using System.Text.Json;
using System.Text.Json.Serialization;
using DeepDrftModels.DTOs;
using DeepDrftModels.Enums;
using Microsoft.AspNetCore.Components;

namespace DeepDrftPublic.Client.Services;

/// <summary>
/// Production <see cref="IPlayEventSink"/> (Phase 16 §2.2; telemetry transport-resilience). Serializes the
/// play classification once and dispatches it down the arm the close chose:
/// <list type="bullet">
/// <item><see cref="EmitPlayAsync"/> posts via the first-party <see cref="IEventPoster"/> — a same-origin
/// <c>HttpClient</c> fetch to <c>api/event/play</c>, used for the normal close paths (organic end /
/// track-switch / stop) that a privacy-hardened browser would block if they used a name-matched
/// <c>sendBeacon</c> module.</item>
/// <item><see cref="EmitPlayOnUnload"/> fires <see cref="BeaconInterop"/> (<c>sendBeacon</c>) for the
/// tab-unload edge, where an awaited fetch would be cancelled.</item>
/// </list>
/// Both arms send byte-identical payloads (same DTO, same anonId, same JSON options). The current
/// <c>anonId</c> (wave 16.3) is read synchronously from the warmed <see cref="IAnonIdProvider"/> cache and
/// omitted when null (storage unavailable / not yet warmed) — an anonId-less play still counts, it just
/// doesn't contribute to the listener tally.
/// </summary>
public sealed class BeaconPlayEventSink : IPlayEventSink
{
    // Omit a null anonId from the wire payload (§2.2 — "omitted entirely" when absent) rather than
    // sending "anonId":null. The API treats absent and null identically, so this is cosmetic minimalism;
    // it does not change the integer enum encoding the 16.1 contract already relies on.
    private static readonly JsonSerializerOptions EventJson =
        new() { DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull };

    private readonly IEventPoster _poster;
    private readonly BeaconInterop _beacon;
    private readonly IAnonIdProvider _anonId;
    private readonly string _playUrl;

    public BeaconPlayEventSink(
        IEventPoster poster, BeaconInterop beacon, IAnonIdProvider anonId, NavigationManager navigation)
    {
        _poster = poster;
        _beacon = beacon;
        _anonId = anonId;
        // The WASM client posts to its own host, which proxies to DeepDrftAPI. BaseUri carries a
        // trailing slash; the route does not lead with one.
        _playUrl = $"{navigation.BaseUri}api/event/play";
    }

    public Task EmitPlayAsync(string trackEntryKey, PlayBucket bucket)
        => _poster.PostAsync(_playUrl, Serialize(trackEntryKey, bucket));

    public void EmitPlayOnUnload(string trackEntryKey, PlayBucket bucket)
        // Fire-and-forget: the beacon survives unload; the C# task may not, and we do not act on the
        // result either way.
        => _ = _beacon.SendAsync(_playUrl, Serialize(trackEntryKey, bucket));

    private string Serialize(string trackEntryKey, PlayBucket bucket)
        => JsonSerializer.Serialize(new PlayEventDto
        {
            TrackEntryKey = trackEntryKey,
            Bucket = bucket,
            AnonId = _anonId.Current,
        }, EventJson);
}