using System;
using System.Collections.Generic;
using System.Data.SQLite;
using System.IO;

namespace DeviceService.Driver
{
    /// <summary>
    /// 驱动信息 SQLite 持久化：数据库文件位于 应用根目录\Config\Drivers.db。
    ///
    /// 表结构：
    /// - DriverPackage：已加载的驱动包（Driver 根目录下的一个子文件夹）
    /// - DriverType：驱动包内带 [DriverDesc] 注解的驱动类型（(类型, 品牌) 定位）
    ///
    /// 所有操作失败仅通过 log 上报，不会中断驱动加载流程。
    /// </summary>
    public sealed class DriverDatabase
    {
        private static readonly object _staticSync = new object();
        private static DriverDatabase _instance;

        public static DriverDatabase Instance
        {
            get
            {
                lock (_staticSync)
                {
                    return _instance ??= new DriverDatabase();
                }
            }
        }

        /// <summary>配置目录：应用根目录\Config。</summary>
        public static string ConfigDirectory =>
            Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "Config");

        /// <summary>数据库文件路径。</summary>
        public static string DatabasePath =>
            Path.Combine(ConfigDirectory, "Drivers.db");

        private readonly object _sync = new object();
        private bool _initialized;

        private DriverDatabase()
        {
        }

        /// <summary>确保 Config 目录与库表结构存在。失败返回 false 并通过 log 上报。</summary>
        private bool EnsureReady(Action<string> log)
        {
            if (_initialized)
            {
                return true;
            }

            try
            {
                if (!Directory.Exists(ConfigDirectory))
                {
                    Directory.CreateDirectory(ConfigDirectory);
                }

                using (var conn = Open())
                using (var cmd = conn.CreateCommand())
                {
                    cmd.CommandText = @"
CREATE TABLE IF NOT EXISTS DriverPackage (
    Folder       TEXT PRIMARY KEY,
    Directory    TEXT NOT NULL,
    AssemblyCount INTEGER NOT NULL DEFAULT 0,
    ScanTime     TEXT NOT NULL
);
CREATE TABLE IF NOT EXISTS DriverType (
    Id            INTEGER PRIMARY KEY AUTOINCREMENT,
    PackageFolder TEXT NOT NULL,
    AssemblyFile  TEXT NOT NULL,
    FullName      TEXT NOT NULL,
    DriverType    TEXT,
    Brand         TEXT,
    UNIQUE(PackageFolder, FullName)
);
CREATE INDEX IF NOT EXISTS IX_DriverType_Type_Brand ON DriverType(DriverType, Brand);";
                    cmd.ExecuteNonQuery();
                }

                _initialized = true;
                return true;
            }
            catch (Exception ex)
            {
                log?.Invoke($"[驱动库] 初始化失败（{DatabasePath}）: {ex.Message}");
                return false;
            }
        }

        private SQLiteConnection Open()
        {
            var conn = new SQLiteConnection($"Data Source={DatabasePath};Version=3;");
            conn.Open();
            return conn;
        }

        /// <summary>写入（覆盖）一个驱动包及其内部全部驱动类型的记录。</summary>
        public void SavePackage(DriverPackage package, Action<string> log = null)
        {
            if (package == null)
            {
                return;
            }

            if (!EnsureReady(log))
            {
                return;
            }

            try
            {
                lock (_sync)
                {
                    using (var conn = Open())
                    using (var tx = conn.BeginTransaction())
                    {
                        ExecuteNonQuery(conn, "DELETE FROM DriverType WHERE PackageFolder = @f",
                            tx, ("@f", package.Folder));
                        ExecuteNonQuery(conn, "DELETE FROM DriverPackage WHERE Folder = @f",
                            tx, ("@f", package.Folder));

                        var assemblies = package.Assemblies ?? new DriverAssemblyInfo[0];
                        ExecuteNonQuery(conn,
                            "INSERT INTO DriverPackage(Folder, Directory, AssemblyCount, ScanTime) VALUES(@f, @d, @c, @t)",
                            tx,
                            ("@f", package.Folder),
                            ("@d", package.Directory ?? string.Empty),
                            ("@c", assemblies.Length.ToString()),
                            ("@t", DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss")));

                        int typeCount = 0;
                        foreach (var asm in assemblies)
                        {
                            foreach (var type in asm.Types ?? new DriverTypeInfo[0])
                            {
                                ExecuteNonQuery(conn,
                                    @"INSERT OR REPLACE INTO DriverType(PackageFolder, AssemblyFile, FullName, DriverType, Brand)
                                      VALUES(@p, @a, @n, @t, @b)",
                                    tx,
                                    ("@p", package.Folder),
                                    ("@a", asm.FileName ?? string.Empty),
                                    ("@n", type.FullName ?? string.Empty),
                                    ("@t", type.DriverType ?? string.Empty),
                                    ("@b", type.Brand ?? string.Empty));
                                typeCount++;
                            }
                        }

                        tx.Commit();
                        log?.Invoke($"[驱动库] 已保存 {package.Folder}（{assemblies.Length} 个 dll，{typeCount} 个驱动类型）");
                    }
                }
            }
            catch (Exception ex)
            {
                log?.Invoke($"[驱动库] 保存 {package.Folder} 失败: {ex.Message}");
            }
        }

        /// <summary>删除一个驱动包（及其全部驱动类型）的记录。</summary>
        public void RemovePackage(string folder, Action<string> log = null)
        {
            if (string.IsNullOrEmpty(folder) || !EnsureReady(log))
            {
                return;
            }

            try
            {
                lock (_sync)
                {
                    using (var conn = Open())
                    using (var tx = conn.BeginTransaction())
                    {
                        ExecuteNonQuery(conn, "DELETE FROM DriverType WHERE PackageFolder = @f", tx, ("@f", folder));
                        ExecuteNonQuery(conn, "DELETE FROM DriverPackage WHERE Folder = @f", tx, ("@f", folder));
                        tx.Commit();
                    }
                }

                log?.Invoke($"[驱动库] 已移除 {folder} 的记录");
            }
            catch (Exception ex)
            {
                log?.Invoke($"[驱动库] 移除 {folder} 失败: {ex.Message}");
            }
        }

        /// <summary>读取库中全部驱动类型记录（供界面/查询使用）。</summary>
        public IReadOnlyList<DriverTypeInfo> LoadDriverTypes(Action<string> log = null)
        {
            var result = new List<DriverTypeInfo>();
            if (!EnsureReady(log))
            {
                return result;
            }

            try
            {
                lock (_sync)
                {
                    using (var conn = Open())
                    using (var cmd = conn.CreateCommand())
                    {
                        cmd.CommandText = "SELECT PackageFolder, AssemblyFile, FullName, DriverType, Brand FROM DriverType ORDER BY DriverType, Brand, FullName";
                        using (var reader = cmd.ExecuteReader())
                        {
                            while (reader.Read())
                            {
                                result.Add(new DriverTypeInfo
                                {
                                    FullName = GetString(reader, "FullName"),
                                    DriverType = GetString(reader, "DriverType"),
                                    Brand = GetString(reader, "Brand")
                                });
                            }
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                log?.Invoke($"[驱动库] 读取驱动类型失败: {ex.Message}");
            }

            return result;
        }

        private static void ExecuteNonQuery(SQLiteConnection conn, string sql, SQLiteTransaction tx,
            params (string Name, string Value)[] parameters)
        {
            using (var cmd = conn.CreateCommand())
            {
                cmd.Transaction = tx;
                cmd.CommandText = sql;
                foreach (var (name, value) in parameters)
                {
                    cmd.Parameters.AddWithValue(name, value);
                }

                cmd.ExecuteNonQuery();
            }
        }

        private static string GetString(SQLiteDataReader reader, string column)
        {
            var value = reader[column];
            return value == DBNull.Value ? string.Empty : value.ToString();
        }
    }
}