using System.Collections.Concurrent;

namespace Campaign_Tracker.Server.LegacyData.Schema;

/// <summary>
/// Stores recent compatibility-check results so administrators can view a
/// history of runs (Story 1.7 AC #5). The default implementation is in-process
/// and bounded; production deployments can swap a durable store via DI.
/// </summary>
public interface ILegacySchemaCheckHistory
{
    void Record(LegacySchemaCheckResult result);

    IReadOnlyList<LegacySchemaCheckResult> GetRecent(int maxCount = 50);
}

public sealed class InMemoryLegacySchemaCheckHistory : ILegacySchemaCheckHistory
{
    private const int Capacity = 200;
    private readonly ConcurrentQueue<LegacySchemaCheckResult> _results = new();
    private readonly object _trimLock = new();

    public void Record(LegacySchemaCheckResult result)
    {
        ArgumentNullException.ThrowIfNull(result);
        _results.Enqueue(result);
        Trim();
    }

    public IReadOnlyList<LegacySchemaCheckResult> GetRecent(int maxCount = 50)
    {
        if (maxCount <= 0) return [];
        return _results.Reverse().Take(maxCount).ToArray();
    }

    private void Trim()
    {
        if (_results.Count <= Capacity) return;
        lock (_trimLock)
        {
            while (_results.Count > Capacity && _results.TryDequeue(out _)) { }
        }
    }
}