using Sirenix.OdinInspector;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Events;
using UnityEngine.EventSystems;
using UnityEngine.UI;

public class PageSwiper : MonoBehaviour, IDragHandler, IEndDragHandler, IPointerUpHandler
{
    private Vector3 m_originPosition;
    private Vector3 panelLocation;
    public float percentThreshold = 0.2f;
    public float easing = 0.5f;
    public UnityEvent OnClick;

    public int totalPages
    {
        get
        {
            return transform.childCount;
        }
    }
    private int currentPage = 1;

    // Start is called before the first frame update
    void Start()
    {
        m_originPosition = transform.position;
        panelLocation = transform.position;
        SetWithScreenSize();
    }

    [Button]
    public void SetWithScreenSize()
    {
        var grid = GetComponent<GridLayoutGroup>();
        var parentRect = transform.parent.GetComponent<RectTransform>();
        //grid.cellSize = new Vector2()
        //{
        //    x = res.x / factor,
        //    y = res.y / factor,
        //};
        grid.cellSize = new Vector2()
        {
            x = parentRect.rect.width,
            y = parentRect.rect.height,
        };
    }

    public int GetPageRatio(out int page1, out float ratio1, out int page2, out float ratio2)
    {
        page1 = default;
        ratio1 = default;
        page2 = default;
        ratio2 = default;

        int pageCount = totalPages;

        if (pageCount <= 0)
        {
            return 0;
        }

        if (pageCount == 1)
        {
            page1 = 0;
            ratio1 = 1.0f;
            return 1;
        }

        float percentage = (transform.position.y - m_originPosition.y) / Screen.height;
        if (percentage < 0)
        {
            page1 = 0;
            ratio1 = 1.0f;
            return 1;
        }

        if (percentage > pageCount - 1)
        {
            page1 = pageCount - 1;
            ratio1 = 1.0f;
            return 1;
        }

        int count = Mathf.FloorToInt(percentage + 0.5f);
        float ratio = percentage - count;
        if (Mathf.Abs(ratio) < 0.01f)
        {
            page1 = count;
            ratio1 = 1.0f;
            return 1;
        }

        count = Mathf.FloorToInt(percentage);
        ratio = percentage - count;

        page1 = count;
        ratio1 = 1 - ratio;
        page2 = count + 1;
        ratio2 = ratio;

        return 2;
    }

    public void OnDrag(PointerEventData data)
    {
        float difference = data.pressPosition.y - data.position.y;
        transform.position = panelLocation - new Vector3(0, difference, 0);
    }

    public void OnEndDrag(PointerEventData data)
    {
        float percentage = (data.pressPosition.y - data.position.y) / Screen.height;
        if (Mathf.Abs(percentage) >= percentThreshold)
        {
            Vector3 newLocation = panelLocation;
            if (percentage < 0 && currentPage < totalPages)
            {
                currentPage++;
                newLocation = m_originPosition + (currentPage - 1) * new Vector3(0, Screen.height, 0);
            }
            else if (percentage > 0 && currentPage > 1)
            {
                currentPage--;
                newLocation = m_originPosition + (currentPage - 1) * new Vector3(0, Screen.height, 0);
            }
            StopAllCoroutines();
            StartCoroutine(SmoothMove(transform.position, newLocation, easing));
            panelLocation = newLocation;
        }
        else
        {
            StopAllCoroutines();
            StartCoroutine(SmoothMove(transform.position, panelLocation, easing));
        }
    }

    IEnumerator SmoothMove(Vector3 startpos, Vector3 endpos, float seconds)
    {
        float t = 0f;
        while (t <= 1.0)
        {
            t += Time.deltaTime / seconds;
            transform.position = Vector3.Lerp(startpos, endpos, Mathf.SmoothStep(0f, 1f, t));
            yield return null;
        }
    }

    public void OnPointerUp(PointerEventData eventData)
    {
        OnClick.Invoke();
    }
}