using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;
using System.Web;
using Microsoft.AspNetCore.Mvc.RazorPages;

namespace webmusic.Pages {
	public class IndexModel : PageModel {
		private const string       Root        = "music";
		public        List<string> Dirs        = new();
		public        string       Displaypath = "";
		public        List<string> Files       = new();
		public        string       Fullpath    = "";
		public        string       Path        = "";
		public        string       PathOneup   = "";

		public void OnGet() {
			if (Request.QueryString.HasValue)
				if (Request.QueryString.Value != null)
					Path = HttpUtility.UrlDecode(Request.QueryString.Value.TrimStart('?').Replace("+", "%2B"));
			if (Path.Contains("/..")) {
				Response.Redirect("/Error");
				return;
			}
			
			if (Path.EndsWith(".m3u"))
				Path = Path.Substring(0, Path.Length - 4);

			if (Path.EndsWith(".lrc"))
				return;

			PathOneup   = Regex.Match(Path, @".*(?=\/)").Value;
			Fullpath    = Root + Path;
			Displaypath = string.IsNullOrWhiteSpace(Path) ? "/" : Path;
			Dirs        = Directory.GetDirectories(Fullpath).Select(System.IO.Path.GetFileName).ToList();
			Dirs.RemoveAll(p => p.StartsWith("."));
			Dirs.Sort();
			Files = Directory.GetFiles(Fullpath).Select(System.IO.Path.GetFileName).ToList();
			Files.RemoveAll(p => p.EndsWith(".m3u"));
			Files.RemoveAll(p => p.EndsWith(".lrc"));
			Files.RemoveAll(p => p.StartsWith("."));
			Files.Sort(new AlphanumComparatorFast());
		}

		public static string Encode(string str) => str.Replace("\"", "%22")
													  .Replace("'", "%27")
													  .Replace("?", "%3F")
													  .Replace("&", "%26")
													  .Replace(" ", "%20");

		private class AlphanumComparatorFast : IComparer<string> {
			public int Compare(string x, string y) {
				var s1 = x;
				if (s1 == null)
					return 0;

				if (!(y is { } s2))
					return 0;

				var len1    = s1.Length;
				var len2    = s2.Length;
				var marker1 = 0;
				var marker2 = 0;

				// Walk through two the strings with two markers.
				while (marker1 < len1 && marker2 < len2) {
					var ch1 = s1[marker1];
					var ch2 = s2[marker2];

					// Some buffers we can build up characters in for each chunk.
					var space1 = new char[len1];
					var loc1   = 0;
					var space2 = new char[len2];
					var loc2   = 0;

					// Walk through all following characters that are digits or
					// characters in BOTH strings starting at the appropriate marker.
					// Collect char arrays.
					do {
						space1[loc1++] = ch1;
						marker1++;

						if (marker1 < len1)
							ch1 = s1[marker1];
						else
							break;
					} while (char.IsDigit(ch1) == char.IsDigit(space1[0]));

					do {
						space2[loc2++] = ch2;
						marker2++;

						if (marker2 < len2)
							ch2 = s2[marker2];
						else
							break;
					} while (char.IsDigit(ch2) == char.IsDigit(space2[0]));

					// If we have collected numbers, compare them numerically.
					// Otherwise, if we have strings, compare them alphabetically.
					var str1 = new string(space1);
					var str2 = new string(space2);

					int result;

					if (char.IsDigit(space1[0]) && char.IsDigit(space2[0])) {
						var thisNumericChunk = int.Parse(str1);
						var thatNumericChunk = int.Parse(str2);
						result = thisNumericChunk.CompareTo(thatNumericChunk);
					}
					else {
						result = string.Compare(str1, str2, StringComparison.Ordinal);
					}

					if (result != 0)
						return result;
				}

				return len1 - len2;
			}
		}
	}
}