using System;
using System.Diagnostics;

namespace Engine.Core;

/// <summary>
/// Represents a 3D sphere.
/// </summary>
/// <param name="center">The center of the sphere.</param>
/// <param name="radius">The radius of the sphere.</param>
/// <remarks>
/// Initializes a new instance of the <see cref="Sphere3D"/> struct with the specified center and radius.
/// </remarks>
[DebuggerDisplay("Center: {Center.ToString(),nq}, Radius: {Radius}")]
public readonly struct Sphere3D(Vector3D center, float radius) : IEquatable<Sphere3D>
{
    /// <summary>
    /// The center of the <see cref="Sphere3D"/>.
    /// </summary>
    public readonly Vector3D Center = center;

    /// <summary>
    /// The radius of the <see cref="Sphere3D"/>.
    /// </summary>
    public readonly float Radius = radius;

    /// <summary>
    /// Gets the squared radius of the <see cref="Sphere3D"/>.
    /// </summary>
    public readonly float RadiusSquared => Radius * Radius;

    /// <summary>
    /// Gets the diameter of the <see cref="Sphere3D"/>.
    /// </summary>
    public readonly float Diameter => 2f * Radius;

    /// <summary>
    /// A predefined unit <see cref="Sphere3D"/> with a center at the origin and a radius of 1.
    /// </summary>
    public static readonly Sphere3D UnitSphere = new(Vector3D.Zero, 1f);

    public static bool operator ==(Sphere3D left, Sphere3D right) => left.Center == right.Center && left.Radius == right.Radius;
    public static bool operator !=(Sphere3D left, Sphere3D right) => left.Center != right.Center || left.Radius != right.Radius;

    /// <summary>
    /// Sets the center of the <see cref="Sphere3D"/>.
    /// </summary>
    public static Sphere3D SetCenter(Sphere3D sphere, Vector3D center) => new(center, sphere.Radius);

    /// <summary>
    /// Sets the radius of the <see cref="Sphere3D"/>.
    /// </summary>
    public static Sphere3D SetRadius(Sphere3D sphere, float radius) => new(sphere.Center, radius);

    /// <summary>
    /// Displaces the <see cref="Sphere3D"/> by the specified <see cref="Vector3D"/>.
    /// </summary>
    public static Sphere3D Displace(Sphere3D sphere, Vector3D displaceVector) => new(sphere.Center + displaceVector, sphere.Radius);

    /// <summary>
    /// Projects the <see cref="Sphere3D"/> onto the specified <see cref="Vector3D"/>.
    /// </summary>
    public static Projection1D Project(Sphere3D sphere, Vector3D projectionVector)
    {
        float projectedCenter = sphere.Center.Dot(projectionVector);
        return new(projectedCenter - sphere.Radius, projectedCenter + sphere.Radius);
    }

    /// <summary>
    /// Transforms the <see cref="Sphere3D"/> by the specified <see cref="ITransform3D"/>.
    /// </summary>
    public static Sphere3D Transform(ITransform3D transform, Sphere3D sphere)
        => new(transform.Transform(sphere.Center), sphere.Radius * (transform.Scale.Magnitude / Vector3D.One.Magnitude));

    /// <summary>
    /// Checks if two <see cref="Sphere3D"/>s are approximately equal.
    /// </summary>
    /// <param name="left">The first <see cref="Sphere3D"/>.</param>
    /// <param name="right">The second <see cref="Sphere3D"/>.</param>
    /// <param name="epsilon">The epsilon range.</param>
    /// <returns><see cref="true"/> if the <see cref="Sphere3D"/>s are approximately equal; otherwise, <see cref="false"/>.</returns>
    public static bool ApproximatelyEquals(Sphere3D left, Sphere3D right, float epsilon = float.Epsilon)
        => left.Center.ApproximatelyEquals(right.Center, epsilon) && left.Radius.ApproximatelyEquals(right.Radius, epsilon);

    /// <summary>
    /// Determines whether the specified object is equal to the current <see cref="Sphere3D"/>.
    /// </summary>
    /// <param name="obj">The object to compare with the current <see cref="Sphere3D"/>.</param>
    /// <returns><see cref="true"/> if the specified object is equal to the current <see cref="Sphere3D"/>; otherwise, <see cref="false"/>.</returns>
    public override bool Equals(object? obj) => obj is Sphere3D sphere && this == sphere;
    public bool Equals(Sphere3D other) => this == other;

    /// <summary>
    /// Generates a hash code for the <see cref="Sphere3D"/>.
    /// </summary>
    /// <returns>A hash code for the <see cref="Sphere3D"/>.</returns>
    public override int GetHashCode() => System.HashCode.Combine(Center, Radius);

    /// <summary>
    /// Converts the <see cref="Sphere3D"/> to its string representation.
    /// </summary>
    /// <returns>A string representation of the <see cref="Sphere3D"/>.</returns>
    public override string ToString() => $"{nameof(Sphere3D)}({Center}, {Radius})";
}

/// <summary>
/// Provides extension methods for the <see cref="Sphere3D"/> struct.
/// </summary>
public static class SphereExtensions
{
    /// <inheritdoc cref="Sphere3D.SetCenter(Sphere3D, Vector3D)" />
    public static Sphere3D SetCenter(this Sphere3D sphere, Vector3D center) => Sphere3D.SetCenter(sphere, center);

    /// <inheritdoc cref="Sphere3D.SetRadius(Sphere3D, float)" />
    public static Sphere3D SetRadius(this Sphere3D sphere, float radius) => Sphere3D.SetRadius(sphere, radius);

    /// <inheritdoc cref="Sphere3D.Displace(Sphere3D, Vector3D)" />
    public static Sphere3D Displace(this Sphere3D sphere, Vector3D displaceVector) => Sphere3D.Displace(sphere, displaceVector);

    /// <inheritdoc cref="Sphere3D.Project(Sphere3D, Vector3D)" />
    public static Projection1D ProjectTo(this Sphere3D sphere, Vector3D projectionVector) => Sphere3D.Project(sphere, projectionVector);

    /// <inheritdoc cref="Sphere3D.Transform(ITransform3D, Sphere3D)" />
    public static Sphere3D Transform(this ITransform3D transform, Sphere3D sphere) => Sphere3D.Transform(transform, sphere);

    /// <inheritdoc cref="Sphere3D.Transform(ITransform3D, Sphere3D)" />
    public static Sphere3D Transform(this Sphere3D sphere, ITransform3D transform) => Sphere3D.Transform(transform, sphere);

    /// <inheritdoc cref="Sphere3D.ApproximatelyEquals(Sphere3D, Sphere3D, float)" />
    public static bool ApproximatelyEquals(this Sphere3D left, Sphere3D right, float epsilon = float.Epsilon) => Sphere3D.ApproximatelyEquals(left, right, epsilon);
}