// 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 System.Linq;
using osu.Framework.Graphics;
using osu.Game.Rulesets.Objects.Drawables;
using osu.Framework.Allocation;
using osu.Framework.Bindables;
using osu.Framework.Extensions.IEnumerableExtensions;
using osu.Framework.Graphics.Containers;
using osu.Game.Beatmaps;
using osu.Game.Rulesets.Mods;
using osuTK;

namespace osu.Game.Rulesets.UI
{
    public abstract class Playfield : CompositeDrawable
    {
        /// <summary>
        /// The <see cref="DrawableHitObject"/> contained in this Playfield.
        /// </summary>
        public HitObjectContainer HitObjectContainer => hitObjectContainerLazy.Value;

        private readonly Lazy<HitObjectContainer> hitObjectContainerLazy;

        /// <summary>
        /// A function that converts gamefield coordinates to screen space.
        /// </summary>
        public Func<Vector2, Vector2> GamefieldToScreenSpace => HitObjectContainer.ToScreenSpace;

        /// <summary>
        /// All the <see cref="DrawableHitObject"/>s contained in this <see cref="Playfield"/> and all <see cref="NestedPlayfields"/>.
        /// </summary>
        public IEnumerable<DrawableHitObject> AllHitObjects => HitObjectContainer?.Objects.Concat(NestedPlayfields.SelectMany(p => p.AllHitObjects)) ?? Enumerable.Empty<DrawableHitObject>();

        /// <summary>
        /// All <see cref="Playfield"/>s nested inside this <see cref="Playfield"/>.
        /// </summary>
        public IEnumerable<Playfield> NestedPlayfields => nestedPlayfields.IsValueCreated ? nestedPlayfields.Value : Enumerable.Empty<Playfield>();

        private readonly Lazy<List<Playfield>> nestedPlayfields = new Lazy<List<Playfield>>();

        /// <summary>
        /// Whether judgements should be displayed by this and and all nested <see cref="Playfield"/>s.
        /// </summary>
        public readonly BindableBool DisplayJudgements = new BindableBool(true);

        /// <summary>
        /// Creates a new <see cref="Playfield"/>.
        /// </summary>
        protected Playfield()
        {
            RelativeSizeAxes = Axes.Both;

            hitObjectContainerLazy = new Lazy<HitObjectContainer>(CreateHitObjectContainer);
        }

        [Resolved]
        private IBindable<WorkingBeatmap> beatmap { get; set; }

        [Resolved]
        private IBindable<IEnumerable<Mod>> selectedMods { get; set; }

        [BackgroundDependencyLoader]
        private void load()
        {
            Cursor = CreateCursor();
            if (Cursor != null)
                AddInternal(Cursor);
        }

        /// <summary>
        /// Performs post-processing tasks (if any) after all DrawableHitObjects are loaded into this Playfield.
        /// </summary>
        public virtual void PostProcess() => NestedPlayfields.ForEach(p => p.PostProcess());

        /// <summary>
        /// Adds a DrawableHitObject to this Playfield.
        /// </summary>
        /// <param name="h">The DrawableHitObject to add.</param>
        public virtual void Add(DrawableHitObject h) => HitObjectContainer.Add(h);

        /// <summary>
        /// Remove a DrawableHitObject from this Playfield.
        /// </summary>
        /// <param name="h">The DrawableHitObject to remove.</param>
        public virtual bool Remove(DrawableHitObject h) => HitObjectContainer.Remove(h);

        /// <summary>
        /// The cursor currently being used by this <see cref="Playfield"/>. May be null if no cursor is provided.
        /// </summary>
        public GameplayCursorContainer Cursor { get; private set; }

        /// <summary>
        /// Provide an optional cursor which is to be used for gameplay.
        /// If providing a cursor, <see cref="CursorTargetContainer"/> must also point to a valid target container.
        /// </summary>
        /// <returns>The cursor, or null if a cursor is not rqeuired.</returns>
        protected virtual GameplayCursorContainer CreateCursor() => null;

        /// <summary>
        /// Registers a <see cref="Playfield"/> as a nested <see cref="Playfield"/>.
        /// This does not add the <see cref="Playfield"/> to the draw hierarchy.
        /// </summary>
        /// <param name="otherPlayfield">The <see cref="Playfield"/> to add.</param>
        protected void AddNested(Playfield otherPlayfield)
        {
            otherPlayfield.DisplayJudgements.BindTo(DisplayJudgements);
            nestedPlayfields.Value.Add(otherPlayfield);
        }

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

            // in the case a consumer forgets to add the HitObjectContainer, we will add it here.
            if (HitObjectContainer.Parent == null)
                AddInternal(HitObjectContainer);
        }

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

            if (beatmap != null)
                foreach (var mod in selectedMods.Value)
                    if (mod is IUpdatableByPlayfield updatable)
                        updatable.Update(this);
        }

        /// <summary>
        /// Creates the container that will be used to contain the <see cref="DrawableHitObject"/>s.
        /// </summary>
        protected virtual HitObjectContainer CreateHitObjectContainer() => new HitObjectContainer();
    }
}