using Microsoft.JSInterop;

namespace DeepDrftPublic.Client.Services;

/// <summary>
/// Production <see cref="IAnonIdProvider"/> over the <c>window.DeepDrftAnonId</c> TS interop. Reads the
/// first-party <c>localStorage</c> GUID once and caches it for the session, so the synchronous emit paths
/// read it with no JS hop. Scoped (per-session) like the other telemetry collaborators; the underlying
/// token itself outlives the session in <c>localStorage</c> — the cache just avoids repeated interop.
/// </summary>
public sealed class AnonIdProvider : IAnonIdProvider
{
    private readonly IJSRuntime _js;
    private bool _loaded;

    public AnonIdProvider(IJSRuntime js)
    {
        _js = js;
    }

    public string? Current { get; private set; }

    public async ValueTask EnsureLoadedAsync()
    {
        if (_loaded) return;

        try
        {
            // The module returns null when localStorage is unavailable; we store that null and still
            // mark loaded so we don't retry every emit. A genuine interop failure (module not yet
            // imported, prerender) is caught below and leaves _loaded false so a later warm can succeed.
            Current = await _js.InvokeAsync<string?>("DeepDrftAnonId.get");
            _loaded = true;
        }
        catch
        {
            // Interop unavailable (prerender / module not loaded). Leave Current null and unloaded so a
            // subsequent warm retries — telemetry simply omits the id until then.
        }
    }
}