using BigRegister.Domain.Features;

namespace BigRegister.Api.Data;

/// One persisted runtime override for a feature flag (only stored once toggled; otherwise the
/// catalog default applies). Key = the flag key from the code catalog (FeatureFlags.Catalog).
public sealed class FeatureFlagEntity
{
  public required string Key { get; init; }
  public bool Enabled { get; set; }
}

/// A flag resolved for a consumer: catalog default overlaid with any stored override.
public sealed record ResolvedFlag(string Key, string Description, bool Enabled);

/// <summary>
/// Runtime feature-flag state (WP-47). SQLite-backed like <see cref="OrgTemplateStore"/>, same
/// single-gate idiom. The CATALOG (which flags exist + their defaults) is code
/// (<see cref="FeatureFlags"/>); this store only holds the admin's on/off overrides. An unknown
/// key is never writable/enabled — the code catalog is the authority.
/// </summary>
public static class FeatureFlagStore
{
  private static readonly object _gate = new();

  /// Catalog defaults overlaid with stored overrides — the whole flag set for the admin UI + FE.
  public static IReadOnlyList<ResolvedFlag> All()
  {
    Dictionary<string, bool> overrides;
    lock (_gate)
    {
      using var db = Db.Create();
      overrides = db.FeatureFlags.ToDictionary(f => f.Key, f => f.Enabled);
    }
    return FeatureFlags.Catalog
        .Select(d => new ResolvedFlag(d.Key, d.Description,
            overrides.TryGetValue(d.Key, out var e) ? e : d.DefaultEnabled))
        .ToList();
  }

  /// Server-side enforcement helper. Unknown key → false (fail closed).
  public static bool IsEnabled(string key)
  {
    var def = FeatureFlags.Catalog.FirstOrDefault(d => d.Key == key);
    if (def is null) return false;
    lock (_gate)
    {
      using var db = Db.Create();
      return db.FeatureFlags.Find(key)?.Enabled ?? def.DefaultEnabled;
    }
  }

  /// Set an override for a KNOWN flag; returns false for an unknown key (caller → 404).
  public static bool Set(string key, bool enabled)
  {
    if (!FeatureFlags.Catalog.Any(d => d.Key == key)) return false;
    lock (_gate)
    {
      using var db = Db.Create();
      var row = db.FeatureFlags.Find(key);
      if (row is null) db.FeatureFlags.Add(new FeatureFlagEntity { Key = key, Enabled = enabled });
      else row.Enabled = enabled;
      db.SaveChanges();
    }
    return true;
  }
}