using MySql.Data.MySqlClient;
using System;

namespace HanvonF710XAttendanceService
{
    /// <summary>
    /// HRMS employee row used for Hanvon display name and portal photo URL.
    /// Device enroll/serial must NOT be treated as employee.id.
    /// </summary>
    internal sealed class HrmsEmployeeInfo
    {
        public HrmsEmployeeInfo(string employeeId, string serialNumberInt, string concatenatedName, string department = "")
        {
            EmployeeId = employeeId ?? "";
            SerialNumberInt = serialNumberInt ?? "";
            ConcatenatedName = concatenatedName ?? "";
            Department = department ?? "";
        }

        /// <summary>employee.id — used for portal photo URL only.</summary>
        public string EmployeeId { get; }

        /// <summary>employee.serial_number_int — matches device / attendance_machine_user.serial_number.</summary>
        public string SerialNumberInt { get; }

        /// <summary>employee.concatenated_name — Hanvon user display name.</summary>
        public string ConcatenatedName { get; }

        /// <summary>Department display name when available; otherwise department_id.</summary>
        public string Department { get; }
    }

    internal sealed class HrmsEmployeeDAO
    {
        /// <summary>
        /// Match device serial (attendance_machine_user.serial_number) to employee.serial_number_int.
        /// </summary>
        public bool TryGetByDeviceSerial(MySqlConnection connection, string deviceSerial, out HrmsEmployeeInfo employee)
        {
            employee = null;
            if (connection == null || string.IsNullOrWhiteSpace(deviceSerial))
            {
                return false;
            }

            string serial = deviceSerial.Trim();

            // Prefer department name; fall back to department_id if departments table/join is unavailable.
            const string queryWithDeptName =
                "SELECT e.id, e.serial_number_int, e.concatenated_name, " +
                "COALESCE(NULLIF(TRIM(d.name), ''), CAST(e.department_id AS CHAR), '') AS department " +
                "FROM hrms.employee e " +
                "LEFT JOIN hrms.departments d ON d.id = e.department_id " +
                "WHERE CAST(e.serial_number_int AS CHAR) = @DeviceSerial " +
                "LIMIT 1";

            const string queryBasic =
                "SELECT e.id, e.serial_number_int, e.concatenated_name, " +
                "CAST(e.department_id AS CHAR) AS department " +
                "FROM hrms.employee e " +
                "WHERE CAST(e.serial_number_int AS CHAR) = @DeviceSerial " +
                "LIMIT 1";

            try
            {
                if (TryReadEmployee(connection, queryWithDeptName, serial, out employee))
                {
                    return true;
                }
            }
            catch
            {
                // departments table/column may differ; fall back.
            }

            return TryReadEmployee(connection, queryBasic, serial, out employee);
        }

        private static bool TryReadEmployee(MySqlConnection connection, string query, string serial, out HrmsEmployeeInfo employee)
        {
            employee = null;
            using (var cmd = new MySqlCommand(query, connection))
            {
                cmd.CommandTimeout = 60;
                cmd.Parameters.AddWithValue("@DeviceSerial", serial);
                using (var reader = cmd.ExecuteReader())
                {
                    if (!reader.Read())
                    {
                        return false;
                    }

                    string id = reader.IsDBNull(0) ? "" : Convert.ToString(reader.GetValue(0))?.Trim();
                    string serialInt = reader.IsDBNull(1) ? "" : Convert.ToString(reader.GetValue(1))?.Trim();
                    string name = reader.IsDBNull(2) ? "" : Convert.ToString(reader.GetValue(2))?.Trim();
                    string department = reader.FieldCount > 3 && !reader.IsDBNull(3)
                        ? Convert.ToString(reader.GetValue(3))?.Trim()
                        : "";

                    if (string.IsNullOrWhiteSpace(id))
                    {
                        return false;
                    }

                    employee = new HrmsEmployeeInfo(id, serialInt, name, department);
                    return true;
                }
            }
        }

        public string ResolveDisplayName(
            MySqlConnection connection,
            string deviceSerial,
            string fallbackName = null)
        {
            if (TryGetByDeviceSerial(connection, deviceSerial, out HrmsEmployeeInfo employee)
                && !string.IsNullOrWhiteSpace(employee.ConcatenatedName))
            {
                return employee.ConcatenatedName;
            }

            if (!string.IsNullOrWhiteSpace(fallbackName))
            {
                return fallbackName.Trim();
            }

            return string.IsNullOrWhiteSpace(deviceSerial) ? "" : deviceSerial.Trim();
        }
    }
}