using System;
using System.Collections.Generic;
using System.Linq;

namespace HanvonF710XAttendanceService
{
    /// <summary>
    /// Pure planning logic for DB_TO_DEVICE jobs (testable without device/DB I/O).
    /// </summary>
    internal static class DbToDevicePlanning
    {
        public const int TemplateLoadBatchSize = 50;

        public static bool ShouldIgnoreSourceDevice(TemplateTransferMode mode)
        {
            return mode == TemplateTransferMode.DB_TO_DEVICE;
        }

        public static List<string> NormalizeEmployeeIds(IEnumerable<string> employeeIds)
        {
            if (employeeIds == null)
            {
                return new List<string>();
            }

            return employeeIds
                .Where(id => !string.IsNullOrWhiteSpace(id))
                .Select(id => id.Trim())
                .Distinct(StringComparer.OrdinalIgnoreCase)
                .ToList();
        }

        /// <summary>
        /// Resolves which employee serial numbers should be synced from HRMS DB to target devices.
        /// </summary>
        public static List<string> ResolveEmployeeIds(
            TemplateTransferJob job,
            Func<IReadOnlyList<string>, List<string>> loadByDepartmentIds,
            Func<List<string>> loadRegisteredOnTargets)
        {
            if (job == null)
            {
                return new List<string>();
            }

            if (job.EmpIds != null && job.EmpIds.Count > 0)
            {
                return NormalizeEmployeeIds(job.EmpIds);
            }

            if (job.DepartmentIds != null && job.DepartmentIds.Count > 0)
            {
                if (loadByDepartmentIds != null)
                {
                    var fromDepartments = loadByDepartmentIds(job.DepartmentIds);
                    if (fromDepartments != null && fromDepartments.Count > 0)
                    {
                        return NormalizeEmployeeIds(fromDepartments);
                    }
                }
            }

            return NormalizeEmployeeIds(loadRegisteredOnTargets != null ? loadRegisteredOnTargets() : null);
        }

        public static int ComputeTemplateLoadBatchCount(int employeeCount)
        {
            if (employeeCount <= 0)
            {
                return 0;
            }

            return (employeeCount + TemplateLoadBatchSize - 1) / TemplateLoadBatchSize;
        }

        public static int ComputeLastTemplateLoadBatchSize(int employeeCount)
        {
            if (employeeCount <= 0)
            {
                return 0;
            }

            int remainder = employeeCount % TemplateLoadBatchSize;
            return remainder == 0 ? TemplateLoadBatchSize : remainder;
        }
    }
}