using Google.Protobuf.WellKnownTypes;
using ZB.MOM.WW.HistorianGateway.Contracts.Grpc;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
using ZB.MOM.WW.OtOpcUa.Core.AlarmHistorian;

namespace ZB.MOM.WW.OtOpcUa.Driver.Historian.Gateway.Mapping;

/// <summary>
/// Maps a driver-agnostic <see cref="AlarmHistorianEvent"/> onto a gateway wire
/// <see cref="HistorianEvent"/> for the <c>SendEvent</c> write path.
/// </summary>
internal static class AlarmEventMapper
{
    /// <summary>
    /// Maps <see cref="AlarmSeverity"/> to the numeric OPC UA Part 9 priority (1-1000) carried in the
    /// wire event's <c>Severity</c> property, per the <see cref="AlarmHistorianEvent.Severity"/>
    /// contract ("Mapped to Historian's numeric priority on the sink side"). The read side
    /// (<see cref="EventMapper.ToHistoricalEvent"/>) <c>int.TryParse</c>s this same property, so it
    /// must stay a numeric string — the enum's <c>.ToString()</c> name (e.g. "High") is NOT
    /// parseable and used to silently collapse every read-back severity to the minimum (1). The
    /// values mirror the existing native-alarm convention
    /// (<c>ZB.MOM.WW.OtOpcUa.Runtime.Drivers.NativeAlarmProjector.MapSeverity</c>).
    /// </summary>
    private static string ToNumericSeverity(AlarmSeverity severity) => severity switch
    {
        AlarmSeverity.Low => "200",
        AlarmSeverity.Medium => "500",
        AlarmSeverity.High => "700",
        AlarmSeverity.Critical => "900",
        _ => "500",
    };

    /// <summary>Maps an alarm historian event to a gateway event.</summary>
    /// <param name="alarm">The driver-agnostic alarm event.</param>
    /// <returns>The gateway wire event ready for <c>SendEvent</c>.</returns>
    public static HistorianEvent ToHistorianEvent(AlarmHistorianEvent alarm)
    {
        // Timestamp.FromDateTime requires a Utc-kind DateTime; coerce defensively (TimestampUtc is
        // already Utc by contract, but a caller could pass Unspecified).
        var eventTime = Timestamp.FromDateTime(DateTime.SpecifyKind(alarm.TimestampUtc, DateTimeKind.Utc));

        var historianEvent = new HistorianEvent
        {
            // Deliberately DO NOT set HistorianEvent.Id: the gateway's SendEvent path rejects a
            // client-supplied event id (the server handler throws and the call fails permanently —
            // confirmed live). The historian assigns event identity server-side; the alarm's own id
            // is preserved below as a property for read-back correlation/traceability.
            SourceName = alarm.EquipmentPath,
            Type = alarm.AlarmTypeName,
            EventTime = eventTime,
            ReceivedTime = eventTime, // the server re-stamps the received time on the SQL path
        };

        // Proto map<string,string> values must be non-null — only insert non-null properties.
        if (!string.IsNullOrWhiteSpace(alarm.AlarmId))
            historianEvent.Properties["AlarmId"] = alarm.AlarmId;
        historianEvent.Properties["AlarmName"] = alarm.AlarmName;
        historianEvent.Properties["EventKind"] = alarm.EventKind;
        historianEvent.Properties["Severity"] = ToNumericSeverity(alarm.Severity);
        historianEvent.Properties["User"] = alarm.User;
        historianEvent.Properties["Message"] = alarm.Message;
        if (alarm.Comment is not null)
            historianEvent.Properties["Comment"] = alarm.Comment;

        return historianEvent;
    }
}