using System;

namespace Chernobyl.Switch
{
    /// <summary>
    /// A switch that requires two events to be received in order before the 
    /// switches output event is raised. In other words, when <see cref="Switch1"/>
    /// and THEN <see cref="Switch2"/> is invoked, <see cref="SwitchedOn"/> will 
    /// be invoked. If <see cref="Switch2"/> is invoked before <see cref="Switch1"/>,
    /// <see cref="SwitchedOn"/> will NOT fire.
    /// </summary>
    public class OneTwoSwitch : ISwitch
    {
        /// <summary>
        /// Constructor.
        /// </summary>
        public OneTwoSwitch() {}

        /// <summary>
        /// Constructor.
        /// </summary>
        /// <param name="onSwitchHandlers">Methods to assign to the event 
        /// <see cref="SwitchedOn"/>.</param>
        public OneTwoSwitch(params EventHandler[] onSwitchHandlers)
        {
            foreach (EventHandler eh in onSwitchHandlers)
                SwitchedOn += eh;
        }

        /// <summary>
        /// An event that is raised when the method <see cref="Switch1"/> and
        /// THEN <see cref="Switch2"/> is invoked. If the methods are invoked 
        /// the other way around, the event will not be invoked.
        /// </summary>
        public event EventHandler SwitchedOn;

        /// <summary>
        /// An event that is raised right after this switch has been switched 
        /// off (or reset).
        /// </summary>
        public event EventHandler SwitchedOff;

        /// <summary>
        /// An event handler that can be assigned to an event. This method must 
        /// be invoked before <see cref="Switch2"/> is invoked for the event
        /// <see cref="SwitchedOn"/> to be invoked.
        /// </summary>
        /// <param name="sender">The sender of the event.</param>
        /// <param name="e">The events arguments.</param>
        public void Switch1(object sender, EventArgs e)
        {
            Switch1Value = true;
        }

        /// <summary>
        /// An event handler that can be assigned to an event. This method must 
        /// be invoked after <see cref="Switch1"/> is invoked for the event
        /// <see cref="SwitchedOn"/> to be invoked.
        /// </summary>
        /// <param name="sender">The sender of the event.</param>
        /// <param name="e">The events arguments.</param>
        public void Switch2(object sender, EventArgs e)
        {
            if (Switch1Value == true && SwitchedOn != null)
                SwitchedOn(this, EventArgs.Empty);
        }

        /// <summary>
        /// Overrides <see cref="ISwitch"/>.
        /// </summary>
        public void Reset()
        {
            Switch1Value = false;

            if (SwitchedOff != null)
                SwitchedOff(this, EventArgs.Empty);
        }

        /// <summary>
        /// Overrides <see cref="ISwitch"/>.
        /// </summary>
        public void Reset(object sender, EventArgs e)
        {
            Reset();
        }

        /// <summary>
        /// True if <see cref="Switch1"/> has been invoked, false if otherwise.
        /// </summary>
        bool Switch1Value;
    }
}