// 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.Audio;
using osu.Framework.Audio.Track;
using osu.Framework.Bindables;
using osu.Framework.Graphics;
using osu.Framework.Timing;
using osu.Game.Beatmaps;
using osu.Game.Beatmaps.ControlPoints;

namespace osu.Game.Screens.Play
{
    /// <summary>
    /// A <see cref="GameplayClockContainer"/> which uses a <see cref="WorkingBeatmap"/> as a source.
    /// <para>
    /// This is the most complete <see cref="GameplayClockContainer"/> which takes into account all user and platform offsets,
    /// and provides implementations for user actions such as skipping or adjusting playback rates that may occur during gameplay.
    /// </para>
    /// </summary>
    /// <remarks>
    /// This is intended to be used as a single controller for gameplay, or as a reference source for other <see cref="GameplayClockContainer"/>s.
    /// </remarks>
    public class MasterGameplayClockContainer : GameplayClockContainer, IBeatSyncProvider
    {
        /// <summary>
        /// Duration before gameplay start time required before skip button displays.
        /// </summary>
        public const double MINIMUM_SKIP_TIME = 1000;

        public readonly BindableNumber<double> UserPlaybackRate = new BindableDouble(1)
        {
            Default = 1,
            MinValue = 0.5,
            MaxValue = 2,
            Precision = 0.1,
        };

        private readonly WorkingBeatmap beatmap;

        private readonly double skipTargetTime;

        private readonly List<Bindable<double>> nonGameplayAdjustments = new List<Bindable<double>>();

        public override IEnumerable<double> NonGameplayAdjustments => nonGameplayAdjustments.Select(b => b.Value);

        /// <summary>
        /// Create a new master gameplay clock container.
        /// </summary>
        /// <param name="beatmap">The beatmap to be used for time and metadata references.</param>
        /// <param name="skipTargetTime">The latest time which should be used when introducing gameplay. Will be used when skipping forward.</param>
        public MasterGameplayClockContainer(WorkingBeatmap beatmap, double skipTargetTime)
            : base(beatmap.Track, true)
        {
            this.beatmap = beatmap;
            this.skipTargetTime = skipTargetTime;

            StartTime = findEarliestStartTime();
        }

        private double findEarliestStartTime()
        {
            // here we are trying to find the time to start playback from the "zero" point.
            // generally this is either zero, or some point earlier than zero in the case of storyboards, lead-ins etc.

            // start with the originally provided latest time (if before zero).
            double time = Math.Min(0, skipTargetTime);

            // if a storyboard is present, it may dictate the appropriate start time by having events in negative time space.
            // this is commonly used to display an intro before the audio track start.
            double? firstStoryboardEvent = beatmap.Storyboard.EarliestEventTime;
            if (firstStoryboardEvent != null)
                time = Math.Min(time, firstStoryboardEvent.Value);

            // some beatmaps specify a current lead-in time which should be used instead of the ruleset-provided value when available.
            // this is not available as an option in the live editor but can still be applied via .osu editing.
            double firstHitObjectTime = beatmap.Beatmap.HitObjects.First().StartTime;
            if (beatmap.BeatmapInfo.AudioLeadIn > 0)
                time = Math.Min(time, firstHitObjectTime - beatmap.BeatmapInfo.AudioLeadIn);

            return time;
        }

        protected override void OnIsPausedChanged(ValueChangedEvent<bool> isPaused)
        {
            if (IsLoaded)
            {
                // During normal operation, the source is stopped after performing a frequency ramp.
                if (isPaused.NewValue)
                {
                    this.TransformBindableTo(GameplayClock.ExternalPauseFrequencyAdjust, 0, 200, Easing.Out).OnComplete(_ =>
                    {
                        if (IsPaused.Value == isPaused.NewValue)
                            base.OnIsPausedChanged(isPaused);
                    });
                }
                else
                    this.TransformBindableTo(GameplayClock.ExternalPauseFrequencyAdjust, 1, 200, Easing.In);
            }
            else
            {
                if (isPaused.NewValue)
                    base.OnIsPausedChanged(isPaused);

                // If not yet loaded, we still want to ensure relevant state is correct, as it is used for offset calculations.
                GameplayClock.ExternalPauseFrequencyAdjust.Value = isPaused.NewValue ? 0 : 1;

                // We must also process underlying gameplay clocks to update rate-adjusted offsets with the new frequency adjustment.
                // Without doing this, an initial seek may be performed with the wrong offset.
                GameplayClock.ProcessFrame();
            }
        }

        public override void Start()
        {
            addSourceClockAdjustments();
            base.Start();
        }

        /// <summary>
        /// Skip forward to the next valid skip point.
        /// </summary>
        public void Skip()
        {
            if (GameplayClock.CurrentTime > skipTargetTime - MINIMUM_SKIP_TIME)
                return;

            double skipTarget = skipTargetTime - MINIMUM_SKIP_TIME;

            if (GameplayClock.CurrentTime < 0 && skipTarget > 6000)
                // double skip exception for storyboards with very long intros
                skipTarget = 0;

            Seek(skipTarget);
        }

        /// <summary>
        /// Changes the backing clock to avoid using the originally provided track.
        /// </summary>
        public void StopUsingBeatmapClock()
        {
            removeSourceClockAdjustments();
            ChangeSource(new TrackVirtual(beatmap.Track.Length));
            addSourceClockAdjustments();
        }

        private bool speedAdjustmentsApplied;

        private void addSourceClockAdjustments()
        {
            if (speedAdjustmentsApplied)
                return;

            if (SourceClock is not Track track)
                return;

            track.AddAdjustment(AdjustableProperty.Frequency, GameplayClock.ExternalPauseFrequencyAdjust);
            track.AddAdjustment(AdjustableProperty.Tempo, UserPlaybackRate);

            nonGameplayAdjustments.Add(GameplayClock.ExternalPauseFrequencyAdjust);
            nonGameplayAdjustments.Add(UserPlaybackRate);

            speedAdjustmentsApplied = true;
        }

        private void removeSourceClockAdjustments()
        {
            if (!speedAdjustmentsApplied)
                return;

            if (SourceClock is not Track track)
                return;

            track.RemoveAdjustment(AdjustableProperty.Frequency, GameplayClock.ExternalPauseFrequencyAdjust);
            track.RemoveAdjustment(AdjustableProperty.Tempo, UserPlaybackRate);

            nonGameplayAdjustments.Remove(GameplayClock.ExternalPauseFrequencyAdjust);
            nonGameplayAdjustments.Remove(UserPlaybackRate);

            speedAdjustmentsApplied = false;
        }

        protected override void Dispose(bool isDisposing)
        {
            base.Dispose(isDisposing);
            removeSourceClockAdjustments();
        }

        ControlPointInfo IBeatSyncProvider.ControlPoints => beatmap.Beatmap.ControlPointInfo;
        IClock IBeatSyncProvider.Clock => this;

        ChannelAmplitudes IHasAmplitudes.CurrentAmplitudes => beatmap.TrackLoaded ? beatmap.Track.CurrentAmplitudes : ChannelAmplitudes.Empty;
    }
}