CartWise/tests/CartWise.Application.Tests/PriceServiceTests.cs

using CartWise.Application.Services;
using CartWise.Domain.Entities;
using CartWise.Domain.Enums;
using CartWise.Infrastructure.Data;
using Microsoft.EntityFrameworkCore;

namespace CartWise.Application.Tests;

public class PriceServiceTests : IDisposable
{
    private static readonly DateTime Now = new(2026, 8, 10, 12, 0, 0, DateTimeKind.Utc);

    private readonly CartWiseDbContext _db;
    private readonly PriceService _sut;

    public PriceServiceTests()
    {
        var options = new DbContextOptionsBuilder<CartWiseDbContext>()
            .UseInMemoryDatabase(Guid.NewGuid().ToString())
            .Options;

        _db = new CartWiseDbContext(options);
        _sut = new PriceService(_db, TimeProvider.System);
    }

    public void Dispose()
    {
        _db.Dispose();
        GC.SuppressFinalize(this);
    }

    [Fact]
    public async Task GetHouseholdPriceInsightAsync_ReturnsNullWhenNoObservationsExist()
    {
        var insight = await _sut.GetHouseholdPriceInsightAsync(Guid.NewGuid(), Guid.NewGuid());

        Assert.Null(insight);
    }

    [Fact]
    public async Task RecordObservationAsync_ThenGetInsight_ReturnsLatestAverageMedianAndLowest()
    {
        var householdId = Guid.NewGuid();
        var productId = Guid.NewGuid();

        await _sut.RecordObservationAsync(productId, 3.00m, Now.AddDays(-2), PriceObservationSourceType.UserEntered, 1m, householdId: householdId);
        await _sut.RecordObservationAsync(productId, 5.00m, Now.AddDays(-1), PriceObservationSourceType.UserEntered, 1m, householdId: householdId);
        await _sut.RecordObservationAsync(productId, 4.00m, Now, PriceObservationSourceType.UserEntered, 1m, householdId: householdId);

        var insight = await _sut.GetHouseholdPriceInsightAsync(householdId, productId);

        Assert.NotNull(insight);
        Assert.Equal(3, insight!.ObservationCount);
        Assert.Equal(4.00m, insight.LatestPrice);
        Assert.Equal(Now, insight.LatestObservedUtc);
        Assert.Equal(4.00m, insight.AveragePrice);
        Assert.Equal(4.00m, insight.MedianPrice);
        Assert.Equal(3.00m, insight.LowestPrice);
    }

    [Fact]
    public async Task GetHouseholdPriceInsightAsync_ComputesMedianForEvenCount()
    {
        var householdId = Guid.NewGuid();
        var productId = Guid.NewGuid();

        await _sut.RecordObservationAsync(productId, 2.00m, Now.AddDays(-1), PriceObservationSourceType.UserEntered, 1m, householdId: householdId);
        await _sut.RecordObservationAsync(productId, 4.00m, Now, PriceObservationSourceType.UserEntered, 1m, householdId: householdId);

        var insight = await _sut.GetHouseholdPriceInsightAsync(householdId, productId);

        Assert.Equal(3.00m, insight!.MedianPrice);
    }

    [Fact]
    public async Task GetHouseholdPriceInsightAsync_DoesNotMixDifferentHouseholds()
    {
        var productId = Guid.NewGuid();
        await _sut.RecordObservationAsync(productId, 3.00m, Now, PriceObservationSourceType.UserEntered, 1m, householdId: Guid.NewGuid());

        var insight = await _sut.GetHouseholdPriceInsightAsync(Guid.NewGuid(), productId);

        Assert.Null(insight);
    }

    [Fact]
    public async Task GetHouseholdPriceHistoryAsync_ReturnsNewestFirst()
    {
        var householdId = Guid.NewGuid();
        var productId = Guid.NewGuid();
        await _sut.RecordObservationAsync(productId, 3.00m, Now.AddDays(-1), PriceObservationSourceType.UserEntered, 1m, householdId: householdId);
        await _sut.RecordObservationAsync(productId, 4.00m, Now, PriceObservationSourceType.UserEntered, 1m, householdId: householdId);

        var history = await _sut.GetHouseholdPriceHistoryAsync(householdId, productId);

        Assert.Equal(2, history.Count);
        Assert.Equal(4.00m, history[0].Price);
        Assert.Equal(3.00m, history[1].Price);
    }

    [Fact]
    public async Task GetHouseholdPricedProductsAsync_ReturnsEmptyWhenNoObservationsExist()
    {
        var products = await _sut.GetHouseholdPricedProductsAsync(Guid.NewGuid());

        Assert.Empty(products);
    }

    [Fact]
    public async Task GetHouseholdPricedProductsAsync_GroupsByProductAndSortsByName()
    {
        var householdId = Guid.NewGuid();
        var milk = new Product("Milk", ProductSourceType.Manual, Now);
        var bread = new Product("Bread", ProductSourceType.Manual, Now);
        _db.Products.Add(milk);
        _db.Products.Add(bread);
        await _db.SaveChangesAsync();

        await _sut.RecordObservationAsync(milk.ProductId, 3.00m, Now.AddDays(-1), PriceObservationSourceType.UserEntered, 1m, householdId: householdId);
        await _sut.RecordObservationAsync(milk.ProductId, 4.00m, Now, PriceObservationSourceType.UserEntered, 1m, householdId: householdId);
        await _sut.RecordObservationAsync(bread.ProductId, 2.50m, Now, PriceObservationSourceType.UserEntered, 1m, householdId: householdId);

        var products = await _sut.GetHouseholdPricedProductsAsync(householdId);

        Assert.Equal(2, products.Count);
        Assert.Equal("Bread", products[0].ProductName);
        Assert.Equal("Milk", products[1].ProductName);
        Assert.Equal(2, products[1].ObservationCount);
        Assert.Equal(4.00m, products[1].LatestPrice);
        Assert.Equal(3.50m, products[1].AveragePrice);
        Assert.Equal(3.00m, products[1].LowestPrice);
    }

    [Fact]
    public async Task GetHouseholdPricedProductsAsync_DoesNotMixDifferentHouseholds()
    {
        var milk = new Product("Milk", ProductSourceType.Manual, Now);
        _db.Products.Add(milk);
        await _db.SaveChangesAsync();

        await _sut.RecordObservationAsync(milk.ProductId, 3.00m, Now, PriceObservationSourceType.UserEntered, 1m, householdId: Guid.NewGuid());

        var products = await _sut.GetHouseholdPricedProductsAsync(Guid.NewGuid());

        Assert.Empty(products);
    }
}