using System.Collections.Concurrent;

namespace NpgsqlRest;

public interface IRoutineCache

{

bool Get(RoutineEndpoint endpoint, string key, out object? result);

void AddOrUpdate(RoutineEndpoint endpoint, string key, object? value);

}

public class RoutineCache : IRoutineCache

{

private class CacheEntry

{

public object? Value { get; set; }

public DateTime? ExpirationTime { get; set; }

public bool IsExpired => ExpirationTime.HasValue && DateTime.UtcNow > ExpirationTime.Value;

}

private static readonly ConcurrentDictionary<int, CacheEntry> _cache = new();

private static readonly ConcurrentDictionary<int, string> _originalKeys = new();

private static Timer? _cleanupTimer;

public static void Start(NpgsqlRestOptions options)

{

_cleanupTimer = new Timer(

_ => CleanupExpiredEntriesInternal(),

null,

TimeSpan.FromSeconds(options.CacheOptions.MemoryCachePruneIntervalSeconds),

TimeSpan.FromSeconds(options.CacheOptions.MemoryCachePruneIntervalSeconds));

}

public static void Shutdown()

{

_cleanupTimer?.Dispose();

_cache.Clear();

_originalKeys.Clear();

}

private static void CleanupExpiredEntriesInternal()

{

var expiredKeys = _cache

.Where(kvp => kvp.Value.IsExpired)

.Select(kvp => kvp.Key)

.ToList();

foreach (var key in expiredKeys)

{

_cache.TryRemove(key, out _);

_originalKeys.TryRemove(key, out _);

}

}

public bool Get(RoutineEndpoint endpoint, string key, out object? result)

{

var hashedKey = key.GetHashCode();

if (_cache.TryGetValue(hashedKey, out var entry))

{

if (_originalKeys.TryGetValue(hashedKey, out var originalKey) && originalKey == key)

{

if (entry.IsExpired)

{

// Remove expired entry

_cache.TryRemove(hashedKey, out _);

_originalKeys.TryRemove(hashedKey, out _);

result = null;

return false;

}

result = entry.Value;

return true;

}

}

result = null;

return false;

}

public void AddOrUpdate(RoutineEndpoint endpoint, string key, object? value)

{

var hashedKey = key.GetHashCode();

var entry = new CacheEntry

{

Value = value,

ExpirationTime = endpoint.CacheExpiresIn.HasValue ? DateTime.UtcNow + endpoint.CacheExpiresIn.Value : null

};

_cache[hashedKey] = entry;

_originalKeys[hashedKey] = key;

}

}