using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Input;
using StardewValley;

#pragma warning disable 809 // obsolete override of non-obsolete method (this is deliberate)
namespace StardewModdingAPI.Framework.Input
{
    /// <summary>Manages the game's input state.</summary>
    internal sealed class SInputState : InputState
    {
        /*********
        ** Accessors
        *********/
        /// <summary>The cursor position on the screen adjusted for the zoom level.</summary>
        private CursorPosition CursorPositionImpl;

        /// <summary>The player's last known tile position.</summary>
        private Vector2? LastPlayerTile;

        /// <summary>The buttons to press until the game next handles input.</summary>
        private readonly HashSet<SButton> CustomPressedKeys = new HashSet<SButton>();

        /// <summary>The buttons to consider released until the actual button is released.</summary>
        private readonly HashSet<SButton> CustomReleasedKeys = new HashSet<SButton>();

        /// <summary>Whether there are new overrides in <see cref="CustomPressedKeys"/> or <see cref="CustomReleasedKeys"/> that haven't been applied to the previous state.</summary>
        private bool HasNewOverrides;

        /// <summary>The game tick when the input state was last updated.</summary>
        private uint? LastUpdateTick;


        /*********
        ** Accessors
        *********/
        /// <summary>The controller state as of the last update, with overrides applied.</summary>
        public GamePadState ControllerState { get; private set; }

        /// <summary>The keyboard state as of the last update, with overrides applied.</summary>
        public KeyboardState KeyboardState { get; private set; }

        /// <summary>The mouse state as of the last update, with overrides applied.</summary>
        public MouseState MouseState { get; private set; }

        /// <summary>The buttons which were pressed, held, or released as of the last update.</summary>
        public IDictionary<SButton, SButtonState> ButtonStates { get; private set; } = new Dictionary<SButton, SButtonState>();

        /// <summary>The cursor position on the screen adjusted for the zoom level.</summary>
        public ICursorPosition CursorPosition => this.CursorPositionImpl;


        /*********
        ** Public methods
        *********/
        /// <summary>Update the current button states for the given tick. This does nothing if the input has already been updated for this tick (e.g. because SMAPI updated it before the game update).</summary>
        public override void Update()
        {
            // skip if already updated
            if (this.LastUpdateTick == SCore.TicksElapsed)
                return;
            this.LastUpdateTick = SCore.TicksElapsed;

            // update base state
            base.Update();

            // update SMAPI extended data
            try
            {
                float zoomMultiplier = (1f / Game1.options.zoomLevel);

                // get real values
                var controller = new GamePadStateBuilder(base.GetGamePadState());
                var keyboard = new KeyboardStateBuilder(base.GetKeyboardState());
                var mouse = new MouseStateBuilder(base.GetMouseState());
                Vector2 cursorAbsolutePos = new Vector2((mouse.X * zoomMultiplier) + Game1.viewport.X, (mouse.Y * zoomMultiplier) + Game1.viewport.Y);
                Vector2? playerTilePos = Context.IsPlayerFree ? Game1.player.getTileLocation() : (Vector2?)null;
                HashSet<SButton> reallyDown = new HashSet<SButton>(this.GetPressedButtons(keyboard, mouse, controller));

                // apply overrides
                bool hasOverrides = false;
                if (this.CustomPressedKeys.Count > 0 || this.CustomReleasedKeys.Count > 0)
                {
                    // reset overrides that no longer apply
                    this.CustomPressedKeys.RemoveWhere(key => reallyDown.Contains(key));
                    this.CustomReleasedKeys.RemoveWhere(key => !reallyDown.Contains(key));

                    // apply overrides
                    if (this.ApplyOverrides(this.CustomPressedKeys, this.CustomReleasedKeys, controller, keyboard, mouse))
                        hasOverrides = true;

                    // remove pressed keys
                    this.CustomPressedKeys.Clear();
                }

                // get button states
                var pressedButtons = hasOverrides
                    ? new HashSet<SButton>(this.GetPressedButtons(keyboard, mouse, controller))
                    : reallyDown;
                var activeButtons = this.DeriveStates(this.ButtonStates, pressedButtons);

                // update
                this.HasNewOverrides = false;
                this.ControllerState = controller.GetState();
                this.KeyboardState = keyboard.GetState();
                this.MouseState = mouse.GetState();
                this.ButtonStates = activeButtons;
                if (cursorAbsolutePos != this.CursorPositionImpl?.AbsolutePixels || playerTilePos != this.LastPlayerTile)
                {
                    this.LastPlayerTile = playerTilePos;
                    this.CursorPositionImpl = this.GetCursorPosition(this.MouseState, cursorAbsolutePos, zoomMultiplier);
                }
            }
            catch (InvalidOperationException)
            {
                // GetState() may crash for some players if window doesn't have focus but game1.IsActive == true
            }
        }

        /// <summary>Get the gamepad state visible to the game.</summary>
        public override GamePadState GetGamePadState()
        {
            return this.ControllerState;
        }

        /// <summary>Get the keyboard state visible to the game.</summary>
        public override KeyboardState GetKeyboardState()
        {
            return this.KeyboardState;
        }

        /// <summary>Get the keyboard state visible to the game.</summary>
        public override MouseState GetMouseState()
        {
            return this.MouseState;
        }

        /// <summary>Override the state for a button.</summary>
        /// <param name="button">The button to override.</param>
        /// <param name="setDown">Whether to mark it pressed; else mark it released.</param>
        public void OverrideButton(SButton button, bool setDown)
        {
            bool changed = setDown
                ? this.CustomPressedKeys.Add(button) | this.CustomReleasedKeys.Remove(button)
                : this.CustomPressedKeys.Remove(button) | this.CustomReleasedKeys.Add(button);

            if (changed)
                this.HasNewOverrides = true;
        }

        /// <summary>Get whether a mod has indicated the key was already handled, so the game shouldn't handle it.</summary>
        /// <param name="button">The button to check.</param>
        public bool IsSuppressed(SButton button)
        {
            return this.CustomReleasedKeys.Contains(button);
        }

        /// <summary>Apply input overrides to the current state.</summary>
        public void ApplyOverrides()
        {
            if (this.HasNewOverrides)
            {
                var controller = new GamePadStateBuilder(this.ControllerState);
                var keyboard = new KeyboardStateBuilder(this.KeyboardState);
                var mouse = new MouseStateBuilder(this.MouseState);

                if (this.ApplyOverrides(pressed: this.CustomPressedKeys, released: this.CustomReleasedKeys, controller, keyboard, mouse))
                {
                    this.ControllerState = controller.GetState();
                    this.KeyboardState = keyboard.GetState();
                    this.MouseState = mouse.GetState();
                }
            }
        }

        /// <summary>Get whether a given button was pressed or held.</summary>
        /// <param name="button">The button to check.</param>
        public bool IsDown(SButton button)
        {
            return this.GetState(this.ButtonStates, button).IsDown();
        }

        /// <summary>Get whether any of the given buttons were pressed or held.</summary>
        /// <param name="buttons">The buttons to check.</param>
        public bool IsAnyDown(InputButton[] buttons)
        {
            return buttons.Any(button => this.IsDown(button.ToSButton()));
        }

        /// <summary>Get the state of a button.</summary>
        /// <param name="button">The button to check.</param>
        public SButtonState GetState(SButton button)
        {
            return this.GetState(this.ButtonStates, button);
        }


        /*********
        ** Private methods
        *********/
        /// <summary>Get the current cursor position.</summary>
        /// <param name="mouseState">The current mouse state.</param>
        /// <param name="absolutePixels">The absolute pixel position relative to the map, adjusted for pixel zoom.</param>
        /// <param name="zoomMultiplier">The multiplier applied to pixel coordinates to adjust them for pixel zoom.</param>
        private CursorPosition GetCursorPosition(MouseState mouseState, Vector2 absolutePixels, float zoomMultiplier)
        {
            Vector2 screenPixels = new Vector2(mouseState.X * zoomMultiplier, mouseState.Y * zoomMultiplier);
            Vector2 tile = new Vector2((int)((Game1.viewport.X + screenPixels.X) / Game1.tileSize), (int)((Game1.viewport.Y + screenPixels.Y) / Game1.tileSize));
            Vector2 grabTile = (Game1.mouseCursorTransparency > 0 && Utility.tileWithinRadiusOfPlayer((int)tile.X, (int)tile.Y, 1, Game1.player)) // derived from Game1.pressActionButton
                ? tile
                : Game1.player.GetGrabTile();
            return new CursorPosition(absolutePixels, screenPixels, tile, grabTile);
        }

        /// <summary>Apply input overrides to the given states.</summary>
        /// <param name="pressed">The buttons to mark pressed.</param>
        /// <param name="released">The buttons to mark released.</param>
        /// <param name="controller">The game's controller state for the current tick.</param>
        /// <param name="keyboard">The game's keyboard state for the current tick.</param>
        /// <param name="mouse">The game's mouse state for the current tick.</param>
        /// <returns>Returns whether any overrides were applied.</returns>
        private bool ApplyOverrides(ISet<SButton> pressed, ISet<SButton> released, GamePadStateBuilder controller, KeyboardStateBuilder keyboard, MouseStateBuilder mouse)
        {
            if (pressed.Count == 0 && released.Count == 0)
                return false;

            // group keys by type
            IDictionary<SButton, SButtonState> keyboardOverrides = new Dictionary<SButton, SButtonState>();
            IDictionary<SButton, SButtonState> controllerOverrides = new Dictionary<SButton, SButtonState>();
            IDictionary<SButton, SButtonState> mouseOverrides = new Dictionary<SButton, SButtonState>();
            foreach (var button in pressed.Concat(released))
            {
                var newState = this.DeriveState(
                    oldState: this.GetState(button),
                    isDown: pressed.Contains(button)
                );

                if (button == SButton.MouseLeft || button == SButton.MouseMiddle || button == SButton.MouseRight || button == SButton.MouseX1 || button == SButton.MouseX2)
                    mouseOverrides[button] = newState;
                else if (button.TryGetKeyboard(out Keys _))
                    keyboardOverrides[button] = newState;
                else if (controller.IsConnected && button.TryGetController(out Buttons _))
                    controllerOverrides[button] = newState;
            }

            // override states
            if (keyboardOverrides.Any())
                keyboard.OverrideButtons(keyboardOverrides);
            if (controller.IsConnected && controllerOverrides.Any())
                controller.OverrideButtons(controllerOverrides);
            if (mouseOverrides.Any())
                mouse.OverrideButtons(mouseOverrides);

            return true;
        }

        /// <summary>Get the state of all pressed or released buttons relative to their previous state.</summary>
        /// <param name="previousStates">The previous button states.</param>
        /// <param name="pressedButtons">The currently pressed buttons.</param>
        private IDictionary<SButton, SButtonState> DeriveStates(IDictionary<SButton, SButtonState> previousStates, HashSet<SButton> pressedButtons)
        {
            IDictionary<SButton, SButtonState> activeButtons = new Dictionary<SButton, SButtonState>();

            // handle pressed keys
            foreach (SButton button in pressedButtons)
                activeButtons[button] = this.DeriveState(this.GetState(previousStates, button), isDown: true);

            // handle released keys
            foreach (KeyValuePair<SButton, SButtonState> prev in previousStates)
            {
                if (prev.Value.IsDown() && !activeButtons.ContainsKey(prev.Key))
                    activeButtons[prev.Key] = SButtonState.Released;
            }

            return activeButtons;
        }

        /// <summary>Get the state of a button relative to its previous state.</summary>
        /// <param name="oldState">The previous button state.</param>
        /// <param name="isDown">Whether the button is currently down.</param>
        private SButtonState DeriveState(SButtonState oldState, bool isDown)
        {
            if (isDown && oldState.IsDown())
                return SButtonState.Held;
            if (isDown)
                return SButtonState.Pressed;
            return SButtonState.Released;
        }

        /// <summary>Get the state of a button.</summary>
        /// <param name="activeButtons">The current button states to check.</param>
        /// <param name="button">The button to check.</param>
        private SButtonState GetState(IDictionary<SButton, SButtonState> activeButtons, SButton button)
        {
            return activeButtons.TryGetValue(button, out SButtonState state)
                ? state
                : SButtonState.None;
        }

        /// <summary>Get the buttons pressed in the given stats.</summary>
        /// <param name="keyboard">The keyboard state.</param>
        /// <param name="mouse">The mouse state.</param>
        /// <param name="controller">The controller state.</param>
        /// <remarks>Thumbstick direction logic derived from <see cref="ButtonCollection"/>.</remarks>
        private IEnumerable<SButton> GetPressedButtons(KeyboardStateBuilder keyboard, MouseStateBuilder mouse, GamePadStateBuilder controller)
        {
            return keyboard
                .GetPressedButtons()
                .Concat(mouse.GetPressedButtons())
                .Concat(controller.GetPressedButtons());
        }
    }
}