using System;
using System.Data;
using System.IO;
using System.Security.Cryptography;
using System.Text;

namespace Aging.Infrastructure.Broker
{
    /// <summary>
    /// 从 DeviceConfig 的 data.db 计算不可变配置快照哈希（INV-04 对账基准）。
    /// 拼接规则与 Plugin.DeviceConfig.Model.DeviceConfigModel.ComputeConfigHash 保持一致：
    /// DEVICE / CHANNEL / SLOT 三段按各自排序拼接后 SHA256（小写十六进制）。
    /// OwnerProcessId 属运行期信息，不参与哈希。
    /// </summary>
    public static class DeviceConfigHash
    {
        public static string Compute(string dataDbPath)
        {
            if (!File.Exists(dataDbPath))
                throw new FileNotFoundException("配置库不存在", dataDbPath);

            var sb = new StringBuilder();
            using (var conn = new System.Data.SQLite.SQLiteConnection(
                       $"Data Source={dataDbPath};Version=3;Read Only=True;"))
            {
                conn.Open();
                AppendRows(conn, "DeviceDefinition", "SELECT * FROM DeviceDefinition ORDER BY DeviceId;", sb, row =>
                {
                    string em = Col(row, "ExecutionMode") ?? "Local";
                    string auth = Col(row, "AuthorityId") ?? "";
                    string bk = Col(row, "BrokerId") ?? "";
                    string sk = Col(row, "PhysicalSessionKey") ?? "";
                    return $"DEVICE:{row["DeviceId"]}|{row["Kind"]}|{row["DriverType"]}|{row["Transport"]}|{row["Endpoint"]}|{em}|{auth}|{bk}|{sk};";
                });
                AppendRows(conn, "DeviceChannel", "SELECT * FROM DeviceChannel ORDER BY DeviceId, ChannelId;", sb, row =>
                    $"CHANNEL:{row["DeviceId"]}|{row["ChannelId"]}|{row["Capability"]}|{row["MaxVoltage"]}|{row["MaxCurrent"]};");
                AppendRows(conn, "SlotDeviceMapping", "SELECT * FROM SlotDeviceMapping ORDER BY SlotId, Capability, Version;", sb, row =>
                    $"SLOT:{row["SlotId"]}|{row["Capability"]}|{row["Version"]}|{row["DeviceId"]}|{row["ChannelId"]};");
            }

            using (var sha = SHA256.Create())
            {
                var hash = sha.ComputeHash(Encoding.UTF8.GetBytes(sb.ToString()));
                return BitConverter.ToString(hash).Replace("-", "").ToLowerInvariant();
            }
        }

        private static void AppendRows(System.Data.SQLite.SQLiteConnection conn, string table, string sql, StringBuilder sb, Func<DataRow, string> fmt)
        {
            // 表缺失时跳过空段：哈希对“不存在的数据”与“零行”结果一致，两侧同函数保证可对账
            using (var probe = conn.CreateCommand())
            {
                probe.CommandText = "SELECT COUNT(*) FROM sqlite_master WHERE type='table' AND name=@t;";
                probe.Parameters.AddWithValue("@t", table);
                var has = Convert.ToInt64(probe.ExecuteScalar()) > 0;
                if (!has) return;
            }
            using (var cmd = conn.CreateCommand())
            {
                cmd.CommandText = sql;
                using (var rd = cmd.ExecuteReader())
                {
                    var dt = new DataTable();
                    dt.Load(rd);
                    foreach (DataRow row in dt.Rows)
                        sb.Append(fmt(row));
                }
            }
        }

        private static string? Col(DataRow row, string name)
        {
            if (row.Table.Columns.Contains(name) && row[name] != DBNull.Value)
                return row[name].ToString();
            return null;
        }
    }
}