'use client';

import { useState, useRef, useEffect } from 'react';
import { Plus, Minus } from 'lucide-react';

interface QuantityDisplayProps {
  itemId: string;
  currentQuantity: number;
  onQuantityChange: (newQty: number) => Promise<void>;
}

export default function QuantityDisplay({
  itemId,
  currentQuantity,
  onQuantityChange,
}: QuantityDisplayProps) {
  const [isEditing, setIsEditing] = useState(false);
  const [localQuantity, setLocalQuantity] = useState(currentQuantity);
  const [isLoading, setIsLoading] = useState(false);
  const inputRef = useRef<HTMLInputElement>(null);

  useEffect(() => {
    setLocalQuantity(currentQuantity);
  }, [currentQuantity]);

  useEffect(() => {
    if (isEditing && inputRef.current) {
      inputRef.current.focus();
      inputRef.current.select();
    }
  }, [isEditing]);

  const handleTapToEdit = () => {
    setIsEditing(true);
  };

  const handleIncrement = () => {
    setLocalQuantity(prev => Math.max(0, prev + 1));
  };

  const handleDecrement = () => {
    setLocalQuantity(prev => Math.max(0, prev - 1));
  };

  const handleInputChange = (e: React.ChangeEvent<HTMLInputElement>) => {
    const value = e.target.value;
    if (value === '' || /^\d+$/.test(value)) {
      setLocalQuantity(value === '' ? 0 : parseInt(value, 10));
    }
  };

  const handleCommit = async () => {
    if (localQuantity === currentQuantity) {
      setIsEditing(false);
      return;
    }

    try {
      setIsLoading(true);
      await onQuantityChange(localQuantity);
      setIsEditing(false);
    } catch (error) {
      // Revert on error
      setLocalQuantity(currentQuantity);
      setIsEditing(false);
    } finally {
      setIsLoading(false);
    }
  };

  const handleCancel = () => {
    setLocalQuantity(currentQuantity);
    setIsEditing(false);
  };

  const handleKeyDown = (e: React.KeyboardEvent<HTMLInputElement>) => {
    if (e.key === 'Enter') {
      handleCommit();
    } else if (e.key === 'Escape') {
      handleCancel();
    }
  };

  if (isEditing) {
    return (
      <div className="flex items-center gap-2 bg-slate-900/50 rounded-lg px-3 py-2">
        <button
          onClick={handleDecrement}
          disabled={isLoading}
          aria-label="Decrease quantity"
          className="p-1 hover:bg-slate-800 rounded text-secondary hover:text-primary transition-colors disabled:opacity-50 disabled:cursor-not-allowed"
        >
          <Minus size={16} />
        </button>

        <input
          ref={inputRef}
          type="text"
          inputMode="numeric"
          value={localQuantity}
          onChange={handleInputChange}
          onBlur={handleCommit}
          onKeyDown={handleKeyDown}
          disabled={isLoading}
          aria-label="Quantity"
          className="w-12 text-center bg-transparent text-primary font-medium focus:outline-none disabled:opacity-50"
        />

        <button
          onClick={handleIncrement}
          disabled={isLoading}
          aria-label="Increase quantity"
          className="p-1 hover:bg-slate-800 rounded text-secondary hover:text-primary transition-colors disabled:opacity-50 disabled:cursor-not-allowed"
        >
          <Plus size={16} />
        </button>
      </div>
    );
  }

  return (
    <button
      onClick={handleTapToEdit}
      disabled={isLoading}
      aria-label={`Quantity: ${currentQuantity}. Tap to edit`}
      className="text-lg font-medium text-primary hover:bg-slate-900/30 px-3 py-2 rounded-lg transition-colors disabled:opacity-50 disabled:cursor-not-allowed"
    >
      {currentQuantity}
    </button>
  );
}