Monogame-Extended/source/MonoGame.Extended/Tilemaps/Properties/TilemapPropertyValue.cs

using System;
using System.Runtime.InteropServices;
using Microsoft.Xna.Framework;

namespace MonoGame.Extended.Tilemaps
{
    /// <summary>
    /// Represents a custom property value that can be of various types.
    /// </summary>
    public readonly struct TilemapPropertyValue
    {
        [StructLayout(LayoutKind.Explicit)]
        private readonly struct ValueData
        {
            [FieldOffset(0)] public readonly int Int32;
            [FieldOffset(0)] public readonly float Single;
            [FieldOffset(0)] public readonly bool Boolean;
            [FieldOffset(0)] public readonly uint ColorPackedValue;

            public ValueData(int value) => Int32 = value;
            public ValueData(float value) => Single = value;
            public ValueData(bool value) => Boolean = value;
            public ValueData(uint value) => ColorPackedValue = value;
        }

        private readonly ValueData _valueData;
        private readonly string _stringValue;

        /// <summary>
        /// Gets the type of this property value.
        /// </summary>
        public TilemapPropertyType Type { get; }

        private TilemapPropertyValue(TilemapPropertyType type, ValueData valueData, string stringValue = null)
        {
            Type = type;
            _valueData = valueData;
            _stringValue = stringValue;
        }

        #region Factory Methods

        /// <summary>
        /// Creates a string property value.
        /// </summary>
        /// <param name="value">The string value.</param>
        /// <returns>A property value containing the string.</returns>
        public static TilemapPropertyValue CreateString(string value)
        {
            return new TilemapPropertyValue(TilemapPropertyType.String, default, value);
        }

        /// <summary>
        /// Creates an integer property value.
        /// </summary>
        /// <param name="value">The integer value.</param>
        /// <returns>A property value containing the integer.</returns>
        public static TilemapPropertyValue CreateInt(int value)
        {
            return new TilemapPropertyValue(TilemapPropertyType.Int, new ValueData(value));
        }

        /// <summary>
        /// Creates a float property value.
        /// </summary>
        /// <param name="value">The float value.</param>
        /// <returns>A property value containing the float.</returns>
        public static TilemapPropertyValue CreateFloat(float value)
        {
            return new TilemapPropertyValue(TilemapPropertyType.Float, new ValueData(value));
        }

        /// <summary>
        /// Creates a boolean property value.
        /// </summary>
        /// <param name="value">The boolean value.</param>
        /// <returns>A property value containing the boolean.</returns>
        public static TilemapPropertyValue CreateBool(bool value)
        {
            return new TilemapPropertyValue(TilemapPropertyType.Bool, new ValueData(value));
        }

        /// <summary>
        /// Creates a color property value.
        /// </summary>
        /// <param name="value">The color value.</param>
        /// <returns>A property value containing the color.</returns>
        public static TilemapPropertyValue CreateColor(Color value)
        {
            return new TilemapPropertyValue(TilemapPropertyType.Color, new ValueData(value.PackedValue));
        }

        /// <summary>
        /// Creates a file path property value.
        /// </summary>
        /// <param name="path">The file path.</param>
        /// <returns>A property value containing the file path.</returns>
        public static TilemapPropertyValue CreateFile(string path)
        {
            return new TilemapPropertyValue(TilemapPropertyType.File, default, path);
        }

        /// <summary>
        /// Creates an object reference property value.
        /// </summary>
        /// <param name="objectId">The object reference ID.</param>
        /// <returns>A property value containing the object ID.</returns>
        public static TilemapPropertyValue CreateObject(int objectId)
        {
            return new TilemapPropertyValue(TilemapPropertyType.Object, new ValueData(objectId));
        }

        #endregion

        #region Type-safe Accessors

        /// <summary>
        /// Gets the value as a string.
        /// </summary>
        /// <returns>The string value.</returns>
        /// <exception cref="InvalidOperationException">The property type is not <see cref="TilemapPropertyType.String"/></exception>
        public string AsString()
        {
            if (Type != TilemapPropertyType.String)
                throw new InvalidOperationException($"Cannot access property of type {Type} as String");

            return _stringValue;
        }

        /// <summary>
        /// Gets the value as an integer.
        /// </summary>
        /// <returns>The integer value.</returns>
        /// <exception cref="InvalidOperationException">The property type is not <see cref="TilemapPropertyType.Int"/></exception>
        public int AsInt()
        {
            if (Type != TilemapPropertyType.Int)
                throw new InvalidOperationException($"Cannot access property of type {Type} as Int.");

            return _valueData.Int32;
        }

        /// <summary>
        /// Gets the value as a float.
        /// </summary>
        /// <returns>The float value.</returns>
        /// <exception cref="InvalidOperationException">The property type is not <see cref="TilemapPropertyType.Float"/></exception>
        public float AsFloat()
        {
            if (Type != TilemapPropertyType.Float)
                throw new InvalidOperationException($"Cannot access property of type {Type} as Float.");

            return _valueData.Single;
        }

        /// <summary>
        /// Gets the value as a boolean.
        /// </summary>
        /// <returns>The bool value.</returns>
        /// <exception cref="InvalidOperationException">The property type is not <see cref="TilemapPropertyType.Bool"/></exception>
        public bool AsBool()
        {
            if (Type != TilemapPropertyType.Bool)
                throw new InvalidOperationException($"Cannot access property of type {Type} as Bool.");

            return _valueData.Boolean;
        }

        /// <summary>
        /// Gets the value as a color.
        /// </summary>
        /// <returns>The color value.</returns>
        /// <exception cref="InvalidOperationException">The property type is not <see cref="TilemapPropertyType.Color"/></exception>
        public Color AsColor()
        {
            if (Type != TilemapPropertyType.Color)
                throw new InvalidOperationException($"Cannot access property of type {Type} as Color.");

            return new Color(_valueData.ColorPackedValue);
        }

        /// <summary>
        /// Gets the value as a file path.
        /// </summary>
        /// <returns>The file path.</returns>
        /// <exception cref="InvalidOperationException">The property type is not <see cref="TilemapPropertyType.File"/></exception>
        public string AsFile()
        {
            if (Type != TilemapPropertyType.File)
                throw new InvalidOperationException($"Cannot access property of type {Type} as File.");

            return _stringValue;
        }

        /// <summary>
        /// Gets the value as an object reference ID.
        /// </summary>
        /// <returns>The object ID.</returns>
        /// <exception cref="InvalidOperationException">The property type is not <see cref="TilemapPropertyType.Object"/></exception>
        public int AsObject()
        {
            if (Type != TilemapPropertyType.Object)
                throw new InvalidOperationException($"Cannot access property of type {Type} as Object.");

            return _valueData.Int32;
        }

        #endregion
    }
}