deepdrft/DeepDrftPublic.Client/Pages/TrackDetail.razor.cs

using DeepDrftModels.DTOs;
using DeepDrftPublic.Client.Services;
using DeepDrftPublic.Client.ViewModels;
using Microsoft.AspNetCore.Components;

namespace DeepDrftPublic.Client.Pages;

public partial class TrackDetail : ComponentBase, IDisposable
{
    private const string PersistKey = "track-detail";

    [Parameter] public required string EntryKey { get; set; }
    [Inject] public required TrackDetailViewModel ViewModel { get; set; }
    [Inject] public required PersistentComponentState PersistentState { get; set; }
    [CascadingParameter] public required IStreamingPlayerService PlayerService { get; set; }

    private IStreamingPlayerService? _subscribedService;
    private PersistingComponentStateSubscription _persistingSubscription;

    protected override async Task OnInitializedAsync()
    {
        // Carry the prerendered track across the prerender -> interactive (WASM) seam.
        // Without this, the WASM pass gets a fresh scoped ViewModel, re-renders the
        // skeleton, and re-fetches. Mirror the TracksView bridge: persist on the way
        // out of prerender, restore on the interactive pass, and only fetch on a miss.
        _persistingSubscription = PersistentState.RegisterOnPersisting(PersistTrack);

        if (PersistentState.TryTakeFromJson<TrackDto>(PersistKey, out var restored) && restored is not null)
        {
            ViewModel.Track = restored;
            ViewModel.IsLoading = false;
        }
        else
        {
            await ViewModel.Load(EntryKey);
        }
    }

    protected override void OnParametersSet()
    {
        // The play button's icon reads off the player's live state (CurrentTrack /
        // IsPlaying / IsPaused), which mutates outside this component's render path.
        // The cascade is IsFixed, so the provider's re-render never reaches us —
        // subscribe to the multicast side-channel and re-render on every state change.
        if (PlayerService != null && !ReferenceEquals(PlayerService, _subscribedService))
        {
            if (_subscribedService != null)
                _subscribedService.StateChanged -= OnPlayerStateChanged;

            PlayerService.StateChanged += OnPlayerStateChanged;
            _subscribedService = PlayerService;
        }
    }

    private void OnPlayerStateChanged() => InvokeAsync(StateHasChanged);

    private Task PersistTrack()
    {
        if (ViewModel.Track is not null)
        {
            PersistentState.PersistAsJson(PersistKey, ViewModel.Track);
        }
        return Task.CompletedTask;
    }

    private async Task PlayTrack()
    {
        if (ViewModel.Track is null) return;

        var isThisTrack = PlayerService.CurrentTrack?.Id == ViewModel.Track.Id;

        // Toggle play/pause if this track is already the active one (playing or paused);
        // otherwise start a fresh stream. SelectTrackStreaming is the live entry point —
        // the buffered SelectTrack path is dead.
        if (isThisTrack && (PlayerService.IsPlaying || PlayerService.IsPaused))
        {
            await PlayerService.TogglePlayPause();
        }
        else
        {
            await PlayerService.SelectTrackStreaming(ViewModel.Track);
        }
    }

    public void Dispose()
    {
        _persistingSubscription.Dispose();

        if (_subscribedService != null)
        {
            _subscribedService.StateChanged -= OnPlayerStateChanged;
            _subscribedService = null;
        }
    }
}