using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class BackgroundManager : MonoBehaviour
{
    [System.Serializable]
    public class BackgroundLayer
    {
        public float yThreshold;
        public Sprite backgroundSprite;
        [Range(0f, 1f)] public float parallaxEffect = 0.5f;
    }

    [SerializeField] private SpriteRenderer spriteRenderer;
    [SerializeField] private SpriteRenderer transitionRenderer; // Add this field
    [SerializeField] private BackgroundLayer[] backgroundLayers;
    [SerializeField] private float transitionDuration = 1f;
    private bool isTransitioning = false; // Add this field

    private Transform cameraTransform;
    private Vector3 lastCameraPosition;
    private int currentLayerIndex = 0;
    private float startPositionX;

    private void Start()
    {
        cameraTransform = Camera.main.transform;
        lastCameraPosition = cameraTransform.position;
        startPositionX = transform.position.x;

        if (spriteRenderer == null)
            spriteRenderer = GetComponent<SpriteRenderer>();

        // Set initial background
        if (backgroundLayers != null && backgroundLayers.Length > 0)
            spriteRenderer.sprite = backgroundLayers[0].backgroundSprite;

        if (transitionRenderer == null)
        {
            var transitionObj = new GameObject("TransitionLayer");
            transitionObj.transform.parent = transform;
            transitionObj.transform.localPosition = new Vector3(0, 0, -2); // Set Z to -2
            transitionObj.transform.localScale = Vector3.one; // Match scale
            transitionRenderer = transitionObj.AddComponent<SpriteRenderer>();
            transitionRenderer.sortingOrder = spriteRenderer.sortingOrder + 1;
            transitionRenderer.sortingLayerName = spriteRenderer.sortingLayerName; // Match background layer
        }
        transitionRenderer.color = new Color(1, 1, 1, 0); // Start fully transparent
    }

    private void Update()
    {
        // Calculate parallax movement
        Vector3 cameraDelta = cameraTransform.position - lastCameraPosition;
        Vector3 newPosition = transform.position;

        // Update X position with parallax
        float parallaxX = (cameraTransform.position.x - startPositionX) * GetCurrentParallaxEffect();
        newPosition.x = startPositionX + parallaxX;

        // Update Y position to follow camera
        newPosition.y = cameraTransform.position.y;

        transform.position = newPosition;

        // Check for background change
        float currentY = cameraTransform.position.y;
        int newLayerIndex = currentLayerIndex;

        for (int i = 0; i < backgroundLayers.Length; i++)
        {
            if (currentY > backgroundLayers[i].yThreshold)
            {
                newLayerIndex = i;
                break;
            }
        }

        if (newLayerIndex != currentLayerIndex && !isTransitioning) // Add transition check
        {
            StartCoroutine(TransitionBackground(backgroundLayers[newLayerIndex].backgroundSprite));
            currentLayerIndex = newLayerIndex;
        }

        lastCameraPosition = cameraTransform.position;
    }

    private float GetCurrentParallaxEffect()
    {
        if (backgroundLayers == null || backgroundLayers.Length == 0)
            return 0.5f;
        return backgroundLayers[currentLayerIndex].parallaxEffect;
    }

    private IEnumerator TransitionBackground(Sprite newSprite)
    {
        if (isTransitioning) yield break;
        isTransitioning = true;

        // Setup transition renderer
        transitionRenderer.sprite = newSprite;
        transitionRenderer.transform.localPosition = Vector3.zero;

        // Fade in new sprite over old one
        float elapsedTime = 0;
        while (elapsedTime < transitionDuration)
        {
            elapsedTime += Time.deltaTime;
            float alpha = elapsedTime / transitionDuration;
            transitionRenderer.color = new Color(1, 1, 1, alpha);
            yield return null;
        }

        // Switch the sprites
        spriteRenderer.sprite = newSprite;
        transitionRenderer.color = new Color(1, 1, 1, 0);

        isTransitioning = false;
    }
}