using Microsoft.Extensions.Logging;
using System.Globalization;
using System.Security.Cryptography;
using System.Text;
using System.Linq;

namespace StellaOps.AdvisoryAI.UnifiedSearch;

public sealed record UnifiedSearchTelemetryEvent(
    string Tenant,
    string QueryHash,
    string Intent,
    int ResultCount,
    long DurationMs,
    bool UsedVector,
    IReadOnlyDictionary<string, double> DomainWeights,
    IReadOnlyList<string> TopDomains);

public interface IUnifiedSearchTelemetrySink
{
    void Record(UnifiedSearchTelemetryEvent telemetryEvent);
}

internal sealed class LoggingUnifiedSearchTelemetrySink : IUnifiedSearchTelemetrySink
{
    private readonly ILogger<LoggingUnifiedSearchTelemetrySink> _logger;

    public LoggingUnifiedSearchTelemetrySink(ILogger<LoggingUnifiedSearchTelemetrySink> logger)
    {
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
    }

    public void Record(UnifiedSearchTelemetryEvent telemetryEvent)
    {
        ArgumentNullException.ThrowIfNull(telemetryEvent);

        var weights = string.Join(
            ",",
            telemetryEvent.DomainWeights
                .OrderBy(static pair => pair.Key, StringComparer.Ordinal)
                .Select(static pair => $"{pair.Key}:{pair.Value.ToString("F3", CultureInfo.InvariantCulture)}"));

        var topDomains = telemetryEvent.TopDomains.Count == 0
            ? "-"
            : string.Join(",", telemetryEvent.TopDomains.OrderBy(static value => value, StringComparer.Ordinal));

        _logger.LogInformation(
            "unified_search telemetry tenant={Tenant} query_hash={QueryHash} intent={Intent} results={ResultCount} duration_ms={DurationMs} used_vector={UsedVector} top_domains={TopDomains} weights={Weights}",
            telemetryEvent.Tenant,
            telemetryEvent.QueryHash,
            telemetryEvent.Intent,
            telemetryEvent.ResultCount,
            telemetryEvent.DurationMs,
            telemetryEvent.UsedVector,
            topDomains,
            weights);
    }
}

internal static class UnifiedSearchTelemetryHash
{
    public static string HashQuery(string query)
    {
        ArgumentNullException.ThrowIfNull(query);
        var bytes = Encoding.UTF8.GetBytes(query);
        var hash = SHA256.HashData(bytes);
        return Convert.ToHexString(hash).ToLowerInvariant();
    }
}