UIHelperFunctions - Part 6.3.4

using UnityEngine;
using UnityEngine.UI;
using UnityEngine.EventSystems;
using System.Collections.Generic;
using TMPro;

public class UIHelperFunctions : MonoBehaviour
{
    public static UIHelperFunctions Instance { get; private set; }

    private void Awake()
    {
        if (Instance == null)
        {
            Instance = this;
            DontDestroyOnLoad(gameObject);
        }
        else
        {
            Destroy(gameObject);
        }
    }

    public void TransferHeldItemsToStorage(InventorySystem inventorySystem, StorageSystem storageSystem, Item currentStorageItem, PlayerMovement playerMovement)
    {
        if (inventorySystem.leftHandItem != null)
        {
            bool added = storageSystem.AddToStorage(currentStorageItem, inventorySystem.leftHandItem);
            if (added)
            {
                inventorySystem.UnequipItem(true);
                playerMovement.UpdateCarryingAnimations();
            }
        }
        if (inventorySystem.rightHandItem != null)
        {
            bool added = storageSystem.AddToStorage(currentStorageItem, inventorySystem.rightHandItem);
            if (added)
            {
                inventorySystem.UnequipItem(false);
                playerMovement.UpdateCarryingAnimations();
            }
        }
    }

    public void PopulateInventoryUI(Item storageItem, Transform inventorySlotParent, StorageSystem storageSystem, UIManager uiManager)
    {
        ClearInventoryUI(inventorySlotParent);
        List<Item> storageInventory = storageSystem.GetStorageInventory(storageItem);

        for (int i = 0; i < storageInventory.Count; i++)
        {
            Transform slot = inventorySlotParent.GetChild(i);
            uiManager.UpdateInventorySlot(slot.gameObject, storageInventory[i]);

            storageSystem.UpdateItemPosition(storageItem, storageInventory[i], i);
        }
    }

    public void UpdateInventorySlot(GameObject slotObject, Item item, GameObject itemIconPrefab, UIManager uiManager)
    {
        ClearInventorySlot(slotObject);

        GameObject iconObject = Instantiate(itemIconPrefab, slotObject.transform);
        Image iconImage = iconObject.GetComponent<Image>();
        if (iconImage != null)
        {
            iconImage.sprite = item.icon;
            iconImage.enabled = true;
        }

        iconObject.AddComponent<ItemReference>().item = item;

        EventTrigger trigger = iconObject.GetComponent<EventTrigger>();
        if (trigger == null) trigger = iconObject.AddComponent<EventTrigger>();

        trigger.triggers.Clear();

        EventTrigger.Entry rightClickEntry = new EventTrigger.Entry();
        rightClickEntry.eventID = EventTriggerType.PointerClick;
        rightClickEntry.callback.AddListener((data) => {
            if (((PointerEventData)data).button == PointerEventData.InputButton.Right)
                uiManager.TryEquipItem(item);
        });

        EventTrigger.Entry dragEntry = new EventTrigger.Entry();
        dragEntry.eventID = EventTriggerType.BeginDrag;
        dragEntry.callback.AddListener((data) => uiManager.BeginDrag(iconObject.transform));

        EventTrigger.Entry dragEndEntry = new EventTrigger.Entry();
        dragEndEntry.eventID = EventTriggerType.EndDrag;
        dragEndEntry.callback.AddListener((data) => uiManager.EndDrag(iconObject.transform));

        EventTrigger.Entry pointerEnterEntry = new EventTrigger.Entry();
        pointerEnterEntry.eventID = EventTriggerType.PointerEnter;
        pointerEnterEntry.callback.AddListener((data) => uiManager.ShowItemDetails(item));

        EventTrigger.Entry pointerExitEntry = new EventTrigger.Entry();
        pointerExitEntry.eventID = EventTriggerType.PointerExit;
        pointerExitEntry.callback.AddListener((data) => uiManager.HideItemDetails());

        trigger.triggers.Add(rightClickEntry);
        trigger.triggers.Add(dragEntry);
        trigger.triggers.Add(dragEndEntry);
        trigger.triggers.Add(pointerEnterEntry);
        trigger.triggers.Add(pointerExitEntry);
    }

    public void ShowItemDetails(Item item, GameObject itemDetailsPanel, TextMeshProUGUI itemTitleText, TextMeshProUGUI itemDescriptionText, TextMeshProUGUI itemUsesText)
    {
        if (item != null && itemDetailsPanel != null)
        {
            itemDetailsPanel.SetActive(true);
            if (itemTitleText != null) itemTitleText.text = item.itemName;
            if (itemDescriptionText != null) itemDescriptionText.text = item.description;
            if (itemUsesText != null) itemUsesText.text = item.itemUses;
        }
    }

    public void HideItemDetails(GameObject itemDetailsPanel)
    {
        if (itemDetailsPanel != null)
        {
            itemDetailsPanel.SetActive(false);
        }
    }

    public void TryEquipItem(Item item, InventorySystem inventorySystem, StorageSystem storageSystem, Item currentStorageItem, InteractionSystem interactionSystem, PlayerMovement playerMovement, UIManager uiManager)
    {
        if (inventorySystem.leftHandItem != null && inventorySystem.rightHandItem != null)
        {
            uiManager.ShowError("Hands are full!");
            return;
        }

        storageSystem.RemoveItemFromStorage(currentStorageItem, item);
        bool isLeftHand = inventorySystem.leftHandItem == null;
        inventorySystem.EquipItem(item, isLeftHand, item.isTwoHanded);
        interactionSystem.UpdateItemPosition(item.gameObject, isLeftHand);
        playerMovement.UpdateCarryingAnimations();
        uiManager.PopulateInventoryUI(currentStorageItem);
        uiManager.HideItemDetails();
    }

    public void BeginDrag(Transform iconTransform, ref Item draggedItem, ref Transform originalSlot, GameObject inventoryPanel)
    {
        ItemReference itemRef = iconTransform.GetComponent<ItemReference>();
        if (itemRef != null && itemRef.item != null)
        {
            draggedItem = itemRef.item;
            originalSlot = iconTransform.parent;
            iconTransform.SetParent(inventoryPanel.transform);
        }
    }

    public void EndDrag(Transform iconTransform, Item draggedItem, Transform originalSlot, Transform inventorySlotParent, Item currentStorageItem, StorageSystem storageSystem, UIManager uiManager)
    {
        if (draggedItem == null) return;

        Transform closestSlot = FindClosestSlot(inventorySlotParent, Input.mousePosition);

        if (closestSlot != null)
        {
            SwapItems(closestSlot, iconTransform, originalSlot, currentStorageItem, storageSystem);
        }
        else
        {
            ReturnItemToOriginalSlot(iconTransform, originalSlot);
        }
    }

    private void ClearInventoryUI(Transform inventorySlotParent)
    {
        for (int i = 0; i < inventorySlotParent.childCount - 3; i++)
        {
            Transform slot = inventorySlotParent.GetChild(i);
            ClearInventorySlot(slot.gameObject);
        }
    }

    private void ClearInventorySlot(GameObject slotObject)
    {
        foreach (Transform child in slotObject.transform)
        {
            Destroy(child.gameObject);
        }
    }

    public int FindFirstEmptySlot(Transform inventorySlotParent)
    {
        for (int i = 0; i < inventorySlotParent.childCount - 3; i++)
        {
            if (inventorySlotParent.GetChild(i).childCount == 0)
            {
                return i;
            }
        }
        return -1;
    }

    private Transform FindClosestSlot(Transform inventorySlotParent, Vector3 position)
    {
        Transform closestSlot = null;
        float minDistance = Mathf.Infinity;

        foreach (Transform slot in inventorySlotParent)
        {
            float dist = Vector3.Distance(slot.position, position);
            if (dist < minDistance)
            {
                minDistance = dist;
                closestSlot = slot;
            }
        }

        return closestSlot;
    }

    private void SwapItems(Transform newSlot, Transform draggedIcon, Transform originalSlot, Item currentStorageItem, StorageSystem storageSystem)
    {
        if (newSlot.childCount > 0)
        {
            Transform existingIcon = newSlot.GetChild(0);
            existingIcon.SetParent(originalSlot);
            existingIcon.localPosition = Vector3.zero;

            Item existingItem = existingIcon.GetComponent<ItemReference>().item;
            storageSystem.UpdateItemPosition(currentStorageItem, existingItem, originalSlot.GetSiblingIndex());
        }

        draggedIcon.SetParent(newSlot);
        draggedIcon.localPosition = Vector3.zero;

        Item draggedItem = draggedIcon.GetComponent<ItemReference>().item;
        storageSystem.UpdateItemPosition(currentStorageItem, draggedItem, newSlot.GetSiblingIndex());
    }

    private void ReturnItemToOriginalSlot(Transform draggedIcon, Transform originalSlot)
    {
        draggedIcon.SetParent(originalSlot);
        draggedIcon.localPosition = Vector3.zero;
    }

    public void TogglePlayerControls(bool enable, PlayerMovement playerMovement)
    {
        if (playerMovement != null)
        {
            playerMovement.enabled = enable;
            playerMovement.GetComponent<MouseMovement>().enabled = enable;
        }

        Cursor.lockState = enable ? CursorLockMode.Locked : CursorLockMode.None;
        Cursor.visible = !enable;
    }
}