'use client';

import { useMemo, useState } from 'react';
import { Check, ChevronsUpDown } from 'lucide-react';

import { Button } from '@/components/ui/button';
import {
  Command,
  CommandEmpty,
  CommandGroup,
  CommandInput,
  CommandItem,
  CommandList,
} from '@/components/ui/command';
import { Popover, PopoverContent, PopoverTrigger } from '@/components/ui/popover';
import { cn } from '@/lib/utils';
import { subdivisionsForCountry } from '@/lib/i18n/subdivisions';
import type { CountryCode } from '@/lib/i18n/countries';

interface SubdivisionComboboxProps {
  value: string | null | undefined;
  onChange: (code: string | null) => void;
  /**
   * Country whose subdivisions populate the dropdown. When the country
   * has no recognized subdivisions, the trigger renders disabled with
   * an empty-state hint so the form still lays out.
   */
  country: CountryCode | null | undefined;
  placeholder?: string;
  disabled?: boolean;
  className?: string;
  clearable?: boolean;
  id?: string;
  'data-testid'?: string;
  /** Open the dropdown on first render. Used by inline-edit wrappers. */
  defaultOpen?: boolean;
  /** Notified whenever the dropdown opens/closes. Inline-edit wrappers use
   *  this to auto-exit edit mode when the user dismisses without picking. */
  onOpenChange?: (open: boolean) => void;
}

export function SubdivisionCombobox({
  value,
  onChange,
  country,
  placeholder = 'Select region…',
  disabled,
  className,
  clearable = true,
  id,
  'data-testid': testId,
  defaultOpen = false,
  onOpenChange,
}: SubdivisionComboboxProps) {
  const [open, setOpen] = useState(defaultOpen);
  const handleOpenChange = (next: boolean) => {
    setOpen(next);
    onOpenChange?.(next);
  };

  const options = useMemo(() => {
    if (!country) return [];
    return subdivisionsForCountry(country);
  }, [country]);

  const selected = value ? options.find((o) => o.code === value) : undefined;
  const noCountry = !country;
  const noSubdivisions = !noCountry && options.length === 0;
  const isDisabled = disabled || noCountry || noSubdivisions;

  let triggerLabel: string;
  if (selected) triggerLabel = selected.name;
  else if (noCountry) triggerLabel = 'Pick a country first';
  else if (noSubdivisions) triggerLabel = 'No regions available';
  else triggerLabel = placeholder;

  return (
    <Popover open={open} onOpenChange={handleOpenChange} modal>
      <PopoverTrigger asChild>
        <Button
          id={id}
          variant="outline"
          role="combobox"
          aria-expanded={open}
          disabled={isDisabled}
          className={cn('w-full justify-between', !selected && 'text-muted-foreground', className)}
          data-testid={testId}
        >
          <span className="truncate text-sm">{triggerLabel}</span>
          <ChevronsUpDown className="ml-2 h-4 w-4 shrink-0 opacity-50" aria-hidden />
        </Button>
      </PopoverTrigger>
      <PopoverContent className="w-[320px] p-0" align="start">
        <Command>
          <CommandInput placeholder={`Search ${country ?? 'regions'}…`} />
          <CommandList>
            <CommandEmpty>No region found.</CommandEmpty>
            {clearable && value ? (
              <CommandGroup>
                <CommandItem
                  value="__clear__"
                  onSelect={() => {
                    onChange(null);
                    setOpen(false);
                  }}
                  className="text-muted-foreground"
                >
                  Clear selection
                </CommandItem>
              </CommandGroup>
            ) : null}
            <CommandGroup>
              {options.map((opt) => (
                <CommandItem
                  key={opt.code}
                  value={`${opt.name} ${opt.code}`}
                  onSelect={() => {
                    onChange(opt.code);
                    setOpen(false);
                  }}
                >
                  <Check
                    className={cn('mr-2 h-4 w-4', value === opt.code ? 'opacity-100' : 'opacity-0')}
                  />
                  <span className="flex-1 truncate text-sm">{opt.name}</span>
                  <span className="text-xs text-muted-foreground">{opt.code}</span>
                </CommandItem>
              ))}
            </CommandGroup>
          </CommandList>
        </Command>
      </PopoverContent>
    </Popover>
  );
}