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

public class Test
{
    public static Func<string,bool> MinimumLength(int _minLength)
    {
        return (password) =>
            password != null
            && password.Length >= _minLength;
    }

    public static bool MustHaveDigits(string password)
    {
        if (password == null) return false;
        return password.ToCharArray().Any(c => char.IsDigit(c));
    }

    public static bool MustHaveUppercase(string password)
    {
        if (password == null) return false;
        return password.ToCharArray().Any(c => char.IsUpper(c));
    }


    public static void Main()
    {
        Func<IEnumerable<Func<string,bool>>, Func<string, bool>> createPasswordPolicy = (policy) => (pw) => policy.All(check => check(pw));
        
        var isValidShort = createPasswordPolicy(new List<Func<string, bool>>() {
        	Test.MinimumLength(8),
        	Test.MustHaveDigits,
        	Test.MustHaveUppercase,
        });
        
        var isValidLong = createPasswordPolicy(new List<Func<string, bool>>() {
        	Test.MinimumLength(10),
        	Test.MustHaveDigits,
        	Test.MustHaveUppercase,
        });
        

        System.Console.WriteLine(isValidShort("Password1"));   // True
        System.Console.WriteLine(isValidShort("Password123")); // True
        System.Console.WriteLine(isValidShort(null));          // False
        System.Console.WriteLine(isValidShort(""));            // False
        
        System.Console.WriteLine(isValidLong("Password123"));  // True
        System.Console.WriteLine(isValidLong("Password1"));    // False
        System.Console.WriteLine(isValidLong(null));           // False
        System.Console.WriteLine(isValidLong(""));             // False
    }

}