using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Diagnostics;

namespace Nuclex.Networking.Gallery3 {

  /// <summary>Contains helper methods for working with gallery URLs</summary>
  internal static class UrlHelper {

    /// <summary>Characters the represent numbers</summary>
    private static char[] Numbers = {
      '0', '1', '2', '3', '4', '5', '6', '7', '8', '9'
    };

    /// <summary>Extracts the ids from a list of URLs ending in an ID</summary>
    /// <param name="urls">Array of urls the ids will be extracted from</param>
    /// <returns>An array of ids matching the IDs contained in the provided urls</returns>
    public static int[] ExtractIdsFromUrls(string[] urls) {
      int[] ids = new int[urls.Length];

      for (int index = 0; index < urls.Length; ++index) {
        int finalSlashIndex = urls[index].LastIndexOf('/');
        if (finalSlashIndex == -1) {
          Debug.Assert(
            false, "List contained an item that's not an URL",
            "The URL list contained an entry that was not an URL ending in " +
            "an ID and thus could not be parsed for its ID"
          );
          finalSlashIndex = 0; // We try to be optimistic (may still fail right below)
        } else {
          ++finalSlashIndex;
        }

        int finalNumberIndex = urls[index].indexNotOfAny(Numbers, finalSlashIndex);
        if (finalNumberIndex == -1) {
          finalNumberIndex = urls[index].Length;
        }

        // Parse the ID from the URL and add it to our list
        ids[index] = int.Parse(
          urls[index].Substring(finalSlashIndex, finalNumberIndex - finalSlashIndex)
        );
      }

      return ids;
    }

    /// <summary>
    ///   Searches for the first occurence of a character other than the characters
    ///   listed in the <paramref name="anyNotOf" /> parameter
    /// </summary>
    /// <param name="haystack">String that will be scanned in</param>
    /// <param name="anyNotOf">Characters to not look for in the scanned string</param>
    /// <returns>
    ///   The index of the first occurence of a character not in the
    ///   <paramref name="anyNotOf" /> array or -1 if all characters in the string were
    ///   present in the <paramref name="anyNotOf" /> array.
    /// </returns>
    private static int indexNotOfAny(this string haystack, char[] anyNotOf) {
      return indexNotOfAny(haystack, anyNotOf, 0, haystack.Length);
    }

    /// <summary>
    ///   Searches for the first occurence of a character other than the characters
    ///   listed in the <paramref name="anyNotOf" /> parameter
    /// </summary>
    /// <param name="haystack">String that will be scanned in</param>
    /// <param name="anyNotOf">Characters to not look for in the scanned string</param>
    /// <param name="startIndex">
    ///   Index of the character in the haystack at which to start scanning
    /// </param>
    /// <returns>
    ///   The index of the first occurence of a character not in the
    ///   <paramref name="anyNotOf" /> array or -1 if all characters in the string were
    ///   present in the <paramref name="anyNotOf" /> array.
    /// </returns>
    private static int indexNotOfAny(this string haystack, char[] anyNotOf, int startIndex) {
      return indexNotOfAny(haystack, anyNotOf, startIndex, haystack.Length - startIndex);
    }

    /// <summary>
    ///   Searches for the first occurence of a character other than the characters
    ///   listed in the <paramref name="anyNotOf" /> parameter
    /// </summary>
    /// <param name="haystack">String that will be scanned in</param>
    /// <param name="anyNotOf">Characters to not look for in the scanned string</param>
    /// <param name="startIndex">
    ///   Index of the character in the haystack at which to start scanning
    /// </param>
    /// <param name="count">Number of characters in the haystack to scan</param>
    /// <returns>
    ///   The index of the first occurence of a character not in the
    ///   <paramref name="anyNotOf" /> array or -1 if all characters in the string were
    ///   present in the <paramref name="anyNotOf" /> array.
    /// </returns>
    private static int indexNotOfAny(
      this string haystack, char[] anyNotOf, int startIndex, int count
    ) {
      int anyLength = anyNotOf.Length;

      count += startIndex;
      while (startIndex < count) {
        char character = haystack[startIndex];

        int index = Array.IndexOf<char>(anyNotOf, character, 0, anyLength);
        if (index == -1) {
          return startIndex;
        }

        ++startIndex;
      }

      return -1;
    }

  }

} // namespace Nuclex.Networking.Gallery3