// vet_reference_primes_up_to_64k.linq
// 2016-04-29
//
// https://primes.utm.edu/lists/small/10000.txt
// http://pari.math.u-bordeaux.fr/gp.html
// 	  forprime(p = 2, 2^16, print(p))
// 	  primes(6542)
//
// see http://codereview.stackexchange.com/q/127024/56653

const string ReferenceFile = "reference_primes_up_to_64k.txt";       // <-- file to be vetted
const string First10K = "d:/dev/cpp/algo/primes/common/10000.txt";   // <-- downloaded file vetted against

void Main ()
{
	var primes = System.IO.File.ReadAllLines(ReferenceFile).Select(ushort.Parse).ToList();

	assert_equal("count", 6542, primes.Count);
	
	var sum = primes.Select((p) => (int)p).Sum();
	
	assert_equal("sum", 202288087, sum);
	
	var primorial_64bit = primes.Select((p) => (ulong)p).Aggregate((product, prime) => product * prime);

	assert_equal("product", 8987519195527561682UL, primorial_64bit);

	if (!primes.SequenceEqual(read_primes_up_to_64K_from_utm_edu_file()))
		throw new Exception("!primes.SequenceEqual(read_primes_up_to_64K_from_utm_edu_file())");

	Console.Write("{0} vetted successfully", ReferenceFile);

	var current_attributes = System.IO.File.GetAttributes(ReferenceFile);

	if ((current_attributes & FileAttributes.ReadOnly) == 0)
	{
		Console.Write(" - making the file read-only");
		
		System.IO.File.SetAttributes(ReferenceFile, current_attributes | FileAttributes.ReadOnly);
	}
}

static void assert_equal<T> (string what, T expected, T value)
{
	if (!EqualityComparer<T>.Default.Equals(value, expected))
		throw new Exception(string.Format("{0}: expected {1}, got {2}", what, expected, value));
}

static List<ushort> read_primes_up_to_64K_from_utm_edu_file (string filename = First10K)
{
	var result = new List<ushort>();

	foreach (var line in System.IO.File.ReadAllLines(filename).Select((s) => s.Trim()))
	{
		if (line.Length > 0 && char.IsDigit(line[0]))
		{
			var numbers = line.Split(' ')
					.Where((x) => x.Length > 0)
					.Select(int.Parse)
					.Where((x) => x <= ushort.MaxValue)
					.Select((x) => (ushort)x);
			
			result.AddRange(numbers);
		}
	}

	return result;
}