using System;

namespace UnityEngine.XR.ARSubsystems
{
    /// <summary>
    /// Represents an entry in an <see cref="XRReferenceImageLibrary"/>.
    /// </summary>
    /// <remarks>
    /// A reference image is an image to look for in the physical environment.
    /// The <see cref="XRReferenceImage"/> does not directly reference a <c>Texture2D</c>
    /// or other image data; it only stores the GUID of the <c>Texture2D</c> as it
    /// appears in the <c>AssetDatabase</c>. At build time, platform specific build steps
    /// may use the guids to look up the source textures and generate an appropriate
    /// image database. At runtime, detected images can be matched up with the source
    /// <see cref="XRReferenceImage"/>.
    /// </remarks>
    [Serializable]
    public struct XRReferenceImage : IEquatable<XRReferenceImage>
    {
        public XRReferenceImage(
            SerializableGuid guid, SerializableGuid textureGuid,
            Vector2? size, string name, Texture2D texture)
        {
            m_SerializedGuid = guid;
            m_SerializedTextureGuid = textureGuid;
            m_SpecifySize = size.HasValue;
            m_Size = size.HasValue ? size.Value : Vector2.zero;
            m_Name = name;
            m_Texture = texture;
        }

        /// <summary>
        /// The <c>Guid</c> associated with this image.
        /// </summary>
        public Guid guid => m_SerializedGuid.guid;

        /// <summary>
        /// The <c>Guid</c> of the source texture as it appeared in the
        /// [AssetDatabase](https://docs.unity3d.com/ScriptReference/AssetDatabase.html)
        /// in the Editor.
        /// </summary>
        public Guid textureGuid => m_SerializedTextureGuid.guid;

        /// <summary>
        /// Must be set to true for <see cref="size"/> to be used.
        /// </summary>
        public bool specifySize => m_SpecifySize;

        /// <summary>
        /// The size of the image, in meters. This can improve image detection,
        /// and may be required by some platforms.
        /// </summary>
        public Vector2 size => m_Size;

        /// <summary>
        /// The width of the image, in meters.
        /// </summary>
        public float width => m_Size.x;

        /// <summary>
        /// The height of the image, in meters.
        /// </summary>
        public float height => m_Size.y;

        /// <summary>
        /// A name associated with this reference image.
        /// </summary>
        public string name => m_Name;

        /// <summary>
        /// The source texture which this reference image represents.
        /// This may be <c>null</c> to avoid including the texture in
        /// the Player build if that is not desired. See
        /// <c>UnityEditor.XR.ARSubsystems.XRReferenceImageLibraryExtensions.SetTexture</c>
        /// for more details.
        /// </summary>
        public Texture2D texture => m_Texture;

        /// <summary>
        /// Provides a string representation suitable for debug logging.
        /// </summary>
        /// <returns>A string representation of the reference image.</returns>
        public override string ToString() =>
            $"GUID: '{guid}', Texture GUID: '{textureGuid}` Size: {(m_SpecifySize ? "" : "NOT ")} specified {m_Size}";

        public override int GetHashCode() => guid.GetHashCode();
        public override bool Equals(object obj) => (obj is XRReferenceImage) && Equals((XRReferenceImage)obj);
        public bool Equals(XRReferenceImage other) => guid.Equals(other.guid);
        public static bool operator ==(XRReferenceImage lhs, XRReferenceImage rhs) => lhs.Equals(rhs);
        public static bool operator !=(XRReferenceImage lhs, XRReferenceImage rhs) => !lhs.Equals(rhs);

#pragma warning disable CS0649
        [SerializeField]
        internal SerializableGuid m_SerializedGuid;

        [SerializeField]
        internal SerializableGuid m_SerializedTextureGuid;

        [SerializeField]
        internal Vector2 m_Size;

        [SerializeField]
        internal bool m_SpecifySize;

        [SerializeField]
        internal string m_Name;

        [SerializeField]
        internal Texture2D m_Texture;
#pragma warning restore CS0649
    }
}