// ============================================================================
// 086 — Expense Tracker
// ============================================================================
// Track expenses by category and generate summaries.
//
// Run:   soma run 086_expense_tracker.cell demo
// Expect:
//   Logged: Coffee ($4)
//   Logged: Lunch ($12)
//   Logged: Taxi ($25)
//   Logged: Books ($35)
//   Logged: Dinner ($45)
//   === Expense Summary ===
//   Total: $121
//   By category:
//     Transport: $25
//     Food: $61
//     Education: $35

cell ExpenseTracker {

    on demo() {
        let expenses = list()

        // Log expenses
        let e1 = map("desc", "Coffee", "amount", 4, "category", "Food")
        expenses = list(expenses, e1)
        print("Logged: {e1.desc} (${e1.amount})")

        let e2 = map("desc", "Lunch", "amount", 12, "category", "Food")
        expenses = list(expenses, e2)
        print("Logged: {e2.desc} (${e2.amount})")

        let e3 = map("desc", "Taxi", "amount", 25, "category", "Transport")
        expenses = list(expenses, e3)
        print("Logged: {e3.desc} (${e3.amount})")

        let e4 = map("desc", "Books", "amount", 35, "category", "Education")
        expenses = list(expenses, e4)
        print("Logged: {e4.desc} (${e4.amount})")

        let e5 = map("desc", "Dinner", "amount", 45, "category", "Food")
        expenses = list(expenses, e5)
        print("Logged: {e5.desc} (${e5.amount})")

        // Summary
        let total = expenses |> sum_by("amount")
        print("=== Expense Summary ===")
        print("Total: ${total}")

        let by_cat = expenses |> agg("category", "amount:sum") |> sort_by("category", "asc")
        print("By category:")
        for row in by_cat {
            print("  {row.category}: ${row.amount_sum}")
        }

        return "done"
    }
}