// Copyright (c) StellaOps. Licensed under the AGPL-3.0-or-later.

using System.ComponentModel.DataAnnotations;
using System.Reflection;
using System.Text.Json.Serialization;
using StellaOps.HybridLogicalClock;

namespace StellaOps.Eventing.Models;

/// <summary>
/// Canonical event envelope for unified timeline.
/// </summary>
public sealed record TimelineEvent
{
    /// <summary>
    /// Deterministic event ID: SHA-256(correlation_id || t_hlc || service || kind)[0:32] as hex.
    /// </summary>
    [JsonPropertyName("event_id")]
    public required string EventId { get; init; }

    /// <summary>
    /// HLC timestamp from StellaOps.HybridLogicalClock.
    /// </summary>
    [JsonPropertyName("t_hlc")]
    public required HlcTimestamp THlc { get; init; }

    /// <summary>
    /// Wall-clock time (informational only).
    /// </summary>
    [JsonPropertyName("ts_wall")]
    public required DateTimeOffset TsWall { get; init; }

    /// <summary>
    /// Service name (e.g., "Scheduler", "AirGap", "Attestor").
    /// </summary>
    [JsonPropertyName("service")]
    public required string Service { get; init; }

    /// <summary>
    /// W3C Trace Context traceparent.
    /// </summary>
    [JsonPropertyName("trace_parent")]
    public string? TraceParent { get; init; }

    /// <summary>
    /// Correlation ID linking related events.
    /// </summary>
    [JsonPropertyName("correlation_id")]
    public required string CorrelationId { get; init; }

    /// <summary>
    /// Event kind (ENQUEUE, EXECUTE, EMIT, etc.).
    /// </summary>
    [JsonPropertyName("kind")]
    public required string Kind { get; init; }

    /// <summary>
    /// RFC 8785 canonicalized JSON payload.
    /// </summary>
    [JsonPropertyName("payload")]
    public required string Payload { get; init; }

    /// <summary>
    /// SHA-256 digest of Payload.
    /// </summary>
    [JsonPropertyName("payload_digest")]
    public required byte[] PayloadDigest { get; init; }

    /// <summary>
    /// Engine version for reproducibility.
    /// </summary>
    [JsonPropertyName("engine_version")]
    public required EngineVersionRef EngineVersion { get; init; }

    /// <summary>
    /// Optional DSSE signature.
    /// </summary>
    [JsonPropertyName("dsse_sig")]
    public string? DsseSig { get; init; }

    /// <summary>
    /// Schema version (current: 1).
    /// </summary>
    [JsonPropertyName("schema_version")]
    public int SchemaVersion { get; init; } = 1;
}

/// <summary>
/// Engine version reference for reproducibility tracking.
/// </summary>
/// <param name="EngineName">The name of the engine/service.</param>
/// <param name="Version">The version string.</param>
/// <param name="SourceDigest">SHA-256 digest of the source or assembly.</param>
public sealed record EngineVersionRef(
    [property: JsonPropertyName("engine_name")] string EngineName,
    [property: JsonPropertyName("version")] string Version,
    [property: JsonPropertyName("source_digest")] string SourceDigest)
{
    /// <summary>
    /// Creates an EngineVersionRef from the specified assembly metadata.
    /// </summary>
    public static EngineVersionRef FromAssembly(Assembly assembly)
    {
        ArgumentNullException.ThrowIfNull(assembly);

        var name = assembly.GetName();
        var version = name.Version?.ToString() ?? "0.0.0";

        // Try to get source digest from assembly metadata
        var sourceDigest = assembly
            .GetCustomAttributes<AssemblyMetadataAttribute>()
            .FirstOrDefault(a => a.Key == "SourceDigest")?.Value
            ?? "unknown";

        return new EngineVersionRef(name.Name ?? "Unknown", version, sourceDigest);
    }

    /// <summary>
    /// Creates an EngineVersionRef from the entry assembly.
    /// </summary>
    public static EngineVersionRef FromEntryAssembly()
    {
        var assembly = Assembly.GetEntryAssembly()
            ?? throw new InvalidOperationException("No entry assembly found");
        return FromAssembly(assembly);
    }
}

/// <summary>
/// Pending event for batch emission.
/// </summary>
/// <param name="CorrelationId">Correlation ID linking related events.</param>
/// <param name="Kind">Event kind (ENQUEUE, EXECUTE, etc.).</param>
/// <param name="Payload">Event payload object.</param>
public sealed record PendingEvent(
    string CorrelationId,
    string Kind,
    object Payload);

/// <summary>
/// Standard event kinds used across StellaOps services.
/// </summary>
public static class EventKinds
{
    // Scheduler events
    public const string Enqueue = "ENQUEUE";
    public const string Dequeue = "DEQUEUE";
    public const string Execute = "EXECUTE";
    public const string Complete = "COMPLETE";
    public const string Fail = "FAIL";

    // AirGap events
    public const string Import = "IMPORT";
    public const string Export = "EXPORT";
    public const string Merge = "MERGE";
    public const string Conflict = "CONFLICT";

    // Attestor events
    public const string Attest = "ATTEST";
    public const string Verify = "VERIFY";

    // Policy events
    public const string Evaluate = "EVALUATE";
    public const string GatePass = "GATE_PASS";
    public const string GateFail = "GATE_FAIL";

    // VexLens events
    public const string Consensus = "CONSENSUS";
    public const string Override = "OVERRIDE";

    // Generic events
    public const string Emit = "EMIT";
    public const string Ack = "ACK";
    public const string Error = "ERR";
}