using System.IO;
using System.Text.Json;

namespace WindowsGotify.Services;

public sealed class StateService
{
    private sealed class StateData
    {
        public long LastMessageId { get; set; }
    }

    private readonly Logger _logger;
    private readonly string _statePath;
    private StateData _state = new();

    public StateService(Logger logger)
    {
        _logger = logger;
        var dir = Path.Combine(
            Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData),
            "WindowsGotify");

        Directory.CreateDirectory(dir);
        _statePath = Path.Combine(dir, "state.json");
    }

    public async Task LoadAsync()
    {
        if (!File.Exists(_statePath))
            return;

        try
        {
            await using var stream = File.OpenRead(_statePath);
            _state = await JsonSerializer.DeserializeAsync<StateData>(stream)
                     ?? new StateData();
        }
        catch (Exception ex)
        {
            _logger.Error("State load failed.", ex);
        }
    }

    public long LastMessageId => _state.LastMessageId;

    public async Task SetLastMessageIdAsync(long id)
    {
        if (id <= _state.LastMessageId)
            return;

        _state.LastMessageId = id;
        await SaveAsync();
    }

    private async Task SaveAsync()
    {
        await using var stream = File.Create(_statePath);
        await JsonSerializer.SerializeAsync(stream, _state, new JsonSerializerOptions
        {
            WriteIndented = true
        });
    }
}