using System;

namespace Vellum.Generator
{
    /// <summary>
    /// Says where in a shape the type arguments of one generic class in a type's chain of base classes are, as plain
    /// data an incremental generator step can compare between runs.
    /// </summary>
    public sealed class BaseArguments : IEquatable<BaseArguments>
    {
        /// <summary>
        /// Holds the name of the generic type the class is made from.
        /// </summary>
        public readonly string Name;

        /// <summary>
        /// Holds where the arguments start in the shape, which keeps them next to each other.
        /// </summary>
        public readonly int FirstChild;

        public readonly int ChildCount;

        public BaseArguments(string name, int firstChild, int childCount)
        {
            Name = name;
            FirstChild = firstChild;
            ChildCount = childCount;
        }

        public bool Equals(BaseArguments other)
        {
            return other != null
                && Name == other.Name
                && FirstChild == other.FirstChild
                && ChildCount == other.ChildCount;
        }

        public override bool Equals(object obj)
        {
            return Equals(obj as BaseArguments);
        }

        public override int GetHashCode()
        {
            return (Name.GetHashCode() * 31 + FirstChild) * 31 + ChildCount;
        }
    }
}