// Exercise 2: GroupBy and aggregation (medium)
//
// Implement TotalSpendByCustomer so that, given a list of orders
// (CustomerName, Amount), it returns a Dictionary mapping each customer
// name to their total spend across all their orders. Use GroupBy + Sum
// (or Aggregate) — no manual dictionary bookkeeping in a loop.
//
// Implement TopSpender so that it returns the customer name with the
// highest total spend, reusing TotalSpendByCustomer.
//
// Run with: dotnet run (inside a console project) or paste into a Main method.

using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
#pragma warning disable IDE0060
    static Dictionary<string, decimal> TotalSpendByCustomer(List<(string CustomerName, decimal Amount)> orders)
    {
        // TODO: GroupBy(o => o.CustomerName), then Sum the Amount per group,
        // and build a Dictionary<string, decimal> keyed by customer name.
        return new Dictionary<string, decimal>();
    }

    static string TopSpender(List<(string CustomerName, decimal Amount)> orders)
    {
        // TODO: call TotalSpendByCustomer, then find the key with the
        // highest value (OrderByDescending + First, or Aggregate/MaxBy).
        return "";
    }
#pragma warning restore IDE0060

    static void Main()
    {
        int pass = 0, total = 0;

        var orders = new List<(string CustomerName, decimal Amount)>
        {
            ("Alice", 50m), ("Bob", 20m), ("Alice", 30m), ("Charlie", 100m), ("Bob", 15m)
        };

        var totals = TotalSpendByCustomer(orders);
        total++;
        if (totals.Count == 3 && totals["Alice"] == 80m && totals["Bob"] == 35m && totals["Charlie"] == 100m)
        { Console.WriteLine("PASS: totals grouped and summed per customer"); pass++; }
        else Console.WriteLine("FAIL: totals grouped and summed per customer, got " +
            string.Join(", ", totals.Select(kv => $"{kv.Key}={kv.Value}")));

        var top = TopSpender(orders);
        total++;
        if (top == "Charlie") { Console.WriteLine("PASS: top spender identified"); pass++; }
        else Console.WriteLine("FAIL: top spender identified, got " + top);

        Console.WriteLine($"--- {pass}/{total} checks passed ---");
    }
}