using System.Diagnostics.Metrics;
using System.Diagnostics;
using Microsoft.Extensions.Logging;
using MarketAlly.AIPlugin.Context.Configuration;

namespace MarketAlly.AIPlugin.Context.Monitoring
{
	/// <summary>
	/// Provides comprehensive metrics and monitoring for context operations
	/// </summary>
	public class ContextMetrics : IDisposable
	{
		private readonly Meter _meter;
		private readonly ILogger<ContextMetrics> _logger;
		private readonly ContextConfiguration _configuration;
		
		// Counters
		private readonly Counter<long> _operationCounter;
		private readonly Counter<long> _errorCounter;
		private readonly Counter<long> _cacheHitCounter;
		private readonly Counter<long> _cacheMissCounter;
		
		// Histograms
		private readonly Histogram<double> _operationDuration;
		private readonly Histogram<double> _fileSize;
		private readonly Histogram<long> _searchResultCount;
		
		// Gauges (using UpDownCounters as approximation)
		private readonly UpDownCounter<long> _activeConnections;
		private readonly UpDownCounter<long> _contextEntriesCount;
		private readonly UpDownCounter<long> _fileCacheSize;

		// Activity sources for distributed tracing
		private readonly ActivitySource _activitySource;

		public ContextMetrics(ILogger<ContextMetrics> logger, ContextConfiguration configuration)
		{
			_logger = logger;
			_configuration = configuration;
			_meter = new Meter("MarketAlly.Context", "1.0.0");
			_activitySource = new ActivitySource("MarketAlly.Context.Operations");

			// Initialize counters
			_operationCounter = _meter.CreateCounter<long>(
				"context_operations_total",
				"Total number of context operations performed",
				"operations");

			_errorCounter = _meter.CreateCounter<long>(
				"context_errors_total", 
				"Total number of context operation errors",
				"errors");

			_cacheHitCounter = _meter.CreateCounter<long>(
				"context_cache_hits_total",
				"Total number of cache hits",
				"hits");

			_cacheMissCounter = _meter.CreateCounter<long>(
				"context_cache_misses_total",
				"Total number of cache misses", 
				"misses");

			// Initialize histograms
			_operationDuration = _meter.CreateHistogram<double>(
				"context_operation_duration_ms",
				"Duration of context operations in milliseconds",
				"ms");

			_fileSize = _meter.CreateHistogram<double>(
				"context_file_size_bytes",
				"Size of context files in bytes",
				"bytes");

			_searchResultCount = _meter.CreateHistogram<long>(
				"context_search_results_count",
				"Number of results returned by search operations",
				"results");

			// Initialize gauges (using UpDownCounters)
			_activeConnections = _meter.CreateUpDownCounter<long>(
				"context_active_connections",
				"Number of active context connections",
				"connections");

			_contextEntriesCount = _meter.CreateUpDownCounter<long>(
				"context_entries_total",
				"Total number of context entries stored",
				"entries");

			_fileCacheSize = _meter.CreateUpDownCounter<long>(
				"context_file_cache_size_bytes",
				"Current size of file cache in bytes",
				"bytes");
		}

		/// <summary>
		/// Records the start of an operation and returns a disposable tracker
		/// </summary>
		public OperationTracker StartOperation(string operationType, Dictionary<string, object>? tags = null)
		{
			var activity = _configuration.Monitoring.EnableTracing ? 
				_activitySource.StartActivity($"context.{operationType}") : null;

			if (activity != null && tags != null)
			{
				foreach (var tag in tags)
				{
					activity.SetTag(tag.Key, tag.Value);
				}
			}

			_activeConnections.Add(1);

			return new OperationTracker(
				operationType, 
				activity, 
				this,
				_logger,
				Stopwatch.StartNew());
		}

		/// <summary>
		/// Records a completed operation
		/// </summary>
		internal void RecordOperation(string operationType, TimeSpan duration, bool success, Dictionary<string, object>? tags = null)
		{
			var operationTags = CreateTags(operationType, success ? "success" : "error", tags);

			_operationCounter.Add(1, operationTags);
			_operationDuration.Record(duration.TotalMilliseconds, operationTags);

			if (!success)
			{
				_errorCounter.Add(1, operationTags);
			}

			_activeConnections.Add(-1);

			if (_configuration.Monitoring.EnableDetailedLogging)
			{
				var logLevel = success ? LogLevel.Debug : LogLevel.Warning;
				_logger.Log(logLevel, 
					"Operation {OperationType} completed in {Duration}ms with status {Status}",
					operationType, duration.TotalMilliseconds, success ? "Success" : "Error");
			}
		}

		/// <summary>
		/// Records cache hit metrics
		/// </summary>
		public void RecordCacheHit(string cacheType, Dictionary<string, object>? tags = null)
		{
			var cacheTags = CreateTags("cache", "hit", tags);
			cacheTags = cacheTags.Append(new KeyValuePair<string, object?>("cache_type", cacheType)).ToArray();
			
			_cacheHitCounter.Add(1, cacheTags);
		}

		/// <summary>
		/// Records cache miss metrics
		/// </summary>
		public void RecordCacheMiss(string cacheType, Dictionary<string, object>? tags = null)
		{
			var cacheTags = CreateTags("cache", "miss", tags);
			cacheTags = cacheTags.Append(new KeyValuePair<string, object?>("cache_type", cacheType)).ToArray();
			
			_cacheMissCounter.Add(1, cacheTags);
		}

		/// <summary>
		/// Records file operation metrics
		/// </summary>
		public void RecordFileOperation(string operation, long fileSizeBytes, TimeSpan duration, bool success)
		{
			var tags = CreateTags("file", success ? "success" : "error", null);
			tags = tags.Append(new KeyValuePair<string, object?>("file_operation", operation)).ToArray();

			_fileSize.Record(fileSizeBytes, tags);
			_operationDuration.Record(duration.TotalMilliseconds, tags);
		}

		/// <summary>
		/// Records search operation metrics
		/// </summary>
		public void RecordSearchOperation(string searchType, int resultCount, TimeSpan duration, bool usedCache = false)
		{
			var tags = CreateTags("search", "success", null);
			tags = tags.Append(new KeyValuePair<string, object?>("search_type", searchType)).ToArray();
			tags = tags.Append(new KeyValuePair<string, object?>("used_cache", usedCache)).ToArray();

			_searchResultCount.Record(resultCount, tags);
			_operationDuration.Record(duration.TotalMilliseconds, tags);
		}

		/// <summary>
		/// Updates the total number of context entries
		/// </summary>
		public void UpdateContextEntriesCount(long newCount)
		{
			// Since we can't set absolute values with UpDownCounter, we need to track the delta
			// This is a simplified approach - in production, you might want to use a different gauge implementation
			var tags = CreateTags("storage", "update", null);
			_contextEntriesCount.Add(newCount, tags);
		}

		/// <summary>
		/// Updates the file cache size
		/// </summary>
		public void UpdateFileCacheSize(long newSizeBytes)
		{
			var tags = CreateTags("cache", "update", null);
			_fileCacheSize.Add(newSizeBytes, tags);
		}

		/// <summary>
		/// Records an error with detailed information
		/// </summary>
		public void RecordError(string operationType, Exception exception, Dictionary<string, object>? tags = null)
		{
			var errorTags = CreateTags(operationType, "error", tags);
			errorTags = errorTags.Append(new KeyValuePair<string, object?>("error_type", exception.GetType().Name)).ToArray();
			
			_errorCounter.Add(1, errorTags);

			_logger.LogError(exception, 
				"Error in {OperationType}: {ErrorMessage}", 
				operationType, exception.Message);
		}

		/// <summary>
		/// Gets current performance metrics
		/// </summary>
		public PerformanceMetrics GetCurrentMetrics()
		{
			// Note: In a real implementation, you'd want to collect these values from the actual meters
			// This is a simplified representation
			return new PerformanceMetrics
			{
				Timestamp = DateTime.UtcNow,
				ActiveConnections = 0, // Would need to track this separately
				TotalOperations = 0,   // Would need to track this separately
				TotalErrors = 0,       // Would need to track this separately
				CacheHitRatio = 0.0,   // Would calculate from hit/miss counters
				AverageOperationDuration = 0.0, // Would calculate from histogram
				MemoryUsage = GC.GetTotalMemory(false),
				IsHealthy = true
			};
		}

		/// <summary>
		/// Creates standardized tags for metrics
		/// </summary>
		private KeyValuePair<string, object?>[] CreateTags(string operationType, string status, Dictionary<string, object>? additionalTags)
		{
			var tags = new List<KeyValuePair<string, object?>>
			{
				new("operation_type", operationType),
				new("status", status),
				new("version", "1.0.0")
			};

			if (additionalTags != null)
			{
				foreach (var tag in additionalTags)
				{
					tags.Add(new KeyValuePair<string, object?>(tag.Key, tag.Value));
				}
			}

			return tags.ToArray();
		}

		public void Dispose()
		{
			_meter?.Dispose();
			_activitySource?.Dispose();
		}
	}

	/// <summary>
	/// Tracks the duration and outcome of an operation
	/// </summary>
	public class OperationTracker : IDisposable
	{
		private readonly string _operationType;
		private readonly Activity? _activity;
		private readonly ContextMetrics _metrics;
		private readonly ILogger _logger;
		private readonly Stopwatch _stopwatch;
		private readonly Dictionary<string, object> _tags;
		private bool _disposed;

		internal OperationTracker(
			string operationType, 
			Activity? activity, 
			ContextMetrics metrics, 
			ILogger logger,
			Stopwatch stopwatch)
		{
			_operationType = operationType;
			_activity = activity;
			_metrics = metrics;
			_logger = logger;
			_stopwatch = stopwatch;
			_tags = new Dictionary<string, object>();
		}

		/// <summary>
		/// Adds a tag to the operation
		/// </summary>
		public OperationTracker AddTag(string key, object value)
		{
			_tags[key] = value;
			_activity?.SetTag(key, value);
			return this;
		}

		/// <summary>
		/// Records the operation as successful
		/// </summary>
		public void RecordSuccess()
		{
			if (!_disposed)
			{
				_stopwatch.Stop();
				_metrics.RecordOperation(_operationType, _stopwatch.Elapsed, true, _tags);
				_activity?.SetStatus(ActivityStatusCode.Ok);
				_disposed = true;
			}
		}

		/// <summary>
		/// Records the operation as failed
		/// </summary>
		public void RecordError(Exception? exception = null)
		{
			if (!_disposed)
			{
				_stopwatch.Stop();
				_metrics.RecordOperation(_operationType, _stopwatch.Elapsed, false, _tags);
				
				if (exception != null)
				{
					_activity?.SetStatus(ActivityStatusCode.Error, exception.Message);
					_metrics.RecordError(_operationType, exception, _tags);
				}
				else
				{
					_activity?.SetStatus(ActivityStatusCode.Error);
				}
				
				_disposed = true;
			}
		}

		public void Dispose()
		{
			if (!_disposed)
			{
				// If not explicitly marked as success or error, assume success
				RecordSuccess();
			}
			
			_activity?.Dispose();
		}
	}

	/// <summary>
	/// Current performance metrics snapshot
	/// </summary>
	public class PerformanceMetrics
	{
		public DateTime Timestamp { get; set; }
		public long ActiveConnections { get; set; }
		public long TotalOperations { get; set; }
		public long TotalErrors { get; set; }
		public double CacheHitRatio { get; set; }
		public double AverageOperationDuration { get; set; }
		public long MemoryUsage { get; set; }
		public bool IsHealthy { get; set; }
	}
}