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using System;
using System.Collections.Generic;
using System.Dynamic;
using System.Linq.Expressions;
using System.Runtime.CompilerServices;
namespace Godot
{
/// <summary>
/// Represents an <see cref="Godot.Object"/> whose members can be dynamically accessed at runtime through the Variant API.
/// </summary>
/// <remarks>
/// <para>
/// The <see cref="Godot.DynamicGodotObject"/> class enables access to the Variant
/// members of a <see cref="Godot.Object"/> instance at runtime.
/// </para>
/// <para>
/// This allows accessing the class members using their original names in the engine as well as the members from the
/// script attached to the <see cref="Godot.Object"/>, regardless of the scripting language it was written in.
/// </para>
/// </remarks>
/// <example>
/// This sample shows how to use <see cref="Godot.DynamicGodotObject"/> to dynamically access the engine members of a <see cref="Godot.Object"/>.
/// <code>
/// dynamic sprite = GetNode("Sprite").DynamicGodotObject;
/// sprite.add_child(this);
///
/// if ((sprite.hframes * sprite.vframes) > 0)
/// sprite.frame = 0;
/// </code>
/// </example>
/// <example>
/// This sample shows how to use <see cref="Godot.DynamicGodotObject"/> to dynamically access the members of the script attached to a <see cref="Godot.Object"/>.
/// <code>
/// dynamic childNode = GetNode("ChildNode").DynamicGodotObject;
///
/// if (childNode.print_allowed)
/// {
/// childNode.message = "Hello from C#";
/// childNode.print_message(3);
/// }
/// </code>
/// The <c>ChildNode</c> node has the following GDScript script attached:
/// <code>
/// // # ChildNode.gd
/// // var print_allowed = true
/// // var message = ""
/// //
/// // func print_message(times):
/// // for i in times:
/// // print(message)
/// </code>
/// </example>
public class DynamicGodotObject : DynamicObject
{
/// <summary>
/// Gets the <see cref="Godot.Object"/> associated with this <see cref="Godot.DynamicGodotObject"/>.
/// </summary>
public Object Value { get; }
/// <summary>
/// Initializes a new instance of the <see cref="Godot.DynamicGodotObject"/> class.
/// </summary>
/// <param name="godotObject">
/// The <see cref="Godot.Object"/> that will be associated with this <see cref="Godot.DynamicGodotObject"/>.
/// </param>
/// <exception cref="System.ArgumentNullException">
/// Thrown when the <paramref name="godotObject"/> parameter is null.
/// </exception>
public DynamicGodotObject(Object godotObject)
{
if (godotObject == null)
throw new ArgumentNullException(nameof(godotObject));
this.Value = godotObject;
}
public override IEnumerable<string> GetDynamicMemberNames()
{
return godot_icall_DynamicGodotObject_SetMemberList(Object.GetPtr(Value));
}
public override bool TryBinaryOperation(BinaryOperationBinder binder, object arg, out object result)
{
switch (binder.Operation)
{
case ExpressionType.Equal:
case ExpressionType.NotEqual:
if (binder.ReturnType == typeof(bool) || binder.ReturnType.IsAssignableFrom(typeof(bool)))
{
if (arg == null)
{
bool boolResult = Object.IsInstanceValid(Value);
if (binder.Operation == ExpressionType.Equal)
boolResult = !boolResult;
result = boolResult;
return true;
}
if (arg is Object other)
{
bool boolResult = (Value == other);
if (binder.Operation == ExpressionType.NotEqual)
boolResult = !boolResult;
result = boolResult;
return true;
}
}
break;
default:
// We're not implementing operators <, <=, >, and >= (LessThan, LessThanOrEqual, GreaterThan, GreaterThanOrEqual).
// These are used on the actual pointers in variant_op.cpp. It's better to let the user do that explicitly.
break;
}
return base.TryBinaryOperation(binder, arg, out result);
}
public override bool TryConvert(ConvertBinder binder, out object result)
{
if (binder.Type == typeof(Object))
{
result = Value;
return true;
}
if (typeof(Object).IsAssignableFrom(binder.Type))
{
// Throws InvalidCastException when the cast fails
result = Convert.ChangeType(Value, binder.Type);
return true;
}
return base.TryConvert(binder, out result);
}
public override bool TryGetIndex(GetIndexBinder binder, object[] indexes, out object result)
{
if (indexes.Length == 1)
{
if (indexes[0] is string name)
{
return godot_icall_DynamicGodotObject_GetMember(Object.GetPtr(Value), name, out result);
}
}
return base.TryGetIndex(binder, indexes, out result);
}
public override bool TryGetMember(GetMemberBinder binder, out object result)
{
return godot_icall_DynamicGodotObject_GetMember(Object.GetPtr(Value), binder.Name, out result);
}
public override bool TryInvokeMember(InvokeMemberBinder binder, object[] args, out object result)
{
return godot_icall_DynamicGodotObject_InvokeMember(Object.GetPtr(Value), binder.Name, args, out result);
}
public override bool TrySetIndex(SetIndexBinder binder, object[] indexes, object value)
{
if (indexes.Length == 1)
{
if (indexes[0] is string name)
{
return godot_icall_DynamicGodotObject_SetMember(Object.GetPtr(Value), name, value);
}
}
return base.TrySetIndex(binder, indexes, value);
}
public override bool TrySetMember(SetMemberBinder binder, object value)
{
return godot_icall_DynamicGodotObject_SetMember(Object.GetPtr(Value), binder.Name, value);
}
[MethodImpl(MethodImplOptions.InternalCall)]
internal extern static string[] godot_icall_DynamicGodotObject_SetMemberList(IntPtr godotObject);
[MethodImpl(MethodImplOptions.InternalCall)]
internal extern static bool godot_icall_DynamicGodotObject_InvokeMember(IntPtr godotObject, string name, object[] args, out object result);
[MethodImpl(MethodImplOptions.InternalCall)]
internal extern static bool godot_icall_DynamicGodotObject_GetMember(IntPtr godotObject, string name, out object result);
[MethodImpl(MethodImplOptions.InternalCall)]
internal extern static bool godot_icall_DynamicGodotObject_SetMember(IntPtr godotObject, string name, object value);
#region We don't override these methods
// Looks like this is not usable from C#
//public override bool TryCreateInstance(CreateInstanceBinder binder, object[] args, out object result);
// Object members cannot be deleted
//public override bool TryDeleteIndex(DeleteIndexBinder binder, object[] indexes);
//public override bool TryDeleteMember(DeleteMemberBinder binder);
// Invokation on the object itself, e.g.: obj(param)
//public override bool TryInvoke(InvokeBinder binder, object[] args, out object result);
// No unnary operations to handle
//public override bool TryUnaryOperation(UnaryOperationBinder binder, out object result);
#endregion
}
}
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