namespace AspClassic.Parser;

/// <summary>
/// Stores the location of a span of text.
/// </summary>
/// <remarks>The end location is exclusive.</remarks>
public struct Span
{
	private readonly Location _Start;

	private readonly Location _Finish;

	/// <summary>
	/// The start location of the span.
	/// </summary>
	public Location Start => _Start;

	/// <summary>
	/// The end location of the span.
	/// </summary>
	public Location Finish => _Finish;

	/// <summary>
	/// Whether the locations in the span are valid.
	/// </summary>
	public bool IsValid => Start.IsValid && Finish.IsValid;

	/// <summary>
	/// Constructs a new span with a specific start and end location.
	/// </summary>
	/// <param name="start">The beginning of the span.</param>
	/// <param name="finish">The end of the span.</param>
	public Span(Location start, Location finish)
	{
		this = default(Span);
		_Start = start;
		_Finish = finish;
	}

	/// <summary>
	/// Compares two specified Span values to see if they are equal.
	/// </summary>
	/// <param name="left">One span to compare.</param>
	/// <param name="right">The other span to compare.</param>
	/// <returns>True if the spans are the same, False otherwise.</returns>
	public static bool operator ==(Span left, Span right)
	{
		return left.Start.Index == right.Start.Index && left.Finish.Index == right.Finish.Index;
	}

	/// <summary>
	/// Compares two specified Span values to see if they are not equal.
	/// </summary>
	/// <param name="left">One span to compare.</param>
	/// <param name="right">The other span to compare.</param>
	/// <returns>True if the spans are not the same, False otherwise.</returns>
	public static bool operator !=(Span left, Span right)
	{
		return left.Start.Index != right.Start.Index || left.Finish.Index != right.Finish.Index;
	}

	public override string ToString()
	{
		return Start.ToString() + " - " + Finish.ToString();
	}

	public override bool Equals(object obj)
	{
		if (obj is Span)
		{
			return this == (Span)obj;
		}
		return false;
	}

	public override int GetHashCode()
	{
		return checked((int)((Start.Index ^ Finish.Index) & 0xFFFFFFFFu));
	}
}