// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
// See the LICENCE file in the repository root for full licence text.

using System;
using System.Collections.Generic;
using osu.Framework.Allocation;
using osu.Framework.Bindables;
using osu.Framework.Graphics;
using osu.Framework.Graphics.OpenGL.Vertices;
using osu.Framework.Graphics.Primitives;
using osu.Framework.Graphics.Shaders;
using osu.Framework.Graphics.Sprites;
using osu.Framework.Graphics.Textures;
using osu.Game.Beatmaps.Timing;
using osu.Game.Graphics;
using osu.Game.Rulesets.Objects;
using osu.Game.Rulesets.Scoring;
using osu.Game.Rulesets.UI;
using osuTK;
using osuTK.Graphics;

namespace osu.Game.Rulesets.Mods
{
    public abstract class ModFlashlight : Mod
    {
        public override string Name => "Flashlight";
        public override string Acronym => "FL";
        public override IconUsage Icon => OsuIcon.ModFlashlight;
        public override ModType Type => ModType.DifficultyIncrease;
        public override string Description => "Restricted view area.";
        public override bool Ranked => true;

        internal ModFlashlight()
        {
        }
    }

    public abstract class ModFlashlight<T> : ModFlashlight, IApplicableToDrawableRuleset<T>, IApplicableToScoreProcessor
        where T : HitObject
    {
        public const double FLASHLIGHT_FADE_DURATION = 800;
        protected readonly BindableInt Combo = new BindableInt();

        public void ApplyToScoreProcessor(ScoreProcessor scoreProcessor)
        {
            Combo.BindTo(scoreProcessor.Combo);
        }

        public virtual void ApplyToDrawableRuleset(DrawableRuleset<T> drawableRuleset)
        {
            var flashlight = CreateFlashlight();
            flashlight.Combo = Combo;
            flashlight.RelativeSizeAxes = Axes.Both;
            flashlight.Colour = Color4.Black;
            drawableRuleset.KeyBindingInputManager.Add(flashlight);

            flashlight.Breaks = drawableRuleset.Beatmap.Breaks;
        }

        public abstract Flashlight CreateFlashlight();

        public abstract class Flashlight : Drawable
        {
            internal BindableInt Combo;
            private IShader shader;

            protected override DrawNode CreateDrawNode() => new FlashlightDrawNode();

            public override bool RemoveCompletedTransforms => false;

            public List<BreakPeriod> Breaks;

            protected override void ApplyDrawNode(DrawNode node)
            {
                base.ApplyDrawNode(node);

                var flashNode = (FlashlightDrawNode)node;

                flashNode.Shader = shader;
                flashNode.ScreenSpaceDrawQuad = ScreenSpaceDrawQuad;
                flashNode.FlashlightPosition = Vector2Extensions.Transform(FlashlightPosition, DrawInfo.Matrix);
                flashNode.FlashlightSize = Vector2Extensions.Transform(FlashlightSize, DrawInfo.Matrix);
                flashNode.FlashlightLightness = FlashlightLightness;
            }

            [BackgroundDependencyLoader]
            private void load(ShaderManager shaderManager)
            {
                shader = shaderManager.Load("PositionAndColour", FragmentShader);
            }

            protected override void LoadComplete()
            {
                base.LoadComplete();

                Combo.ValueChanged += OnComboChange;

                this.FadeInFromZero(FLASHLIGHT_FADE_DURATION);

                foreach (var breakPeriod in Breaks)
                {
                    if (breakPeriod.Duration < FLASHLIGHT_FADE_DURATION * 2) continue;

                    this.Delay(breakPeriod.StartTime + FLASHLIGHT_FADE_DURATION).FadeOutFromOne(FLASHLIGHT_FADE_DURATION);
                    this.Delay(breakPeriod.EndTime - FLASHLIGHT_FADE_DURATION).FadeInFromZero(FLASHLIGHT_FADE_DURATION);
                }
            }

            protected abstract void OnComboChange(ValueChangedEvent<int> e);

            protected abstract string FragmentShader { get; }

            private Vector2 flashlightPosition;

            protected Vector2 FlashlightPosition
            {
                get => flashlightPosition;
                set
                {
                    if (flashlightPosition == value) return;

                    flashlightPosition = value;
                    Invalidate(Invalidation.DrawNode);
                }
            }

            private Vector2 flashlightSize;

            protected Vector2 FlashlightSize
            {
                get => flashlightSize;
                set
                {
                    if (flashlightSize == value) return;

                    flashlightSize = value;
                    Invalidate(Invalidation.DrawNode);
                }
            }

            private float flashlightLightness = 1.0f;

            public float FlashlightLightness
            {
                get => flashlightLightness;
                set
                {
                    if (flashlightLightness == value) return;

                    flashlightLightness = value;
                    Invalidate(Invalidation.DrawNode);
                }
            }
        }

        private class FlashlightDrawNode : DrawNode
        {
            public IShader Shader;
            public Quad ScreenSpaceDrawQuad;
            public Vector2 FlashlightPosition;
            public Vector2 FlashlightSize;
            public float FlashlightLightness;

            public override void Draw(Action<TexturedVertex2D> vertexAction)
            {
                base.Draw(vertexAction);

                Shader.Bind();

                Shader.GetUniform<Vector2>("flashlightPos").UpdateValue(ref FlashlightPosition);
                Shader.GetUniform<Vector2>("flashlightSize").UpdateValue(ref FlashlightSize);
                Shader.GetUniform<float>("flashlightLightness").UpdateValue(ref FlashlightLightness);

                Texture.WhitePixel.DrawQuad(ScreenSpaceDrawQuad, DrawColourInfo.Colour, vertexAction: vertexAction);

                Shader.Unbind();
            }
        }
    }
}