using System;
using System.Diagnostics.CodeAnalysis;
using System.Linq;
using Content.Server.Hands.Components;
using Content.Server.Interaction;
using Content.Server.Inventory.Components;
using Content.Server.Items;
using Content.Server.Stack;
using Content.Server.Storage.Components;
using Content.Server.Throwing;
using Content.Shared.Examine;
using Content.Shared.Hands;
using Content.Shared.Hands.Components;
using Content.Shared.Input;
using Content.Shared.Notification.Managers;
using Content.Shared.Physics.Pull;
using JetBrains.Annotations;
using Robust.Server.Player;
using Robust.Shared.GameObjects;
using Robust.Shared.Input.Binding;
using Robust.Shared.IoC;
using Robust.Shared.Localization;
using Robust.Shared.Map;
using Robust.Shared.Maths;
using Robust.Shared.Players;
using Robust.Shared.Utility;
using static Content.Shared.Inventory.EquipmentSlotDefines;

namespace Content.Server.Hands
{
    [UsedImplicitly]
    internal sealed class HandsSystem : SharedHandsSystem
    {
        [Dependency] private readonly InteractionSystem _interactionSystem = default!;
        [Dependency] private readonly StackSystem _stackSystem = default!;

        public override void Initialize()
        {
            base.Initialize();

            SubscribeLocalEvent<HandsComponent, ExaminedEvent>(HandleExamined);
            SubscribeNetworkEvent<ActivateInHandMsg>(HandleActivateInHand);
            SubscribeNetworkEvent<ClientInteractUsingInHandMsg>(HandleInteractUsingInHand);
            SubscribeNetworkEvent<UseInHandMsg>(HandleUseInHand);
            SubscribeNetworkEvent<MoveItemFromHandMsg>(HandleMoveItemFromHand);

            SubscribeLocalEvent<HandsComponent, PullAttemptMessage>(HandlePullAttempt);
            SubscribeLocalEvent<HandsComponent, PullStartedMessage>(HandlePullStarted);
            SubscribeLocalEvent<HandsComponent, PullStoppedMessage>(HandlePullStopped);

            CommandBinds.Builder
                .Bind(ContentKeyFunctions.ActivateItemInHand, InputCmdHandler.FromDelegate(HandleActivateItem))
                .Bind(ContentKeyFunctions.ThrowItemInHand, new PointerInputCmdHandler(HandleThrowItem))
                .Bind(ContentKeyFunctions.SmartEquipBackpack, InputCmdHandler.FromDelegate(HandleSmartEquipBackpack))
                .Bind(ContentKeyFunctions.SmartEquipBelt, InputCmdHandler.FromDelegate(HandleSmartEquipBelt))
                .Bind(ContentKeyFunctions.SwapHands, InputCmdHandler.FromDelegate(SwapHandsPressed, handle: false))
                .Bind(ContentKeyFunctions.Drop, new PointerInputCmdHandler(DropPressed))
                .Register<HandsSystem>();
        }

        private static void HandlePullAttempt(EntityUid uid, HandsComponent component, PullAttemptMessage args)
        {
            // Cancel pull if all hands full.
            if (component.Hands.All(hand => !hand.IsEmpty))
                args.Cancelled = true;
        }

        private void HandlePullStarted(EntityUid uid, HandsComponent component, PullStartedMessage args)
        {
            foreach (var handName in component.ActivePriorityEnumerable())
            {
                var hand = component.GetHand(handName);
                if (!hand.IsEmpty)
                    continue;

                var pos = component.Owner.Transform.Coordinates;
                var virtualPull = EntityManager.SpawnEntity("HandVirtualPull", pos);
                var virtualPullComp = virtualPull.GetComponent<HandVirtualPullComponent>();
                virtualPullComp.PulledEntity = args.Pulled.Owner.Uid;
                component.PutEntityIntoHand(hand, virtualPull);
                return;
            }

            DebugTools.Assert("Unable to find available hand when starting pulling??");
        }

        private void HandlePullStopped(EntityUid uid, HandsComponent component, PullStoppedMessage args)
        {
            // Try find hand that is doing this pull.
            // and clear it.
            foreach (var hand in component.Hands)
            {
                if (hand.HeldEntity == null
                    || !hand.HeldEntity.TryGetComponent(out HandVirtualPullComponent? virtualPull)
                    || virtualPull.PulledEntity != args.Pulled.Owner.Uid)
                    continue;

                hand.HeldEntity.Delete();
                break;
            }
        }

        private void SwapHandsPressed(ICommonSession? session)
        {
            var player = session?.AttachedEntity;

            if (player == null)
                return;

            if (!player.TryGetComponent(out SharedHandsComponent? hands))
                return;

            if (!hands.TryGetSwapHandsResult(out var nextHand))
                return;

            hands.ActiveHand = nextHand;
        }

        private bool DropPressed(ICommonSession? session, EntityCoordinates coords, EntityUid uid)
        {
            var player = session?.AttachedEntity;

            if (player == null)
                return false;

            if (!player.TryGetComponent(out SharedHandsComponent? hands))
                return false;

            var activeHand = hands.ActiveHand;

            if (activeHand == null)
                return false;

            hands.TryDropHand(activeHand, coords);
            return false;
        }

        private void HandleMoveItemFromHand(MoveItemFromHandMsg msg, EntitySessionEventArgs args)
        {
            if (!TryGetHandsComp(args.SenderSession, out var hands))
                return;

            hands.TryMoveHeldEntityToActiveHand(msg.HandName);
        }

        private void HandleUseInHand(UseInHandMsg msg, EntitySessionEventArgs args)
        {
            if (!TryGetHandsComp(args.SenderSession, out var hands))
                return;

            hands.UseActiveHeldEntity();
        }

        private void HandleInteractUsingInHand(ClientInteractUsingInHandMsg msg, EntitySessionEventArgs args)
        {
            if (!TryGetHandsComp(args.SenderSession, out var hands))
                return;

            hands.InteractHandWithActiveHand(msg.HandName);
        }

        public override void Shutdown()
        {
            base.Shutdown();

            CommandBinds.Unregister<HandsSystem>();
        }

        private void HandleActivateInHand(ActivateInHandMsg msg, EntitySessionEventArgs args)
        {
            if (!TryGetHandsComp(args.SenderSession, out var hands))
                return;

            hands.ActivateHeldEntity(msg.HandName);
        }

        protected override void DropAllItemsInHands(IEntity entity, bool doMobChecks = true)
        {
            base.DropAllItemsInHands(entity, doMobChecks);

            if (!entity.TryGetComponent(out IHandsComponent? hands)) return;

            foreach (var heldItem in hands.GetAllHeldItems())
            {
                hands.Drop(heldItem.Owner, doMobChecks, intentional:false);
            }
        }

        //TODO: Actually shows all items/clothing/etc.
        private void HandleExamined(EntityUid uid, HandsComponent component, ExaminedEvent args)
        {
            foreach (var inhand in component.GetAllHeldItems())
            {
                args.Message.AddText($"\n{Loc.GetString("comp-hands-examine", ("user", component.Owner), ("item", inhand.Owner))}");
            }
        }

        private static bool TryGetHandsComp(
            ICommonSession? session,
            [NotNullWhen(true)] out SharedHandsComponent? hands)
        {
            hands = default;

            if (session is not IPlayerSession playerSession)
                return false;

            var playerEnt = playerSession.AttachedEntity;

            if (playerEnt == null || !playerEnt.IsValid())
                return false;

            return playerEnt.TryGetComponent(out hands);
        }

        private void HandleActivateItem(ICommonSession? session)
        {
            if (!TryGetHandsComp(session, out var hands))
                return;

            hands.UseActiveHeldEntity();
        }

        private bool HandleThrowItem(ICommonSession? session, EntityCoordinates coords, EntityUid uid)
        {
            if (session is not IPlayerSession playerSession)
                return false;

            var playerEnt = playerSession.AttachedEntity;

            if (playerEnt == null || !playerEnt.IsValid() || !playerEnt.TryGetComponent(out SharedHandsComponent? hands))
                return false;

            if (!hands.TryGetActiveHeldEntity(out var throwEnt))
                return false;

            if (!_interactionSystem.TryThrowInteraction(hands.Owner, throwEnt))
                return false;

            if (throwEnt.TryGetComponent(out StackComponent? stack) && stack.Count > 1 && stack.ThrowIndividually)
            {
                var splitStack = _stackSystem.Split(throwEnt.Uid, stack, 1, playerEnt.Transform.Coordinates);

                if (splitStack == null)
                    return false;

                throwEnt = splitStack;
            }
            else if (!hands.TryDropEntityToFloor(throwEnt))
                return false;

            var direction = coords.ToMapPos(EntityManager) - playerEnt.Transform.WorldPosition;
            if (direction == Vector2.Zero)
                return true;

            direction = direction.Normalized * Math.Min(direction.Length, hands.ThrowRange);

            var throwStrength = hands.ThrowForceMultiplier;
            throwEnt.TryThrow(direction, throwStrength, playerEnt);

            return true;
        }

        private void HandleSmartEquipBackpack(ICommonSession? session)
        {
            HandleSmartEquip(session, Slots.BACKPACK);
        }

        private void HandleSmartEquipBelt(ICommonSession? session)
        {
            HandleSmartEquip(session, Slots.BELT);
        }

        private void HandleSmartEquip(ICommonSession? session, Slots equipmentSlot)
        {
            if (session is not IPlayerSession playerSession)
                return;

            var plyEnt = playerSession.AttachedEntity;

            if (plyEnt == null || !plyEnt.IsValid())
                return;

            if (!plyEnt.TryGetComponent(out SharedHandsComponent? hands) ||
                !plyEnt.TryGetComponent(out InventoryComponent? inventory))
                return;

            if (!inventory.TryGetSlotItem(equipmentSlot, out ItemComponent? equipmentItem) ||
                !equipmentItem.Owner.TryGetComponent(out ServerStorageComponent? storageComponent))
            {
                plyEnt.PopupMessage(Loc.GetString("hands-system-missing-equipment-slot", ("slotName", SlotNames[equipmentSlot].ToLower())));
                return;
            }

            if (hands.ActiveHandIsHoldingEntity())
            {
                storageComponent.PlayerInsertHeldEntity(plyEnt);
            }
            else if (storageComponent.StoredEntities != null)
            {
                if (storageComponent.StoredEntities.Count == 0)
                {
                    plyEnt.PopupMessage(Loc.GetString("hands-system-empty-equipment-slot", ("slotName", SlotNames[equipmentSlot].ToLower())));
                }
                else
                {
                    var lastStoredEntity = Enumerable.Last(storageComponent.StoredEntities);
                    if (storageComponent.Remove(lastStoredEntity))
                    {
                        if (!hands.TryPickupEntityToActiveHand(lastStoredEntity))
                            lastStoredEntity.Transform.Coordinates = plyEnt.Transform.Coordinates;
                    }
                }
            }
        }
    }
}