using System;
using System.IO;
using System.Net.Http;
using System.Linq;

namespace AdventOfCode.InputFetcher
{
    class Program
    {
        private static readonly string AdventOfCodeEndpoint = "https://adventofcode.com/{YEAR}/day";
        private static HttpClient _client;
        static void Main(string[] args)
        {
            Console.WriteLine("Please select your year! Default: 2023");
            var year = SanitizeInput(Console.ReadLine(), "2023");
            Console.WriteLine("Please enter your session key for advent of code:");
            var sessionKey = Console.ReadLine();
            Console.WriteLine("Please input the target directory for the input files! Default: Current working directory");
            var targetDir = SanitizeInput(Console.ReadLine(), Directory.GetCurrentDirectory());
            Console.WriteLine("File Name Format? Default: \"{YEAR}_{TYPE}_Day_{DAY}{PART}.txt\" => 2022_Input_Day_1.txt or 2022_Answer_Day_1-PartB");
            var format = SanitizeInput(Console.ReadLine(), "{YEAR}_{TYPE}_Day_{DAY}{PART}.txt");
            Console.WriteLine("Pull Answers? (Y/N) Default: Y");
            var answer = SanitizeInput(Console.ReadLine(), "Y");
            Console.WriteLine("Overwrite? (Y/N) Default: N");
            var overwrite = SanitizeInput(Console.ReadLine(), "N");

            _client = new HttpClient();
            _client.DefaultRequestHeaders.Add("Cookie", $"session={sessionKey}");

            var filesOnDisk = new DirectoryInfo(targetDir);
            for (int day = 1; day <= 25; day++)
            {
                var dataFileName = format.Replace("{DAY}", day.ToString()).Replace("{TYPE}", "Input").Replace("{PART}", "").Replace("{YEAR}", year);
                var answerFileNameA = format.Replace("{DAY}", day.ToString()).Replace("{TYPE}", "Answer").Replace("{PART}", "A").Replace("{YEAR}", year);
                var answerFileNameB = format.Replace("{DAY}", day.ToString()).Replace("{TYPE}", "Answer").Replace("{PART}", "B").Replace("{YEAR}", year);
                bool dataFileExistsOnDisk = filesOnDisk.EnumerateFiles().Any(x => x.Name == dataFileName);
                if (!dataFileExistsOnDisk || (overwrite.ToUpper() == "Y"))
                {
                    try
                    {
                        File.WriteAllText(targetDir + Path.DirectorySeparatorChar + dataFileName, PullDataForDay(year, day));
                    }catch(FileNotFoundException e)
                    {
                        //Input data not available yet
                        continue;
                    }
                    
                }


                if (answer.ToUpper() == "Y")
                {
                    bool answerFileAExistsOnDisk = filesOnDisk.EnumerateFiles().Any(x => x.Name == answerFileNameA);
                    bool answerFileBExistsOnDisk = filesOnDisk.EnumerateFiles().Any(x => x.Name == answerFileNameB);
                    if ((!answerFileBExistsOnDisk && !answerFileBExistsOnDisk) || (overwrite.ToUpper() == "Y"))
                    {
                        var answers = PullAnswerForDay(year, day);
                        if (!string.IsNullOrWhiteSpace(answers.Item1))
                            File.WriteAllText(targetDir + Path.DirectorySeparatorChar + answerFileNameA, answers.Item1);
                        if (!string.IsNullOrWhiteSpace(answers.Item2))
                            File.WriteAllText(targetDir + Path.DirectorySeparatorChar + answerFileNameB, answers.Item2);
                    }
                }

            }

        }

        private static string PullDataForDay(string year, int day)
        {
            return ExecuteWebRequest(string.Format("{0}/{1}/input", AdventOfCodeEndpoint.Replace("{YEAR}", year), day));
        }

        private static readonly string SearchString = "Your puzzle answer was";
        private static Tuple<string, string> PullAnswerForDay(string year, int day)
        {
            var html = ExecuteWebRequest(string.Format("{0}/{1}", AdventOfCodeEndpoint.Replace("{YEAR}", year), day));
            var answerStart = html.IndexOf(SearchString);
            if (answerStart < 0) return Tuple.Create("", "");
            var startingIndex = html.IndexOf("<code>", answerStart) + "<code>".Length;
            var endIndex = html.IndexOf("</code>", answerStart);
            var partA = startingIndex < 0 || endIndex < 0 ? "No Answer Found yet." : html.Substring(startingIndex, (endIndex-startingIndex));

            html = html.Substring(endIndex + 1);
            answerStart = html.IndexOf(SearchString);
            startingIndex = html.IndexOf("<code>", answerStart) + "<code>".Length;
            endIndex = html.IndexOf("</code>", answerStart);
            var partB = startingIndex < 0 || endIndex < 0 ? "No Answer Found yet." : html.Substring(startingIndex, (endIndex - startingIndex));

            return Tuple.Create(partA, partB);
        }

        private static string ExecuteWebRequest(string url)
        {
            var resp = _client.GetAsync(url).Result;
            if (resp.StatusCode == System.Net.HttpStatusCode.NotFound) throw new FileNotFoundException("No day input was found!");
            return resp.Content.ReadAsStringAsync().Result;
        }

        private static string SanitizeInput(string input, string defaultText)
        {
            if (string.IsNullOrWhiteSpace(input)) return defaultText;
            return input;
        }
    }
}