#nullable enable
using System;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;

using Swan.Formatters;

namespace Swan {
  /// <summary>
  /// String related extension methods.
  /// </summary>
  public static class StringExtensions {
    #region Private Declarations

    private const RegexOptions StandardRegexOptions = RegexOptions.Multiline | RegexOptions.Compiled | RegexOptions.CultureInvariant;

    private static readonly Lazy<Regex> SplitLinesRegex = new Lazy<Regex>(() => new Regex("\r\n|\r|\n", StandardRegexOptions));

    #endregion

    /// <summary>
    /// Returns a string that represents the given item
    /// It tries to use InvariantCulture if the ToString(IFormatProvider)
    /// overload exists.
    /// </summary>
    /// <param name="this">The item.</param>
    /// <returns>A <see cref="String" /> that represents the current object.</returns>
    public static String ToStringInvariant(this Object? @this) {
      if(@this == null) {
        return String.Empty;
      }

      Type itemType = @this.GetType();

      return itemType == typeof(String) ? @this as String ?? String.Empty : Definitions.BasicTypesInfo.Value.ContainsKey(itemType) ? Definitions.BasicTypesInfo.Value[itemType].ToStringInvariant(@this) : @this.ToString()!;
    }

    /// <summary>
    /// Returns a string that represents the given item
    /// It tries to use InvariantCulture if the ToString(IFormatProvider)
    /// overload exists.
    /// </summary>
    /// <typeparam name="T">The type to get the string.</typeparam>
    /// <param name="item">The item.</param>
    /// <returns>A <see cref="String" /> that represents the current object.</returns>
    public static String ToStringInvariant<T>(this T item) => typeof(String) == typeof(T) ? item as String ?? String.Empty : ToStringInvariant(item as Object);

    /// <summary>
    /// Removes the control characters from a string except for those specified.
    /// </summary>
    /// <param name="value">The input.</param>
    /// <param name="excludeChars">When specified, these characters will not be removed.</param>
    /// <returns>
    /// A string that represents the current object.
    /// </returns>
    /// <exception cref="ArgumentNullException">input.</exception>
    // [Obsolete("NEED", false)]
    public static String RemoveControlCharsExcept(this String value, params Char[]? excludeChars) {
      if(value == null) {
        throw new ArgumentNullException(nameof(value));
      }

      if(excludeChars == null) {
        excludeChars = Array.Empty<Char>();
      }

      return new String(value.Where(c => Char.IsControl(c) == false || excludeChars.Contains(c)).ToArray());
    }

    /// <summary>
    /// Returns text representing the properties of the specified object in a human-readable format.
    /// While this method is fairly expensive computationally speaking, it provides an easy way to
    /// examine objects.
    /// </summary>
    /// <param name="this">The object.</param>
    /// <returns>A <see cref="String" /> that represents the current object.</returns>
    // [Obsolete("NEED", false)]
    public static String Stringify(this Object @this) {
      if(@this == null) {
        return "(null)";
      }

      try {
        String jsonText = Json.Serialize(@this, false, "$type");
        Object? jsonData = Json.Deserialize(jsonText);

        return new HumanizeJson(jsonData, 0).GetResult();
      } catch {
        return @this.ToStringInvariant();
      }
    }

    /// <summary>
    /// Retrieves a section of the string, inclusive of both, the start and end indexes.
    /// This behavior is unlike JavaScript's Slice behavior where the end index is non-inclusive
    /// If the string is null it returns an empty string.
    /// </summary>
    /// <param name="this">The string.</param>
    /// <param name="startIndex">The start index.</param>
    /// <param name="endIndex">The end index.</param>
    /// <returns>Retrieves a substring from this instance.</returns>
    public static String Slice(this String @this, Int32 startIndex, Int32 endIndex) {
      if(@this == null) {
        return String.Empty;
      }

      Int32 end = endIndex.Clamp(startIndex, @this.Length - 1);

      return startIndex >= end ? String.Empty : @this.Substring(startIndex, end - startIndex + 1);
    }

    /// <summary>
    /// Gets a part of the string clamping the length and startIndex parameters to safe values.
    /// If the string is null it returns an empty string. This is basically just a safe version
    /// of string.Substring.
    /// </summary>
    /// <param name="this">The string.</param>
    /// <param name="startIndex">The start index.</param>
    /// <param name="length">The length.</param>
    /// <returns>Retrieves a substring from this instance.</returns>
    // [Obsolete("NEED", false)]
    public static String SliceLength(this String @this, Int32 startIndex, Int32 length) {
      if(@this == null) {
        return String.Empty;
      }

      Int32 start = startIndex.Clamp(0, @this.Length - 1);
      Int32 len = length.Clamp(0, @this.Length - start);

      return len == 0 ? String.Empty : @this.Substring(start, len);
    }

    /// <summary>
    /// Splits the specified text into r, n or rn separated lines.
    /// </summary>
    /// <param name="this">The text.</param>
    /// <returns>
    /// An array whose elements contain the substrings from this instance 
    /// that are delimited by one or more characters in separator.
    /// </returns>
    public static String[] ToLines(this String @this) => @this == null ? Array.Empty<String>() : SplitLinesRegex.Value.Split(@this);

    /// <summary>
    /// Indents the specified multi-line text with the given amount of leading spaces
    /// per line.
    /// </summary>
    /// <param name="value">The text.</param>
    /// <param name="spaces">The spaces.</param>
    /// <returns>A <see cref="String" /> that represents the current object.</returns>
    // [Obsolete("NEED", false)]
    public static String Indent(this String value, Int32 spaces = 4) {
      if(value == null) {
        value = String.Empty;
      }

      if(spaces <= 0) {
        return value;
      }

      String[] lines = value.ToLines();
      StringBuilder builder = new StringBuilder();
      String indentStr = new String(' ', spaces);

      foreach(String line in lines) {
        _ = builder.AppendLine($"{indentStr}{line}");
      }

      return builder.ToString().TrimEnd();
    }

    /// <summary>
    /// Gets the line and column number (i.e. not index) of the
    /// specified character index. Useful to locate text in a multi-line
    /// string the same way a text editor does.
    /// Please not that the tuple contains first the line number and then the
    /// column number.
    /// </summary>
    /// <param name="value">The string.</param>
    /// <param name="charIndex">Index of the character.</param>
    /// <returns>A 2-tuple whose value is (item1, item2).</returns>
    public static Tuple<Int32, Int32> TextPositionAt(this String value, Int32 charIndex) {
      if(value == null) {
        return Tuple.Create(0, 0);
      }

      Int32 index = charIndex.Clamp(0, value.Length - 1);

      Int32 lineIndex = 0;
      Int32 colNumber = 0;

      for(Int32 i = 0; i <= index; i++) {
        if(value[i] == '\n') {
          lineIndex++;
          colNumber = 0;
          continue;
        }

        if(value[i] != '\r') {
          colNumber++;
        }
      }

      return Tuple.Create(lineIndex + 1, colNumber);
    }
  }
}