using System;

namespace Framework.Support {

  /// <summary>Helper methods for the dialogue parser</summary>
  public static class ParserHelper {

    /// <summary>Returns how far the contents of a line have been indented</summary>
    /// <param name="line">Line whose indentation will be checked</param>
    /// <returns>The indentation level of the provided line</returns>
    public static int GetIndentationLevel(string line) {
      if(string.IsNullOrEmpty(line)) {
        return 0;
      }

      // Look for the first non-whitespace character, its index is the indentation level
      for(int index = 0; index < line.Length; ++index) {
        if(!char.IsWhiteSpace(line[index])) {
          return index;
        }
      }

      // Line consists of only whitespace
      return 0;
    }

    /// <summary>Advances the index past any whitespace in the string</summary>
    /// <param name="text">String which is being indexed</param>
    /// <param name="index">Index that will be advanced</param>
    public static void SkipSpaces(string text, ref int index) {
      if(text == null) {
        return;
      }

      int length = text.Length;
      while(index < length) {
        if(!char.IsWhiteSpace(text, index)) {
          break;
        }

        ++index;
      }
    }

    /// <summary>Advances the index past any whitespace in the string</summary>
    /// <param name="text">String which is being indexed</param>
    /// <param name="index">Index that will be advanced</param>
    public static void SkipAlphaNumerics(string text, ref int index) {
      if(text == null) {
        return;
      }

      int length = text.Length;
      while(index < length) {
        if(!char.IsLetterOrDigit(text, index)) {
          break;
        }

        ++index;
      }
    }

    /// <summary>Advances the index past the specified character, if encountered</summary>
    /// <param name="text">String which is being indexed</param>
    /// <param name="index">Index that will be advanced</param>
    /// <returns>True if the character was encountered and skipped</returns>
    public static bool SkipCharacter(string text, char character, ref int index) {
      if(text == null) {
        return false;
      }

      int length = text.Length;
      if(index < length) {
        if(text[index] == character) {
          ++index;
          return true;
        }
      }

      return false;
    }

    /// <summary>Advances the index to the next whitespace in the string</summary>
    /// <param name="text">String which is being indexed</param>
    /// <param name="index">Index that will be advanced</param>
    public static void SkipNonSpaces(string text, ref int index) {
      if(text == null) {
        return;
      }

      int length = text.Length;
      while(index < length) {
        if(char.IsWhiteSpace(text, index)) {
          break;
        }

        ++index;
      }
    }

    /// <summary>Skips an integer in the provided string</summary>
    /// <param name="text">String in which an integer will be skipped</param>
    /// <param name="index">Index at which the integer begins</param>
    /// <returns>True if an integer was found and skipped, otherwise false</returns>
    public static bool SkipInteger(string text, ref int index) {
      if(text == null) {
        return false;
      }

      int length = text.Length;
      if(index >= length) {
        return false;
      }

      // If the number begins with a minus or plus sign, skip over the sign
      if((text[index] == '-') || (text[index] == '+')) {
        int nextIndex = index + 1;
        if(nextIndex == length) {
          return false;
        }
        if(!char.IsNumber(text, nextIndex)) {
          return false;
        }

        index = nextIndex;
      }

      // Eat all numbers until we reach another character or the end of the string
      while(char.IsNumber(text, index)) {
        ++index;
        if(index >= length) {
          break;
        }
      }

      return true;
    }

    /// <summary>Locates the first non-space character in the string</summary>
    /// <param name="text">Text in which the first non-space character will be found</param>
    /// <returns>The index of the first non-space character or -1 if none found</returns>
    public static int FindNonSpace(string text) {
      return FindNonSpace(text, 0);
    }

    /// <summary>Locates the next non-space character in the string</summary>
    /// <param name="text">Text in which the next non-space character will be found</param>
    /// <param name="startIndex">Index at which the search will begin</param>
    /// <returns>The index of the next non-space character or -1 if none found</returns>
    public static int FindNonSpace(string text, int startIndex) {
      while(startIndex < text.Length) {
        if(!char.IsWhiteSpace(text, startIndex)) {
          return startIndex;
        }

        ++startIndex;
      }

      return -1;
    }

    /// <summary>Locates the first whitespace character in the string</summary>
    /// <param name="text">Text in which the first whitespace character will be found</param>
    /// <returns>The index of the first whitespace character or -1 if none found</returns>
    public static int FindSpace(string text) {
      return FindSpace(text, 0);
    }

    /// <summary>Locates the next nonwhitespace character in the string</summary>
    /// <param name="text">Text in which the next nonwhitespace character will be found</param>
    /// <param name="startIndex">Index at which the search will begin</param>
    /// <returns>The index of the next whitespace character or -1 if none found</returns>
    public static int FindSpace(string text, int startIndex) {
      while(startIndex < text.Length) {
        if(char.IsWhiteSpace(text, startIndex)) {
          return startIndex;
        }

        ++startIndex;
      }

      return -1;
    }

  }

} // namespace Framework.Support