#if NET
using System.Text.Json;
using Microsoft.Extensions.Caching.Distributed;
using EnvelopeGenerator.Application.Common.Dto;
using EnvelopeGenerator.Application.Common.Interfaces.Services;

namespace EnvelopeGenerator.Infrastructure;

/// <summary>
/// Implements user preferences storage using the distributed cache (dbo.TBDD_CACHE).
/// No DB schema changes required — uses the existing SQL Server distributed cache table.
/// Cache key schema: "signflow.user-preferences:{username}"
/// Expiration: indefinite (no TTL) — preferences persist until explicitly overwritten.
/// </summary>
public sealed class UserPreferencesService(IDistributedCache cache) : IUserPreferencesService
{
    private const string KeyPrefix = "signflow.user-preferences:";

    private static string BuildKey(string username) => $"{KeyPrefix}{username}";

    /// <inheritdoc />
    public async Task<UserPreferencesDto> GetAsync(string username, CancellationToken ct = default)
    {
        var json = await cache.GetStringAsync(BuildKey(username), ct);

        if (json is null)
            return new UserPreferencesDto();

        return JsonSerializer.Deserialize<UserPreferencesDto>(json) ?? new UserPreferencesDto();
    }

    /// <inheritdoc />
    public async Task SaveAsync(string username, UserPreferencesDto preferences, CancellationToken ct = default)
    {
        var json = JsonSerializer.Serialize(preferences);

        // No expiration — preferences are stored indefinitely.
        await cache.SetStringAsync(BuildKey(username), json, new DistributedCacheEntryOptions(), ct);
    }
}
#endif