using Xunit;
using System.Collections.Generic;

namespace csharpcore
{
    public class BasicItemTest
    {
        [Fact]
        public void ShouldUpdateQuality()
        {
            const int startSellIn = 31;
            const int startQuality = 20;

            var item = new Item {Name = "+5 Dexterity Vest", SellIn = startSellIn, Quality = startQuality};
            var app = new GildedRose(new List<Item> {item});
            
            app.UpdateQuality();
            Assert.Equal("+5 Dexterity Vest", item.Name);
            Assert.Equal(startSellIn - 1, item.SellIn);
            Assert.Equal(startQuality - 1, item.Quality);
        }

        [Theory]
        [InlineData(1, 1)]
        [InlineData(0, 2)] /* Once the sell by date has passed, Quality degrades twice as fast. */
        [InlineData(-1, 2)] /* Once the sell by date has passed, Quality degrades twice as fast. */
        public void ShouldDecrementQualityAccordingToSellInValue(int sellIn, int expectedDecrement)
        {
            const int startQuality = 20;

            var item = new Item {Name = "+5 Dexterity Vest", SellIn = sellIn, Quality = startQuality};
            var app = new GildedRose(new List<Item> {item});
            
            app.UpdateQuality();

            Assert.Equal(startQuality - expectedDecrement, item.Quality);
        }

        [Fact]
        public void ShouldNotSetDecrementQualityToNegativeValue()
        {
            const int startQuality = 0;

            var item = new Item {Name = "+5 Dexterity Vest", SellIn = 1, Quality = startQuality};
            var app = new GildedRose(new List<Item> {item});
            
            app.UpdateQuality();
            app.UpdateQuality();
            app.UpdateQuality();
            app.UpdateQuality();

            Assert.Equal(0, item.Quality);
        }
    }
}