// Copyright (c) 2007-2017 ppy Pty Ltd <contact@ppy.sh>.
// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE

using OpenTK;
using osu.Framework;
using osu.Framework.Graphics;
using osu.Framework.Graphics.Containers;
using osu.Framework.Graphics.Transformations;
using osu.Framework.MathUtils;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using osu.Framework.Allocation;

namespace osu.Game.Graphics.UserInterface
{
    public class StarCounter : Container
    {
        private readonly Container starContainer;
        private readonly List<TextAwesome> stars = new List<TextAwesome>();

        private double transformStartTime = 0;

        /// <summary>
        /// Maximum amount of stars displayed.
        /// </summary>
        /// <remarks>
        /// This does not limit the counter value, but the amount of stars displayed.
        /// </remarks>
        public int MaxStars
        {
            get;
            protected set;
        }

        private double animationDelay => 80;

        private double scalingDuration => 500;
        private EasingTypes scalingEasing => EasingTypes.OutElasticHalf;
        private float minStarScale => 0.3f;

        private double fadingDuration => 100;
        private float minStarAlpha => 0.5f;

        public float StarSize = 20;
        public float StarSpacing = 4;

        public float VisibleValue
        {
            get
            {
                double elapsedTime = Time.Current - transformStartTime;
                double expectedElapsedTime = Math.Abs(prevCount - count) * animationDelay;
                if (elapsedTime >= expectedElapsedTime)
                    return count;
                return Interpolation.ValueAt(elapsedTime, prevCount, count, 0, expectedElapsedTime);
            }
        }

        private float prevCount;
        private float count;

        /// <summary>
        /// Amount of stars represented.
        /// </summary>
        public float Count
        {
            get
            {
                return count;
            }

            set
            {
                if (IsLoaded)
                {
                    prevCount = VisibleValue;
                    transformCount(prevCount, value);
                }

                count = value;
            }
        }

        /// <summary>
        /// Shows a float count as stars (up to 10). Used as star difficulty display.
        /// </summary>
        public StarCounter() : this(10)
        {
            AutoSizeAxes = Axes.Both;
        }

        /// <summary>
        /// Shows a float count as stars. Used as star difficulty display.
        /// </summary>
        /// <param name="maxstars">Maximum amount of stars to display.</param>
        public StarCounter(int maxstars)
        {
            MaxStars = Math.Max(maxstars, 0);

            Children = new Drawable[]
            {
                starContainer = new Container
                {
                    Anchor = Anchor.CentreLeft,
                    Origin = Anchor.CentreLeft,
                }
            };

            starContainer.Width = MaxStars * StarSize + Math.Max(MaxStars - 1, 0) * StarSpacing;
            starContainer.Height = StarSize;

            for (int i = 0; i < MaxStars; i++)
            {
                TextAwesome star = new TextAwesome
                {
                    Icon = FontAwesome.fa_star,
                    Anchor = Anchor.CentreLeft,
                    Origin = Anchor.Centre,
                    TextSize = StarSize,
                    Scale = new Vector2(minStarScale),
                    Alpha = minStarAlpha,
                    Position = new Vector2((StarSize + StarSpacing) * i + (StarSize + StarSpacing) / 2, 0),
                };

                //todo: user Container<T> once we have it.
                stars.Add(star);
                starContainer.Add(star);
            }
        }

        protected override void LoadComplete()
        {
            base.LoadComplete();
            // Animate initial state from zero.
            transformCount(0, Count);
        }

        public void ResetCount()
        {
            Count = 0;
            StopAnimation();
        }

        public void StopAnimation()
        {
            prevCount = count;
            transformStartTime = Time.Current;

            for (int i = 0; i < MaxStars; i++)
                transformStarQuick(i, count);
        }

        private float getStarScale(int i, float value)
        {
            if (value <= i)
                return minStarScale;
            if (i + 1 <= value)
                return 1.0f;
            return Interpolation.ValueAt(value, minStarScale, 1.0f, i, i + 1);
        }

        private void transformStar(int i, float value)
        {
            stars[i].FadeTo(i < value ? 1.0f : minStarAlpha, fadingDuration);
            stars[i].ScaleTo(getStarScale(i, value), scalingDuration, scalingEasing);
        }

        private void transformStarQuick(int i, float value)
        {
            stars[i].FadeTo(i < value ? 1.0f : minStarAlpha);
            stars[i].ScaleTo(getStarScale(i, value));
        }

        private void transformCount(float currentValue, float newValue)
        {
            for (int i = 0; i < MaxStars; i++)
            {
                stars[i].ClearTransformations();
                if (currentValue <= newValue)
                    stars[i].Delay(Math.Max(i - currentValue, 0) * animationDelay);
                else
                    stars[i].Delay(Math.Max(currentValue - 1 - i, 0) * animationDelay);
                transformStar(i, newValue);
                stars[i].DelayReset();
            }
            transformStartTime = Time.Current;
        }
    }
}