MeterVault/src/Infrastructure/Dashboard/MeterDetailService.cs

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

namespace MeterVault.Infrastructure.Dashboard;

/// <summary>
/// Read model for the meter-detail view (SDD §8.6). Bounds the raw-reading and consumption pulls
/// (this is the one place the UI touches raw rows) and gathers source status, the applicable tariff
/// timeline and lifecycle events. DbContext factory keeps it Blazor-circuit safe.
/// </summary>
public sealed class MeterDetailService(IDbContextFactory<MeterVaultDbContext> contextFactory)
{
    private const int MaxRows = 200;

    private readonly IDbContextFactory<MeterVaultDbContext> _contextFactory = contextFactory;

    public async Task<MeterDetailView?> GetAsync(int meterId, CancellationToken cancellationToken = default)
    {
        await using var db = await _contextFactory.CreateDbContextAsync(cancellationToken).ConfigureAwait(false);

        var meter = await db.Meters.AsNoTracking()
            .Include(m => m.EnergyType)
            .Include(m => m.Sources)
            .FirstOrDefaultAsync(m => m.Id == meterId, cancellationToken).ConfigureAwait(false);
        if (meter is null)
        {
            return null;
        }

        var readingCount = await db.Readings.AsNoTracking().CountAsync(r => r.MeterId == meterId, cancellationToken).ConfigureAwait(false);
        var consumptionCount = await db.Consumption.AsNoTracking().CountAsync(c => c.MeterId == meterId, cancellationToken).ConfigureAwait(false);

        var first = await db.Readings.AsNoTracking().Where(r => r.MeterId == meterId)
            .OrderBy(r => r.Time).Select(r => new { r.Time, r.Value })
            .FirstOrDefaultAsync(cancellationToken).ConfigureAwait(false);
        var last = await db.Readings.AsNoTracking().Where(r => r.MeterId == meterId)
            .OrderByDescending(r => r.Time).Select(r => new { r.Time, r.Value })
            .FirstOrDefaultAsync(cancellationToken).ConfigureAwait(false);

        var totalConsumption = await db.Consumption.AsNoTracking()
            .Where(c => c.MeterId == meterId && c.Kind == ConsumptionKind.Consumption)
            .SumAsync(c => (double?)c.Amount, cancellationToken).ConfigureAwait(false) ?? 0;
        var totalGeneration = await db.Consumption.AsNoTracking()
            .Where(c => c.MeterId == meterId && c.Kind == ConsumptionKind.Generation)
            .SumAsync(c => (double?)c.Amount, cancellationToken).ConfigureAwait(false) ?? 0;

        var recentReadings = await db.Readings.AsNoTracking()
            .Where(r => r.MeterId == meterId)
            .OrderByDescending(r => r.Time).Take(MaxRows)
            .Select(r => new ReadingRow(r.Time, r.Value, r.Quality, r.Flags))
            .ToListAsync(cancellationToken).ConfigureAwait(false);

        var recentConsumption = await db.Consumption.AsNoTracking()
            .Where(c => c.MeterId == meterId)
            .OrderByDescending(c => c.Time).Take(MaxRows)
            .Select(c => new ConsumptionDetailRow(c.Time, c.Amount, c.Kind, c.Quality))
            .ToListAsync(cancellationToken).ConfigureAwait(false);

        var events = await db.MeterEvents.AsNoTracking()
            .Where(e => e.MeterId == meterId)
            .OrderByDescending(e => e.Time)
            .Select(e => new EventRow(e.Time, e.EventType, e.Amount, e.PrevValue, e.NewValue, e.Unit, e.Notes))
            .ToListAsync(cancellationToken).ConfigureAwait(false);

        var energyTypeId = meter.EnergyTypeId;
        var tariffs = await db.Tariffs.AsNoTracking()
            .Where(t => t.ScopeType == TariffScope.Global
                || (t.ScopeType == TariffScope.EnergyType && t.ScopeId == energyTypeId)
                || (t.ScopeType == TariffScope.Meter && t.ScopeId == meterId))
            .OrderBy(t => t.Component).ThenBy(t => t.ValidFrom)
            .Select(t => new TariffRow(t.ScopeType, t.ScopeId, t.Component, t.Value, t.Unit, t.ValidFrom, t.ValidTo))
            .ToListAsync(cancellationToken).ConfigureAwait(false);

        return new MeterDetailView(
            meter.Id, meter.Name, meter.EnergyType?.DisplayName ?? "—", meter.Mode, meter.Unit,
            meter.Location, meter.SerialNumber, meter.Manufacturer, meter.Model, meter.InitialBaseline, meter.IsActive,
            readingCount, consumptionCount,
            first?.Time, last?.Time, first?.Value, last?.Value,
            totalConsumption, totalGeneration,
            recentReadings, recentConsumption, events, tariffs, meter.Sources.Count);
    }
}