import React, { useState, useRef, useMemo } from 'react';
import { useTranslation } from 'react-i18next';
import { useOutletContext } from 'react-router-dom';
import { Plus, Pencil, Trash2, Clock, DollarSign, X, Loader2, GripVertical, Eye, ChevronRight, Upload, ImagePlus, Image, AlertTriangle } from 'lucide-react';
import { useServices, useCreateService, useUpdateService, useDeleteService, useReorderServices } from '../hooks/useServices';
import { Service, User, Business } from '../types';
import { getOverQuotaServiceIds } from '../utils/quotaUtils';

interface ServiceFormData {
  name: string;
  durationMinutes: number;
  price: number;
  description: string;
  photos: string[];
}

const Services: React.FC = () => {
  const { t } = useTranslation();
  const { user } = useOutletContext<{ user: User, business: Business }>();
  const { data: services, isLoading, error } = useServices();
  const createService = useCreateService();
  const updateService = useUpdateService();
  const deleteService = useDeleteService();
  const reorderServices = useReorderServices();

  // Calculate over-quota services (will be auto-archived when grace period ends)
  const overQuotaServiceIds = useMemo(
    () => getOverQuotaServiceIds(services || [], user.quota_overages),
    [services, user.quota_overages]
  );

  const [isModalOpen, setIsModalOpen] = useState(false);
  const [editingService, setEditingService] = useState<Service | null>(null);
  const [formData, setFormData] = useState<ServiceFormData>({
    name: '',
    durationMinutes: 60,
    price: 0,
    description: '',
    photos: [],
  });

  // Photo gallery state
  const [isDraggingPhoto, setIsDraggingPhoto] = useState(false);
  const [draggedPhotoIndex, setDraggedPhotoIndex] = useState<number | null>(null);
  const [dragOverPhotoIndex, setDragOverPhotoIndex] = useState<number | null>(null);

  // Drag and drop state
  const [draggedId, setDraggedId] = useState<string | null>(null);
  const [dragOverId, setDragOverId] = useState<string | null>(null);
  const [localServices, setLocalServices] = useState<Service[] | null>(null);
  const dragNodeRef = useRef<HTMLDivElement | null>(null);

  // Use local state during drag, otherwise use fetched data
  const displayServices = localServices ?? services;

  // Drag handlers
  const handleDragStart = (e: React.DragEvent<HTMLDivElement>, serviceId: string) => {
    setDraggedId(serviceId);
    dragNodeRef.current = e.currentTarget;
    e.dataTransfer.effectAllowed = 'move';
    // Add a slight delay to allow the drag image to be set
    setTimeout(() => {
      if (dragNodeRef.current) {
        dragNodeRef.current.style.opacity = '0.5';
      }
    }, 0);
  };

  const handleDragEnd = () => {
    if (dragNodeRef.current) {
      dragNodeRef.current.style.opacity = '1';
    }
    setDraggedId(null);
    setDragOverId(null);
    dragNodeRef.current = null;

    // If we have local changes, save them
    if (localServices) {
      const orderedIds = localServices.map(s => s.id);
      reorderServices.mutate(orderedIds, {
        onSettled: () => {
          setLocalServices(null);
        }
      });
    }
  };

  const handleDragOver = (e: React.DragEvent<HTMLDivElement>, serviceId: string) => {
    e.preventDefault();
    if (draggedId === serviceId) return;

    setDragOverId(serviceId);

    // Reorder locally for visual feedback
    const currentServices = localServices ?? services ?? [];
    const draggedIndex = currentServices.findIndex(s => s.id === draggedId);
    const targetIndex = currentServices.findIndex(s => s.id === serviceId);

    if (draggedIndex === -1 || targetIndex === -1 || draggedIndex === targetIndex) return;

    const newServices = [...currentServices];
    const [removed] = newServices.splice(draggedIndex, 1);
    newServices.splice(targetIndex, 0, removed);

    setLocalServices(newServices);
  };

  const handleDragLeave = () => {
    setDragOverId(null);
  };

  // Photo upload handlers
  const handlePhotoDrop = (e: React.DragEvent<HTMLDivElement>) => {
    e.preventDefault();
    e.stopPropagation();
    setIsDraggingPhoto(false);

    const files = e.dataTransfer.files;
    if (files && files.length > 0) {
      Array.from(files).forEach((file) => {
        if (file.type.startsWith('image/')) {
          const reader = new FileReader();
          reader.onloadend = () => {
            setFormData((prev) => ({
              ...prev,
              photos: [...prev.photos, reader.result as string],
            }));
          };
          reader.readAsDataURL(file);
        }
      });
    }
  };

  const handlePhotoDragOver = (e: React.DragEvent<HTMLDivElement>) => {
    e.preventDefault();
    e.stopPropagation();
    setIsDraggingPhoto(true);
  };

  const handlePhotoDragLeave = (e: React.DragEvent<HTMLDivElement>) => {
    e.preventDefault();
    e.stopPropagation();
    setIsDraggingPhoto(false);
  };

  const handlePhotoUpload = (e: React.ChangeEvent<HTMLInputElement>) => {
    const files = e.target.files;
    if (files && files.length > 0) {
      Array.from(files).forEach((file) => {
        if (file.type.startsWith('image/')) {
          const reader = new FileReader();
          reader.onloadend = () => {
            setFormData((prev) => ({
              ...prev,
              photos: [...prev.photos, reader.result as string],
            }));
          };
          reader.readAsDataURL(file);
        }
      });
    }
    // Reset input
    e.target.value = '';
  };

  const removePhoto = (index: number) => {
    setFormData((prev) => ({
      ...prev,
      photos: prev.photos.filter((_, i) => i !== index),
    }));
  };

  // Photo reorder drag handlers
  const handlePhotoReorderStart = (e: React.DragEvent<HTMLDivElement>, index: number) => {
    setDraggedPhotoIndex(index);
    e.dataTransfer.effectAllowed = 'move';
  };

  const handlePhotoReorderOver = (e: React.DragEvent<HTMLDivElement>, index: number) => {
    e.preventDefault();
    if (draggedPhotoIndex === null || draggedPhotoIndex === index) return;
    setDragOverPhotoIndex(index);

    // Reorder photos
    const newPhotos = [...formData.photos];
    const [removed] = newPhotos.splice(draggedPhotoIndex, 1);
    newPhotos.splice(index, 0, removed);
    setFormData((prev) => ({ ...prev, photos: newPhotos }));
    setDraggedPhotoIndex(index);
  };

  const handlePhotoReorderEnd = () => {
    setDraggedPhotoIndex(null);
    setDragOverPhotoIndex(null);
  };

  const openCreateModal = () => {
    setEditingService(null);
    setFormData({
      name: '',
      durationMinutes: 60,
      price: 0,
      description: '',
      photos: [],
    });
    setIsModalOpen(true);
  };

  const openEditModal = (service: Service) => {
    setEditingService(service);
    setFormData({
      name: service.name,
      durationMinutes: service.durationMinutes,
      price: service.price,
      description: service.description || '',
      photos: service.photos || [],
    });
    setIsModalOpen(true);
  };

  const closeModal = () => {
    setIsModalOpen(false);
    setEditingService(null);
  };

  const handleSubmit = async (e: React.FormEvent) => {
    e.preventDefault();

    try {
      if (editingService) {
        await updateService.mutateAsync({
          id: editingService.id,
          updates: formData,
        });
      } else {
        await createService.mutateAsync(formData);
      }
      closeModal();
    } catch (error) {
      console.error('Failed to save service:', error);
    }
  };

  const handleDelete = async (id: string) => {
    if (window.confirm(t('services.confirmDelete', 'Are you sure you want to delete this service?'))) {
      try {
        await deleteService.mutateAsync(id);
      } catch (error) {
        console.error('Failed to delete service:', error);
      }
    }
  };

  if (isLoading) {
    return (
      <div className="p-8">
        <div className="flex items-center justify-center h-64">
          <Loader2 className="h-8 w-8 animate-spin text-brand-600" />
        </div>
      </div>
    );
  }

  if (error) {
    return (
      <div className="p-8">
        <div className="text-center text-red-600 dark:text-red-400">
          {t('common.error')}: {error instanceof Error ? error.message : 'Unknown error'}
        </div>
      </div>
    );
  }

  return (
    <div className="p-8 space-y-6">
      <div className="flex items-center justify-between">
        <div>
          <h2 className="text-2xl font-bold text-gray-900 dark:text-white">
            {t('services.title', 'Services')}
          </h2>
          <p className="text-gray-500 dark:text-gray-400">
            {t('services.description', 'Manage the services your business offers')}
          </p>
        </div>
        <button
          onClick={openCreateModal}
          className="flex items-center gap-2 px-4 py-2 bg-brand-600 text-white rounded-lg hover:bg-brand-700 transition-colors"
        >
          <Plus className="h-4 w-4" />
          {t('services.addService', 'Add Service')}
        </button>
      </div>

      {displayServices && displayServices.length === 0 ? (
        <div className="text-center py-12 bg-white dark:bg-gray-800 rounded-xl border border-gray-100 dark:border-gray-700">
          <div className="text-gray-500 dark:text-gray-400 mb-4">
            {t('services.noServices', 'No services yet. Add your first service to get started.')}
          </div>
          <button
            onClick={openCreateModal}
            className="inline-flex items-center gap-2 px-4 py-2 bg-brand-600 text-white rounded-lg hover:bg-brand-700 transition-colors"
          >
            <Plus className="h-4 w-4" />
            {t('services.addService', 'Add Service')}
          </button>
        </div>
      ) : (
        <div className="grid grid-cols-1 lg:grid-cols-2 gap-8">
          {/* Left Column - Editable Services List */}
          <div>
            <p className="text-sm text-gray-500 dark:text-gray-400 mb-4">
              {t('services.dragToReorder', 'Drag services to reorder how they appear in menus')}
            </p>
            <div className="space-y-3">
              {displayServices?.map((service) => {
                const isOverQuota = overQuotaServiceIds.has(service.id);
                return (
                <div
                  key={service.id}
                  draggable
                  onDragStart={(e) => handleDragStart(e, service.id)}
                  onDragEnd={handleDragEnd}
                  onDragOver={(e) => handleDragOver(e, service.id)}
                  onDragLeave={handleDragLeave}
                  className={`p-4 border rounded-xl shadow-sm cursor-move transition-all ${
                    isOverQuota
                      ? 'bg-amber-50/50 dark:bg-amber-900/10 border-amber-300 dark:border-amber-600 opacity-70'
                      : draggedId === service.id
                      ? 'opacity-50 border-brand-500 bg-white dark:bg-gray-800'
                      : dragOverId === service.id
                      ? 'border-brand-500 ring-2 ring-brand-500/50 bg-white dark:bg-gray-800'
                      : 'border-gray-100 dark:border-gray-700 bg-white dark:bg-gray-800'
                  }`}
                  title={isOverQuota ? 'Over quota - will be archived if not resolved' : undefined}
                >
                  <div className="flex items-center gap-3">
                    {isOverQuota ? (
                      <AlertTriangle className="h-5 w-5 text-amber-600 dark:text-amber-400 shrink-0" />
                    ) : (
                      <GripVertical className="h-5 w-5 text-gray-400 cursor-grab active:cursor-grabbing shrink-0" />
                    )}
                    <div className="flex-1 min-w-0">
                      <div className="flex items-center justify-between">
                        <h3 className={`font-semibold truncate ${isOverQuota ? 'text-amber-800 dark:text-amber-300' : 'text-gray-900 dark:text-white'}`}>
                          {service.name}
                          {isOverQuota && (
                            <span className="ml-2 inline-flex items-center px-1.5 py-0.5 rounded text-[10px] font-medium bg-amber-100 text-amber-700 dark:bg-amber-800/50 dark:text-amber-400">
                              Over quota
                            </span>
                          )}
                        </h3>
                        <div className="flex items-center gap-1 shrink-0 ml-2">
                          <button
                            onClick={() => openEditModal(service)}
                            className="p-1.5 text-gray-400 hover:text-brand-600 dark:hover:text-brand-400 transition-colors"
                            title={t('common.edit', 'Edit')}
                          >
                            <Pencil className="h-4 w-4" />
                          </button>
                          <button
                            onClick={() => handleDelete(service.id)}
                            className="p-1.5 text-gray-400 hover:text-red-600 dark:hover:text-red-400 transition-colors"
                            title={t('common.delete', 'Delete')}
                          >
                            <Trash2 className="h-4 w-4" />
                          </button>
                        </div>
                      </div>
                      {service.description && (
                        <p className="text-sm text-gray-500 dark:text-gray-400 mt-1 line-clamp-1">
                          {service.description}
                        </p>
                      )}
                      <div className="flex items-center gap-4 mt-2 text-sm">
                        <span className="text-gray-600 dark:text-gray-300 flex items-center gap-1">
                          <Clock className="h-3.5 w-3.5" />
                          {service.durationMinutes} {t('common.minutes', 'min')}
                        </span>
                        <span className="text-gray-600 dark:text-gray-300 flex items-center gap-1">
                          <DollarSign className="h-3.5 w-3.5" />
                          ${service.price.toFixed(2)}
                        </span>
                        {service.photos && service.photos.length > 0 && (
                          <span className="text-gray-500 dark:text-gray-400 flex items-center gap-1">
                            <Image className="h-3.5 w-3.5" />
                            {service.photos.length}
                          </span>
                        )}
                      </div>
                    </div>
                  </div>
                </div>
                );
              })}
            </div>
          </div>

          {/* Right Column - Customer Preview Mockup */}
          <div>
            <div className="flex items-center gap-2 mb-4">
              <Eye className="h-5 w-5 text-gray-500 dark:text-gray-400" />
              <h3 className="text-lg font-semibold text-gray-900 dark:text-white">
                {t('services.customerPreview', 'Customer Preview')}
              </h3>
            </div>

            {/* Mockup Container - styled like a booking widget */}
            <div className="sticky top-8">
              <div className="bg-white dark:bg-gray-800 rounded-2xl shadow-xl border border-gray-200 dark:border-gray-700 overflow-hidden">
                {/* Mockup Header */}
                <div className="bg-brand-600 px-6 py-4">
                  <h4 className="text-white font-semibold text-lg">{t('services.selectService', 'Select a Service')}</h4>
                  <p className="text-white/70 text-sm">{t('services.chooseFromMenu', 'Choose from our available services')}</p>
                </div>

                {/* Services List */}
                <div className="divide-y divide-gray-100 dark:divide-gray-700 max-h-[500px] overflow-y-auto">
                  {displayServices?.map((service) => (
                    <div
                      key={`preview-${service.id}`}
                      className="px-6 py-4 hover:bg-gray-50 dark:hover:bg-gray-700/50 transition-colors cursor-pointer group"
                    >
                      <div className="flex items-center justify-between">
                        <div className="flex-1 min-w-0">
                          <h5 className="font-medium text-gray-900 dark:text-white truncate">
                            {service.name}
                          </h5>
                          {service.description && (
                            <p className="text-sm text-gray-500 dark:text-gray-400 mt-0.5 line-clamp-1">
                              {service.description}
                            </p>
                          )}
                          <div className="flex items-center gap-3 mt-2 text-sm">
                            <span className="text-gray-600 dark:text-gray-300 flex items-center gap-1">
                              <Clock className="h-3.5 w-3.5" />
                              {service.durationMinutes} min
                            </span>
                            <span className="font-semibold text-brand-600 dark:text-brand-400">
                              ${service.price.toFixed(2)}
                            </span>
                          </div>
                        </div>
                        <ChevronRight className="h-5 w-5 text-gray-400 group-hover:text-brand-600 dark:group-hover:text-brand-400 transition-colors shrink-0 ml-4" />
                      </div>
                    </div>
                  ))}
                </div>

                {/* Mockup Footer */}
                <div className="bg-gray-50 dark:bg-gray-900/50 px-6 py-3 text-center border-t border-gray-100 dark:border-gray-700">
                  <p className="text-xs text-gray-400 dark:text-gray-500">
                    {t('services.mockupNote', 'Preview only - not clickable')}
                  </p>
                </div>
              </div>
            </div>
          </div>
        </div>
      )}

      {/* Modal */}
      {isModalOpen && (
        <div className="fixed inset-0 z-50 flex items-center justify-center bg-black/50">
          <div className="bg-white dark:bg-gray-800 rounded-xl shadow-xl max-w-lg w-full mx-4 max-h-[90vh] flex flex-col">
            <div className="flex items-center justify-between p-6 border-b border-gray-100 dark:border-gray-700 shrink-0">
              <h3 className="text-lg font-semibold text-gray-900 dark:text-white">
                {editingService
                  ? t('services.editService', 'Edit Service')
                  : t('services.addService', 'Add Service')}
              </h3>
              <button
                onClick={closeModal}
                className="p-2 text-gray-400 hover:text-gray-600 dark:hover:text-gray-300"
              >
                <X className="h-5 w-5" />
              </button>
            </div>

            <form onSubmit={handleSubmit} className="flex flex-col flex-1 overflow-hidden">
              <div className="p-6 space-y-4 overflow-y-auto flex-1">
                <div>
                  <label className="block text-sm font-medium text-gray-700 dark:text-gray-300 mb-1">
                    {t('services.name', 'Name')} *
                  </label>
                  <input
                    type="text"
                    value={formData.name}
                    onChange={(e) => setFormData({ ...formData, name: e.target.value })}
                    required
                    className="w-full px-3 py-2 border border-gray-300 dark:border-gray-600 rounded-lg bg-white dark:bg-gray-700 text-gray-900 dark:text-white focus:ring-2 focus:ring-brand-500 focus:border-brand-500"
                    placeholder={t('services.namePlaceholder', 'e.g., Haircut, Massage, Consultation')}
                  />
                </div>

                <div className="grid grid-cols-2 gap-4">
                  <div>
                    <label className="block text-sm font-medium text-gray-700 dark:text-gray-300 mb-1">
                      {t('services.duration', 'Duration (min)')} *
                    </label>
                    <input
                      type="number"
                      value={formData.durationMinutes}
                      onChange={(e) => setFormData({ ...formData, durationMinutes: parseInt(e.target.value) || 0 })}
                      required
                      min={5}
                      step={5}
                      className="w-full px-3 py-2 border border-gray-300 dark:border-gray-600 rounded-lg bg-white dark:bg-gray-700 text-gray-900 dark:text-white focus:ring-2 focus:ring-brand-500 focus:border-brand-500"
                    />
                  </div>
                  <div>
                    <label className="block text-sm font-medium text-gray-700 dark:text-gray-300 mb-1">
                      {t('services.price', 'Price ($)')} *
                    </label>
                    <input
                      type="number"
                      value={formData.price}
                      onChange={(e) => setFormData({ ...formData, price: parseFloat(e.target.value) || 0 })}
                      required
                      min={0}
                      step={0.01}
                      className="w-full px-3 py-2 border border-gray-300 dark:border-gray-600 rounded-lg bg-white dark:bg-gray-700 text-gray-900 dark:text-white focus:ring-2 focus:ring-brand-500 focus:border-brand-500"
                    />
                  </div>
                </div>

                <div>
                  <label className="block text-sm font-medium text-gray-700 dark:text-gray-300 mb-1">
                    {t('services.descriptionLabel', 'Description')}
                  </label>
                  <textarea
                    value={formData.description}
                    onChange={(e) => setFormData({ ...formData, description: e.target.value })}
                    rows={3}
                    className="w-full px-3 py-2 border border-gray-300 dark:border-gray-600 rounded-lg bg-white dark:bg-gray-700 text-gray-900 dark:text-white focus:ring-2 focus:ring-brand-500 focus:border-brand-500 resize-none"
                    placeholder={t('services.descriptionPlaceholder', 'Optional description of the service...')}
                  />
                </div>

                {/* Photo Gallery */}
                <div>
                  <label className="block text-sm font-medium text-gray-700 dark:text-gray-300 mb-2">
                    {t('services.photos', 'Photos')}
                  </label>

                  {/* Photo Grid */}
                  {formData.photos.length > 0 && (
                    <div className="grid grid-cols-4 gap-3 mb-3">
                      {formData.photos.map((photo, index) => (
                        <div
                          key={index}
                          draggable
                          onDragStart={(e) => handlePhotoReorderStart(e, index)}
                          onDragOver={(e) => handlePhotoReorderOver(e, index)}
                          onDragEnd={handlePhotoReorderEnd}
                          className={`relative group aspect-square rounded-lg overflow-hidden border-2 cursor-move transition-all ${
                            draggedPhotoIndex === index
                              ? 'opacity-50 border-brand-500'
                              : dragOverPhotoIndex === index
                              ? 'border-brand-500 ring-2 ring-brand-500/50'
                              : 'border-gray-200 dark:border-gray-600'
                          }`}
                        >
                          <img
                            src={photo}
                            alt={`Photo ${index + 1}`}
                            className="w-full h-full object-cover"
                          />
                          <div className="absolute inset-0 bg-black/50 opacity-0 group-hover:opacity-100 transition-opacity flex items-center justify-center gap-2">
                            <div className="absolute top-1 left-1 text-white/70">
                              <GripVertical className="h-4 w-4" />
                            </div>
                            <button
                              type="button"
                              onClick={() => removePhoto(index)}
                              className="p-1.5 bg-red-500 hover:bg-red-600 text-white rounded-full transition-colors"
                            >
                              <Trash2 className="h-3.5 w-3.5" />
                            </button>
                          </div>
                          <div className="absolute bottom-1 right-1 bg-black/60 text-white text-[10px] px-1.5 py-0.5 rounded">
                            {index + 1}
                          </div>
                        </div>
                      ))}
                    </div>
                  )}

                  {/* Drop Zone */}
                  <div
                    onDrop={handlePhotoDrop}
                    onDragOver={handlePhotoDragOver}
                    onDragLeave={handlePhotoDragLeave}
                    className={`border-2 border-dashed rounded-lg p-6 text-center transition-colors ${
                      isDraggingPhoto
                        ? 'border-brand-500 bg-brand-50 dark:bg-brand-900/20'
                        : 'border-gray-300 dark:border-gray-600 hover:border-gray-400 dark:hover:border-gray-500'
                    }`}
                  >
                    <ImagePlus className={`mx-auto mb-2 h-8 w-8 ${isDraggingPhoto ? 'text-brand-500' : 'text-gray-400'}`} />
                    <p className={`text-sm ${isDraggingPhoto ? 'text-brand-600 dark:text-brand-400' : 'text-gray-500 dark:text-gray-400'}`}>
                      {isDraggingPhoto ? t('services.dropImagesHere', 'Drop images here') : t('services.dragAndDropImages', 'Drag and drop images here, or')}
                    </p>
                    {!isDraggingPhoto && (
                      <>
                        <input
                          type="file"
                          id="service-photo-upload"
                          className="hidden"
                          accept="image/*"
                          multiple
                          onChange={handlePhotoUpload}
                        />
                        <label
                          htmlFor="service-photo-upload"
                          className="inline-flex items-center gap-1 mt-2 px-3 py-1.5 text-sm font-medium text-brand-600 dark:text-brand-400 hover:text-brand-700 dark:hover:text-brand-300 cursor-pointer"
                        >
                          <Upload className="h-3.5 w-3.5" />
                          {t('services.browseFiles', 'browse files')}
                        </label>
                      </>
                    )}
                  </div>
                  <p className="text-xs text-gray-500 dark:text-gray-400 mt-2">
                    {t('services.photosHint', 'Drag photos to reorder. First photo is the primary image.')}
                  </p>
                </div>
              </div>

              <div className="flex justify-end gap-3 p-6 border-t border-gray-100 dark:border-gray-700 bg-gray-50 dark:bg-gray-900/50 shrink-0">
                <button
                  type="button"
                  onClick={closeModal}
                  className="px-4 py-2 text-gray-700 dark:text-gray-300 hover:bg-gray-100 dark:hover:bg-gray-700 rounded-lg transition-colors"
                >
                  {t('common.cancel', 'Cancel')}
                </button>
                <button
                  type="submit"
                  disabled={createService.isPending || updateService.isPending}
                  className="px-4 py-2 bg-brand-600 text-white rounded-lg hover:bg-brand-700 disabled:opacity-50 disabled:cursor-not-allowed transition-colors flex items-center gap-2"
                >
                  {(createService.isPending || updateService.isPending) && (
                    <Loader2 className="h-4 w-4 animate-spin" />
                  )}
                  {editingService ? t('common.save', 'Save') : t('common.create', 'Create')}
                </button>
              </div>
            </form>
          </div>
        </div>
      )}
    </div>
  );
};

export default Services;