/// <summary>
/// Returns a delegate that will attempt to coerce supplied arguments into the specified delegate and return the result.
/// </summary>
/// <param name="func"></param>
/// <returns></returns>
private JavaScriptNativeFunction CreateNativeFunctionForDelegate(Delegate func)
{
//This is crazy fun.
var funcParams = func.Method.GetParameters();
JavaScriptNativeFunction fnDelegate = (IntPtr callee, bool isConstructCall, IntPtr[] arguments, ushort argumentCount, IntPtr callbackData) =>
{
//Make sure that we have argument values for each parameter.
var nativeArgs = new object[funcParams.Length];
for (int i = 0; i < funcParams.Length; i++)
{
var targetParameterType = funcParams[i].ParameterType;
var currentArgument = arguments.ElementAtOrDefault(i);
if (currentArgument == default(IntPtr))
{
//If the argument wasn't specified, use the default value for the target parameter.
nativeArgs[i] = targetParameterType.GetDefaultValue();
}
else
{
//As the argument has been specified, convert the JsValue back to an Object using
//the conversion strategy associated with the context.
var argValueHandle = new JavaScriptValueSafeHandle(currentArgument);
var jsValue = CreateValue(argValueHandle);
//Keep the first argument as the this JsObject.
if (i == 0)
{
nativeArgs[i] = jsValue as JsObject;
}
//If the target type is the same as the value type (The delegate expects a JsValue) don't convert.
else if (targetParameterType.IsSameOrSubclass(jsValue.GetType()))
{
nativeArgs[i] = jsValue;
}
else if (Context.Converter.TryToObject(Context, jsValue, out object obj))
{
try
{
nativeArgs[i] = Convert.ChangeType(obj, targetParameterType);
}
catch (Exception)
{
//Something went wrong, use the default value.
nativeArgs[i] = targetParameterType.GetDefaultValue();
}
}
else
{
//If we couldn't convert the type, use the default value.
nativeArgs[i] = targetParameterType.GetDefaultValue();
}
}
}
try
{
var nativeResult = func.DynamicInvoke(nativeArgs);
if (Context.Converter.TryFromObject(Context, nativeResult, out JsValue valueResult))
{
return(valueResult.Handle.DangerousGetHandle());
}
else
{
return(Context.Undefined.Handle.DangerousGetHandle());
}
}
catch (TargetInvocationException exceptionResult)
{
var jsError = CreateError(exceptionResult.InnerException);
m_engine.JsSetException(jsError.Handle);
return(Context.Undefined.Handle.DangerousGetHandle());
}
};
return(fnDelegate);
}
