'use client';

import { useState, useEffect } from 'react';
import { z } from 'zod';
import { zodResolver } from '@hookform/resolvers/zod';
import { useForm } from 'react-hook-form';
import { Save, X, Loader2 } from 'lucide-react';
import { Button } from '@/components/ui/button';
import {
  Form,
  FormControl,
  FormDescription,
  FormField,
  FormItem,
  FormLabel,
  FormMessage,
} from '@/components/ui/form';
import { Input } from '@/components/ui/input';
import { RadioGroup, RadioGroupItem } from "@/components/ui/radio-group";
import { Switch } from '@/components/ui/switch';
import { Textarea } from '@/components/ui/textarea';
import { toast } from '@/components/ui/use-toast';
import { Promotion, PromotionFormData } from '@/lib/types/promotion';
import { fetchClient } from '@/lib/api';
import ProductSelector from './ProductSelector';

// Form schema validation with Zod (same as NewPromotionForm)
const formSchema = z.object({
  code: z.string()
    .min(3, 'Code must be at least 3 characters')
    .max(20, 'Code cannot exceed 20 characters')
    .regex(/^[A-Za-z0-9]+$/, 'Only letters and numbers are allowed'),
  discountType: z.enum(['percentage', 'fixed']),
  discountValue: z.coerce.number()
    .positive('Discount value must be positive')
    .refine(val => val <= 100, {
      message: 'Percentage discount cannot exceed 100%',
      path: ['discountValue'],
      // Only validate this rule if discount type is percentage
      params: { type: 'percentage' },
    }),
  minOrderAmount: z.coerce.number()
    .min(0, 'Minimum order amount cannot be negative'),
  maxUsage: z.coerce.number()
    .nullable()
    .optional(),
  isActive: z.boolean().default(true),
  startDate: z.string().optional(),
  endDate: z.string().nullable().optional(),
  description: z.string().max(200, 'Description cannot exceed 200 characters').optional(),
  blacklistedProducts: z.array(z.string()).default([]),
  applicableProducts: z.enum(['all', 'specific', 'exclude_specific']).default('all'),
  specificProducts: z.array(z.string()).default([]),
});

interface EditPromotionFormProps {
  promotion: Promotion;
  onSuccess: () => void;
  onCancel: () => void;
}

export default function EditPromotionForm({ promotion, onSuccess, onCancel }: EditPromotionFormProps) {
  const [isSubmitting, setIsSubmitting] = useState(false);
  const [discountType, setDiscountType] = useState<'percentage' | 'fixed'>(promotion.discountType);

  // Format dates from ISO to YYYY-MM-DD for input elements
  const formatDateForInput = (dateString: string | null) => {
    if (!dateString) return '';
    return new Date(dateString).toISOString().split('T')[0];
  };

  // Initialize form with promotion values
  const form = useForm<z.infer<typeof formSchema>>({
    resolver: zodResolver(formSchema),
    defaultValues: {
      code: promotion.code,
      discountType: promotion.discountType,
      discountValue: promotion.discountValue,
      minOrderAmount: promotion.minOrderAmount,
      maxUsage: promotion.maxUsage,
      isActive: promotion.isActive,
      description: promotion.description,
      startDate: formatDateForInput(promotion.startDate),
      endDate: formatDateForInput(promotion.endDate),
      blacklistedProducts: promotion.blacklistedProducts || [],
      applicableProducts: promotion.applicableProducts || 'all',
      specificProducts: promotion.specificProducts || [],
    },
  });

  // Keep local state in sync with form
  useEffect(() => {
    const subscription = form.watch((value, { name }) => {
      if (name === 'discountType') {
        setDiscountType(value.discountType as 'percentage' | 'fixed');
      }
    });
    return () => subscription.unsubscribe();
  }, [form, form.watch]);

  // Form submission handler
  async function onSubmit(data: z.infer<typeof formSchema>) {
    setIsSubmitting(true);
    
    try {
      await fetchClient(`/promotions/${promotion._id}`, {
        method: 'PUT',
        body: data,
      });
      
      toast({
        title: 'Success',
        description: 'Promotion updated successfully',
      });
      
      onSuccess();
    } catch (error) {
      console.error('Error updating promotion:', error);
      // Error toast is already shown by fetchClient
    } finally {
      setIsSubmitting(false);
    }
  }

  return (
    <Form {...form}>
      <form onSubmit={form.handleSubmit(onSubmit)} className="space-y-8">
        <div className="grid grid-cols-1 gap-6">
          <FormField
            control={form.control}
            name="code"
            render={({ field }) => (
              <FormItem>
                <FormLabel className="text-sm font-medium">Promotion Code</FormLabel>
                <FormControl>
                  <Input 
                    placeholder="SUMMER20" 
                    {...field} 
                    onChange={(e) => field.onChange(e.target.value.toUpperCase())}
                    className="h-10"
                  />
                </FormControl>
                <FormDescription className="text-xs">
                  Enter a unique code for your promotion. Only letters and numbers.
                </FormDescription>
                <FormMessage />
              </FormItem>
            )}
          />
        </div>

        <div className="grid grid-cols-4 gap-6">
          <FormField
            control={form.control}
            name="discountType"
            render={({ field }) => (
              <FormItem className="col-span-1">
                <FormLabel className="text-sm font-medium">Discount Type</FormLabel>
                <FormControl>
                  <RadioGroup
                    onValueChange={(value) => {
                      field.onChange(value);
                      setDiscountType(value as 'percentage' | 'fixed');
                    }}
                    value={field.value}
                    className="flex flex-col space-y-2"
                  >
                    <div className="flex items-center space-x-2">
                      <RadioGroupItem value="percentage" id="edit-percentage" />
                      <label htmlFor="edit-percentage" className="cursor-pointer">Percentage (%)</label>
                    </div>
                    <div className="flex items-center space-x-2">
                      <RadioGroupItem value="fixed" id="edit-fixed" />
                      <label htmlFor="edit-fixed" className="cursor-pointer">Fixed Amount (£)</label>
                    </div>
                  </RadioGroup>
                </FormControl>
                <FormMessage />
              </FormItem>
            )}
          />

          <FormField
            control={form.control}
            name="discountValue"
            render={({ field }) => (
              <FormItem className="col-span-1">
                <FormLabel className="text-sm font-medium">Discount Value</FormLabel>
                <FormControl>
                  <Input 
                    type="number" 
                    step={discountType === 'percentage' ? '1' : '0.01'}
                    min={0}
                    max={discountType === 'percentage' ? 100 : undefined}
                    className="h-10"
                    {...field}
                  />
                </FormControl>
                <FormDescription className="text-xs">
                  {discountType === 'percentage' 
                    ? 'Enter a percentage (1-100%)' 
                    : 'Enter an amount in £'}
                </FormDescription>
                <FormMessage />
              </FormItem>
            )}
          />
          
          <FormField
            control={form.control}
            name="minOrderAmount"
            render={({ field }) => (
              <FormItem className="col-span-1">
                <FormLabel className="text-sm font-medium">Minimum Order Amount (£)</FormLabel>
                <FormControl>
                  <Input type="number" step="0.01" min="0" className="h-10" {...field} />
                </FormControl>
                <FormDescription className="text-xs">
                  Minimum purchase required
                </FormDescription>
                <FormMessage />
              </FormItem>
            )}
          />
          
          <FormField
            control={form.control}
            name="maxUsage"
            render={({ field }) => (
              <FormItem className="col-span-1">
                <FormLabel className="text-sm font-medium">Maximum Usage Count</FormLabel>
                <FormControl>
                  <Input 
                    type="number" 
                    min="1"
                    placeholder="Unlimited" 
                    className="h-10"
                    {...field}
                    value={field.value === null ? '' : field.value}
                    onChange={(e) => {
                      const value = e.target.value;
                      field.onChange(value === '' ? null : parseInt(value, 10));
                    }}
                  />
                </FormControl>
                <FormDescription className="text-xs">
                  Leave empty for unlimited usage (currently used: {promotion.usageCount} times)
                </FormDescription>
                <FormMessage />
              </FormItem>
            )}
          />
        </div>

        <div className="grid grid-cols-2 gap-6">
          <FormField
            control={form.control}
            name="startDate"
            render={({ field }) => (
              <FormItem>
                <FormLabel className="text-sm font-medium">Start Date</FormLabel>
                <FormControl>
                  <Input type="date" className="h-10" {...field} />
                </FormControl>
                <FormMessage />
              </FormItem>
            )}
          />

          <FormField
            control={form.control}
            name="endDate"
            render={({ field }) => (
              <FormItem>
                <FormLabel className="text-sm font-medium">End Date (Optional)</FormLabel>
                <FormControl>
                  <Input 
                    type="date" 
                    className="h-10"
                    {...field}
                    value={field.value || ''}
                    onChange={(e) => {
                      const value = e.target.value;
                      field.onChange(value === '' ? null : value);
                    }}
                  />
                </FormControl>
                <FormDescription className="text-xs">
                  Leave empty for no expiration
                </FormDescription>
                <FormMessage />
              </FormItem>
            )}
          />
        </div>

        <FormField
          control={form.control}
          name="isActive"
          render={({ field }) => (
            <FormItem className="flex flex-row items-center justify-between rounded-lg border p-4">
              <div className="space-y-0.5">
                <FormLabel className="text-base">Active Status</FormLabel>
                <FormDescription>
                  Enable or disable this promotion
                </FormDescription>
              </div>
              <FormControl>
                <Switch
                  checked={field.value}
                  onCheckedChange={field.onChange}
                />
              </FormControl>
            </FormItem>
          )}
        />

        {/* Product Applicability Section */}
        <div className="space-y-4 border rounded-lg p-4">
          <h3 className="text-lg font-semibold">Product Applicability</h3>
          
          <FormField
            control={form.control}
            name="applicableProducts"
            render={({ field }) => (
              <FormItem>
                <FormLabel className="text-sm font-medium">Apply Promotion To</FormLabel>
                <FormControl>
                  <RadioGroup
                    onValueChange={field.onChange}
                    value={field.value}
                    className="flex flex-col space-y-2"
                  >
                    <div className="flex items-center space-x-2">
                      <RadioGroupItem value="all" id="edit-all-products" />
                      <label htmlFor="edit-all-products" className="cursor-pointer">All products</label>
                    </div>
                    <div className="flex items-center space-x-2">
                      <RadioGroupItem value="specific" id="edit-specific-products" />
                      <label htmlFor="edit-specific-products" className="cursor-pointer">Only specific products</label>
                    </div>
                    <div className="flex items-center space-x-2">
                      <RadioGroupItem value="exclude_specific" id="edit-exclude-products" />
                      <label htmlFor="edit-exclude-products" className="cursor-pointer">All products except specific ones</label>
                    </div>
                  </RadioGroup>
                </FormControl>
                <FormMessage />
              </FormItem>
            )}
          />

          {/* Show blacklist selector for "all" and "exclude_specific" modes */}
          {(form.watch('applicableProducts') === 'all' || form.watch('applicableProducts') === 'exclude_specific') && (
            <FormField
              control={form.control}
              name="blacklistedProducts"
              render={({ field }) => (
                <FormItem>
                  <FormLabel className="text-sm font-medium">
                    {form.watch('applicableProducts') === 'all' 
                      ? 'Exclude Products (Blacklist)' 
                      : 'Products to Exclude'}
                  </FormLabel>
                  <FormControl>
                    <ProductSelector
                      selectedProductIds={field.value}
                      onSelectionChange={field.onChange}
                      placeholder={
                        form.watch('applicableProducts') === 'all'
                          ? "Select products to exclude from this promotion..."
                          : "Select additional products to exclude..."
                      }
                    />
                  </FormControl>
                  <FormDescription className="text-xs">
                    {form.watch('applicableProducts') === 'all'
                      ? 'Select products that should not be eligible for this promotion'
                      : 'Select products to exclude in addition to those selected above'}
                  </FormDescription>
                  <FormMessage />
                </FormItem>
              )}
            />
          )}

          {/* Show specific products selector for "specific" and "exclude_specific" modes */}
          {(form.watch('applicableProducts') === 'specific' || form.watch('applicableProducts') === 'exclude_specific') && (
            <FormField
              control={form.control}
              name="specificProducts"
              render={({ field }) => (
                <FormItem>
                  <FormLabel className="text-sm font-medium">
                    {form.watch('applicableProducts') === 'specific' 
                      ? 'Select Specific Products' 
                      : 'Products to Exclude'}
                  </FormLabel>
                  <FormControl>
                    <ProductSelector
                      selectedProductIds={field.value}
                      onSelectionChange={field.onChange}
                      placeholder={
                        form.watch('applicableProducts') === 'specific'
                          ? "Select products eligible for this promotion..."
                          : "Select products to exclude..."
                      }
                    />
                  </FormControl>
                  <FormDescription className="text-xs">
                    {form.watch('applicableProducts') === 'specific'
                      ? 'Only selected products will be eligible for this promotion'
                      : 'Selected products will be excluded from this promotion'}
                  </FormDescription>
                  <FormMessage />
                </FormItem>
              )}
            />
          )}
        </div>

        <FormField
          control={form.control}
          name="description"
          render={({ field }) => (
            <FormItem>
              <FormLabel>Description (Optional)</FormLabel>
              <FormControl>
                <Textarea
                  placeholder="Enter a brief description for this promotion"
                  {...field}
                />
              </FormControl>
              <FormDescription>
                Internal notes about this promotion
              </FormDescription>
              <FormMessage />
            </FormItem>
          )}
        />

        <div className="flex justify-end gap-3 pt-4">
          <Button
            type="button"
            variant="outline"
            onClick={onCancel}
            disabled={isSubmitting}
          >
            <X className="h-4 w-4 mr-2" />
            Cancel
          </Button>
          <Button
            type="submit"
            disabled={isSubmitting}
          >
            {isSubmitting ? (
              <>
                <Loader2 className="h-4 w-4 mr-2 animate-spin" />
                Updating...
              </>
            ) : (
              <>
                <Save className="h-4 w-4 mr-2" />
                Update Promotion
              </>
            )}
          </Button>
        </div>
      </form>
    </Form>
  );
}