Hy2026/backend/Infrastructure/Persistence/TrendService.cs

using SurrealDb.Net;
using TarninaHub.Application.Abstractions;
using TarninaHub.Application.Dtos;

namespace TarninaHub.Infrastructure.Persistence;

public sealed class TrendService : ITrendService
{
    private readonly ISurrealDbClient _client;

    public TrendService(ISurrealDbClient client)
    {
        _client = client;
    }

    public async Task<TrendsResponse> GetAsync(
        string? challengeId,
        DateTimeOffset from,
        DateTimeOffset to,
        CancellationToken cancellationToken)
    {
        var counts = await CountSubmissionsAsync(challengeId, from, to, cancellationToken);
        var challenges = await LoadChallengesAsync(cancellationToken);

        var points = challenges
            .Where(challenge => string.IsNullOrWhiteSpace(challengeId)
                || string.Equals(challenge.Id, challengeId, StringComparison.Ordinal))
            .Select(challenge => new TrendPoint(
                challenge.Id,
                challenge.Name,
                counts.GetValueOrDefault(challenge.Id)))
            .OrderByDescending(point => point.SubmissionCount)
            .ToList();

        return new TrendsResponse(from, to, points);
    }

    private async Task<Dictionary<string, int>> CountSubmissionsAsync(
        string? challengeId,
        DateTimeOffset from,
        DateTimeOffset to,
        CancellationToken cancellationToken)
    {
        var parameters = new Dictionary<string, object?> { ["from"] = from, ["to"] = to };
        var clauses = new List<string> { "created_at >= $from", "created_at <= $to" };

        if (!string.IsNullOrWhiteSpace(challengeId))
        {
            var (table, id) = SurrealRecordId.Split(challengeId);
            clauses.Add("problem.challenge = type::record($challengeTable, $challengeId)");
            parameters["challengeTable"] = table;
            parameters["challengeId"] = id;
        }

        var response = await _client.RawQuery(
            "SELECT type::string(problem.challenge) AS challenge FROM submission WHERE " +
            string.Join(" AND ", clauses) + ";",
            parameters,
            cancellationToken);
        response.EnsureAllOks();

        var rows = response.GetValue<List<TrendSubmissionRow>>(0) ?? [];

        return rows
            .Where(row => !string.IsNullOrWhiteSpace(row.Challenge))
            .GroupBy(row => row.Challenge)
            .ToDictionary(group => group.Key, group => group.Count());
    }

    private async Task<List<ChallengeRow>> LoadChallengesAsync(CancellationToken cancellationToken)
    {
        var response = await _client.RawQuery(
            "SELECT type::string(id) AS id, name, order FROM social_challenge ORDER BY order;",
            cancellationToken: cancellationToken);
        response.EnsureAllOks();

        return response.GetValue<List<ChallengeRow>>(0) ?? [];
    }
}