using MeterVault.Core.Domain;
using MeterVault.Infrastructure.Normalization;
using MeterVault.Infrastructure.Persistence;
using Microsoft.EntityFrameworkCore;

namespace MeterVault.Infrastructure.Import;

/// <summary>
/// Loads the four bundled <em>Energiebilanz</em> sheets as a ready-made demo/starter dataset:
/// creates the reference meters, tank, tariff history and category memberships, then imports each
/// sheet through the normal <see cref="ImportService"/>. Idempotent — a marker meter guards reruns.
/// </summary>
public sealed class ReferenceDataImporter(MeterVaultDbContext db, ImportService importService, CsvImporter csvImporter)
{
    public const string ElectricityFile = "Energiebilanz - Strom Verbrauch.csv";
    public const string WaterFile = "Energiebilanz - Wasser.csv";
    public const string OilFile = "Energiebilanz - Heizöl Verbrauch.csv";
    public const string CostsFile = "Energiebilanz - Kosten.csv";

    private const string MarkerName = "Zähler Haus";

    private readonly MeterVaultDbContext _db = db;
    private readonly ImportService _importService = importService;
    private readonly CsvImporter _csvImporter = csvImporter;

    public async Task<bool> IsLoadedAsync(CancellationToken cancellationToken = default) =>
        await _db.Meters.AnyAsync(m => m.Name == MarkerName, cancellationToken).ConfigureAwait(false);

    public async Task LoadAsync(string sampleDataDirectory, CancellationToken cancellationToken = default)
    {
        if (await IsLoadedAsync(cancellationToken).ConfigureAwait(false))
        {
            return;
        }

        // Fail fast BEFORE creating the marker meter: if the CSVs are missing (e.g. not shipped in
        // the image) we must not seed a half-loaded dataset that IsLoadedAsync then reports as done.
        EnsureSampleFilesPresent(sampleDataDirectory);

        await DatabaseSeeder.SeedAsync(_db, cancellationToken).ConfigureAwait(false);

        var electricity = await EnergyTypeIdAsync("electricity", cancellationToken).ConfigureAwait(false);
        var water = await EnergyTypeIdAsync("water", cancellationToken).ConfigureAwait(false);
        var oil = await EnergyTypeIdAsync("heating_oil", cancellationToken).ConfigureAwait(false);

        var haus = Meter(MarkerName, electricity, MeterMode.CumulativeCounter, "kWh");
        var netz = Meter("Zähler Netz", electricity, MeterMode.CumulativeCounter, "kWh");
        var auto = Meter("Zähler Auto", electricity, MeterMode.CumulativeCounter, "kWh");
        var solar1 = Meter("Zähler Solar 1", electricity, MeterMode.GenerationCounter, "kWh");
        var solar2 = Meter("Zähler Solar 2", electricity, MeterMode.GenerationCounter, "kWh");
        var wasser = Meter("Zähler Wasser", water, MeterMode.CumulativeCounter, "m3", initialBaseline: 820);
        var oilTank = Meter("Öltank", oil, MeterMode.ConsumableBalance, "L");
        var burner = Meter("Brenner", oil, MeterMode.RuntimeCounter, "h");
        // A virtual "sum" meter: no readings of its own — in the flow view it equals Solar 1 + Solar 2.
        var sumSolar = Meter("Summe Solar", electricity, MeterMode.Virtual, "kWh");

        // Tag the PV meters' roles (config, not hardcoded names) so the Solar panel can derive
        // self-consumption = total_load − grid_import and savings generically (SDD §8.4).
        haus.Meta = MeterMeta.WithRole(haus.Meta, MeterRoles.TotalLoad);
        netz.Meta = MeterMeta.WithRole(netz.Meta, MeterRoles.GridImport);

        _db.Meters.AddRange(haus, netz, auto, solar1, solar2, wasser, oilTank, burner, sumSolar);
        await _db.SaveChangesAsync(cancellationToken).ConfigureAwait(false);

        _db.Tanks.Add(new Tank
        {
            MeterId = oilTank.Id,
            Capacity = 7000,
            Unit = "L",
            Calibration = $"{{\"volumePerUnit\":{ReferenceProfiles.OilLitresPerCm.ToString(System.Globalization.CultureInfo.InvariantCulture)}}}",
        });

        // Demo flow chain (electricity /energy view): Solar 1 + Solar 2 → Summe Solar; then
        // Grid + Summe Solar → Haus → Auto + "Other". The remainder under Grid/Summe Solar is the
        // input that didn't reach the house load (solar export / battery / inverter losses).
        _db.MeterLinks.AddRange(
            new MeterLink { FromMeterId = solar1.Id, ToMeterId = sumSolar.Id },
            new MeterLink { FromMeterId = solar2.Id, ToMeterId = sumSolar.Id },
            new MeterLink { FromMeterId = netz.Id, ToMeterId = haus.Id },
            new MeterLink { FromMeterId = sumSolar.Id, ToMeterId = haus.Id },
            new MeterLink { FromMeterId = haus.Id, ToMeterId = auto.Id });

        AddElectricityTariffs(electricity);
        AddTariff(TariffScope.EnergyType, water, 5.00, "EUR/m3", new DateOnly(2022, 11, 1));
        // Strom and Wasser costs are computed from meters + tariffs; only Heizung comes from the
        // Kosten sheet (oil has no tariff). Linking a meter AND importing its Kosten column into the
        // same category would double-count, so we keep exactly one cost source per category.
        await LinkStromAndWasserAsync(haus.Id, netz.Id, auto.Id, solar1.Id, solar2.Id, wasser.Id, cancellationToken).ConfigureAwait(false);
        await _db.SaveChangesAsync(cancellationToken).ConfigureAwait(false);

        var meterIds = new ReferenceMeterIds(haus.Id, netz.Id, auto.Id, solar1.Id, solar2.Id, wasser.Id, oilTank.Id, burner.Id);
        var categoryIds = await CategoryIdsAsync(cancellationToken).ConfigureAwait(false);

        await ImportSheetAsync(sampleDataDirectory, ElectricityFile, ReferenceProfiles.Electricity(meterIds), cancellationToken).ConfigureAwait(false);
        await ImportSheetAsync(sampleDataDirectory, WaterFile, ReferenceProfiles.Water(meterIds), cancellationToken).ConfigureAwait(false);
        await ImportSheetAsync(sampleDataDirectory, OilFile, ReferenceProfiles.HeatingOil(meterIds), cancellationToken).ConfigureAwait(false);
        await ImportSheetAsync(sampleDataDirectory, CostsFile, HeizungCostsProfile(categoryIds.Heizung), cancellationToken).ConfigureAwait(false);
    }

    /// <summary>Kosten profile that imports only the Heizung column — Strom/Wasser are metered.</summary>
    private static MappingProfile HeizungCostsProfile(int heizungCategoryId) => new()
    {
        Name = "Energiebilanz — Kosten (Heizung)",
        DateColumn = 0,
        DateKind = DateKind.MonthName,
        FirstDataRowIndex = 1,
        Columns = [new ColumnMapping { Index = 3, Role = MappingRole.ManualCost, CategoryId = heizungCategoryId }],
    };

    private static readonly string[] RequiredFiles = [ElectricityFile, WaterFile, OilFile, CostsFile];

    /// <summary>Throws a clear error if the sample directory or any reference CSV is missing, so a
    /// failed load surfaces to the user instead of silently seeding meters with no data.</summary>
    private static void EnsureSampleFilesPresent(string sampleDataDirectory)
    {
        if (!Directory.Exists(sampleDataDirectory))
        {
            throw new DirectoryNotFoundException(
                $"Reference-data directory not found: '{sampleDataDirectory}'. The bundled Energiebilanz CSVs are missing from this deployment.");
        }

        var missing = RequiredFiles.Where(f => !File.Exists(Path.Combine(sampleDataDirectory, f))).ToList();
        if (missing.Count > 0)
        {
            throw new FileNotFoundException(
                $"Reference CSV(s) missing from '{sampleDataDirectory}': {string.Join(", ", missing)}.");
        }
    }

    private async Task ImportSheetAsync(string dir, string file, MappingProfile profile, CancellationToken cancellationToken)
    {
        var path = Path.Combine(dir, file);
        if (!File.Exists(path))
        {
            throw new FileNotFoundException($"Reference CSV disappeared during import: '{path}'.", path);
        }

        StagedImport staged;
        using (var reader = new StreamReader(path))
        {
            staged = _csvImporter.Stage(profile, reader);
        }

        var mappingJson = System.Text.Json.JsonSerializer.Serialize(new { profile = profile.Name });
        await _importService.CommitAsync(staged, file, mappingJson, cancellationToken).ConfigureAwait(false);
    }

    private static Meter Meter(string name, short energyTypeId, MeterMode mode, string unit, double initialBaseline = 0) => new()
    {
        Name = name,
        EnergyTypeId = energyTypeId,
        Mode = mode,
        Unit = unit,
        InitialBaseline = initialBaseline,
    };

    private void AddElectricityTariffs(short energyTypeId)
    {
        AddTariff(TariffScope.EnergyType, energyTypeId, 0.16, "EUR/kWh", new DateOnly(2022, 9, 1));
        AddTariff(TariffScope.EnergyType, energyTypeId, 0.44, "EUR/kWh", new DateOnly(2023, 1, 1));
        AddTariff(TariffScope.EnergyType, energyTypeId, 0.37, "EUR/kWh", new DateOnly(2023, 5, 1));
        AddTariff(TariffScope.EnergyType, energyTypeId, 0.27, "EUR/kWh", new DateOnly(2023, 11, 1));
        AddTariff(TariffScope.EnergyType, energyTypeId, 0.36, "EUR/kWh", new DateOnly(2025, 1, 1));
        AddTariff(TariffScope.EnergyType, energyTypeId, 0.27, "EUR/kWh", new DateOnly(2026, 1, 1));
    }

    private void AddTariff(TariffScope scope, int scopeId, double value, string unit, DateOnly validFrom) =>
        _db.Tariffs.Add(new Tariff
        {
            ScopeType = scope,
            ScopeId = scopeId,
            Component = TariffComponent.UnitPrice,
            Value = value,
            Unit = unit,
            ValidFrom = validFrom,
        });

    private async Task LinkStromAndWasserAsync(
        int haus, int netz, int auto, int solar1, int solar2, int wasser, CancellationToken cancellationToken)
    {
        var categories = await CategoryIdsAsync(cancellationToken).ConfigureAwait(false);
        foreach (var meterId in new[] { haus, netz, auto, solar1, solar2 })
        {
            _db.CostCategoryMembers.Add(new CostCategoryMember { CategoryId = categories.Strom, MeterId = meterId });
        }

        _db.CostCategoryMembers.Add(new CostCategoryMember { CategoryId = categories.Wasser, MeterId = wasser });
        // Heizung (oil) cost comes from the imported Kosten column, not a meter — no link (avoids double-count).
    }

    private async Task<ReferenceCategoryIds> CategoryIdsAsync(CancellationToken cancellationToken)
    {
        var categories = await _db.CostCategories.ToListAsync(cancellationToken).ConfigureAwait(false);
        int Find(string name) => categories.FirstOrDefault(c => c.Name == name)?.Id ?? 0;
        return new ReferenceCategoryIds(Find("Heizung"), Find("Strom"), Find("Wasser"), Find("Pool Betrieb"));
    }

    private async Task<short> EnergyTypeIdAsync(string key, CancellationToken cancellationToken) =>
        (await _db.EnergyTypes.FirstAsync(t => t.Key == key, cancellationToken).ConfigureAwait(false)).Id;
}