// Exercise 1: fix the classic bugs (easy)
//
// Each method below contains a well-known C# gotcha. Fix them so the checks pass:
//   - MakeCounters(): the returned functions must return 0, 1, 2 (closure capture in a for loop).
//   - ApplyDiscount(): must actually change the prices in the list (List<PriceTag> of mutable structs).
//   - TotalPrice(): 0.1 + 0.2 + 0.3 must be exactly 0.6 (use decimal for money).
//   - Normalize(): must return the trimmed, upper-cased string (strings are immutable).
//
// Run with: dotnet run (inside a console project).

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

struct PriceTag { public string Sku; public decimal Price; }

class Program
{
    static List<Func<int>> MakeCounters()
    {
        var list = new List<Func<int>>();
        for (int i = 0; i < 3; i++) list.Add(() => i);
        return list;
    }

    static void ApplyDiscount(List<PriceTag> tags, decimal factor)
    {
        foreach (var t in tags)
        {
            var copy = t;
            copy.Price *= factor;
        }
    }

    static bool TotalIsExact()
    {
        double total = 0.1 + 0.2 + 0.3;
        return total == 0.6;
    }

    static string Normalize(string s)
    {
        s.Trim();
        s.ToUpperInvariant();
        return s;
    }

    static void Main()
    {
        int pass = 0, total = 0;
        void Check(string name, bool ok) { total++; if (ok) pass++; Console.WriteLine($"{(ok ? "PASS" : "FAIL")}: {name}"); }

        Check("closures capture per-iteration values", string.Join(",", MakeCounters().Select(f => f())) == "0,1,2");
        var tags = new List<PriceTag> { new PriceTag { Sku = "a", Price = 10m }, new PriceTag { Sku = "b", Price = 20m } };
        ApplyDiscount(tags, 0.5m);
        Check("struct elements updated", tags[0].Price == 5m && tags[1].Price == 10m);
        Check("decimal arithmetic is exact", TotalIsExact());
        Check("strings are immutable", Normalize("  hello ") == "HELLO");

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