using Disco.Data.Repository;
using Disco.Models.Repository;
using Disco.Plugins.ADCompare.Models;
using Disco.Services.Interop.ActiveDirectory;
using System;
using System.Collections.Generic;
using System.Linq;

namespace Disco.Plugins.ADCompare.Features
{
    public class DeviceCompareService
    {
        private readonly DiscoDataContext database;

        public DeviceCompareService(DiscoDataContext database)
        {
            this.database = database;
        }

        public DeviceComparisonSummary CompareAllDevices()
        {
            var summary = new DeviceComparisonSummary();

            var devices = database.Devices
                .Include("AssignedUser")
                .Where(d => d.DeviceDomainId != null && d.DecommissionedDate == null)
                .ToList();

            // Only process devices with a valid DOMAIN\ComputerName format
            var validDevices = devices.Where(d => d.DeviceDomainId.Contains("\\")).ToList();
            summary.TotalDevices = validDevices.Count;
            summary.SkippedDevices = devices.Count - validDevices.Count;

            foreach (var device in validDevices)
            {
                var result = CompareDevice(device);

                // Skip devices not found in AD - only keep ones we can actually compare
                if (!result.FoundInAD)
                {
                    summary.DevicesNotInAD++;
                    continue;
                }

                summary.Results.Add(result);
            }

            summary.DevicesWithAssignment = summary.Results.Count(r => r.HasAssignment);
            summary.DevicesMatched = summary.Results.Count(r => r.IsMatch);
            summary.DevicesMismatched = summary.Results.Count(r => !r.IsMatch);
            summary.DevicesNoAssignment = summary.Results.Count(r => !r.HasAssignment);
            summary.DevicesNoManagedBy = summary.Results.Count(r => !r.HasManagedBy);
            summary.DevicesADDisabled = summary.Results.Count(r => r.ADAccountDisabled);

            return summary;
        }

        public DeviceComparisonResult CompareDevice(Device device)
        {
            var result = new DeviceComparisonResult();
            result.SerialNumber = device.SerialNumber;
            result.DeviceDomainId = device.DeviceDomainId;
            result.ComputerName = device.ComputerName;
            result.DiscoAssignedUserId = device.AssignedUserId;
            result.DiscoAssignedUserDisplayName = device.AssignedUser != null ? device.AssignedUser.DisplayName : null;
            result.HasAssignment = !string.IsNullOrEmpty(device.AssignedUserId);

            try
            {
                var adAccount = ActiveDirectory.RetrieveADMachineAccount(device.DeviceDomainId, new[] { "managedBy" });

                if (adAccount == null)
                {
                    result.FoundInAD = false;
                    result.MismatchReason = "Computer not found in AD";
                    return result;
                }

                result.FoundInAD = true;
                result.ADAccountDisabled = adAccount.IsDisabled;

                var managedByDN = adAccount.GetPropertyValue<string>("managedBy");
                result.ADManagedByDN = managedByDN;
                result.HasManagedBy = !string.IsNullOrEmpty(managedByDN);

                if (result.HasManagedBy)
                {
                    result.ADManagedByDisplayName = ExtractCNFromDN(managedByDN);
                }

                string assignedUserDN = null;
                if (result.HasAssignment)
                {
                    try
                    {
                        var assignedUserAD = ActiveDirectory.RetrieveADUserAccount(device.AssignedUserId);
                        if (assignedUserAD != null)
                        {
                            assignedUserDN = assignedUserAD.DistinguishedName;
                            result.ADManagedByUserId = device.AssignedUserId;
                        }
                    }
                    catch { }
                }

                if (!result.HasAssignment && !result.HasManagedBy)
                {
                    result.IsMatch = true;
                }
                else if (result.HasAssignment && result.HasManagedBy && assignedUserDN != null)
                {
                    result.IsMatch = string.Equals(assignedUserDN, managedByDN, StringComparison.OrdinalIgnoreCase);
                    if (result.IsMatch)
                    {
                        result.ADManagedByUserId = device.AssignedUserId;
                    }
                }
                else
                {
                    result.IsMatch = false;
                }

                if (!result.IsMatch)
                {
                    result.MismatchReason = DetermineMismatchReason(result, assignedUserDN);
                }
            }
            catch (Exception ex)
            {
                result.FoundInAD = false;
                result.MismatchReason = "AD lookup error: " + ex.Message;
            }

            return result;
        }

        private string DetermineMismatchReason(DeviceComparisonResult result, string assignedUserDN)
        {
            if (!result.FoundInAD)
                return "Computer not found in AD";

            if (result.HasAssignment && !result.HasManagedBy)
                return "Assigned in Disco but AD managedBy is empty";

            if (!result.HasAssignment && result.HasManagedBy)
                return string.Format("Not assigned in Disco but AD managedBy is set to {0}",
                    ExtractCNFromDN(result.ADManagedByDN));

            if (result.HasAssignment && result.HasManagedBy)
            {
                var managedByName = ExtractCNFromDN(result.ADManagedByDN);
                return string.Format("Different users: Disco={0} ({1}), AD managedBy={2}",
                    result.DiscoAssignedUserId,
                    result.DiscoAssignedUserDisplayName ?? "?",
                    managedByName);
            }

            return "Unknown mismatch";
        }

        private string ExtractCNFromDN(string dn)
        {
            if (string.IsNullOrEmpty(dn))
                return null;

            if (dn.StartsWith("CN=", StringComparison.OrdinalIgnoreCase))
            {
                var commaIndex = dn.IndexOf(',');
                if (commaIndex > 3)
                    return dn.Substring(3, commaIndex - 3);
                return dn.Substring(3);
            }

            return dn;
        }
    }
}