MeterVault/tests/Integration.Tests/MeterPeriodServiceTests.cs

using MeterVault.Core.Domain;
using MeterVault.Infrastructure.Costing;
using MeterVault.Infrastructure.Dashboard;
using MeterVault.Infrastructure.Options;
using MeterVault.Infrastructure.Persistence;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Options;

namespace MeterVault.Integration.Tests;

/// <summary>
/// The meter-detail headline numbers: month/year totals bucketed in the instance timezone, and the
/// generation-vs-consumption split that decides which of the two a meter reports.
/// </summary>
[Collection("Timescale")]
public sealed class MeterPeriodServiceTests(TimescaleFixture fx)
{
    [Fact]
    public async Task Buckets_by_local_month_and_compares_with_the_previous_one()
    {
        await using var db = fx.CreateContext();
        var meterId = await SetupAsync(db, MeterMode.CumulativeCounter);
        var today = DateOnly.FromDateTime(DateTime.UtcNow);
        var thisMonth = new DateOnly(today.Year, today.Month, 1);
        var lastMonth = thisMonth.AddMonths(-1);

        await AddConsumptionAsync(db, meterId, ConsumptionKind.Consumption, thisMonth.AddDays(1), 30);
        await AddConsumptionAsync(db, meterId, ConsumptionKind.Consumption, lastMonth.AddDays(3), 100);

        var view = await NewService().GetAsync(meterId);

        Assert.NotNull(view);
        Assert.Equal("Consumption", view!.Label);
        Assert.Equal(30d, view.MonthToDate, 3);
        Assert.Equal(100d, view.LastMonth, 3);
        Assert.Equal(130d, view.YearToDate, 3);

        // Projection scales the partial month up, so it must be at least what has already happened.
        Assert.True(view.MonthProjected >= view.MonthToDate);

        await CleanupAsync(db, meterId);
    }

    [Fact]
    public async Task A_generation_counter_reports_generation_not_consumption()
    {
        // Regression: a PV meter showed "0 kWh consumption", which is true and useless.
        await using var db = fx.CreateContext();
        var meterId = await SetupAsync(db, MeterMode.GenerationCounter);
        var today = DateOnly.FromDateTime(DateTime.UtcNow);

        await AddConsumptionAsync(
            db, meterId, ConsumptionKind.Generation, new DateOnly(today.Year, today.Month, 1).AddDays(1), 42);

        var view = await NewService().GetAsync(meterId);

        Assert.NotNull(view);
        Assert.Equal("Generation", view!.Label);
        Assert.Equal(42d, view.MonthToDate, 3);

        await CleanupAsync(db, meterId);
    }

    [Fact]
    public async Task A_meter_with_no_consumption_yields_an_empty_history_rather_than_a_flat_line()
    {
        await using var db = fx.CreateContext();
        var meterId = await SetupAsync(db, MeterMode.CumulativeCounter);

        var view = await NewService().GetAsync(meterId);

        Assert.NotNull(view);
        Assert.False(view!.HasHistory);
        Assert.Empty(view.Last12Months);
        Assert.Null(view.MonthChange); // no previous month to divide by

        await CleanupAsync(db, meterId);
    }

    [Fact]
    public async Task A_negative_previous_period_reports_no_basis_rather_than_an_inverted_percentage()
    {
        // Net export: -100 -> -150 is half again as much exported, but dividing by a negative
        // baseline would render it "+50%", which reads as more consumption.
        await using var db = fx.CreateContext();
        var meterId = await SetupAsync(db, MeterMode.CumulativeCounter);
        var today = DateOnly.FromDateTime(DateTime.UtcNow);
        var thisMonth = new DateOnly(today.Year, today.Month, 1);

        await AddConsumptionAsync(db, meterId, ConsumptionKind.Consumption, thisMonth.AddDays(1), -150);
        await AddConsumptionAsync(db, meterId, ConsumptionKind.Consumption, thisMonth.AddMonths(-1).AddDays(3), -100);

        var view = await NewService().GetAsync(meterId);

        Assert.NotNull(view);
        Assert.Null(view!.MonthChange);

        await CleanupAsync(db, meterId);
    }

    private MeterPeriodService NewService()
    {
        var options = Microsoft.Extensions.Options.Options.Create(
            new MeterVaultOptions { TimeZone = "Europe/Berlin", Currency = "EUR" });
        return new MeterPeriodService(fx, new CostService(fx), options);
    }

    private static async Task<int> SetupAsync(MeterVaultDbContext db, MeterMode mode)
    {
        await DatabaseSeeder.SeedAsync(db);
        var type = await db.EnergyTypes.FirstAsync(t => t.Key == "electricity");

        var meter = new Meter
        {
            Name = $"period-{Guid.NewGuid():N}",
            EnergyTypeId = type.Id,
            Mode = mode,
            Unit = "kWh",
        };
        db.Meters.Add(meter);
        await db.SaveChangesAsync();
        return meter.Id;
    }

    private static async Task AddConsumptionAsync(
        MeterVaultDbContext db, int meterId, ConsumptionKind kind, DateOnly day, double amount)
    {
        db.Consumption.Add(new Consumption
        {
            MeterId = meterId,
            // Midday local, so the row cannot drift into an adjacent month through the UTC offset.
            Time = new DateTimeOffset(day.Year, day.Month, day.Day, 12, 0, 0, TimeSpan.Zero),
            Kind = kind,
            Amount = amount,
            Quality = ReadingQuality.Measured,
        });
        await db.SaveChangesAsync();
    }

    private static async Task CleanupAsync(MeterVaultDbContext db, int meterId)
    {
        await db.Consumption.Where(c => c.MeterId == meterId).ExecuteDeleteAsync();
        await db.Meters.Where(m => m.Id == meterId).ExecuteDeleteAsync();
    }
}