namespace AdventOfCodeLibrary._2022.Day_07
{
    public class Directory
    {
        public Directory? ParentDirectory { get; set; }
        public string Name { get; set; } = string.Empty;
        public List<Directory> Directories { get; set; } = new();
        public List<File> Files { get; set; } = new();

        public int GetSizeOfAllFiles() => Files.Sum(f => f.Size) + Directories.Sum(d => d.GetSizeOfAllFiles());
    }

    public struct File
    {
        public string Name { get; set; }

        public int Size { get; set; }
    }

    internal class DirectoryManager
    {
        readonly Directory RootDirectory;
        Directory CurrentDirectory;

        internal DirectoryManager()
        {
            RootDirectory = new Directory { Name = "/", ParentDirectory = null };
            CurrentDirectory = RootDirectory;
        }

        internal void ParseTerminalOutput(string[] lines)
        {
            for (int lineIndex = 0; lineIndex < lines.Length; lineIndex++)
            {
                string[] parts = lines[lineIndex].Split(' ');

                // it is a command
                if (parts[0] == "$")
                {
                    // move to other folder
                    if (parts[1] == "cd")
                    {
                        switch (parts[2])
                        {
                            // go to root
                            case "/":
                                CurrentDirectory = RootDirectory;
                                continue;
                            // go to parent
                            case "..":
                                CurrentDirectory = CurrentDirectory.ParentDirectory;
                                continue;
                            // go to sub
                            default:
                                CurrentDirectory = CurrentDirectory.Directories.Single(dir => dir.Name == parts[2]);
                                break;
                        }
                    }

                    // if none of the about, just skip
                    continue;
                }

                // if not a command it is the output from the ls command
                if (parts[0] == "dir")
                {
                    CurrentDirectory.Directories.Add(new Directory { Name = parts[1], ParentDirectory = CurrentDirectory });
                    continue;
                }

                // it should be a number indicating the size of a file
                CurrentDirectory.Files.Add(new File { Name = parts[1], Size = Convert.ToInt32(parts[0]) });
            }
        }

        internal string GetDirectoriesWithMaxFilesSize(int maxSize)
        {
            return GetDirectories(RootDirectory).Where(d => d.GetSizeOfAllFiles() <= maxSize).Sum(d => d.GetSizeOfAllFiles()).ToString();
        }

        internal string GetDirectoriesClosestTo(int totalSize, int sizeNeeded)
        {
            sizeNeeded -= totalSize - RootDirectory.GetSizeOfAllFiles();
            return GetDirectories(RootDirectory).Where(d => d.GetSizeOfAllFiles() >= sizeNeeded).Min(d => d.GetSizeOfAllFiles()).ToString();
        }

        private IEnumerable<Directory> GetDirectories(Directory source)
        {
            yield return source;
            foreach (Directory dir in source.Directories.SelectMany(GetDirectories))
            {
                yield return dir;
            }
        }
    }
}