using ZB.MOM.WW.OtOpcUa.Commons.OpcUa;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;

namespace ZB.MOM.WW.OtOpcUa.Runtime.Drivers;

/// <summary>
///     Derives a full Part 9 <see cref="AlarmConditionSnapshot"/> from each native
///     <see cref="AlarmEventArgs"/> delta, tracking per-condition-NodeId prior state. Owned by the
///     single-threaded <c>DriverHostActor</c> (no locking). Native alarms carry only a transition
///     <see cref="AlarmTransitionKind"/>, not a full state machine, so this is the translation the
///     scripted-alarm engine does internally.
/// </summary>
public sealed class NativeAlarmProjector
{
    private readonly Dictionary<string, (bool Active, bool Acked, string? Message, ushort Severity)> _prior =
        new(StringComparer.Ordinal);

    /// <summary>Project an alarm transition onto the full condition snapshot for <paramref name="nodeId"/>.</summary>
    /// <param name="nodeId">The materialised condition node's id (the projection's state key).</param>
    /// <param name="e">The native alarm transition.</param>
    /// <returns>The full Part 9 condition snapshot to write to the node.</returns>
    public AlarmConditionSnapshot Project(string nodeId, AlarmEventArgs e) => Project(nodeId, e, out IReadOnlyList<AlarmTransitionKind> _);

    /// <summary>
    ///     Project an alarm transition, reporting whether it was a <b>re-statement</b> — a transition that writes no
    ///     <c>alerts</c> row (see <see cref="Project(string, AlarmEventArgs, out IReadOnlyList{AlarmTransitionKind})"/>).
    /// </summary>
    /// <param name="nodeId">The materialised condition node's id (the projection's state key).</param>
    /// <param name="e">The native alarm transition.</param>
    /// <param name="restatement">True when <paramref name="e"/> produced no history row.</param>
    /// <returns>The full Part 9 condition snapshot to write to the node.</returns>
    public AlarmConditionSnapshot Project(string nodeId, AlarmEventArgs e, out bool restatement)
    {
        var snapshot = Project(nodeId, e, out IReadOnlyList<AlarmTransitionKind> historyKinds);
        restatement = historyKinds.Count == 0;
        return snapshot;
    }

    /// <summary>
    ///     Project an alarm transition and report the <c>alerts</c> history rows it warrants, in order. Node state
    ///     and history are decided separately: a transition always projects a snapshot, but only a transition that
    ///     actually CHANGED what the condition shows (or that a source reports as genuinely new) writes a row.
    ///     <list type="bullet">
    ///         <item>Gitea #647 review — a <see cref="AlarmTransitionKind.Raise"/> on a condition already projected
    ///         Active WITH THE SAME MESSAGE (re-review R1 — a different message is a different alarm, and un-acks) is a
    ///         re-statement: what a driver whose told-record died with its instance sends after a deploy respawns
    ///         it. The acknowledgement is KEPT and no row is written. Only <see cref="AlarmTransitionKind.Retrigger"/>
    ///         (or inactive → active) un-acknowledges.</item>
    ///         <item>Gitea #656 — <see cref="AlarmTransitionKind.ActiveAcknowledged"/> projects Active+acked in ONE
    ///         update (never an Active+unacked intermediate a client could see) and writes "Activated" only when the
    ///         condition was not already showing that alarm active, then "Acknowledged" only when it was not acked.</item>
    ///         <item>Gitea #656 — a <see cref="AlarmEventArgs.IsRestatement"/> event (a source re-stating upstream's
    ///         current state: a reconnect snapshot, first sight after a respawn) writes no row when it changes nothing
    ///         the condition shows: a Retrigger on an Active+unacked condition with the same message AND severity, or
    ///         a Clear on an already-inactive condition. Unflagged sources (FOCAS, MTConnect, AbCip, live Galaxy
    ///         transitions) are unaffected — a live Retrigger is a genuine re-occurrence and keeps its row.</item>
    ///     </list>
    /// </summary>
    /// <param name="nodeId">The materialised condition node's id (the projection's state key).</param>
    /// <param name="e">The native alarm transition.</param>
    /// <param name="historyKinds">
    ///     The <c>alerts</c> rows to write, in order — each a <see cref="AlarmTransitionKind.Raise"/>/<see cref="AlarmTransitionKind.Retrigger"/>
    ///     ("Activated"), <see cref="AlarmTransitionKind.Acknowledge"/>, <see cref="AlarmTransitionKind.Clear"/> or
    ///     <see cref="AlarmTransitionKind.Unspecified"/>. Empty when the transition is a re-statement.
    /// </param>
    /// <returns>The full Part 9 condition snapshot to write to the node.</returns>
    public AlarmConditionSnapshot Project(string nodeId, AlarmEventArgs e, out IReadOnlyList<AlarmTransitionKind> historyKinds)
    {
        var prev = _prior.TryGetValue(nodeId, out var p)
            ? p : (Active: false, Acked: true, Message: (string?)null, Severity: (ushort)0);
        // #626: a source with a finer scale than the four buckets supplies the exact Part 9 severity.
        var sev = e.OpcUaSeverity is { } exact ? (ushort)Math.Clamp(exact, 1, 1000) : MapSeverity(e.Severity);
        // Gitea #647 re-review R1: only a statement saying the SAME thing the condition already shows is a re-statement.
        // A respawned driver cannot tell "the alarm I was showing" from "a different one that appeared while I was
        // down", so a different message is treated as a new statement — un-acked, with its alerts row. Comparing the
        // message is conservative: any difference (a sources' messages are deterministic for an unchanged statement)
        // errs toward showing the operator an unacknowledged alarm, never toward hiding one behind a stale ack.
        var sameMessage = prev.Active
            && string.Equals(prev.Message?.Trim(), e.Message.Trim(), StringComparison.Ordinal);
        bool active, acked;
        switch (e.Kind)
        {
            case AlarmTransitionKind.Raise when sameMessage:
                (active, acked, historyKinds) = (true, prev.Acked, []);
                break;
            // #656: a source re-stating an Active+unacked condition that already shows exactly this (message AND
            // severity — an MTConnect Warning→Fault escalation can keep the text) changes nothing the node shows.
            case AlarmTransitionKind.Retrigger when e.IsRestatement && sameMessage && !prev.Acked && prev.Severity == sev:
                (active, acked, historyKinds) = (true, false, []);
                break;
            case AlarmTransitionKind.Raise or AlarmTransitionKind.Retrigger:
                (active, acked, historyKinds) = (true, false, [e.Kind]);
                break;
            case AlarmTransitionKind.ActiveAcknowledged:
                (active, acked) = (true, true);
                historyKinds = !sameMessage
                    ? [AlarmTransitionKind.Raise, AlarmTransitionKind.Acknowledge]
                    : !prev.Acked ? [AlarmTransitionKind.Acknowledge] : [];
                break;
            case AlarmTransitionKind.Acknowledge:
                (active, acked, historyKinds) = (prev.Active, true, [AlarmTransitionKind.Acknowledge]);
                break;
            // #656: a re-stated Clear of a condition that is already inactive changes nothing (Galaxy replays every
            // Inactive snapshot entry on each reconnect).
            case AlarmTransitionKind.Clear when e.IsRestatement && !prev.Active:
                (active, acked, historyKinds) = (false, prev.Acked, []);
                break;
            case AlarmTransitionKind.Clear:
                (active, acked, historyKinds) = (false, prev.Acked, [AlarmTransitionKind.Clear]);
                break;
            // A message/severity-only update of an ALREADY-ACTIVE condition that the source flags as a re-statement
            // (AbCip ALMA: the governing limit changed but no new occurrence started, e.g. HH dropped back to H).
            // The node's text/severity move; active/acked are kept; NO row (an "Activated" row would be false).
            case AlarmTransitionKind.Unspecified when e.IsRestatement && prev.Active:
                (active, acked, historyKinds) = (true, prev.Acked, []);
                break;
            default:
                // Unspecified (a message/severity-only update) or an unknown future kind: keep the state. The row is
                // written as before (Unspecified renders "Activated") — unchanged behaviour.
                (active, acked, historyKinds) = (prev.Active, prev.Acked, [e.Kind]);
                break;
        }

        _prior[nodeId] = (active, acked, e.Message, sev);
        return new AlarmConditionSnapshot(
            Active: active, Acknowledged: acked, Confirmed: true, Enabled: true,
            Shelving: AlarmShelvingKind.Unshelved, Severity: sev, Message: e.Message,
            // #626: a per-condition source quality (MTConnect Unavailable) when the driver reports one. Absent
            // (every pre-#626 source) ⇒ Good, as before — driver-wide comms loss stays the host's
            // out-of-band WriteAlarmQuality annotation (#477), not something the projector infers.
            StatusCode: e.QualityStatusCode ?? OpcUaStatus.Good);
    }

    /// <summary>
    ///     Gitea #641 review — record a client acknowledgement the node manager applied to <paramref name="nodeId"/>
    ///     and routed toward the driver. The projector otherwise never sees it, and a later Clear would project the
    ///     stale unacknowledged prior. An untracked condition already defaults to acknowledged.
    /// </summary>
    /// <param name="nodeId">The acknowledged condition node id.</param>
    public void MarkAcknowledged(string nodeId)
    {
        if (_prior.TryGetValue(nodeId, out var p)) _prior[nodeId] = p with { Acked = true };
    }

    /// <summary>Clears all tracked per-node state.</summary>
    public void Clear() => _prior.Clear();

    /// <summary>
    ///     Gitea #641 — drop the tracked state of every condition NOT in <paramref name="deployedNodeIds"/>, keeping
    ///     the rest. Called on every apply instead of <see cref="Clear"/>: a condition that is still deployed keeps
    ///     its state across the deploy (the node manager carries the node's state across a rebuild too), so the
    ///     next Acknowledge does not project <c>Active = false</c> onto an active alarm and the next Clear does not
    ///     project <c>Acked = true</c> onto an unacknowledged one. A removed condition is forgotten, so a later
    ///     re-add starts from the default.
    /// </summary>
    /// <param name="deployedNodeIds">The condition node ids the new composition still materialises.</param>
    public void RetainOnly(IReadOnlySet<string> deployedNodeIds)
    {
        ArgumentNullException.ThrowIfNull(deployedNodeIds);
        foreach (var nodeId in _prior.Keys.Where(k => !deployedNodeIds.Contains(k)).ToList())
            _prior.Remove(nodeId);
    }

    private static ushort MapSeverity(AlarmSeverity s) => s switch
    {
        AlarmSeverity.Low => 200,
        AlarmSeverity.Medium => 500,
        AlarmSeverity.High => 700,
        AlarmSeverity.Critical => 900,
        _ => 500,
    };
}