using System;
using System.Reflection;
using System.Windows;
using System.Windows.Input;

namespace HandyControl.Interactivity
{
    public sealed class InvokeCommandAction : TriggerAction<DependencyObject>
    {
        public static readonly DependencyProperty CommandProperty =
            DependencyProperty.Register(nameof(Command), typeof(ICommand), typeof(InvokeCommandAction), null);

        public static readonly DependencyProperty CommandParameterProperty =
            DependencyProperty.Register(nameof(CommandParameter), typeof(object), typeof(InvokeCommandAction),
                null);

        private string _commandName;

        public string CommandName
        {
            get
            {
                ReadPreamble();
                return _commandName;
            }
            set
            {
                if (CommandName == value)
                    return;
                WritePreamble();
                _commandName = value;
                WritePostscript();
            }
        }

        public ICommand Command
        {
            get => (ICommand) GetValue(CommandProperty);
            set => SetValue(CommandProperty, value);
        }

        public object CommandParameter
        {
            get => GetValue(CommandParameterProperty);
            set => SetValue(CommandParameterProperty, value);
        }

        protected override void Invoke(object parameter)
        {
            if (AssociatedObject == null)
                return;
            var command = ResolveCommand();
            if (command == null || !command.CanExecute(CommandParameter))
                return;
            command.Execute(CommandParameter);
        }

        private ICommand ResolveCommand()
        {
            var command = (ICommand) null;
            if (Command != null)
                command = Command;
            else if (AssociatedObject != null)
                foreach (var property in AssociatedObject.GetType()
                    .GetProperties(BindingFlags.Instance | BindingFlags.Public))
                    if (typeof(ICommand).IsAssignableFrom(property.PropertyType) &&
                        string.Equals(property.Name, CommandName, StringComparison.Ordinal))
                        command = (ICommand) property.GetValue(AssociatedObject, null);
            return command;
        }
    }
}
