fengling-risk-control/Fengling.RiskControl.Client/Sampling/SamplingService.cs

using Fengling.RiskControl.Configuration;
using Fengling.RiskControl.Evaluation;
using Microsoft.Extensions.Logging;
using System.Globalization;

namespace Fengling.RiskControl.Sampling;

public interface ISamplingService
{
    bool ShouldSample(RiskEvaluationResult result);
}

public class SamplingService : ISamplingService
{
    private readonly RiskControlClientOptions _options;
    private readonly ILogger<SamplingService> _logger;
    private readonly Random _random = new();

    public SamplingService(
        RiskControlClientOptions options,
        ILogger<SamplingService> logger)
    {
        _options = options;
        _logger = logger;
    }

    public bool ShouldSample(RiskEvaluationResult result)
    {
        if (!_options.Sampling.Enabled)
            return false;

        foreach (var rule in _options.Sampling.Rules)
        {
            if (EvaluateCondition(rule.Condition, result))
            {
                var sampleRate = rule.Rate;
                var sampled = _random.NextDouble() < sampleRate;
                _logger.LogDebug("Sampling check: condition={Condition}, rate={Rate}, sampled={Sampled}",
                    rule.Condition, sampleRate, sampled);
                return sampled;
            }
        }

        var defaultSampled = _random.NextDouble() < _options.Sampling.DefaultRate;
        _logger.LogDebug("Default sampling: rate={Rate}, sampled={Sampled}",
            _options.Sampling.DefaultRate, defaultSampled);
        return defaultSampled;
    }

    private bool EvaluateCondition(string condition, RiskEvaluationResult result)
    {
        return condition switch
        {
            string c when c.Contains("RiskLevel == High", StringComparison.OrdinalIgnoreCase)
                => result.RiskLevel == RiskLevel.High,
            string c when c.Contains("RiskLevel == Medium", StringComparison.OrdinalIgnoreCase)
                => result.RiskLevel == RiskLevel.Medium,
            string c when c.Contains("RiskLevel == Low", StringComparison.OrdinalIgnoreCase)
                => result.RiskLevel == RiskLevel.Low,
            string c when c.Contains("IsBlocked == true", StringComparison.OrdinalIgnoreCase)
                => result.Blocked,
            string c when c.Contains("BlockedOnly", StringComparison.OrdinalIgnoreCase)
                => result.Blocked,
            _ => false
        };
    }
}