Error Handling and Refinement

let income = 0.0;

// An array of expense objects, e.g. [{ category: "Food", amount: number }]
let expenses = [];

// Allowed categories
const allowedCategories = [
  "Food", "Rent", "Transport", "Entertainment",
  "Utilities", "Health", "Education", "Other"
];

// --- Core functions ---

function addIncome(amount) {
  // Set or update the monthly income
  income = Number(amount);
  console.log("Income set to $" + income.toFixed(2));
}

function addExpense(category, amount) {
  // Record an expense item
  if (!allowedCategories.includes(category)) {
    console.log("Invalid category. Please choose from: " + allowedCategories.join(", "));
    return;
  }
  expenses.push({ category: category, amount: Number(amount) });
  console.log(`Expense added: ${category} - $${Number(amount).toFixed(2)}`);
}

function deleteExpense(idx) {
  // Delete an expense by zero-based index
  if (idx >= 0 && idx < expenses.length) {
    let removed = expenses.splice(idx, 1)[0];
    console.log(`Deleted expense: ${removed.category} - $${removed.amount.toFixed(2)}`);
    return removed;
  } else {
    console.log("Invalid index. No expense deleted.");
    return null;
  }
}

function totalSpent(expensesList = null) {
  // Return the sum of all expense amounts from a list or the global store
  const list = expensesList || expenses;
  let sum = 0;
  for (let entry of list) {
    sum += entry.amount;
  }
  return sum;
}

function computeCategoryTotals(expensesList = null) {
  // Return an object mapping category -> total amount from expenses
  const list = expensesList || expenses;
  const totals = {};
  for (let entry of list) {
    if (!totals[entry.category]) {
      totals[entry.category] = 0;
    }
    totals[entry.category] += entry.amount;
  }
  return totals;
}

function printReport(incomeValue = null, expensesList = null) {
  // Print a formatted budget report with category totals and status line
  const inc = incomeValue !== null ? Number(incomeValue) : income;
  const list = expensesList || expenses;
  const total = totalSpent(list);
  const remaining = inc - total;
  const categoryTotals = computeCategoryTotals(list);

  console.log("\n--- Budget Report ---");
  console.log(`Income: $${inc.toFixed(2)}`);
  console.log(`Total Spent: $${total.toFixed(2)}`);

  console.log("\nCategory Spending:");
  for (let category in categoryTotals) {
    console.log(`  - ${category}: $${categoryTotals[category].toFixed(2)}`);
  }

  console.log("---------------------------");
  console.log(`Remaining Balance: $${remaining.toFixed(2)}`);
}

function showMenu() {
  // Display simple command menu for the CLI
  console.log("\n--- Budget Tracker Menu ---");
  console.log("1. Set Monthly Income");
  console.log("2. Add an Expense");
  console.log("3. Delete an Expense");
  console.log("4. Show Budget Report");
  console.log("5. Reset All Data");
  console.log("6. Exit");
}

function listExpenses() {
  // Display all expenses with their index
  if (expenses.length === 0) {
    console.log("No expenses recorded yet.");
    return;
  }
  console.log("\nCurrent Expenses:");
  expenses.forEach((expense, i) => {
    console.log(`${i}: ${expense.category} - $${expense.amount.toFixed(2)}`);
  });
}

function resetData() {
  // Clear income and expenses; return to a clean initial state
  income = 0.0;
  expenses = [];
  console.log("All budget data has been cleared.");
}

// --- CLI main loop ---
function runCLI() {
  // Command-line style interface
  while (true) {
    showMenu();
    let choice = prompt("Choose an option (1-6): ");

    if (choice === "1") {
      let amount = prompt("Enter your monthly income: $");
      addIncome(amount);

    } else if (choice === "2") {
      console.log("\nAvailable Categories: " + allowedCategories.join(", "));
      let category = prompt("Enter the expense category: ");
      let amount = prompt("Enter the expense amount: $");
      addExpense(category, amount);

    } else if (choice === "3") {
      listExpenses();
      if (expenses.length > 0) {
        let idx = Number(prompt("Enter the index of the expense to delete: "));
        deleteExpense(idx);
      }

    } else if (choice === "4") {
      printReport();

    } else if (choice === "5") {
      resetData();

    } else if (choice === "6") {
      console.log("Exiting Budget Tracker.");
      break;

    } else {
      console.log("Invalid choice. Please select a valid option.");
    }
  }
}

// Kick off the app
runCLI();