using Microsoft.Extensions.Configuration;
using System.IO;
using System.Net.Http;
using System.Text;
using System.Text.Json;
using System.Text.Json.Serialization;
using System.Web;
using Prism.Events;
using YY.Admin.Core;
using YY.Admin.Core.Entity;
using YY.Admin.Core.Events;
using YY.Admin.Core.Services;

namespace YY.Admin.Services.Service.Customer;

public class CustomerService : ICustomerService, ISingletonDependency
{
    private readonly IHttpClientFactory _httpClientFactory;
    private readonly IConfiguration _configuration;
    private readonly INetworkMonitor _networkMonitor;
    private readonly IEventAggregator _eventAggregator;
    private readonly ILoggerService _logger;
    private readonly SemaphoreSlim _syncLock = new(1, 1);
    private readonly object _cacheLock = new();
    private readonly string _pendingOpsFilePath;
    private readonly string _cacheFilePath;
    private List<CustomerPendingOperation> _pendingOps = new();
    private List<MesXslCustomer> _localCache = new();

    private static readonly JsonSerializerOptions _jsonOpts = new()
    {
        PropertyNameCaseInsensitive = true,
        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
        Converters = { new NullableDateTimeJsonConverter() }
    };

    public CustomerService(
        IHttpClientFactory httpClientFactory,
        IConfiguration configuration,
        INetworkMonitor networkMonitor,
        IEventAggregator eventAggregator,
        ILoggerService logger)
    {
        _httpClientFactory = httpClientFactory;
        _configuration = configuration;
        _networkMonitor = networkMonitor;
        _eventAggregator = eventAggregator;
        _logger = logger;

        var appDataDir = Path.Combine(
            Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData),
            "YY.Admin", "sync-cache");
        Directory.CreateDirectory(appDataDir);
        _pendingOpsFilePath = Path.Combine(appDataDir, "mes-xsl-customer-pending-ops.json");
        _cacheFilePath = Path.Combine(appDataDir, "mes-xsl-customer-cache.json");

        LoadPendingOpsFromDisk();
        LoadCacheFromDisk();
        _logger.Information($"[客户同步] 服务初始化，缓存={_localCache.Count}，待上传={_pendingOps.Count}，在线={_networkMonitor.IsOnline}");

        _networkMonitor.StatusChanged += OnNetworkStatusChanged;
        if (_networkMonitor.IsOnline)
            _ = Task.Run(() => SyncAfterReconnectAsync(CancellationToken.None));
    }

    private const int MaxPendingRetries = 5;

    private string BaseUrl => (_configuration.GetValue<string>("JeecgIntegration:BaseUrl") ?? "http://localhost:8080/jeecg-boot").TrimEnd('/');
    private int DefaultTenantId => (int?)_configuration.GetValue<long?>("JeecgIntegration:DefaultTenantId") ?? 1002;

    private HttpClient CreateClient() => _httpClientFactory.CreateClient("JeecgApi");

    // ── 分页 ──────────────────────────────────────────────────────────────

    public async Task<CustomerPageResult> PageAsync(int pageNo, int pageSize,
        string? customerCode = null, string? customerName = null,
        string? status = null, string? customerRegion = null,
        CancellationToken ct = default)
    {
        List<MesXslCustomer>? source = null;
        if (_networkMonitor.IsOnline)
        {
            try
            {
                source = await FetchRemoteListAsync(ct).ConfigureAwait(false);
                lock (_cacheLock)
                {
                    _localCache = source.Select(Clone).ToList();
                    SaveCacheToDiskUnsafe();
                }
                _logger.Information($"[客户列表] 远端拉取成功 count={source.Count}");
            }
            catch (Exception ex)
            {
                source = null;
                _logger.Warning($"[客户列表] 远端拉取失败，回退缓存：{ex.Message}");
            }
        }

        lock (_cacheLock)
        {
            source ??= _localCache.Select(Clone).ToList();
            source = ApplyPendingOpsSnapshotUnsafe(source);
        }

        var filtered = ApplyFilters(source, customerCode, customerName, status, customerRegion);
        var total = filtered.Count;
        var records = filtered.Skip(Math.Max(0, (pageNo - 1) * pageSize)).Take(pageSize).ToList();
        return new CustomerPageResult(records, total, pageNo, pageSize);
    }

    // ── 详情 ──────────────────────────────────────────────────────────────

    public async Task<MesXslCustomer?> GetByIdAsync(string id, CancellationToken ct = default)
    {
        if (_networkMonitor.IsOnline)
        {
            try
            {
                var url = $"{BaseUrl}/xslmes/mesXslCustomer/anon/queryById?id={Uri.EscapeDataString(id)}&tenantId={DefaultTenantId}";
                using var client = CreateClient();
                var resp = await client.GetAsync(url, ct).ConfigureAwait(false);
                if (!resp.IsSuccessStatusCode) return null;
                var json = await resp.Content.ReadAsStringAsync(ct).ConfigureAwait(false);
                using var doc = JsonDocument.Parse(json);
                if (!doc.RootElement.TryGetProperty("result", out var resultEl)) return null;
                return resultEl.Deserialize<MesXslCustomer>(_jsonOpts);
            }
            catch (Exception ex)
            {
                _logger.Warning($"[客户详情] 远端查询失败 id={id}，回退缓存：{ex.Message}");
            }
        }
        lock (_cacheLock)
        {
            return _localCache.FirstOrDefault(c => string.Equals(c.Id, id, StringComparison.OrdinalIgnoreCase)) is { } found
                ? Clone(found) : null;
        }
    }

    // ── 新增 ──────────────────────────────────────────────────────────────

    public async Task<bool> AddAsync(MesXslCustomer customer, CancellationToken ct = default)
    {
        if (!customer.TenantId.HasValue || customer.TenantId.Value <= 0)
            customer.TenantId = DefaultTenantId;

        var local = Clone(customer);
        if (string.IsNullOrWhiteSpace(local.Id))
            local.Id = $"local-{Guid.NewGuid():N}";
        if (string.IsNullOrWhiteSpace(local.Status))
            local.Status = "0";
        SyncIzEnable(local);

        if (_networkMonitor.IsOnline)
        {
            try
            {
                var ok = await RemoteAddAsync(local, ct).ConfigureAwait(false);
                if (ok) { UpsertLocalCache(local); return true; }
                return false;
            }
            catch (Exception ex)
            {
                _logger.Warning($"[客户新增] 远端失败，转离线入队：{ex.Message}");
            }
        }

        EnqueuePendingOperation(new CustomerPendingOperation
            { OpType = CustomerOperationType.Add, CustomerId = local.Id, Customer = local });
        UpsertLocalCache(local);
        return true;
    }

    // ── 编辑 ──────────────────────────────────────────────────────────────

    public async Task<bool> EditAsync(MesXslCustomer customer, CancellationToken ct = default)
    {
        if (!customer.TenantId.HasValue || customer.TenantId.Value <= 0)
            customer.TenantId = DefaultTenantId;

        var local = Clone(customer);
        SyncIzEnable(local);

        if (_networkMonitor.IsOnline)
        {
            try
            {
                var (ok, _) = await RemoteEditAsync(local, ct).ConfigureAwait(false);
                if (ok) { UpsertLocalCache(local); return true; }
                return false;
            }
            catch (Exception ex)
            {
                _logger.Warning($"[客户编辑] 远端失败，转离线入队：{ex.Message}");
            }
        }

        EnqueuePendingOperation(new CustomerPendingOperation
            {
                OpType = CustomerOperationType.Edit,
                CustomerId = local.Id,
                Customer = local,
                AnchorUpdateTime = local.UpdateTime
            });
        UpsertLocalCache(local);
        return true;
    }

    // ── 删除 ──────────────────────────────────────────────────────────────

    public async Task<bool> DeleteAsync(string id, CancellationToken ct = default)
    {
        if (_networkMonitor.IsOnline)
        {
            try
            {
                var ok = await RemoteDeleteAsync(id, ct).ConfigureAwait(false);
                if (ok) { RemoveFromLocalCache(id); return true; }
                return false;
            }
            catch (Exception ex)
            {
                _logger.Warning($"[客户删除] 远端失败，转离线入队：{ex.Message}");
            }
        }

        DateTime? anchor;
        lock (_cacheLock)
        {
            anchor = _localCache.FirstOrDefault(c => string.Equals(c.Id, id, StringComparison.OrdinalIgnoreCase))?.UpdateTime;
        }
        EnqueuePendingOperation(new CustomerPendingOperation
            {
                OpType = CustomerOperationType.Delete,
                CustomerId = id,
                AnchorUpdateTime = anchor
            });
        RemoveFromLocalCache(id);
        return true;
    }

    // ── 状态切换 ──────────────────────────────────────────────────────────

    public async Task<bool> UpdateStatusAsync(string id, string status, CancellationToken ct = default)
    {
        if (_networkMonitor.IsOnline)
        {
            try
            {
                var ok = await RemoteUpdateStatusAsync(id, status, ct).ConfigureAwait(false);
                if (ok) { UpdateLocalStatus(id, status); return true; }
                return false;
            }
            catch (Exception ex)
            {
                _logger.Warning($"[客户状态] 远端失败，转离线入队：{ex.Message}");
            }
        }

        DateTime? anchor;
        lock (_cacheLock)
        {
            anchor = _localCache.FirstOrDefault(c => string.Equals(c.Id, id, StringComparison.OrdinalIgnoreCase))?.UpdateTime;
        }
        EnqueuePendingOperation(new CustomerPendingOperation
            {
                OpType = CustomerOperationType.UpdateStatus,
                CustomerId = id,
                Status = status,
                AnchorUpdateTime = anchor
            });
        UpdateLocalStatus(id, status);
        return true;
    }

    // ── 远端调用 ──────────────────────────────────────────────────────────

    private async Task<List<MesXslCustomer>> FetchRemoteListAsync(CancellationToken ct)
    {
        var query = HttpUtility.ParseQueryString(string.Empty);
        query["pageNo"] = "1";
        query["pageSize"] = "10000";
        query["tenantId"] = DefaultTenantId.ToString();
        var url = $"{BaseUrl}/xslmes/mesXslCustomer/anon/list?{query}";
        using var client = CreateClient();
        var resp = await client.GetAsync(url, ct).ConfigureAwait(false);
        resp.EnsureSuccessStatusCode();
        var json = await resp.Content.ReadAsStringAsync(ct).ConfigureAwait(false);
        using var doc = JsonDocument.Parse(json);
        return doc.RootElement.GetProperty("result").GetProperty("records")
            .Deserialize<List<MesXslCustomer>>(_jsonOpts) ?? new();
    }

    private async Task<bool> RemoteAddAsync(MesXslCustomer customer, CancellationToken ct)
    {
        var url = $"{BaseUrl}/xslmes/mesXslCustomer/anon/add?tenantId={DefaultTenantId}";
        var payload = Clone(customer);
        if (IsLocalTempId(payload.Id)) payload.Id = null;
        return await PostJsonAsync(url, payload, ct).ConfigureAwait(false);
    }

    private async Task<(bool Ok, bool IsVersionConflict)> RemoteEditAsync(MesXslCustomer customer, CancellationToken ct)
    {
        var url = $"{BaseUrl}/xslmes/mesXslCustomer/anon/edit?tenantId={DefaultTenantId}";
        return await PostJsonCheckVersionAsync(url, customer, ct).ConfigureAwait(false);
    }

    private async Task<bool> RemoteDeleteAsync(string id, CancellationToken ct)
    {
        var url = $"{BaseUrl}/xslmes/mesXslCustomer/anon/delete?id={Uri.EscapeDataString(id)}&tenantId={DefaultTenantId}";
        using var client = CreateClient();
        var resp = await client.DeleteAsync(url, ct).ConfigureAwait(false);
        return resp.IsSuccessStatusCode && await IsSuccessResultAsync(resp, ct).ConfigureAwait(false);
    }

    private async Task<bool> RemoteUpdateStatusAsync(string id, string status, CancellationToken ct)
    {
        var url = $"{BaseUrl}/xslmes/mesXslCustomer/anon/updateStatus?id={Uri.EscapeDataString(id)}&status={Uri.EscapeDataString(status)}&tenantId={DefaultTenantId}";
        using var client = CreateClient();
        var resp = await client.PostAsync(url, null, ct).ConfigureAwait(false);
        return resp.IsSuccessStatusCode && await IsSuccessResultAsync(resp, ct).ConfigureAwait(false);
    }

    private async Task<bool> PostJsonAsync(string url, object body, CancellationToken ct)
    {
        var content = new StringContent(JsonSerializer.Serialize(body, _jsonOpts), Encoding.UTF8, "application/json");
        using var client = CreateClient();
        var resp = await client.PostAsync(url, content, ct).ConfigureAwait(false);
        return resp.IsSuccessStatusCode && await IsSuccessResultAsync(resp, ct).ConfigureAwait(false);
    }

    private async Task<(bool Ok, bool IsVersionConflict)> PostJsonCheckVersionAsync(string url, object body, CancellationToken ct)
    {
        var content = new StringContent(JsonSerializer.Serialize(body, _jsonOpts), Encoding.UTF8, "application/json");
        using var client = CreateClient();
        var resp = await client.PostAsync(url, content, ct).ConfigureAwait(false);
        if (!resp.IsSuccessStatusCode) return (false, false);
        try
        {
            var json = await resp.Content.ReadAsStringAsync(ct).ConfigureAwait(false);
            using var doc = JsonDocument.Parse(json);
            int code = 200;
            if (doc.RootElement.TryGetProperty("code", out var codeEl)) code = codeEl.GetInt32();
            if (code == 200) return (true, false);
            if (doc.RootElement.TryGetProperty("message", out var msgEl))
            {
                var msg = msgEl.GetString() ?? "";
                if (msg.Contains("已被他人修改")) return (false, true);
            }
            return (false, false);
        }
        catch { return (true, false); }
    }

    private static async Task<bool> IsSuccessResultAsync(HttpResponseMessage resp, CancellationToken ct)
    {
        try
        {
            var json = await resp.Content.ReadAsStringAsync(ct).ConfigureAwait(false);
            using var doc = JsonDocument.Parse(json);
            if (doc.RootElement.TryGetProperty("code", out var code)) return code.GetInt32() == 200;
            if (doc.RootElement.TryGetProperty("success", out var success)) return success.GetBoolean();
            return true;
        }
        catch { return true; }
    }

    // ── 断线续连 ──────────────────────────────────────────────────────────

    private void OnNetworkStatusChanged(bool isOnline)
    {
        if (!isOnline) return;
        _ = Task.Run(() => SyncAfterReconnectAsync(CancellationToken.None));
    }

    private async Task SyncAfterReconnectAsync(CancellationToken ct)
    {
        var pushResult = await PushPendingOnReconnectAsync(ct).ConfigureAwait(false);
        if (!_networkMonitor.IsOnline) return;
        try
        {
            var remote = await FetchRemoteListAsync(ct).ConfigureAwait(false);
            lock (_cacheLock)
            {
                _localCache = remote.Select(Clone).ToList();
                SaveCacheToDiskUnsafe();
            }
            _eventAggregator.GetEvent<CustomerChangedEvent>()
                .Publish(new CustomerChangedPayload { Action = "pull" });
            _logger.Information($"[客户重连] 全量回拉成功 count={remote.Count}");
        }
        catch (Exception ex)
        {
            _logger.Warning($"[客户重连] 全量回拉失败：{ex.Message}");
        }

        var hasActivity = pushResult.PushedCount > 0
                           || pushResult.ConflictCount > 0
                           || pushResult.NewRecordsPushed > 0;
        if (hasActivity)
        {
            _eventAggregator.GetEvent<SyncConflictEvent>()
                .Publish(new SyncConflictPayload
                {
                    EntityName = "客户",
                    PushedCount = pushResult.PushedCount,
                    ConflictCount = pushResult.ConflictCount,
                    NewRecordsPushed = pushResult.NewRecordsPushed
                });
        }
    }

    private async Task<PushPendingResult> PushPendingOnReconnectAsync(CancellationToken ct)
    {
        if (!await _syncLock.WaitAsync(0, ct).ConfigureAwait(false))
            return new PushPendingResult(0, 0, 0);
        try
        {
            List<CustomerPendingOperation> snapshot;
            lock (_cacheLock) { snapshot = _pendingOps.OrderBy(x => x.CreatedAt).ToList(); }
            _logger.Information($"[客户回放] pending={snapshot.Count}");

            int pushed = 0, conflicts = 0, newPushed = 0;

            foreach (var op in snapshot)
            {
                if (!_networkMonitor.IsOnline) break;

                // 如果该 op 已在上一条冲突处理中被清理，则跳过
                lock (_cacheLock)
                {
                    if (!_pendingOps.Any(x => x.Id == op.Id)) continue;
                }

                var result = await ExecutePendingOpWithConflictAsync(op, ct).ConfigureAwait(false);
                if (!result.Ok)
                {
                    lock (_cacheLock)
                    {
                        op.RetryCount++;
                        if (op.RetryCount >= MaxPendingRetries)
                        {
                            _logger.Warning($"[客户回放] op={op.OpType} 超过最大重试次数({MaxPendingRetries})，放弃 customerId={op.CustomerId}");
                            _pendingOps.RemoveAll(x => x.Id == op.Id);
                            SavePendingOpsToDiskUnsafe();
                            continue;
                        }
                        SavePendingOpsToDiskUnsafe();
                    }
                    break;
                }

                if (result.IsConflict)
                {
                    conflicts++;
                    // 冲突时：以服务器版本为准，直接丢弃同一条记录的所有 pending
                    if (!string.IsNullOrWhiteSpace(result.EntityId))
                        RemovePendingOpsByCustomerId(result.EntityId);
                }
                else if (op.OpType == CustomerOperationType.Add)
                {
                    newPushed++;
                    lock (_cacheLock)
                    {
                        _pendingOps.RemoveAll(x => x.Id == op.Id);
                        SavePendingOpsToDiskUnsafe();
                    }
                }
                else
                {
                    pushed++;
                    lock (_cacheLock)
                    {
                        _pendingOps.RemoveAll(x => x.Id == op.Id);
                        SavePendingOpsToDiskUnsafe();
                    }
                }
            }

            return new PushPendingResult(pushed, conflicts, newPushed);
        }
        finally { _syncLock.Release(); }
    }

    private sealed record PendingReplayResult(bool Ok, bool IsConflict, string? EntityId);

    private async Task<PendingReplayResult> ExecutePendingOpWithConflictAsync(CustomerPendingOperation op, CancellationToken ct)
    {
        try
        {
            return op.OpType switch
            {
                CustomerOperationType.Add => await ExecuteAddAsync(op, ct).ConfigureAwait(false),
                CustomerOperationType.Edit => await ExecuteEditWithConflictAsync(op, ct).ConfigureAwait(false),
                CustomerOperationType.Delete => await ExecuteDeleteWithConflictAsync(op, ct).ConfigureAwait(false),
                CustomerOperationType.UpdateStatus => await ExecuteUpdateStatusWithConflictAsync(op, ct).ConfigureAwait(false),
                _ => new PendingReplayResult(true, false, null)
            };
        }
        catch (Exception ex)
        {
            _logger.Warning($"[客户回放] 执行失败 op={op.OpType}：{ex.Message}");
            return new PendingReplayResult(false, false, null);
        }
    }

    private async Task<PendingReplayResult> ExecuteAddAsync(CustomerPendingOperation op, CancellationToken ct)
    {
        var ok = op.Customer != null && await RemoteAddAsync(op.Customer, ct).ConfigureAwait(false);
        return ok
            ? new PendingReplayResult(true, false, op.CustomerId)
            : new PendingReplayResult(false, false, null);
    }

    private async Task<PendingReplayResult> ExecuteEditWithConflictAsync(CustomerPendingOperation op, CancellationToken ct)
    {
        var id = op.Customer?.Id;
        if (string.IsNullOrWhiteSpace(id))
            return new PendingReplayResult(false, false, null);

        // 冲突检测：服务器 UpdateTime != 本地 AnchorUpdateTime
        var remote = await FetchRemoteSingleAsync(id!, ct).ConfigureAwait(false);
        if (remote != null && op.AnchorUpdateTime != null && remote.UpdateTime != op.AnchorUpdateTime)
        {
            UpsertLocalCache(remote);
            return new PendingReplayResult(true, true, id);
        }

        var (ok, isVersionConflict) = await RemoteEditAsync(op.Customer!, ct).ConfigureAwait(false);
        if (isVersionConflict)
        {
            var fresh = await FetchRemoteSingleAsync(id!, ct).ConfigureAwait(false);
            if (fresh != null) UpsertLocalCache(fresh);
            return new PendingReplayResult(true, true, id);
        }
        return ok
            ? new PendingReplayResult(true, false, id)
            : new PendingReplayResult(false, false, null);
    }

    private async Task<PendingReplayResult> ExecuteDeleteWithConflictAsync(CustomerPendingOperation op, CancellationToken ct)
    {
        if (string.IsNullOrWhiteSpace(op.CustomerId))
            return new PendingReplayResult(false, false, null);

        var id = op.CustomerId!;
        var remote = await FetchRemoteSingleAsync(id, ct).ConfigureAwait(false);
        if (remote == null)
        {
            // 后端已不存在：删除无需操作，也视为“成功清理 pending”
            return new PendingReplayResult(true, false, id);
        }

        if (op.AnchorUpdateTime != null && remote.UpdateTime != op.AnchorUpdateTime)
        {
            // 冲突：服务器版本获胜，恢复到服务器版本
            UpsertLocalCache(remote);
            return new PendingReplayResult(true, true, id);
        }

        var ok = await RemoteDeleteAsync(id, ct).ConfigureAwait(false);
        return ok
            ? new PendingReplayResult(true, false, id)
            : new PendingReplayResult(false, false, null);
    }

    private async Task<PendingReplayResult> ExecuteUpdateStatusWithConflictAsync(CustomerPendingOperation op, CancellationToken ct)
    {
        if (string.IsNullOrWhiteSpace(op.CustomerId) || string.IsNullOrWhiteSpace(op.Status))
            return new PendingReplayResult(false, false, null);

        var id = op.CustomerId!;
        var remote = await FetchRemoteSingleAsync(id, ct).ConfigureAwait(false);
        if (remote != null && op.AnchorUpdateTime != null && remote.UpdateTime != op.AnchorUpdateTime)
        {
            UpsertLocalCache(remote);
            return new PendingReplayResult(true, true, id);
        }

        var ok = await RemoteUpdateStatusAsync(id, op.Status!, ct).ConfigureAwait(false);
        return ok
            ? new PendingReplayResult(true, false, id)
            : new PendingReplayResult(false, false, null);
    }

    private void RemovePendingOpsByCustomerId(string customerId)
    {
        lock (_cacheLock)
        {
            _pendingOps.RemoveAll(x =>
                (x.CustomerId != null && string.Equals(x.CustomerId, customerId, StringComparison.OrdinalIgnoreCase)) ||
                (x.Customer?.Id != null && string.Equals(x.Customer.Id, customerId, StringComparison.OrdinalIgnoreCase)));
            SavePendingOpsToDiskUnsafe();
        }
    }

    private async Task<MesXslCustomer?> FetchRemoteSingleAsync(string id, CancellationToken ct)
    {
        try
        {
            var url = $"{BaseUrl}/xslmes/mesXslCustomer/anon/queryById?id={Uri.EscapeDataString(id)}&tenantId={DefaultTenantId}";
            using var client = CreateClient();
            var resp = await client.GetAsync(url, ct).ConfigureAwait(false);
            if (!resp.IsSuccessStatusCode) return null;

            var json = await resp.Content.ReadAsStringAsync(ct).ConfigureAwait(false);
            using var doc = JsonDocument.Parse(json);
            if (doc.RootElement.TryGetProperty("result", out var resultEl))
                return resultEl.Deserialize<MesXslCustomer>(_jsonOpts);
            return null;
        }
        catch
        {
            return null;
        }
    }

    // ── 本地缓存操作 ──────────────────────────────────────────────────────

    private static List<MesXslCustomer> ApplyFilters(List<MesXslCustomer> source,
        string? customerCode, string? customerName, string? status, string? customerRegion)
    {
        IEnumerable<MesXslCustomer> q = source;
        if (!string.IsNullOrWhiteSpace(customerCode))
            q = q.Where(c => (c.CustomerCode ?? "").Contains(customerCode, StringComparison.OrdinalIgnoreCase));
        if (!string.IsNullOrWhiteSpace(customerName))
            q = q.Where(c => (c.CustomerName ?? "").Contains(customerName, StringComparison.OrdinalIgnoreCase));
        if (!string.IsNullOrWhiteSpace(status))
            q = q.Where(c => string.Equals(c.Status, status, StringComparison.OrdinalIgnoreCase));
        if (!string.IsNullOrWhiteSpace(customerRegion))
            q = q.Where(c => string.Equals(c.CustomerRegion, customerRegion, StringComparison.OrdinalIgnoreCase));
        return q.OrderByDescending(c => c.CreateTime ?? DateTime.MinValue).ToList();
    }

    private List<MesXslCustomer> ApplyPendingOpsSnapshotUnsafe(List<MesXslCustomer> source)
    {
        var map = source.Where(c => !string.IsNullOrWhiteSpace(c.Id))
            .ToDictionary(c => c.Id!, Clone, StringComparer.OrdinalIgnoreCase);
        foreach (var op in _pendingOps.OrderBy(x => x.CreatedAt))
        {
            switch (op.OpType)
            {
                case CustomerOperationType.Add:
                case CustomerOperationType.Edit:
                    if (op.Customer?.Id != null) map[op.Customer.Id] = Clone(op.Customer);
                    break;
                case CustomerOperationType.Delete:
                    if (op.CustomerId != null) map.Remove(op.CustomerId);
                    break;
                case CustomerOperationType.UpdateStatus:
                    if (op.CustomerId != null && op.Status != null && map.TryGetValue(op.CustomerId, out var c))
                    {
                        c.Status = op.Status;
                        SyncIzEnable(c);
                    }
                    break;
            }
        }
        return map.Values.ToList();
    }

    private void EnqueuePendingOperation(CustomerPendingOperation op)
    {
        lock (_cacheLock) { _pendingOps.Add(op); SavePendingOpsToDiskUnsafe(); }
    }

    private void UpsertLocalCache(MesXslCustomer customer)
    {
        lock (_cacheLock)
        {
            var idx = _localCache.FindIndex(c => string.Equals(c.Id, customer.Id, StringComparison.OrdinalIgnoreCase));
            if (idx >= 0) _localCache[idx] = Clone(customer);
            else _localCache.Insert(0, Clone(customer));
            SaveCacheToDiskUnsafe();
        }
    }

    private void RemoveFromLocalCache(string id)
    {
        lock (_cacheLock)
        {
            _localCache.RemoveAll(c => string.Equals(c.Id, id, StringComparison.OrdinalIgnoreCase));
            SaveCacheToDiskUnsafe();
        }
    }

    private void UpdateLocalStatus(string id, string status)
    {
        lock (_cacheLock)
        {
            var item = _localCache.FirstOrDefault(c => string.Equals(c.Id, id, StringComparison.OrdinalIgnoreCase));
            if (item != null) { item.Status = status; SyncIzEnable(item); SaveCacheToDiskUnsafe(); }
        }
    }

    private void LoadPendingOpsFromDisk()
    {
        try
        {
            if (!File.Exists(_pendingOpsFilePath)) return;
            _pendingOps = JsonSerializer.Deserialize<List<CustomerPendingOperation>>(
                File.ReadAllText(_pendingOpsFilePath), _jsonOpts) ?? new();
        }
        catch { _pendingOps = new(); }
    }

    private void LoadCacheFromDisk()
    {
        try
        {
            if (!File.Exists(_cacheFilePath)) return;
            _localCache = JsonSerializer.Deserialize<List<MesXslCustomer>>(
                File.ReadAllText(_cacheFilePath), _jsonOpts) ?? new();
        }
        catch { _localCache = new(); }
    }

    private void SavePendingOpsToDiskUnsafe() =>
        File.WriteAllText(_pendingOpsFilePath, JsonSerializer.Serialize(_pendingOps, _jsonOpts));

    private void SaveCacheToDiskUnsafe() =>
        File.WriteAllText(_cacheFilePath, JsonSerializer.Serialize(_localCache, _jsonOpts));

    // ── 辅助方法 ──────────────────────────────────────────────────────────

    // status "0"启用 → izEnable=1；status "1"停用 → izEnable=0
    private static void SyncIzEnable(MesXslCustomer c) =>
        c.IzEnable = c.Status == "1" ? 0 : 1;

    private static bool IsLocalTempId(string? id) =>
        !string.IsNullOrWhiteSpace(id) && id.StartsWith("local-", StringComparison.OrdinalIgnoreCase);

    private static MesXslCustomer Clone(MesXslCustomer c) => new()
    {
        Id = c.Id, CustomerCode = c.CustomerCode, CustomerName = c.CustomerName,
        CustomerShortName = c.CustomerShortName, CustomerRegion = c.CustomerRegion,
        ErpCode = c.ErpCode, Status = c.Status, IzEnable = c.IzEnable,
        CustomerDesc = c.CustomerDesc, TenantId = c.TenantId,
        CreateBy = c.CreateBy, CreateTime = c.CreateTime,
        UpdateBy = c.UpdateBy, UpdateTime = c.UpdateTime, SysOrgCode = c.SysOrgCode
    };

    // ── 内部类型 ──────────────────────────────────────────────────────────

    private sealed class CustomerPendingOperation
    {
        public string Id { get; set; } = Guid.NewGuid().ToString("N");
        public CustomerOperationType OpType { get; set; }
        public string? CustomerId { get; set; }
        public string? Status { get; set; }
        public MesXslCustomer? Customer { get; set; }
        // 冲突检测用的版本锚点：当本地首次针对该记录产生修改时，记录当时的服务器 UpdateTime
        public DateTime? AnchorUpdateTime { get; set; }
        public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
        public int RetryCount { get; set; } = 0;
    }

    private enum CustomerOperationType { Add = 1, Edit = 2, Delete = 3, UpdateStatus = 4 }

    private sealed class NullableDateTimeJsonConverter : JsonConverter<DateTime?>
    {
        private static readonly string[] Formats =
        [
            "yyyy-MM-dd HH:mm:ss", "yyyy-MM-dd HH:mm:ss.fff",
            "yyyy-MM-ddTHH:mm:ss", "yyyy-MM-ddTHH:mm:ss.fff",
            "yyyy-MM-ddTHH:mm:ssZ", "yyyy-MM-ddTHH:mm:ss.fffZ"
        ];

        public override DateTime? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
        {
            if (reader.TokenType == JsonTokenType.Null) return null;
            if (reader.TokenType == JsonTokenType.String)
            {
                var raw = reader.GetString();
                if (string.IsNullOrWhiteSpace(raw)) return null;
                if (DateTime.TryParseExact(raw, Formats, System.Globalization.CultureInfo.InvariantCulture,
                    System.Globalization.DateTimeStyles.AssumeLocal, out var dt)) return dt;
                if (DateTime.TryParse(raw, out var fb)) return fb;
            }
            throw new JsonException($"无法转换为 DateTime?，token={reader.TokenType}");
        }

        public override void Write(Utf8JsonWriter writer, DateTime? value, JsonSerializerOptions options)
        {
            if (value.HasValue) writer.WriteStringValue(value.Value.ToString("yyyy-MM-dd HH:mm:ss"));
            else writer.WriteNullValue();
        }
    }
}