using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using RecrownedAthenaeum.Camera;
using System.Collections.Generic;
using System.Linq;

namespace RecrownedAthenaeum.UI.Book
{
    /// <summary>
    /// Contains the pages.
    /// </summary>
    public class Book
    {
        Camera2D camera;
        Page targetPage;
        Rectangle dimensions;
        Dictionary<string, Page> pages = new Dictionary<string, Page>();

        /// <summary>
        /// Should be called whenever a valid camera and dimensions for the book exist.
        /// Initializes book with given parameters.
        /// </summary>
        /// <param name="camera">Camera game is currently using.</param>
        /// <param name="dimensions">Dimensions of the book and the dimensions the pages will use.</param>
        public void Initiate(Camera2D camera, Rectangle dimensions)
        {
            this.camera = camera;
            this.dimensions = dimensions;
        }

        /// <summary>
        /// Draws the pages.
        /// </summary>
        /// <param name="batch">Batch used to draw.</param>
        public void Draw(SpriteBatch batch)
        {
            for (int pageIndex = 0; pageIndex < pages.Count; pageIndex++)
            {
                Page page = pages.ElementAt(pageIndex).Value;
                page.Draw(batch);
            }
        }

        /// <summary>
        /// Updates the book.
        /// </summary>
        /// <param name="gameTime">Snapshot of information of the game time.</param>
        public void Update(GameTime gameTime)
        {
            if (targetPage != null)
            {
                Vector2 position;
                Rectangle targetBounds = targetPage.bounds;
                position.X = targetBounds.X + (targetBounds.Width * 0.5f);
                position.Y = targetBounds.Y + (targetBounds.Height * 0.5f);
                camera.LinearInterpolationToPosition(0.4f, position, (float)gameTime.ElapsedGameTime.TotalSeconds);
                if (camera.Position == position)
                {
                    targetPage = null;
                }
            }

            for (int pageIndex = 0; pageIndex < pages.Count; pageIndex++)
            {
                Page page = pages.ElementAt(pageIndex).Value;
                if (page.NeedsSizeUpdate) page.ApplySize(dimensions.Width, dimensions.Height);
                page.Update(gameTime);
            }
        }

        /// <summary>
        /// Adds the page(s).
        /// </summary>
        /// <param name="pages">The page(s) to add.</param>
        public void AddPages(params Page[] pages)
        {
            foreach (Page page in pages)
            {
                this.pages.Add(page.Name, page);
            }
        }

        /// <summary>
        /// Removes the page.
        /// </summary>
        /// <param name="page">Page to remove.</param>
        public void RemovePage(Page page)
        {
            RemovePage(page.Name);
        }

        /// <summary>
        /// Removes the page.
        /// </summary>
        /// <param name="name">Name of page to remove.</param>
        public void RemovePage(string name)
        {
            pages.Remove(name);
        }

        /// <summary>
        /// Perform a step of linear interpolation to the given page.
        /// </summary>
        /// <param name="page">The page to lerp to.</param>
        public void LerpToPage(Page page)
        {
            targetPage = page;
        }

        /// <summary>
        /// Goes to page instantly.
        /// </summary>
        /// <param name="page">Page to go to.</param>
        public void GoToPage(Page page)
        {
            Rectangle targetBounds = page.bounds;
            camera.Position.X = targetBounds.X + (targetBounds.Width * 0.5f);
            camera.Position.Y = targetBounds.Y + (targetBounds.Height * 0.5f);
        }
    }
}