using System.ComponentModel.DataAnnotations;
using System.Text;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;

namespace ZB.MOM.WW.OtOpcUa.Driver.Mqtt;

/// <summary>
///     MQTT / Sparkplug B driver configuration. Bound from <c>DriverConfig</c> JSON at
///     driver-host registration time. Models the settings documented in
///     <c>docs/plans/2026-07-15-mqtt-sparkplug-driver-design.md</c> §5.1.
/// </summary>
/// <remarks>
///     A record (not a plain class) so a future secret-resolution seam can produce a
///     credential-resolved copy with a <c>with</c> expression — mirrors
///     <c>OpcUaClientDriverOptions</c>. <see cref="Mode"/> selects the ingest shape;
///     <see cref="Sparkplug"/> and <see cref="Plain"/> are nullable sub-objects — only the one
///     matching <see cref="Mode"/> is populated.
/// </remarks>
public sealed record MqttDriverOptions
{
    /// <summary>Broker hostname or IP address.</summary>
    public string Host { get; init; } = "localhost";

    /// <summary>Broker TCP port.</summary>
    [Range(1, 65535)]
    public int Port { get; init; } = 8883;

    /// <summary>
    ///     MQTT client identifier sent at CONNECT. Leave unset to let the driver generate one
    ///     (a stable per-instance id is recommended so broker-side ACLs / session state persist
    ///     across reconnects).
    /// </summary>
    public string? ClientId { get; init; }

    /// <summary>
    ///     When <c>true</c>, connect over TLS. Default <c>true</c> — this driver never ships an
    ///     anonymous/plaintext-by-default posture; a deployment must opt into <c>false</c> for an
    ///     on-prem/dev broker with no TLS listener.
    /// </summary>
    public bool UseTls { get; init; } = true;

    /// <summary>
    ///     When <c>true</c>, accept any self-signed / untrusted broker certificate. Dev/on-prem
    ///     escape hatch only — mirrors the <c>ServerHistorian</c> TLS knobs. Must stay
    ///     <c>false</c> in production so MITM attacks against the broker connection fail closed.
    /// </summary>
    public bool AllowUntrustedServerCertificate { get; init; } = false;

    /// <summary>
    ///     PEM CA file pinning the broker's TLS chain. <c>null</c>/empty uses the OS trust
    ///     store.
    /// </summary>
    public string? CaCertificatePath { get; init; }

    /// <summary>Username for broker authentication. <c>null</c> connects without a username.</summary>
    public string? Username { get; init; }

    /// <summary>
    ///     Password for broker authentication. Blank in committed JSON — supply via env, never
    ///     commit or log.
    /// </summary>
    public string? Password { get; init; } = "";

    /// <summary>MQTT protocol version to negotiate at CONNECT.</summary>
    public MqttProtocolVersion ProtocolVersion { get; init; } = MqttProtocolVersion.V500;

    /// <summary>Whether to request a clean session (v3.1.1) / clean start (v5.0) at CONNECT.</summary>
    public bool CleanSession { get; init; } = true;

    /// <summary>Keep-alive interval sent at CONNECT.</summary>
    [Range(1, int.MaxValue)]
    public int KeepAliveSeconds { get; init; } = 30;

    /// <summary>Bounded connect deadline (see design §8) — the driver never hangs past this.</summary>
    [Range(1, int.MaxValue)]
    public int ConnectTimeoutSeconds { get; init; } = 15;

    /// <summary>Initial reconnect backoff after a connection drop.</summary>
    [Range(1, int.MaxValue)]
    public int ReconnectMinBackoffSeconds { get; init; } = 1;

    /// <summary>Cap on the exponential reconnect backoff.</summary>
    [Range(1, int.MaxValue)]
    public int ReconnectMaxBackoffSeconds { get; init; } = 30;

    /// <summary>
    ///     Ceiling on an inbound message body, in bytes. A larger message is refused before any
    ///     decode or parse and degrades its own tags to <c>BadDecodingError</c>. Default 1 MiB.
    /// </summary>
    /// <remarks>
    ///     Decode and parse both run synchronously on MQTTnet's shared dispatcher thread, so their
    ///     cost is paid by <i>every</i> subscription, not just the offending topic — without a bound,
    ///     one publisher shipping a multi-megabyte body stalls the whole driver's delivery. "Unbounded"
    ///     is deliberately not offered; a non-positive value falls back to the driver's own 1 MiB
    ///     default. The literal is duplicated from <c>MqttSubscriptionManager.DefaultMaxPayloadBytes</c>
    ///     because this <c>.Contracts</c> assembly is <i>referenced by</i> the driver assembly and
    ///     cannot reference it back; the manager's constructor is the single enforcement point.
    /// </remarks>
    [Range(1, int.MaxValue)]
    public int MaxPayloadBytes { get; init; } = 1024 * 1024;

    /// <summary>Selects the ingest shape — Plain topics or Sparkplug B.</summary>
    public MqttMode Mode { get; init; } = MqttMode.Plain;

    /// <summary>
    ///     The cluster's authored raw MQTT tags, as delivered by the deploy artifact: each carries the
    ///     tag's <b>RawPath</b> (its v3 identity and driver wire reference) plus its <c>TagConfig</c>
    ///     blob. <see cref="MqttDriver"/> maps each through <see cref="MqttTagDefinitionFactory"/> at
    ///     initialize and re-registers the set <b>wholesale</b> on every reinitialize, so a redeploy
    ///     that drops a tag stops feeding it.
    /// </summary>
    /// <remarks>
    ///     This is also the <b>only</b> source of the driver's discoverable node set — plain MQTT has
    ///     no browsable address space, and a tag that is not authored here is never materialized no
    ///     matter how much traffic its topic carries. Mirrors <c>ModbusDriverOptions.RawTags</c> /
    ///     <c>FocasDriverOptions.RawTags</c>.
    /// </remarks>
    public IReadOnlyList<RawTagEntry> RawTags { get; init; } = [];

    /// <summary>
    ///     Sparkplug-only settings. Populated when <see cref="Mode"/> is
    ///     <see cref="MqttMode.SparkplugB"/>; <c>null</c> in Plain mode.
    /// </summary>
    public MqttSparkplugOptions? Sparkplug { get; init; }

    /// <summary>
    ///     Plain-mode-only settings. Populated when <see cref="Mode"/> is
    ///     <see cref="MqttMode.Plain"/>; <c>null</c> in Sparkplug B mode.
    /// </summary>
    public MqttPlainOptions? Plain { get; init; }

    /// <summary>
    ///     Record-generated <c>ToString()</c> member printer, overridden so <see cref="Password"/>
    ///     never renders in plaintext — this DTO routinely lands in logs / exception messages /
    ///     debugger watches, and the plan's cross-cutting rule is explicit: never commit or log
    ///     creds. A set password prints as <c>***</c>; unset (<c>null</c>/empty) renders
    ///     distinguishably so the redaction can't be mistaken for a real secret.
    /// </summary>
    private bool PrintMembers(StringBuilder builder)
    {
        var passwordDisplay = Password switch
        {
            null => "<null>",
            "" => "<empty>",
            _ => "***",
        };

        builder.Append("Host = ").Append(Host);
        builder.Append(", Port = ").Append(Port);
        builder.Append(", ClientId = ").Append(ClientId);
        builder.Append(", UseTls = ").Append(UseTls);
        builder.Append(", AllowUntrustedServerCertificate = ").Append(AllowUntrustedServerCertificate);
        builder.Append(", CaCertificatePath = ").Append(CaCertificatePath);
        builder.Append(", Username = ").Append(Username);
        builder.Append(", Password = ").Append(passwordDisplay);
        builder.Append(", ProtocolVersion = ").Append(ProtocolVersion);
        builder.Append(", CleanSession = ").Append(CleanSession);
        builder.Append(", KeepAliveSeconds = ").Append(KeepAliveSeconds);
        builder.Append(", ConnectTimeoutSeconds = ").Append(ConnectTimeoutSeconds);
        builder.Append(", ReconnectMinBackoffSeconds = ").Append(ReconnectMinBackoffSeconds);
        builder.Append(", ReconnectMaxBackoffSeconds = ").Append(ReconnectMaxBackoffSeconds);
        builder.Append(", MaxPayloadBytes = ").Append(MaxPayloadBytes);
        builder.Append(", Mode = ").Append(Mode);
        builder.Append(", Sparkplug = ").Append(Sparkplug);
        builder.Append(", Plain = ").Append(Plain);
        // Count only: a deployment routinely authors thousands of raw tags and each carries a full
        // TagConfig blob, so printing the list would turn any log of this DTO into a config dump.
        builder.Append(", RawTags = ").Append(RawTags.Count).Append(" tag(s)");
        return true;
    }
}

/// <summary>
///     Sparkplug B settings for an <see cref="MqttDriverOptions"/> instance in
///     <see cref="MqttMode.SparkplugB"/> mode. See
///     <c>docs/plans/2026-07-15-mqtt-sparkplug-driver-design.md</c> §5.1.
/// </summary>
public sealed record MqttSparkplugOptions
{
    /// <summary>Sparkplug group id — the driver subscribes <c>spBv1.0/{GroupId}/#</c>.</summary>
    public string GroupId { get; init; } = "";

    /// <summary>
    ///     Sparkplug Host Application identity — published as <c>spBv1.0/STATE/{HostId}</c>
    ///     (Sparkplug v3.0).
    /// </summary>
    public string HostId { get; init; } = "";

    /// <summary>
    ///     When <c>true</c>, this driver instance acts as the Sparkplug Primary Host
    ///     Application. At most one primary host may exist per host-id per broker.
    /// </summary>
    /// <remarks>
    ///     Implemented by <c>SparkplugPrimaryHost</c> (Gitea #511) on a dedicated broker connection
    ///     whose lifetime <i>is</i> the claim, and gated on the redundancy Primary role so the two nodes
    ///     of a pair never both claim. Requires <see cref="HostId"/>; set without one, the driver warns
    ///     and declines rather than publishing to a malformed topic.
    /// </remarks>
    public bool ActAsPrimaryHost { get; init; } = false;

    /// <summary>
    ///     When <c>true</c>, a detected sequence-number gap triggers a Sparkplug rebirth
    ///     request (NCMD) rather than silently continuing with stale metric state.
    /// </summary>
    public bool RequestRebirthOnGap { get; init; } = true;

    /// <summary>
    ///     How long, in seconds, browse/discovery collects NBIRTH/DBIRTH traffic before
    ///     considering the observed metric set stable.
    /// </summary>
    [Range(1, int.MaxValue)]
    public int BirthObservationWindowSeconds { get; init; } = 15;
}

/// <summary>
///     Plain-MQTT-mode settings for an <see cref="MqttDriverOptions"/> instance in
///     <see cref="MqttMode.Plain"/> mode. See
///     <c>docs/plans/2026-07-15-mqtt-sparkplug-driver-design.md</c> §5.1.
/// </summary>
public sealed record MqttPlainOptions
{
    /// <summary>
    ///     Optional prefix prepended when the driver needs to compose a topic (e.g. discovery
    ///     scoping); per-tag topics are authored explicitly and are unaffected.
    /// </summary>
    public string TopicPrefix { get; init; } = "";

    /// <summary>Default QoS used when a tag's own <c>qos</c> is unset.</summary>
    [Range(0, 2)]
    public int DefaultQos { get; init; } = 1;
}