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

public class BookDisplay : MonoBehaviour {

    public BookAsset thisBookAsset;     //The scriptable object that contains info about this book.
    public Canvas bookCanvasLeft;       //The canvas that the content of the book will be displayed on.
    public Canvas bookCanvasRight;      //The canvas that the content of the book will be displayed on.

    public TextMesh frontBookTitle;     //The text title of the book.
    public Text bookTextLeft;           //The UI text where the book content will show.
    public Text bookTextRight;          //The UI text where the book content will show.
    public Button nextBtn;              //The button to turn the page.
    public Button prevBtn;              //The button to go to the previous page.

    Animator anim;                      //Referance to the animator.
    List<string> pages;                 //A list of pages to be displayed on the book.
    int pageNum = -2;                   //The page number the coresponding page will be displayed on.


    private void Start () {
        //---------Referances-------------------------------------------------------------------------------------
        anim = (anim == null ? GetComponent<Animator>() : anim);
        frontBookTitle = (frontBookTitle == null ? GetComponentInChildren<TextMesh>() : frontBookTitle);

        frontBookTitle.text = thisBookAsset.title.Replace("\\n", "\n");
        pages = TextPages(thisBookAsset.content, 30, 20);
        pages.Insert(0, "---");
        pages.Insert(1, "\n\n\n\n\n"+ thisBookAsset.title.Replace("\\n", " ") + "\n\n\n\n" + thisBookAsset.blurb);
        //---------------------------------------------------------------------------------------------------------

        bookCanvasLeft.gameObject.SetActive(false);
        bookCanvasRight.gameObject.SetActive(false);
    }

    public void Activate()
    {
        bookCanvasLeft.gameObject.SetActive(true);
        bookCanvasRight.gameObject.SetActive(true);

        nextBtn.onClick.AddListener(NextButton);
        prevBtn.onClick.AddListener(PreviousButton);

        prevBtn.interactable = true;
        nextBtn.interactable = true;

        NextButton();

    }
    public void Deactivate()
    {
        bookCanvasLeft.gameObject.SetActive(false);
        bookCanvasRight.gameObject.SetActive(false);
    }


    //Called when next page button is clicked.
    private void NextButton()
    {
        anim.SetTrigger("flipForward");

        pageNum = pageNum + 2;
        PopulatePage(pageNum,pageNum+1);

    }

    //Called when previous page button is clicked.
    private void PreviousButton()
    {
        anim.SetTrigger("flipBack");

        pageNum = pageNum - 2;
        PopulatePage(pageNum, pageNum+1);
    }

    //Populate the right and left page of the book.
    private void PopulatePage(int lPage, int rPage)
    {
        //Display data.
        if (lPage > 0 && lPage < pages.Count) bookTextLeft.text = pages[lPage];
        else bookTextLeft.text = "";
        if (rPage > 0 && rPage < pages.Count) bookTextRight.text = pages[rPage];
        else bookTextRight.text = "";


        //Check wether or not to show next/prev button.
        if (pageNum <= 0)
        {
            prevBtn.interactable = false;
        }
        else
        {
            prevBtn.interactable = true;
        }


        if (pageNum >= pages.Count-2)
        {
            nextBtn.interactable = false;
        }
        else
        {
            nextBtn.interactable = true;
        }

    }



    /// <summary>
    /// Seperates a long string into pages returns strings as list.
    /// </summary>
    private List<string> TextPages(string text, int charPerLine, int linesPerPage)
    {
        List<string> parts = new List<string>();
        List<string> pages = new List<string>();
        //----------------Make a line---------------------------------------------------
        while (text.Length > 0)
        {
            if (text.Length <= charPerLine)
            {
                parts.Add(text);
                text = string.Empty;
            }
            else
            {
                int length = charPerLine;
                while (char.IsLetter(text[length]) && char.IsLetter(text[length - 1]))
                {
                    length--;
                }

                parts.Add(text.Substring(0, length).Trim());
                text = text.Substring(length);
            }
        }
        //-----------Make a page---------------------------------------------------------
        int count = 0;
        string page = "";

        for (int i = 0; i < parts.Count; i++)
        {
            count++;
            page += parts[i] + "\n";

            if (count >= linesPerPage)
            {
                pages.Add(page);
                page = "";
                count = 0;
            }
            if (i == parts.Count - 1)
            {
                // this is the last item in the list
                pages.Add(page);
            }
        }
        return pages;
    }
}