using System.Data.SQLite;
using System;
using System.Threading;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace AIK.DataAccess
{
    public static class SQLiteCore
    {
        private static  string _databasePath;
        private static bool _isInitialized = false;
        private static readonly object _initLock = new object();
        // 连接池（线程安全队列），最大连接数控制为 5（SQLite 推荐）
        private static readonly ConcurrentQueue<SQLiteConnection> _connectionPool = new ConcurrentQueue<SQLiteConnection>();
        private const int MaxConnections = 5;
        private static int _activeConnections = 0;
        /// <summary>
        /// 初始化 SQLitePCL 和数据库路径
        /// </summary>
        private static void Initialize()
        {
            lock (_initLock)
            {
                if (!_isInitialized)
                {
                    InitializeDatabasePath();
                    _isInitialized = true;
                }
            }
        }

        /// <summary>
        /// 获取池化连接（返回包装类，支持 using 自动归还）
        /// </summary>
        public static SqlitePooledConnection GetConnection()
        {
            Initialize();

            // 尝试从池子里取空闲连接
            if (_connectionPool.TryDequeue(out var connection) && connection.State == System.Data.ConnectionState.Open)
            {
                Interlocked.Decrement(ref _activeConnections);
                return new SqlitePooledConnection(connection); // 用包装类包裹
            }

            // 池子里没有空闲连接，创建新连接
            if (Interlocked.Increment(ref _activeConnections) > MaxConnections)
            {
                Interlocked.Decrement(ref _activeConnections);
                throw new InvalidOperationException("SQLite 连接池已达最大连接数，建议优化事务执行速度或调整 MaxConnections");
            }

            var newConn = new SQLiteConnection($"Data Source={_databasePath}");
            newConn.Open();
            using (var cmd = newConn.CreateCommand())
            {
                cmd.CommandText = @"
                PRAGMA journal_mode = WAL;
                PRAGMA synchronous = NORMAL;
                PRAGMA foreign_keys = ON;
                PRAGMA busy_timeout = 3000;
            ";
                cmd.ExecuteNonQuery();
            }

            return new SqlitePooledConnection(newConn); // 用包装类包裹
        }

        
        /// <summary>
        /// 将连接归还到连接池（避免重复创建）
        /// </summary>
        public static void ReturnConnection(SQLiteConnection connection)
        {
            try
            {
                if (connection == null || connection.State != System.Data.ConnectionState.Open)
                {
                    connection?.Dispose();
                    Interlocked.Decrement(ref _activeConnections);
                    return;
                }

                // 归还到池子里（供下次复用）
                _connectionPool.Enqueue(connection);
                Interlocked.Decrement(ref _activeConnections);
            }
            catch (Exception)
            {

            }
            
        }

        /// <summary>
        /// 释放所有连接（程序退出时调用）
        /// </summary>
        public static void DisposePool()
        {
            while (_connectionPool.TryDequeue(out var connection))
            {
                connection.Dispose();
            }
            _activeConnections = 0;
        }
        #region 单例模式
        /// <summary>
        /// 创建配置好的数据库连接
        /// </summary>
        //public static SQLiteConnection CreateConnection()
        //{
        //    InitializeSQLitePCL();
        //    // 数据库文件路径
        //    _databasePath = DatabasePath;

        //    // 确保目录存在
        //    Directory.CreateDirectory(Path.GetDirectoryName(_databasePath));
        //    var connection = new SQLiteConnection($"Data Source={_databasePath}");
        //    connection.Open();

        //    // 基本优化设置
        //    using (var cmd = connection.CreateCommand())
        //    {
        //        cmd.CommandText = @"
        //        PRAGMA journal_mode = WAL;
        //        PRAGMA synchronous = NORMAL;
        //        PRAGMA foreign_keys = ON;
        //    ";
        //        cmd.ExecuteNonQuery();
        //    }

        //    return connection;
        //}
        //private static void InitializeSQLitePCL()
        //{
        //    lock (_initLock)
        //    {
        //        if (!_isInitialized)
        //        {
        //            try
        //            {
        //                _isInitialized = true;
        //                Console.WriteLine("SQLitePCL initialized successfully.");
        //            }
        //            catch (Exception ex)
        //            {
        //                Console.WriteLine($"SQLitePCL initialization failed: {ex.Message}");
        //                throw;
        //            }
        //        }
        //    }
        //}
        #endregion
        private static void InitializeDatabasePath()
        {
            #region(旧版本路径，未区分国内外版本)
            //_databasePath = Path.Combine(
            //    Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData),
            //    "AIKKey", "Cache", "aikcache.db");
            #endregion
            // 1. 获取 AppData 基础路径
            string appDataPath = Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData);

            // 2. 定义公司和应用的基础目录名
            string companyName = "AIKKey";
            string baseFolderName = "Cache";
            string databaseFileName = "aikcache.db";
            string versionFolderName;
#if CN
    versionFolderName = "CN"; // 国内版使用 "CN" 子目录
#elif TEST
    versionFolderName = "TEST"; 
#else
            versionFolderName = "Global"; // 国外版使用 "Global" 子目录
#endif
            _databasePath = Path.Combine(appDataPath, companyName, baseFolderName, versionFolderName, databaseFileName);
            // 确保目录存在
            Directory.CreateDirectory(Path.GetDirectoryName(_databasePath));
        }
        public static string DatabasePath
        {
            get
            {
                InitializeDatabasePath();
                return _databasePath;
            }
        }
    }
}