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

namespace Tau.Acuvim.Portal.Services;

public sealed class MeasurementQueryService(AppDbContext db)
{
    private static readonly Dictionary<string, string> AllowedBuckets = new(StringComparer.OrdinalIgnoreCase)
    {
        ["minute"] = "1 minute",
        ["5min"]   = "5 minutes",
        ["15min"]  = "15 minutes",
        ["hour"]   = "1 hour",
        ["day"]    = "1 day",
    };

    public bool IsValidBucket(string bucket) => AllowedBuckets.ContainsKey(bucket);

    public async Task<List<MeasurementBucketDto>> GetBucketsAsync(
        Guid deviceId, DateTime fromUtc, DateTime toUtc, string bucket, CancellationToken ct = default)
    {
        if (!AllowedBuckets.TryGetValue(bucket, out var interval))
        {
            throw new ArgumentException($"Unsupported bucket '{bucket}'.", nameof(bucket));
        }

        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
                time_bucket(INTERVAL '{interval}', "Time") AS bucket,
                avg("ActivePowerKw")            AS avg_kw,
                max("ActivePowerKw")            AS max_kw,
                min("ActivePowerKw")            AS min_kw,
                max("EnergyImportedKwh") - min("EnergyImportedKwh") AS imp_delta,
                max("EnergyExportedKwh") - min("EnergyExportedKwh") AS exp_delta,
                count(*)                        AS samples
            FROM monitoring."PowerMeasurements"
            WHERE "DeviceId" = @deviceId
              AND "Time" >= @fromUtc
              AND "Time" <  @toUtc
            GROUP BY bucket
            ORDER BY bucket;
            """;
        cmd.Parameters.Add(new NpgsqlParameter("@deviceId", deviceId));
        cmd.Parameters.Add(new NpgsqlParameter("@fromUtc", DateTime.SpecifyKind(fromUtc, DateTimeKind.Utc)));
        cmd.Parameters.Add(new NpgsqlParameter("@toUtc", DateTime.SpecifyKind(toUtc, DateTimeKind.Utc)));

        var results = new List<MeasurementBucketDto>();
        await using var reader = await cmd.ExecuteReaderAsync(ct);
        while (await reader.ReadAsync(ct))
        {
            results.Add(new MeasurementBucketDto(
                BucketStart: reader.GetDateTime(0),
                AvgActivePowerKw: reader.GetDouble(1),
                MaxActivePowerKw: reader.GetDouble(2),
                MinActivePowerKw: reader.GetDouble(3),
                EnergyImportedKwhDelta: reader.IsDBNull(4) ? null : reader.GetDouble(4),
                EnergyExportedKwhDelta: reader.IsDBNull(5) ? null : reader.GetDouble(5),
                SampleCount: reader.GetInt32(6)));
        }
        return results;
    }
}