using System.Text.RegularExpressions;

using System;

using System.Collections.Generic;

using System.Linq;

using System.IO;

using System.Collections.Immutable;

​

public class Program

{

    public static Dictionary<(string, ImmutableList<int>), long> cache = new Dictionary<(string, ImmutableList<int>), long>();

    public static void Main()

    {

        WriteFile("test.txt");

        // Read all lines from the text document

        string[] lines = File.ReadAllLines("test.txt");

        long total = 0;

        foreach (var line in lines)

        {

            var split = line.Split(" ", StringSplitOptions.RemoveEmptyEntries);

            var symbols = string.Join("?", Enumerable.Repeat(split.First(), 1));

            var numbers = string.Join(",", Enumerable.Repeat(split.Last(), 1))

                .Split(",", StringSplitOptions.RemoveEmptyEntries)

                .Select(int.Parse).ToImmutableList();

            var springInfo = new SpringInformation(symbols, numbers);

            total += Count(springInfo.Symbols, springInfo.Numbers);

        }

        Console.WriteLine($"Part 1 result: {total}");

    }

    public static long Count(string symbols, ImmutableList<int> numbers)

    {

        // When there are no more symbols, there can be no more numbers to be valid

        if(string.IsNullOrEmpty(symbols))

            return numbers.IsEmpty ? 1 : 0;

        // When there are no more numbers, there can be no more # in symbols to be valid

        if(numbers.IsEmpty)

            return symbols.Contains("#") ? 0 : 1;

        var key = (symbols, numbers);

        if(cache.ContainsKey(key))

            return cache[key];

        long result = 0;

        // If the first character is '?' or '.' we assume it is '.' and skip it

        if((".?").Contains(symbols[0]))

        {

            result += Count(symbols.Substring(1), numbers);

        }

        // If the first character is '?' or '#' we assume it is '#'

        if(("#?").Contains(symbols[0]))

        {

            // Validate if i have enough symbols for the number I need and contains no '.' 

            if(

                //Validate if i have enough symbols for the number N

                numbers[0] <= symbols.Length

                // Validate if I have a block with N symbols != '.'

                && !symbols.Substring(0,numbers[0]).Contains(".")

                // Validate if is there are no more symbols or the next one is not '#', because there are no adjacent blocks

                && (numbers[0] == symbols.Length || symbols[numbers[0]] != '#'))

            {

                if(numbers[0] == symbols.Length)

                    result += Count(symbols.Substring(numbers[0]), numbers.Skip(1).ToImmutableList());

                else

                    result += Count(symbols.Substring(numbers[0] + 1), numbers.Skip(1).ToImmutableList());

            }

        }

        cache[key] = result;

        return result;

    }

​

    public class SpringInformation

    {

        public SpringInformation(string symbols, ImmutableList<int> numbers)

        {

            Symbols = symbols;

            Numbers = numbers;

        }

        public string Symbols { get; set; }

        public ImmutableList<int> Numbers { get; set; }

    }

    public static void WriteFile(string path)

    {

        File.WriteAllText(path, 

@"???.### 1,1,3

.??..??...?##. 1,1,3

?#?#?#?#?#?#?#? 1,3,1,6

????.#...#... 4,1,1

????.######..#####. 1,6,5

?###???????? 3,2,1");

    }

}