JensKrumsieck/ChemSharp

using System.Numerics;

namespace ChemSharp.Molecules;

/// <summary>
///     Atom represents an Element in 3d Space
/// </summary>
public class Atom : Element, IEquatable<Atom>
{
    private string _title = "";

    /// <inheritdoc />
    public Atom(string symbol) : base(symbol) { }

    public Atom(string symbol, float x, float y, float z) : this(symbol) => Location = new Vector3(x, y, z);

    /// <summary>
    ///     Location in 3D Space
    /// </summary>
    public Vector3 Location { get; set; }

    /// <summary>
    ///     Gets or Sets the Atom title
    /// </summary>
    public string Title
    {
        get => !string.IsNullOrEmpty(_title) ? _title : Symbol;
        set => _title = value;
    }

    /// <summary>
    ///     Gets or sets the Residue Type
    /// </summary>
    public string Residue { get; set; } = "";

    /// <summary>
    /// Gets or sets the residue id
    /// </summary>
    public int ResidueId { get; set; }

    public char ChainId { get; set; }

    public bool Equals(Atom? other) =>
        other is not null &&
        (ReferenceEquals(this, other)
         || Symbol == other.Symbol && Location.Equals(other.Location));

    /// <summary>
    ///     Computes Distance To Other Atom
    ///     Wrapper from Vector3.Distance
    /// </summary>
    /// <param name="test"></param>
    /// <returns></returns>
    public float DistanceTo(Atom test) => Vector3.Distance(Location, test.Location);

    /// <summary>
    ///     Returns squared Distance of two atoms
    /// </summary>
    /// <param name="test"></param>
    /// <returns></returns>
    public float DistanceToSquared(Atom test) => Vector3.DistanceSquared(Location, test.Location);

    public override string ToString() => $"{Title}: {Location}";

    /// <summary>
    ///     Gets HashCode, defined by Symbol and location
    /// </summary>
    /// <returns></returns>
    public override int GetHashCode() => (Title, Symbol, Location).GetHashCode();

    public override bool Equals(object? obj) =>
        obj is not null &&
        (ReferenceEquals(this, obj)
         || obj.GetType() == GetType() && Equals((Atom)obj));

    public static bool operator ==(Atom? a, Atom? b) =>
        a is null && b is null
        || a is not null && b is not null
                         && (ReferenceEquals(a, b) || a.Equals(b));

    public static bool operator !=(Atom? a, Atom? b) =>
        !(a == b);
}