using Microsoft.EntityFrameworkCore;
using Npgsql;
using Tau.Acuvim.Portal.Data;
using Tau.Acuvim.Portal.DTOs;

namespace Tau.Acuvim.Portal.Services;

public sealed class FleetQueryService(AdminDbContext db)
{
    private static readonly TimeSpan ActiveWindow = TimeSpan.FromHours(1);

    public async Task<FleetDashboardDto> GetDashboardAsync(CancellationToken ct = default)
    {
        var nowUtc = DateTime.UtcNow;
        var activeThreshold = nowUtc - ActiveWindow;
        var dayStart = DateTime.SpecifyKind(nowUtc.Date, DateTimeKind.Utc);

        var customers = await db.Customers.AsNoTracking()
            .OrderBy(c => c.Code)
            .Select(c => new { c.Id, c.Code, c.Name, c.IsActive, c.LastSeenAt })
            .ToListAsync(ct);

        var siteCounts = await db.FleetSites.AsNoTracking()
            .GroupBy(s => s.CustomerId)
            .Select(g => new { CustomerId = g.Key, N = g.Count() })
            .ToDictionaryAsync(x => x.CustomerId, x => x.N, ct);

        var deviceCounts = await db.FleetDevices.AsNoTracking()
            .GroupBy(d => d.CustomerId)
            .Select(g => new { CustomerId = g.Key, N = g.Count() })
            .ToDictionaryAsync(x => x.CustomerId, x => x.N, ct);

        var todayStats = await GetTodayStatsAsync(dayStart, ct);

        var summaries = customers.Select(c => new FleetCustomerSummary(
            c.Id, c.Code, c.Name, c.IsActive, c.LastSeenAt,
            siteCounts.GetValueOrDefault(c.Id, 0),
            deviceCounts.GetValueOrDefault(c.Id, 0),
            todayStats.TryGetValue(c.Id, out var s) ? s.Measurements : 0,
            todayStats.TryGetValue(c.Id, out s) ? s.KwhImported : null
        )).ToList();

        var activeCount = customers.Count(c => c.LastSeenAt >= activeThreshold);
        var oldestActive = customers
            .Where(c => c.LastSeenAt is not null && c.LastSeenAt >= activeThreshold)
            .Min(c => c.LastSeenAt);

        return new FleetDashboardDto(
            TotalCustomers: customers.Count,
            ActiveCustomers: activeCount,
            TotalMeasurementsToday: summaries.Sum(x => x.MeasurementsToday),
            TotalKwhImportedToday: summaries.Sum(x => x.KwhImportedToday ?? 0),
            OldestActiveLastSeenAt: oldestActive,
            Customers: summaries);
    }

    public async Task<FleetCustomerDetailDto?> GetCustomerDetailAsync(Guid id, CancellationToken ct = default)
    {
        var c = await db.Customers.AsNoTracking().FirstOrDefaultAsync(x => x.Id == id, ct);
        if (c is null) return null;

        var sites = await db.FleetSites.AsNoTracking()
            .Where(s => s.CustomerId == id)
            .OrderBy(s => s.Name)
            .Select(s => new FleetSiteDto(s.Id, s.Name, s.Address, s.LocalMunicipalityId, s.IsActive))
            .ToListAsync(ct);

        var devices = await db.FleetDevices.AsNoTracking()
            .Where(d => d.CustomerId == id)
            .OrderBy(d => d.Name)
            .Select(d => new FleetDeviceDto(d.Id, d.SiteId, d.Name, d.ExternalId, d.Description, d.IsActive))
            .ToListAsync(ct);

        var deviceNameMap = devices.ToDictionary(d => d.Id, d => d.Name);

        var recent = await db.FleetPowerMeasurements.AsNoTracking()
            .Where(m => m.CustomerId == id)
            .OrderByDescending(m => m.Time)
            .Take(50)
            .Select(m => new { m.Time, m.DeviceId, m.ActivePowerKw, m.EnergyImportedKwh })
            .ToListAsync(ct);

        var recentDtos = recent.Select(r => new FleetRecentMeasurementDto(
            r.Time, r.DeviceId, deviceNameMap.GetValueOrDefault(r.DeviceId, "(unknown)"),
            r.ActivePowerKw, r.EnergyImportedKwh)).ToList();

        var events = await db.IngestEvents.AsNoTracking()
            .Where(e => e.CustomerId == id)
            .OrderByDescending(e => e.ReceivedAt)
            .Take(20)
            .Select(e => new FleetIngestEventDto(
                e.ReceivedAt, e.BatchType, e.RowsAccepted, e.RowsRejected,
                e.BatchBytes, e.ClientHwm, e.TimeSpread, e.Error))
            .ToListAsync(ct);

        return new FleetCustomerDetailDto(
            c.Id, c.Code, c.Name, c.IsActive,
            c.FirstSeenAt, c.LastSeenAt, c.CreatedAt,
            sites, devices, recentDtos, events);
    }

    // Per-customer today: measurement count + kWh imported delta via raw SQL hitting
    // the realtime continuous aggregate (falls back to live raw scan for the unmaterialized tail).
    private async Task<Dictionary<Guid, (long Measurements, double? KwhImported)>> GetTodayStatsAsync(
        DateTime dayStartUtc, CancellationToken ct)
    {
        var conn = db.Database.GetDbConnection();
        if (conn.State != System.Data.ConnectionState.Open) await conn.OpenAsync(ct);

        await using var cmd = conn.CreateCommand();
        cmd.CommandText = """
            SELECT "CustomerId",
                   SUM(samples)::bigint AS rows,
                   SUM(COALESCE(kwh_imported_delta, 0))::double precision AS kwh
            FROM fleet.hourly_per_device
            WHERE bucket >= @dayStart
            GROUP BY "CustomerId";
            """;
        cmd.Parameters.Add(new NpgsqlParameter("@dayStart", DateTime.SpecifyKind(dayStartUtc, DateTimeKind.Utc)));

        var map = new Dictionary<Guid, (long, double?)>();
        await using var reader = await cmd.ExecuteReaderAsync(ct);
        while (await reader.ReadAsync(ct))
        {
            var custId = reader.GetGuid(0);
            var rows = reader.GetInt64(1);
            var kwh = reader.IsDBNull(2) ? (double?)null : reader.GetDouble(2);
            map[custId] = (rows, kwh);
        }
        return map;
    }
}