using System;
using System.Collections.Generic;
using System.Linq;
using StardewModdingAPI.Framework.Input;

namespace StardewModdingAPI.Events
{
    /// <summary>Event arguments when any buttons were pressed or released.</summary>
    public class ButtonsChangedEventArgs : EventArgs
    {
        /*********
        ** Fields
        *********/
        /// <summary>The buttons that were pressed, held, or released since the previous tick.</summary>
        private readonly Lazy<Dictionary<SButtonState, SButton[]>> ButtonsByState;


        /*********
        ** Accessors
        *********/
        /// <summary>The current cursor position.</summary>
        public ICursorPosition Cursor { get; }

        /// <summary>The buttons which were pressed since the previous tick.</summary>
        public IEnumerable<SButton> Pressed => this.ButtonsByState.Value[SButtonState.Pressed];

        /// <summary>The buttons which were held since the previous tick.</summary>
        public IEnumerable<SButton> Held => this.ButtonsByState.Value[SButtonState.Held];

        /// <summary>The buttons which were released since the previous tick.</summary>
        public IEnumerable<SButton> Released => this.ButtonsByState.Value[SButtonState.Released];


        /*********
        ** Public methods
        *********/
        /// <summary>Construct an instance.</summary>
        /// <param name="cursor">The cursor position.</param>
        /// <param name="inputState">The game's current input state.</param>
        internal ButtonsChangedEventArgs(ICursorPosition cursor, SInputState inputState)
        {
            this.Cursor = cursor;
            this.ButtonsByState = new Lazy<Dictionary<SButtonState, SButton[]>>(() => this.GetButtonsByState(inputState));
        }


        /*********
        ** Private methods
        *********/
        /// <summary>Get the buttons that were pressed, held, or released since the previous tick.</summary>
        /// <param name="inputState">The game's current input state.</param>
        private Dictionary<SButtonState, SButton[]> GetButtonsByState(SInputState inputState)
        {
            Dictionary<SButtonState, SButton[]> lookup = inputState.ButtonStates
                .GroupBy(p => p.Value)
                .ToDictionary(p => p.Key, p => p.Select(p => p.Key).ToArray());

            foreach (var state in new[] { SButtonState.Pressed, SButtonState.Held, SButtonState.Released })
            {
                if (!lookup.ContainsKey(state))
                    lookup[state] = Array.Empty<SButton>();
            }

            return lookup;
        }
    }
}