// WARNING: DO NOT modify the Item class - the goblin in the corner will insta-rage!

class Item {
  String name;
  int sellIn;
  int quality;

  Item(this.name, this.sellIn, this.quality);

  @override
  String toString() => '$name, $sellIn, $quality';
}

/// Quality bounds - domain constraints
const int _minQuality = 0;
const int _maxQuality = 50;

/// Helper methods for quality management
void _degradeQuality(Item item, int amount) {
  item.quality = (item.quality - amount).clamp(_minQuality, _maxQuality);
}

void _improveQuality(Item item, int amount) {
  item.quality = (item.quality + amount).clamp(_minQuality, _maxQuality);
}

/// Strategy pattern: Each item type has its own update behavior
abstract class ItemUpdater {
  void update(Item item);
}

class NormalItemUpdater implements ItemUpdater {
  @override
  void update(Item item) {
    // Quality decreases by 1 each day
    _degradeQuality(item, 1);

    item.sellIn -= 1;

    // After sell-by date, quality degrades twice as fast
    if (item.sellIn < 0) {
      _degradeQuality(item, 1);
    }
  }
}

class AgedBrieUpdater implements ItemUpdater {
  @override
  void update(Item item) {
    // Quality increases as it ages
    _improveQuality(item, 1);

    item.sellIn -= 1;

    // After sell-by date, quality increases twice as fast
    if (item.sellIn < 0) {
      _improveQuality(item, 1);
    }
  }
}

class BackstagePassUpdater implements ItemUpdater {
  @override
  void update(Item item) {
    // Base quality increase
    _improveQuality(item, 1);

    // 10 days or less: +1 additional
    if (item.sellIn <= 10) {
      _improveQuality(item, 1);
    }

    // 5 days or less: +1 additional (total +3/day)
    if (item.sellIn <= 5) {
      _improveQuality(item, 1);
    }

    item.sellIn -= 1;

    // After concert, quality drops to 0
    if (item.sellIn < 0) {
      item.quality = _minQuality;
    }
  }
}

class SulfurasUpdater implements ItemUpdater {
  @override
  void update(Item item) {
    // Legendary item never changes
    // Quality always 80, sellIn never decreases
  }
}

class ConjuredItemUpdater implements ItemUpdater {
  @override
  void update(Item item) {
    // Conjured items degrade twice as fast as normal items
    _degradeQuality(item, 2);

    item.sellIn -= 1;

    // After sell-by date, quality degrades twice as fast (4x total)
    if (item.sellIn < 0) {
      _degradeQuality(item, 2);
    }
  }
}

class GildedRose {
  List<Item> items;

  GildedRose(this.items);

  void updateQuality() {
    for (final item in items) {
      final updater = _selectUpdater(item);
      updater.update(item);
    }
  }

  ItemUpdater _selectUpdater(Item item) {
    if (item.name == 'Sulfuras, Hand of Ragnaros') {
      return SulfurasUpdater();
    } else if (item.name == 'Aged Brie') {
      return AgedBrieUpdater();
    } else if (item.name == 'Backstage passes to a TAFKAL80ETC concert') {
      return BackstagePassUpdater();
    } else if (item.name.startsWith('Conjured')) {
      return ConjuredItemUpdater();
    } else {
      return NormalItemUpdater();
    }
  }
}