using Serilog.Core;
using Serilog.Events;
using ZB.MOM.WW.OtOpcUa.Commons.Messages.Logging;

namespace ZB.MOM.WW.OtOpcUa.Core.Scripting;

/// <summary>
///     Serilog sink that converts each script <see cref="LogEvent"/> into a
///     <see cref="ScriptLogEntry"/> and forwards it to an <see cref="IScriptLogPublisher"/>.
///     The publisher implementation (supplied by a later task) routes the entry onto the
///     Akka DPS <c>script-logs</c> topic so the live Script-log Admin UI page can display it.
/// </summary>
/// <remarks>
///     <para>
///         Expected to be registered in the root script-logger pipeline alongside the
///         rolling <c>scripts-*.log</c> file sink and the
///         <see cref="ScriptLogCompanionSink"/>. Events below the configured minimum level
///         are silently discarded so Debug/Verbose noise does not saturate the cluster bus
///         in production deployments.
///     </para>
///     <para>
///         Identity properties (<c>ScriptId</c>, <c>VirtualTagId</c>, <c>AlarmId</c>,
///         <c>EquipmentId</c>) are lifted from the event's structured-property bag. If
///         <c>ScriptId</c> is absent the sink falls back to the legacy <c>ScriptName</c>
///         property so pipelines that pre-date this sink continue to work correctly. If
///         neither property is present <c>ScriptId</c> defaults to <c>"unknown"</c>.
///     </para>
/// </remarks>
public sealed class ScriptLogTopicSink : ILogEventSink
{
    private readonly IScriptLogPublisher _publisher;
    private readonly LogEventLevel _min;

    /// <summary>Initializes a new instance of the <see cref="ScriptLogTopicSink"/> class.</summary>
    /// <param name="publisher">The publisher that routes entries to the cluster bus. Must not be <c>null</c>.</param>
    /// <param name="min">Minimum log level to forward. Events below this level are discarded (default: <see cref="LogEventLevel.Information"/>).</param>
    /// <exception cref="ArgumentNullException">Thrown when <paramref name="publisher"/> is <c>null</c>.</exception>
    public ScriptLogTopicSink(IScriptLogPublisher publisher, LogEventLevel min = LogEventLevel.Information)
    {
        _publisher = publisher ?? throw new ArgumentNullException(nameof(publisher));
        _min = min;
    }

    /// <summary>
    ///     Converts the <paramref name="logEvent"/> to a <see cref="ScriptLogEntry"/> and
    ///     publishes it, unless the event is below the configured minimum level.
    /// </summary>
    /// <param name="logEvent">The Serilog event to process. Silently ignored when <c>null</c>.</param>
    public void Emit(LogEvent logEvent)
    {
        if (logEvent is null || logEvent.Level < _min) return;

        // Extract a string scalar property by key, returning null when absent or non-string.
        string? P(string key) =>
            logEvent.Properties.TryGetValue(key, out var v) && v is ScalarValue { Value: string s }
                ? s
                : null;

        _publisher.Publish(new ScriptLogEntry(
            ScriptId: P(ScriptLoggerFactory.ScriptIdProperty)
                      ?? P(ScriptLoggerFactory.ScriptNameProperty)
                      ?? "unknown",
            Level: logEvent.Level.ToString(),
            Message: logEvent.RenderMessage(),
            TimestampUtc: logEvent.Timestamp.UtcDateTime,
            VirtualTagId: P(ScriptLoggerFactory.VirtualTagIdProperty),
            AlarmId: P(ScriptLoggerFactory.AlarmIdProperty),
            EquipmentId: P(ScriptLoggerFactory.EquipmentIdProperty)));
    }
}