using System.Collections.Concurrent;

namespace ZB.MOM.WW.OtOpcUa.Core.ScriptedAlarms;

/// <summary>
///     Persistence for <see cref="AlarmConditionState"/> across server restarts. Phase 7
///     plan decision #14: operator-supplied state (EnabledState / AckedState /
///     ConfirmedState / ShelvingState + audit trail) persists; ActiveState is
///     recomputed from the live predicate on startup so operators never re-ack.
/// </summary>
/// <remarks>
///     Stream E wires this to a SQL-backed store against the <c>ScriptedAlarmState</c>
///     table with audit logging through <see cref="Core.Abstractions"/> IAuditLogger.
///     Tests + local dev use <see cref="InMemoryAlarmStateStore"/>.
/// </remarks>
public interface IAlarmStateStore
{
    Task<AlarmConditionState?> LoadAsync(string alarmId, CancellationToken ct);
    Task<IReadOnlyList<AlarmConditionState>> LoadAllAsync(CancellationToken ct);
    Task SaveAsync(AlarmConditionState state, CancellationToken ct);
    Task RemoveAsync(string alarmId, CancellationToken ct);
}

/// <summary>In-memory default — used by tests + by dev deployments without a SQL backend.</summary>
public sealed class InMemoryAlarmStateStore : IAlarmStateStore
{
    private readonly ConcurrentDictionary<string, AlarmConditionState> _map
        = new(StringComparer.Ordinal);

    public Task<AlarmConditionState?> LoadAsync(string alarmId, CancellationToken ct)
        => Task.FromResult(_map.TryGetValue(alarmId, out var v) ? v : null);

    public Task<IReadOnlyList<AlarmConditionState>> LoadAllAsync(CancellationToken ct)
        => Task.FromResult<IReadOnlyList<AlarmConditionState>>(_map.Values.ToArray());

    public Task SaveAsync(AlarmConditionState state, CancellationToken ct)
    {
        _map[state.AlarmId] = state;
        return Task.CompletedTask;
    }

    public Task RemoveAsync(string alarmId, CancellationToken ct)
    {
        _map.TryRemove(alarmId, out _);
        return Task.CompletedTask;
    }
}