using System;
using System.Diagnostics;
using Teigha.Runtime;

namespace DwgExtractorManual.Models
{
    /// <summary>
    /// Singleton class to manage Teigha Services lifecycle and prevent disposal conflicts
    /// </summary>
    public sealed class TeighaServicesManager
    {
        private static readonly object _lock = new object();
        private static TeighaServicesManager? _instance = null;
        private static Services? _services = null;
        private static int _referenceCount = 0;
        private static bool _isActivated = false;

        private TeighaServicesManager()
        {
            // Private constructor for singleton
        }

        public static TeighaServicesManager Instance
        {
            get
            {
                if (_instance == null)
                {
                    lock (_lock)
                    {
                        if (_instance == null)
                        {
                            _instance = new TeighaServicesManager();
                        }
                    }
                }
                return _instance;
            }
        }

        /// <summary>
        /// Acquires Teigha Services (creates if needed, increments reference count)
        /// </summary>
        /// <returns>The Services instance</returns>
        public Services AcquireServices()
        {
            lock (_lock)
            {
                try
                {
                    Debug.WriteLine($"[TeighaManager] AcquireServices - Current ref count: {_referenceCount}");
                    
                    if (!_isActivated)
                    {
                        Debug.WriteLine("[TeighaManager] Activating ODA for first time...");
                        ActivateODA();
                        _isActivated = true;
                    }

                    if (_services == null)
                    {
                        Debug.WriteLine("[TeighaManager] Creating new Services instance...");
                        _services = new Services();
                        Debug.WriteLine("[TeighaManager] Services instance created successfully");
                    }

                    _referenceCount++;
                    Debug.WriteLine($"[TeighaManager] Services acquired - New ref count: {_referenceCount}");
                    return _services;
                }
                catch (Teigha.Runtime.Exception ex)
                {
                    Debug.WriteLine($"[TeighaManager] Error acquiring services: {ex.Message}");
                    throw;
                }
            }
        }

        /// <summary>
        /// Releases Teigha Services (decrements reference count, disposes when count reaches 0)
        /// </summary>
        public void ReleaseServices()
        {
            lock (_lock)
            {
                try
                {
                    Debug.WriteLine($"[TeighaManager] ReleaseServices - Current ref count: {_referenceCount}");
                    
                    if (_referenceCount > 0)
                    {
                        _referenceCount--;
                        Debug.WriteLine($"[TeighaManager] Services released - New ref count: {_referenceCount}");
                    }

                    // Don't dispose Services until app shutdown to prevent conflicts
                    // Just track reference count for debugging
                    if (_referenceCount == 0)
                    {
                        Debug.WriteLine("[TeighaManager] All references released (Services kept alive for app lifetime)");
                    }
                }
                catch (Teigha.Runtime.Exception ex)
                {
                    Debug.WriteLine($"[TeighaManager] Error releasing services: {ex.Message}");
                    // Don't throw on release to prevent cascade failures
                }
            }
        }

        /// <summary>
        /// Force dispose Services (only call on application shutdown)
        /// </summary>
        public void ForceDisposeServices()
        {
            lock (_lock)
            {
                try
                {
                    Debug.WriteLine("[TeighaManager] Force disposing Services...");
                    
                    if (_services != null)
                    {
                        _services.Dispose();
                        Debug.WriteLine("[TeighaManager] Services disposed successfully");
                    }
                    
                    _services = null;
                    _referenceCount = 0;
                    _isActivated = false;
                    
                    Debug.WriteLine("[TeighaManager] Force dispose completed");
                }
                catch (Teigha.Runtime.Exception ex)
                {
                    Debug.WriteLine($"[TeighaManager] Error during force dispose: {ex.Message}");
                    // Reset state even if disposal fails
                    _services = null;
                    _referenceCount = 0;
                    _isActivated = false;
                }
            }
        }

        /// <summary>
        /// Get current reference count (for debugging)
        /// </summary>
        public int ReferenceCount
        {
            get
            {
                lock (_lock)
                {
                    return _referenceCount;
                }
            }
        }

        /// <summary>
        /// Check if Services is active and valid
        /// </summary>
        public bool IsServicesActive
        {
            get
            {
                lock (_lock)
                {
                    return _services != null && _isActivated;
                }
            }
        }

        private void ActivateODA()
        {
            try
            {
                Debug.WriteLine("[TeighaManager] Activating ODA...");
                
                var userInfo = "c2FtYW4gZW5naW5lZXJpbmc=";
                var userSignature = "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";
                
                Services.odActivate(userInfo, userSignature);
                Debug.WriteLine("[TeighaManager] ODA activation successful");
            }
            catch (Teigha.Runtime.Exception ex)
            {
                Debug.WriteLine($"[TeighaManager] ODA activation failed: {ex.Message}");
                throw;
            }
        }
    }
}