using UnityEngine;
using UnityEngine.UI;

public class InventoryUI : MonoBehaviour
{
    public RectTransform content;
    public Text outputText;
    public Font uiFont;
    public Color textColor = new Color(0.92f, 0.9f, 0.82f);

    private float refreshTimer;
    private string lastSignature;

    private void OnEnable()
    {
        Subscribe();
        Refresh();
    }

    private void Start()
    {
        Subscribe();
        Refresh();
    }

    private void OnDisable()
    {
        if (Inventory.Instance != null)
        {
            Inventory.Instance.OnInventoryChanged -= Refresh;
        }
    }

    private void Update()
    {
        refreshTimer -= Time.unscaledDeltaTime;
        if (refreshTimer > 0f)
        {
            return;
        }

        refreshTimer = 0.25f;
        Subscribe();

        string signature = BuildSignature();
        if (signature != lastSignature)
        {
            lastSignature = signature;
            Refresh();
        }
    }

    private void Subscribe()
    {
        if (Inventory.Instance != null)
        {
            Inventory.Instance.OnInventoryChanged -= Refresh;
            Inventory.Instance.OnInventoryChanged += Refresh;
        }
    }

    public void Refresh()
    {
        if (outputText != null)
        {
            outputText.text = BuildDisplayText();
            return;
        }

        if (content == null)
        {
            return;
        }

        ClearContent();

        if (Inventory.Instance == null || Inventory.Instance.Slots.Count == 0)
        {
            CreateLine("Пусто");
            return;
        }

        foreach (Inventory.InventorySlot slot in Inventory.Instance.Slots)
        {
            if (slot.item == null)
            {
                continue;
            }

            CreateLine($"{slot.item.itemName} x{slot.amount}");
        }
    }

    private string BuildDisplayText()
    {
        if (Inventory.Instance == null || Inventory.Instance.Slots.Count == 0)
        {
            return "Пусто";
        }

        System.Text.StringBuilder builder = new System.Text.StringBuilder();
        foreach (Inventory.InventorySlot slot in Inventory.Instance.Slots)
        {
            if (slot.item == null)
            {
                continue;
            }

            builder.AppendLine($"{slot.item.itemName} x{slot.amount}");
        }

        return builder.Length > 0 ? builder.ToString().TrimEnd() : "Пусто";
    }

    private string BuildSignature()
    {
        if (Inventory.Instance == null)
        {
            return "inventory:null";
        }

        System.Text.StringBuilder builder = new System.Text.StringBuilder();
        foreach (Inventory.InventorySlot slot in Inventory.Instance.Slots)
        {
            if (slot.item == null)
            {
                continue;
            }

            builder.Append(slot.item.itemId).Append(':').Append(slot.amount).Append('|');
        }

        return builder.ToString();
    }

    private void ClearContent()
    {
        for (int i = content.childCount - 1; i >= 0; i--)
        {
            Destroy(content.GetChild(i).gameObject);
        }
    }

    private void CreateLine(string value)
    {
        GameObject line = new GameObject("Inventory Line", typeof(RectTransform), typeof(Text));
        line.transform.SetParent(content, false);

        Text text = line.GetComponent<Text>();
        text.font = uiFont != null ? uiFont : Resources.GetBuiltinResource<Font>("Arial.ttf");
        text.fontSize = 16;
        text.color = textColor;
        text.text = value;

        RectTransform rect = line.GetComponent<RectTransform>();
        rect.sizeDelta = new Vector2(0f, 24f);
    }
}