using System;
using System.Collections.Generic;
using RebootKit.Engine.Foundation;

namespace RebootReality.jelycho.Items {
    public class Inventory {
        static readonly Logger s_Logger = new Logger(nameof(Inventory));

        class SlotState {
            public ushort ActorID;
            public ItemActor Actor;

            public void EmptySlot() {
                ActorID = 0;
                Actor = null;
            }
        }

        readonly SlotState[] m_Slots;
        
        public event Action<ItemActor> OnItemPickedUp = delegate { };
        public event Action<ItemActor> OnItemDropped = delegate { };
        public event Action<int> OnSlotUpdated = delegate { };

        public int SlotsCount {
            get {
                return m_Slots.Length;
            }
        }

        public Inventory(int slotsCount) {
            m_Slots = new SlotState[slotsCount];

            for (int i = 0; i < slotsCount; i++) {
                m_Slots[i] = new SlotState();
            }
        }
        
        //
        // @MARK: Server API
        //
        public bool TryPickup(ItemActor actor) {
            if (Contains(actor)) {
                s_Logger.Error($"Item {actor.name} is already in the inventory.");
                return false;
            }
            
            (int slotIndex, SlotState freeItemState) = FindFreeItemState();
            if (freeItemState == null) {
                s_Logger.Error("Inventory is full, cannot pick up item.");
                return false;
            }

            freeItemState.Actor = actor;
            OnItemPickedUp?.Invoke(actor);
            OnSlotUpdated?.Invoke(slotIndex);
            return true;
        }

        public bool TryDrop(int slotIndex, out ItemActor actor) {
            if (slotIndex < 0 || slotIndex >= m_Slots.Length) {
                s_Logger.Error($"Slot index {slotIndex} is out of range.");
                actor = null;
                return false;
            }

            if (m_Slots[slotIndex].Actor == null) {
                s_Logger.Error($"No items in slot {slotIndex} to drop.");
                actor = null;
                return false;
            }

            actor = m_Slots[slotIndex].Actor;
            m_Slots[slotIndex].Actor = null;

            OnItemDropped?.Invoke(actor);
            OnSlotUpdated?.Invoke(slotIndex);
            return actor;
        }
        
        //
        // @MARK: Common API
        //
        public void SetItem(int slotIndex, ItemActor actor) {
            if (slotIndex < 0 || slotIndex >= m_Slots.Length) {
                throw new ArgumentOutOfRangeException(nameof(slotIndex), "Slot index is out of range.");
            }

            if (actor == null) {
                m_Slots[slotIndex].EmptySlot();
                OnSlotUpdated?.Invoke(slotIndex);
                return;
            }

            if (Contains(actor)) {
                s_Logger.Error($"Item {actor.name} is already in the inventory.");
                return;
            }

            m_Slots[slotIndex].Actor = actor;
            m_Slots[slotIndex].ActorID = actor.ActorID;
            OnSlotUpdated?.Invoke(slotIndex);
        }
        
        public ItemActor GetItem(int slotIndex) {
            if (slotIndex < 0 || slotIndex >= m_Slots.Length) {
                throw new ArgumentOutOfRangeException(nameof(slotIndex), "Slot index is out of range.");
            }

            return m_Slots[slotIndex].Actor;
        }

        public bool Contains(ItemActor actor) {
            for (int i = 0; i < m_Slots.Length; i++) {
                if (m_Slots[i].Actor == actor) {
                    return true;
                }
            }
            return false;
        }

        (int slot, SlotState state) FindFreeItemState() {
            for (int i = 0; i < m_Slots.Length; i++) {
                if (m_Slots[i].Actor == null) {
                    return (i, m_Slots[i]);
                }
            }

            return (-1, null);
        }

        //
        // @MARK: Client API
        //
        
    }
}