using System.Collections.Concurrent;
using WindowsGotify.Models;

namespace WindowsGotify.Services;

/// <summary>
/// 缓存 Gotify Applications 列表(从 GET /application 拉取),供 UI 用来把消息的 AppId 解析为可读应用名。
/// </summary>
public sealed class ApplicationCache
{
    private readonly ConcurrentDictionary<long, GotifyApplication> _apps = new();
    private readonly GotifyApiService _api;
    private readonly Logger _logger;
    private DateTimeOffset _lastFetchedAt = DateTimeOffset.MinValue;

    public ApplicationCache(GotifyApiService api, Logger logger)
    {
        _api = api;
        _logger = logger;
    }

    public int Count => _apps.Count;

    public event EventHandler? Updated;

    /// <summary>
    /// 拉一次最新的应用列表。失败抛异常,调用方决定怎么处理(忽略 / 重试 / 提示)。
    /// </summary>
    public async Task RefreshAsync(CancellationToken ct = default)
    {
        var list = await _api.GetApplicationsAsync(ct);
        _apps.Clear();
        foreach (var app in list)
        {
            _apps[app.Id] = app;
        }
        _lastFetchedAt = DateTimeOffset.UtcNow;
        _logger.Info($"ApplicationCache refreshed. count={list.Count}");
        Updated?.Invoke(this, EventArgs.Empty);
    }

    /// <summary>
    /// 把 appId 解析为应用名。缓存里没有就回退 "App {id}"。
    /// </summary>
    public string GetName(long appId)
    {
        return _apps.TryGetValue(appId, out var app) && !string.IsNullOrWhiteSpace(app.Name)
            ? app.Name
            : $"App {appId}";
    }

    public GotifyApplication? Get(long appId)
    {
        _apps.TryGetValue(appId, out var app);
        return app;
    }

    public DateTimeOffset LastFetchedAt => _lastFetchedAt;
}