick_params(axis='x', rotation=45)

    chart_canvas.draw()


def clear_fields():
    desc_entry.delete(0, tk.END)
    amount_entry.delete(0, tk.END)
    type_var.set("Income")
    category_var.set("General")
    currency_var.set("USD")

def delete_transaction():
    selected_item = tree.selection()
    if not selected_item:
        result_label.config(text="No transaction selected.", fg="red")
        return

    item = selected_item[0]
    values = list(tree.item(item, "values"))

    try:
        transactions.remove(values)
        tree.delete(item)
        save_transactions()
        update_summary()
        update_charts()  # keep charts in sync after deletion
        result_label.config(text="Transaction deleted.", fg="green")
    except ValueError:
        for i, t in enumerate(transactions):
            print(f"{i}: {t==values} - {t} vs {values}")
        result_label.config(text="Could not delete transaction.", fg="red")

def filter_and_display():
    for transaction in tree.get_children():
        tree.delete(transaction)

    now = datetime.now()
    selected = filter_var.get()
    filtered = []

    # ["Today", "last 3 days", "last 7 days", "last 30 days", "all transactions"]
    if selected == "Today":
        cutoff = now.replace(hour=0, minute=0, second=0, microsecond=0)
    elif selected == "last 3 days":
        cutoff = now - timedelta(days=3)
    elif selected == "last 7 days":
        cutoff = now - timedelta(days=7)
    elif selected == "last 30 days":
        cutoff = now - timedelta(days=30)
    elif selected == "all transactions":
        cutoff = datetime.min

    for t in transactions:
        t_date = datetime.strptime(t[0], "%Y-%m-%d")

        if t_date >= cutoff:
            filtered.append(t)

    for t in filtered:
        tree.insert("", "end", values=t)

    update_summary()
    update_charts()

# --- Input Form ---
form_frame = tk.Frame(root, pady=10)
form_frame.pack()

# Row 0 – Description and Type
tk.Label(form_frame, text="Description").grid(row=0, column=0, padx=5, sticky="e")
desc_entry = tk.Entry(form_frame, width=25)
desc_entry.grid(row=0, column=1, padx=5)

tk.Label(form_frame, text="Type").grid(row=0, column=2, padx=5, sticky="e")
type_var = tk.StringVar(value="Income")
ttk.Combobox(form_frame, textvariable=type_var, values=["Income", "Expense"], width=10).grid(row=0, column=3, padx=5)

# Row 1 – Amount
tk.Label(form_frame, text="Amount").grid(row=1, column=0, padx=5, sticky="e")
amount_entry = tk.Entry(form_frame, width=25)
amount_entry.grid(row=1, column=1, padx=5, sticky="w")

# Row 2 – Currency below Amount
tk.Label(form_frame, text="Currency").grid(row=2, column=0, padx=5, sticky="e")
currency_var = tk.StringVar(value="USD")
ttk.Combobox(form_frame, textvariable=currency_var, values=currencies, width=10).grid(row=2, column=1, padx=5, sticky="w")

# Row 2 – Category and Add button
tk.Label(form_frame, text="Category").grid(row=1, column=2, padx=5, sticky="e")
category_var = tk.StringVar(value="General")
ttk.Combobox(form_frame, textvariable=category_var, values=["Meals & Dining", "Transport", "Salary", "Bills", "General"], width=10).grid(row=1, column=3, padx=5)

# Add Button
tk.Button(form_frame, text="Add", width=20, command=add_transactions).grid(row=2, column=2, columnspan=2, padx=10)

# Delete Button
tk.Button(form_frame, text="Delete Selected", width=20, command=delete_transaction).grid(row=3, column=2, columnspan=2, padx=10, pady=5)

# Result label
result_label = tk.Label(form_frame, text="", fg="green")
result_label.grid(row=3, column=0, columnspan=5, pady=5)

# --- Transaction Table ---
table_frame = tk.Frame(root)
table_frame.pack(pady=10)

columns = ("Date", "Description", "Category", "Amount", "Currency", "Type")
tree = ttk.Treeview(table_frame, columns=columns, show="headings", height=10)

for col in columns:
    tree.heading(col, text=col)
    tree.column(col, anchor=tk.CENTER, width=130)

tree.pack()

currency_frame = tk.Frame(root)
currency_frame.pack(pady=5)

tk.Label(currency_frame, text="Display summary in:").pack(side="left", padx=5)
default_currency_var = tk.StringVar(value="USD")
default_currency_menu = ttk.Combobox(currency_frame, textvariable=default_currency_var, values=currencies, width=10)
default_currency_menu.pack(side="left", padx=10)

# transaction history
tk.Label(currency_frame, text="Display : ").pack(side="left", padx=5)
filter_var = tk.StringVar(value="last 7 days")
time_options = ["Today", "last 3 days", "last 7 days", "last 30 days", "all transactions"]
filter_menu = ttk.Combobox(currency_frame, textvariable=filter_var, values=time_options, width=10)
filter_menu.pack(side="left")


def on_currency_change(*args):
    update_summary()
    update_charts()  # ensure charts follow selected currency

default_currency_var.trace_add("write", on_currency_change)
filter_var.trace_add("write", lambda *args: filter_and_display())

# --- Summary ---
summary_label = tk.Label(root, text="Income: USD 0.00   Expense: USD 0.00   Balance:  USD 0.00", font=("Arial", 12, "bold"))
summary_label.pack(pady=10)

# --- Chart Area ---
chart_frame = tk.Frame(root)
chart_frame.pack(fill="both", expand=True, pady=10)

fig = Figure(figsize=(7, 3), dpi=100)
pie_ax = fig.add_subplot(121)
bar_ax = fig.add_subplot(122)

chart_canvas = FigureCanvasTkAgg(fig, master=chart_frame)
chart_canvas.get_tk_widget().pack(fill="both", expand=True)

# --- Run the App ---
load_transactions()
root.mainloop()