// 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 JetBrains.Annotations;
using osu.Framework.Allocation;
using osu.Framework.Audio.Sample;
using osu.Framework.Bindables;
using osu.Framework.Graphics;
using osu.Framework.Graphics.Containers;
using osu.Framework.Graphics.OpenGL.Textures;
using osu.Framework.Graphics.Textures;
using osu.Game.Audio;

namespace osu.Game.Skinning
{
    /// <summary>
    /// A container which adds a local <see cref="ISkinSource"/> to the hierarchy.
    /// </summary>
    public class SkinProvidingContainer : Container, ISkinSource
    {
        public event Action SourceChanged;

        [CanBeNull]
        private readonly ISkin skin;

        [CanBeNull]
        private ISkinSource fallbackSource;

        private readonly NoFallbackProxy noFallbackLookupProxy;

        protected virtual bool AllowDrawableLookup(ISkinComponent component) => true;

        protected virtual bool AllowTextureLookup(string componentName) => true;

        protected virtual bool AllowSampleLookup(ISampleInfo componentName) => true;

        protected virtual bool AllowConfigurationLookup => true;

        protected virtual bool AllowColourLookup => true;

        public SkinProvidingContainer(ISkin skin)
        {
            this.skin = skin;

            RelativeSizeAxes = Axes.Both;

            noFallbackLookupProxy = new NoFallbackProxy(this);

            if (skin is ISkinSource source)
                source.SourceChanged += TriggerSourceChanged;
        }

        public ISkin FindProvider(Func<ISkin, bool> lookupFunction)
        {
            if (skin is ISkinSource source)
            {
                if (source.FindProvider(lookupFunction) is ISkin found)
                    return found;
            }
            else if (skin != null)
            {
                // a proxy must be used here to correctly pass through the "Allow" checks without implicitly falling back to the fallbackSource.
                if (lookupFunction(noFallbackLookupProxy))
                    return skin;
            }

            return fallbackSource?.FindProvider(lookupFunction);
        }

        public Drawable GetDrawableComponent(ISkinComponent component)
            => GetDrawableComponent(component, true);

        public Drawable GetDrawableComponent(ISkinComponent component, bool fallback)
        {
            Drawable sourceDrawable;
            if (AllowDrawableLookup(component) && (sourceDrawable = skin?.GetDrawableComponent(component)) != null)
                return sourceDrawable;

            if (!fallback)
                return null;

            return fallbackSource?.GetDrawableComponent(component);
        }

        public Texture GetTexture(string componentName, WrapMode wrapModeS, WrapMode wrapModeT)
            => GetTexture(componentName, wrapModeS, wrapModeT, true);

        public Texture GetTexture(string componentName, WrapMode wrapModeS, WrapMode wrapModeT, bool fallback)
        {
            Texture sourceTexture;
            if (AllowTextureLookup(componentName) && (sourceTexture = skin?.GetTexture(componentName, wrapModeS, wrapModeT)) != null)
                return sourceTexture;

            if (!fallback)
                return null;

            return fallbackSource?.GetTexture(componentName, wrapModeS, wrapModeT);
        }

        public ISample GetSample(ISampleInfo sampleInfo)
            => GetSample(sampleInfo, true);

        public ISample GetSample(ISampleInfo sampleInfo, bool fallback)
        {
            ISample sourceChannel;
            if (AllowSampleLookup(sampleInfo) && (sourceChannel = skin?.GetSample(sampleInfo)) != null)
                return sourceChannel;

            if (!fallback)
                return null;

            return fallbackSource?.GetSample(sampleInfo);
        }

        public IBindable<TValue> GetConfig<TLookup, TValue>(TLookup lookup)
            => GetConfig<TLookup, TValue>(lookup, true);

        public IBindable<TValue> GetConfig<TLookup, TValue>(TLookup lookup, bool fallback)
        {
            if (skin != null)
            {
                if (lookup is GlobalSkinColours || lookup is SkinCustomColourLookup)
                    return lookupWithFallback<TLookup, TValue>(lookup, AllowColourLookup, fallback);

                return lookupWithFallback<TLookup, TValue>(lookup, AllowConfigurationLookup, fallback);
            }

            if (!fallback)
                return null;

            return fallbackSource?.GetConfig<TLookup, TValue>(lookup);
        }

        private IBindable<TValue> lookupWithFallback<TLookup, TValue>(TLookup lookup, bool canUseSkinLookup, bool canUseFallback)
        {
            if (canUseSkinLookup)
            {
                var bindable = skin?.GetConfig<TLookup, TValue>(lookup);
                if (bindable != null)
                    return bindable;
            }

            if (!canUseFallback)
                return null;

            return fallbackSource?.GetConfig<TLookup, TValue>(lookup);
        }

        protected virtual void TriggerSourceChanged() => SourceChanged?.Invoke();

        protected override IReadOnlyDependencyContainer CreateChildDependencies(IReadOnlyDependencyContainer parent)
        {
            var dependencies = new DependencyContainer(base.CreateChildDependencies(parent));

            fallbackSource = dependencies.Get<ISkinSource>();
            if (fallbackSource != null)
                fallbackSource.SourceChanged += TriggerSourceChanged;

            dependencies.CacheAs<ISkinSource>(this);

            return dependencies;
        }

        protected override void Dispose(bool isDisposing)
        {
            // Must be done before base.Dispose()
            SourceChanged = null;

            base.Dispose(isDisposing);

            if (fallbackSource != null)
                fallbackSource.SourceChanged -= TriggerSourceChanged;

            if (skin is ISkinSource source)
                source.SourceChanged -= TriggerSourceChanged;
        }

        private class NoFallbackProxy : ISkinSource
        {
            private readonly SkinProvidingContainer provider;

            public NoFallbackProxy(SkinProvidingContainer provider)
            {
                this.provider = provider;
            }

            public Drawable GetDrawableComponent(ISkinComponent component)
                => provider.GetDrawableComponent(component, false);

            public Texture GetTexture(string componentName, WrapMode wrapModeS, WrapMode wrapModeT)
                => provider.GetTexture(componentName, wrapModeS, wrapModeT, false);

            public ISample GetSample(ISampleInfo sampleInfo)
                => provider.GetSample(sampleInfo, false);

            public IBindable<TValue> GetConfig<TLookup, TValue>(TLookup lookup)
                => provider.GetConfig<TLookup, TValue>(lookup, false);

            public event Action SourceChanged
            {
                add => provider.SourceChanged += value;
                remove => provider.SourceChanged -= value;
            }

            public ISkin FindProvider(Func<ISkin, bool> lookupFunction) =>
                provider.FindProvider(lookupFunction);
        }
    }
}