using MeterVault.Core.Domain;
using MeterVault.Core.Normalization;
using static MeterVault.Core.Tests.TestData;

namespace MeterVault.Core.Tests;

public sealed class CumulativeCounterNormalizerTests
{
    private readonly INormalizationEngine _engine = NormalizationEngine.CreateDefault();

    [Fact]
    public void Straight_deltas_match_the_electricity_house_meter()
    {
        // Zähler Haus: Sept 0 → Okt 411 → Nov 1153 → Dez 1968 (SDD reference data).
        var ctx = new NormalizationContext
        {
            Meter = new MeterConfig { MeterId = 1, Mode = MeterMode.CumulativeCounter, Unit = "kWh" },
            Readings =
            [
                Reading(1, Month(2022, 9), 0),
                Reading(1, Month(2022, 10), 411),
                Reading(1, Month(2022, 11), 1153),
                Reading(1, Month(2022, 12), 1968),
            ],
        };

        var result = _engine.Normalize(ctx);

        Assert.Equal([0d, 411d, 742d, 815d], result.Select(c => c.Amount));
        Assert.All(result, c => Assert.Equal(ConsumptionKind.Consumption, c.Kind));
    }

    [Fact]
    public void First_reading_books_the_full_register_against_a_zero_baseline()
    {
        // Zähler Auto appears mid-series: first reading 3755 → month-one consumption 3755.
        var ctx = new NormalizationContext
        {
            Meter = new MeterConfig { MeterId = 3, Mode = MeterMode.CumulativeCounter, Unit = "kWh" },
            Readings = [Reading(3, Month(2023, 5), 3755), Reading(3, Month(2023, 6), 3960)],
        };

        var result = _engine.Normalize(ctx);

        Assert.Equal([3755d, 205d], result.Select(c => c.Amount));
    }

    [Fact]
    public void Counter_reset_rebaselines_at_new_value()
    {
        var ctx = new NormalizationContext
        {
            Meter = new MeterConfig
            {
                MeterId = 1,
                Mode = MeterMode.CumulativeCounter,
                Unit = "kWh",
                InitialBaseline = 90,
            },
            Readings =
            [
                Reading(1, Month(2023, 1), 100),
                Reading(1, Month(2023, 2), 150),
                Reading(1, Month(2023, 3), 30),
                Reading(1, Month(2023, 4), 80),
            ],
            Events = [Reset(1, Month(2023, 3), newValue: 0)],
        };

        var result = _engine.Normalize(ctx);

        Assert.Equal([10d, 50d, 30d, 50d], result.Select(c => c.Amount));
    }

    [Fact]
    public void Counter_reset_with_a_final_register_books_the_stretch_before_the_reset()
    {
        // The register climbed 150 → 170 after the February reading, then reset to 0 and reached 30
        // by March. Knowing the 170 turns the reset from "lose 20" into the swap formula: 20 + 30.
        var ctx = new NormalizationContext
        {
            Meter = new MeterConfig { MeterId = 1, Mode = MeterMode.CumulativeCounter, Unit = "kWh", InitialBaseline = 90 },
            Readings =
            [
                Reading(1, Month(2023, 1), 100),
                Reading(1, Month(2023, 2), 150),
                Reading(1, Month(2023, 3), 30),
                Reading(1, Month(2023, 4), 80),
            ],
            Events = [Reset(1, Month(2023, 3), newValue: 0, prevValue: 170)],
        };

        var result = _engine.Normalize(ctx);

        Assert.Equal([10d, 50d, 50d, 50d], result.Select(c => c.Amount));
    }

    [Fact]
    public void Swap_recorded_with_the_new_meters_start_reading_at_the_same_instant_books_the_tail_there()
    {
        // What the meter page records for "the meter was swapped today": the swap event and a reading of
        // the new register's start value, both at the swap instant. The old meter's tail (873 − 861)
        // lands at the swap, and the next reading counts from the new register's start.
        var swapAt = Month(2023, 3).AddDays(16).AddHours(9);
        var ctx = new NormalizationContext
        {
            Meter = new MeterConfig { MeterId = 10, Mode = MeterMode.CumulativeCounter, Unit = "m3", InitialBaseline = 848 },
            Readings =
            [
                DayReading(10, Month(2023, 3), 861),
                Reading(10, swapAt, 2),
                Reading(10, swapAt.AddDays(1), 2.5),
            ],
            Events = [Swap(10, swapAt, prevValue: 873, newValue: 2)],
        };

        var result = _engine.Normalize(ctx);

        Assert.Equal([13d, 12d, 0.5d], result.Select(c => c.Amount));
        Assert.Equal(swapAt, result[1].Time);
    }

    [Fact]
    public void Unexplained_decrease_yields_zero_and_marks_quality()
    {
        var ctx = new NormalizationContext
        {
            Meter = new MeterConfig { MeterId = 1, Mode = MeterMode.CumulativeCounter, Unit = "kWh" },
            Readings = [Reading(1, Month(2023, 1), 100), Reading(1, Month(2023, 2), 60)],
        };

        var result = _engine.Normalize(ctx);

        Assert.Equal(0d, result[1].Amount);
        Assert.Equal(ReadingQuality.Estimated, result[1].Quality);
    }

    [Fact]
    public void Generation_meter_emits_generation_kind()
    {
        // Solar 2: Okt 0 → Nov 0 → ... → first real reading 7 in Feb.
        var ctx = new NormalizationContext
        {
            Meter = new MeterConfig { MeterId = 5, Mode = MeterMode.GenerationCounter, Unit = "kWh" },
            Readings = [Reading(5, Month(2023, 1), 0), Reading(5, Month(2023, 2), 7)],
        };

        var result = _engine.Normalize(ctx);

        Assert.Equal([0d, 7d], result.Select(c => c.Amount));
        Assert.All(result, c => Assert.Equal(ConsumptionKind.Generation, c.Kind));
    }
}