ScadaBridge/src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Shared/AlarmTriggerEditor.razor

@namespace ZB.MOM.WW.ScadaBridge.CentralUI.Components.Shared
@using System.Globalization
@using ZB.MOM.WW.ScadaBridge.Commons.Types.Enums

@* Rich alarm trigger configuration editor. Replaces the raw JSON text field
   used for TemplateAlarm.TriggerConfiguration. The editor emits the same JSON
   shape that AlarmActor.ParseEvalConfig consumes:
     ValueMatch       { attributeName, matchValue }      ("!=X" prefix = not equals)
     RangeViolation   { attributeName, min, max }
     RateOfChange     { attributeName, thresholdPerSecond, windowSeconds, direction } *@

<div class="border rounded bg-body p-3">

    @* ── Monitored attribute ───────────────────────────────────────────── *@
    @* Expression triggers reference attributes inside the C# expression itself,
       so they do not use the single-attribute picker. *@
    @if (TriggerType != AlarmTriggerType.Expression)
    {
    <div class="mb-3">
        <label for="alarm-attr-select" class="form-label small text-uppercase text-muted fw-semibold mb-1">
            Monitored attribute
        </label>

        <div class="input-group input-group-sm">
            <select id="alarm-attr-select"
                    class="form-select"
                    @bind="_attributeName"
                    @bind:after="OnAttributeChanged">
                <option value="">— select attribute —</option>
                @{
                    var groups = AvailableAttributes
                        .GroupBy(c => c.Source)
                        .OrderBy(g => SourceOrder(g.Key))
                        .ToList();
                }
                @foreach (var grp in groups)
                {
                    <optgroup label="@grp.Key">
                        @foreach (var choice in grp.OrderBy(c => c.CanonicalName, StringComparer.Ordinal))
                        {
                            var label = $"{choice.CanonicalName}  ({choice.DataType})";
                            var disabled = !IsAttributeCompatible(choice);
                            <option value="@choice.CanonicalName" disabled="@disabled">@label</option>
                        }
                    </optgroup>
                }
                @* If the saved attribute name isn't in the current list, keep it selectable so it's visible. *@
                @if (!string.IsNullOrEmpty(_model.AttributeName) && _selectedChoice == null)
                {
                    <optgroup label="Unknown">
                        <option value="@_model.AttributeName">@_model.AttributeName (not found)</option>
                    </optgroup>
                }
            </select>
            @if (_selectedDataType is { } dt)
            {
                <span class="input-group-text bg-body-secondary text-body-secondary small">@dt</span>
            }
        </div>

        @if (_selectedChoice != null && !IsAttributeCompatible(_selectedChoice))
        {
            <div class="form-text text-danger">
                Selected attribute is @_selectedChoice.DataType — this trigger type requires a numeric attribute.
            </div>
        }
        else if (_selectedChoice == null && !string.IsNullOrWhiteSpace(_model.AttributeName))
        {
            <div class="form-text text-warning-emphasis">
                "@_model.AttributeName" is not in the current template. Save will still write it as-is.
            </div>
        }
    </div>
    }

    @* ── Type-specific block ───────────────────────────────────────────── *@
    @switch (TriggerType)
    {
        case AlarmTriggerType.ValueMatch:
            @RenderValueMatch();
            break;
        case AlarmTriggerType.RangeViolation:
            @RenderRangeViolation();
            break;
        case AlarmTriggerType.RateOfChange:
            @RenderRateOfChange();
            break;
        case AlarmTriggerType.HiLo:
            @RenderHiLo();
            break;
        case AlarmTriggerType.Expression:
            @RenderExpression();
            break;
    }

    @* ── Hint ──────────────────────────────────────────────────────────── *@
    <div class="mt-3 pt-2 border-top small text-muted">
        @BuildHint()
    </div>
</div>

@code {
    // ── Parameters ─────────────────────────────────────────────────────────

    [Parameter] public AlarmTriggerType TriggerType { get; set; }
    [Parameter] public string? Value { get; set; }
    [Parameter] public EventCallback<string?> ValueChanged { get; set; }

    /// <summary>
    /// Flattened attribute list (direct + inherited + composed). Used to drive
    /// the picker and to determine the selected attribute's data type for
    /// type-aware inputs.
    /// </summary>
    [Parameter] public IReadOnlyList<AlarmAttributeChoice> AvailableAttributes { get; set; } =
        Array.Empty<AlarmAttributeChoice>();

    // ── Internal state ─────────────────────────────────────────────────────

    private AlarmTriggerModel _model = new AlarmTriggerModel();
    private AlarmTriggerType _lastSeenType;
    private string? _lastSeenJson;

    /// <summary>The choice currently selected from <see cref="AvailableAttributes"/>, if any.</summary>
    private AlarmAttributeChoice? _selectedChoice;

    private string? _selectedDataType => _selectedChoice?.DataType;

    // ── Parse / serialize lifecycle ────────────────────────────────────────

    protected override void OnParametersSet()
    {
        var typeChanged = _lastSeenType != TriggerType;
        var jsonChanged = Value != _lastSeenJson;

        if (!typeChanged && !jsonChanged) return;

        _lastSeenType = TriggerType;
        _lastSeenJson = Value;

        // Preserve attribute name across type changes — re-parse the JSON in
        // the context of the new type. Missing/unparseable keys fall back to
        // empty defaults.
        var preservedAttr = _model.AttributeName;
        _model = AlarmTriggerConfigCodec.Parse(Value, TriggerType);
        if (jsonChanged == false && typeChanged && !string.IsNullOrEmpty(preservedAttr))
            _model.AttributeName = preservedAttr;

        RefreshSelectedChoice();
        SyncTextMirrors();
    }

    private void RefreshSelectedChoice()
    {
        _selectedChoice = AvailableAttributes.FirstOrDefault(
            c => string.Equals(c.CanonicalName, _model.AttributeName, StringComparison.Ordinal));
    }

    private async Task Emit()
    {
        var json = AlarmTriggerConfigCodec.Serialize(_model, TriggerType);
        _lastSeenJson = json;
        await ValueChanged.InvokeAsync(json);
    }

    // ── Attribute picker ───────────────────────────────────────────────────

    /// <summary>
    /// String mirror for the attribute picker — required because @bind needs a
    /// settable backing field, not a computed expression.
    /// </summary>
    private string _attributeName = string.Empty;

    private async Task OnAttributeChanged()
    {
        _model.AttributeName = _attributeName;
        RefreshSelectedChoice();
        await Emit();
    }

    private static int SourceOrder(string source) => source switch
    {
        "Direct" => 0,
        "Inherited" => 1,
        "Composed" => 2,
        _ => 3
    };

    private bool IsAttributeCompatible(AlarmAttributeChoice choice) =>
        TriggerType == AlarmTriggerType.ValueMatch
            || IsNumericType(choice.DataType);

    private static bool IsNumericType(string dataType) => dataType switch
    {
        "Integer" or "Int32" or "Int64" or "Float" or "Double" or "Number" => true,
        _ => false
    };

    // ── ValueMatch ─────────────────────────────────────────────────────────

    private RenderFragment RenderValueMatch() => __builder =>
    {
        <div class="row g-2">
            <div class="col-md-4">
                <label class="form-label small text-uppercase text-muted fw-semibold mb-1">
                    Operator
                </label>
                <select class="form-select form-select-sm"
                        @bind="_operatorText"
                        @bind:after="OnOperatorChanged">
                    <option value="eq">equals</option>
                    <option value="ne">not equals</option>
                </select>
            </div>
            <div class="col-md-8">
                <label class="form-label small text-uppercase text-muted fw-semibold mb-1">
                    Match value
                </label>
                @{
                    var t = _selectedChoice?.DataType;
                    if (t == "Boolean")
                    {
                        <select class="form-select form-select-sm"
                                data-test="alarm-matchvalue-input"
                                @bind="_matchValueText"
                                @bind:after="OnMatchValueChanged">
                            <option value="True">True</option>
                            <option value="False">False</option>
                        </select>
                    }
                    else if (IsNumericType(t ?? ""))
                    {
                        <input type="number" step="any" class="form-control form-control-sm"
                               data-test="alarm-matchvalue-input"
                               @bind="_matchValueText"
                               @bind:event="oninput"
                               @bind:after="OnMatchValueChanged" />
                    }
                    else
                    {
                        <input type="text" class="form-control form-control-sm"
                               data-test="alarm-matchvalue-input"
                               placeholder="value"
                               @bind="_matchValueText"
                               @bind:event="oninput"
                               @bind:after="OnMatchValueChanged" />
                    }
                }
            </div>
        </div>
    };

    // ── RangeViolation ─────────────────────────────────────────────────────

    private RenderFragment RenderRangeViolation() => __builder =>
    {
        <div class="row g-2 align-items-end">
            <div class="col-md-5">
                <label class="form-label small text-uppercase text-muted fw-semibold mb-1">
                    Minimum
                </label>
                <input type="number" step="any" class="form-control form-control-sm"
                       @bind="_minText"
                       @bind:event="oninput"
                       @bind:after="OnMinChanged" />
            </div>
            <div class="col-md-2 text-center pb-1 text-muted small">to</div>
            <div class="col-md-5">
                <label class="form-label small text-uppercase text-muted fw-semibold mb-1">
                    Maximum
                </label>
                <input type="number" step="any" class="form-control form-control-sm"
                       @bind="_maxText"
                       @bind:event="oninput"
                       @bind:after="OnMaxChanged" />
            </div>
        </div>

        <div class="mt-3" aria-hidden="true">
            <svg viewBox="0 0 200 12" preserveAspectRatio="none"
                 style="width:100%; height:10px; border-radius:5px; overflow:hidden;">
                @* Token-driven fills, not literal hex: this preview renders on a
                   #1b1d21 surface under [data-bs-theme="dark"], where Bootstrap's
                   light subtle tints read as bright pastel bars. *@
                <rect x="0"   y="0" width="20"  height="12" fill="var(--bad-bg)" />
                <rect x="20"  y="0" width="160" height="12" fill="var(--ok-bg)" />
                <rect x="180" y="0" width="20"  height="12" fill="var(--bad-bg)" />
            </svg>
            <div class="d-flex justify-content-between small text-muted mt-1">
                <span>alarm</span>
                <span>normal</span>
                <span>alarm</span>
            </div>
        </div>
    };

    private async Task OnMinChanged()
    {
        _model.Min = ParseDouble(_minText);
        await Emit();
    }

    private async Task OnMaxChanged()
    {
        _model.Max = ParseDouble(_maxText);
        await Emit();
    }

    // ── RateOfChange ───────────────────────────────────────────────────────

    private RenderFragment RenderRateOfChange() => __builder =>
    {
        <div class="row g-2 align-items-end">
            <div class="col-md-6">
                <label class="form-label small text-uppercase text-muted fw-semibold mb-1">
                    Rate threshold
                </label>
                <div class="input-group input-group-sm">
                    <input type="number" step="any" class="form-control"
                           @bind="_thresholdText"
                           @bind:event="oninput"
                           @bind:after="OnThresholdChanged" />
                    <span class="input-group-text">units / sec</span>
                </div>
            </div>
            <div class="col-md-6">
                <label class="form-label small text-uppercase text-muted fw-semibold mb-1">
                    Sampling window
                </label>
                <div class="input-group input-group-sm">
                    <input type="number" step="any" min="0" class="form-control"
                           @bind="_windowText"
                           @bind:event="oninput"
                           @bind:after="OnWindowChanged" />
                    <span class="input-group-text">sec</span>
                </div>
            </div>
        </div>

        <div class="mt-3 row g-2">
            <div class="col-md-6">
                <label class="form-label small text-uppercase text-muted fw-semibold mb-1">
                    Direction
                </label>
                <select class="form-select form-select-sm"
                        @bind="_directionText"
                        @bind:after="OnDirectionChanged">
                    <option value="rising">Rising only</option>
                    <option value="falling">Falling only</option>
                    <option value="either">Either direction</option>
                </select>
            </div>
        </div>
    };

    private async Task OnThresholdChanged()
    {
        _model.ThresholdPerSecond = ParseDouble(_thresholdText);
        await Emit();
    }

    private async Task OnWindowChanged()
    {
        _model.WindowSeconds = ParseDouble(_windowText);
        await Emit();
    }

    private async Task OnDirectionChanged()
    {
        _model.Direction = _directionText;
        await Emit();
    }

    private string _directionText = "either";

    // ── HiLo ───────────────────────────────────────────────────────────────

    private RenderFragment RenderHiLo() => __builder =>
    {
        <div class="small text-muted mb-2 fst-italic">
            Set any subset of the four setpoints. The most-severe matching band
            wins (LoLo/HiHi outrank Lo/Hi). Per-setpoint priority overrides the
            alarm-level priority for that band. Deadband (optional) relaxes the
            deactivation threshold by the configured amount to prevent flapping.
        </div>

        @HiLoSetpointRow("HIGH-HIGH (critical)",
            _hiHiText, v => _hiHiText = v, OnHiHiChanged,
            _hiHiDeadbandText, v => _hiHiDeadbandText = v, OnHiHiDeadbandChanged,
            _hiHiPriorityText, v => _hiHiPriorityText = v, OnHiHiPriorityChanged,
            _hiHiMessageText, v => _hiHiMessageText = v, OnHiHiMessageChanged,
            "text-danger", "alarm-hilo-hihi")

        @HiLoSetpointRow("HIGH (warning)",
            _hiText, v => _hiText = v, OnHiChanged,
            _hiDeadbandText, v => _hiDeadbandText = v, OnHiDeadbandChanged,
            _hiPriorityText, v => _hiPriorityText = v, OnHiPriorityChanged,
            _hiMessageText, v => _hiMessageText = v, OnHiMessageChanged,
            "text-warning-emphasis", "alarm-hilo-hi")

        @HiLoSetpointRow("LOW (warning)",
            _loText, v => _loText = v, OnLoChanged,
            _loDeadbandText, v => _loDeadbandText = v, OnLoDeadbandChanged,
            _loPriorityText, v => _loPriorityText = v, OnLoPriorityChanged,
            _loMessageText, v => _loMessageText = v, OnLoMessageChanged,
            "text-warning-emphasis", "alarm-hilo-lo")

        @HiLoSetpointRow("LOW-LOW (critical)",
            _loLoText, v => _loLoText = v, OnLoLoChanged,
            _loLoDeadbandText, v => _loLoDeadbandText = v, OnLoLoDeadbandChanged,
            _loLoPriorityText, v => _loLoPriorityText = v, OnLoLoPriorityChanged,
            _loLoMessageText, v => _loLoMessageText = v, OnLoLoMessageChanged,
            "text-danger", "alarm-hilo-lolo")
    };

    /// <summary>
    /// Renders one setpoint row: value (number) + priority (int). Both are
    /// optional — leaving a value blank disables that band. The
    /// <paramref name="severityClass"/> tints the label to convey relative
    /// severity at a glance.
    /// </summary>
    private RenderFragment HiLoSetpointRow(
        string label,
        string? value, Action<string?> valueSetter, Func<Task> onValueChanged,
        string? deadband, Action<string?> deadbandSetter, Func<Task> onDeadbandChanged,
        string? priority, Action<string?> prioritySetter, Func<Task> onPriorityChanged,
        string? message, Action<string?> messageSetter, Func<Task> onMessageChanged,
        string severityClass, string setpointTestId) => __builder =>
    {
        <div class="row g-2 align-items-end mb-1">
            <div class="col-md-5">
                <label class="form-label small text-uppercase fw-semibold mb-1 @severityClass">
                    @label
                </label>
                <div class="input-group input-group-sm">
                    <span class="input-group-text">setpoint</span>
                    <input type="number" step="any" class="form-control"
                           data-test="@setpointTestId"
                           placeholder="—"
                           value="@value"
                           @oninput="@(e => { valueSetter(e.Value?.ToString()); _ = onValueChanged(); })" />
                </div>
            </div>
            <div class="col-md-3">
                <label class="form-label small text-uppercase text-muted fw-semibold mb-1">
                    Deadband
                </label>
                <div class="input-group input-group-sm">
                    <span class="input-group-text">±</span>
                    <input type="number" step="any" min="0" class="form-control"
                           placeholder="0"
                           value="@deadband"
                           @oninput="@(e => { deadbandSetter(e.Value?.ToString()); _ = onDeadbandChanged(); })" />
                </div>
            </div>
            <div class="col-md-4">
                <label class="form-label small text-uppercase text-muted fw-semibold mb-1">
                    Priority
                </label>
                <div class="input-group input-group-sm">
                    <input type="number" min="0" max="1000" class="form-control"
                           placeholder="@_priority"
                           value="@priority"
                           @oninput="@(e => { prioritySetter(e.Value?.ToString()); _ = onPriorityChanged(); })" />
                </div>
            </div>
        </div>
        <div class="row g-2 mb-3">
            <div class="col-12">
                <input type="text" class="form-control form-control-sm"
                       placeholder="Optional operator message for this band…"
                       value="@message"
                       @oninput="@(e => { messageSetter(e.Value?.ToString()); _ = onMessageChanged(); })" />
            </div>
        </div>
    };

    // Setpoint text mirrors — separate from the model so blank fields stay
    // blank (rather than appearing as 0) and we can detect "unset" cleanly.
    private string? _loLoText;
    private string? _loText;
    private string? _hiText;
    private string? _hiHiText;
    private string? _loLoPriorityText;
    private string? _loPriorityText;
    private string? _hiPriorityText;
    private string? _hiHiPriorityText;
    private string? _loLoDeadbandText;
    private string? _loDeadbandText;
    private string? _hiDeadbandText;
    private string? _hiHiDeadbandText;
    private string? _loLoMessageText;
    private string? _loMessageText;
    private string? _hiMessageText;
    private string? _hiHiMessageText;

    // Mirrored on the parent so the placeholder shows the right fallback.
    [Parameter] public int FallbackPriority { get; set; } = 500;
    private int _priority => FallbackPriority;

    private async Task OnLoLoChanged()        { _model.LoLo  = ParseDouble(_loLoText); await Emit(); }
    private async Task OnLoChanged()          { _model.Lo    = ParseDouble(_loText);   await Emit(); }
    private async Task OnHiChanged()          { _model.Hi    = ParseDouble(_hiText);   await Emit(); }
    private async Task OnHiHiChanged()        { _model.HiHi  = ParseDouble(_hiHiText); await Emit(); }
    private async Task OnLoLoPriorityChanged() { _model.LoLoPriority = ParseInt(_loLoPriorityText); await Emit(); }
    private async Task OnLoPriorityChanged()   { _model.LoPriority   = ParseInt(_loPriorityText);   await Emit(); }
    private async Task OnHiPriorityChanged()   { _model.HiPriority   = ParseInt(_hiPriorityText);   await Emit(); }
    private async Task OnHiHiPriorityChanged() { _model.HiHiPriority = ParseInt(_hiHiPriorityText); await Emit(); }
    private async Task OnLoLoDeadbandChanged() { _model.LoLoDeadband = ParseDouble(_loLoDeadbandText); await Emit(); }
    private async Task OnLoDeadbandChanged()   { _model.LoDeadband   = ParseDouble(_loDeadbandText);   await Emit(); }
    private async Task OnHiDeadbandChanged()   { _model.HiDeadband   = ParseDouble(_hiDeadbandText);   await Emit(); }
    private async Task OnHiHiDeadbandChanged() { _model.HiHiDeadband = ParseDouble(_hiHiDeadbandText); await Emit(); }
    private async Task OnLoLoMessageChanged()  { _model.LoLoMessage  = _loLoMessageText; await Emit(); }
    private async Task OnLoMessageChanged()    { _model.LoMessage    = _loMessageText;   await Emit(); }
    private async Task OnHiMessageChanged()    { _model.HiMessage    = _hiMessageText;   await Emit(); }
    private async Task OnHiHiMessageChanged()  { _model.HiHiMessage  = _hiHiMessageText; await Emit(); }

    private static int? ParseInt(string? s) =>
        int.TryParse(s, NumberStyles.Integer, CultureInfo.InvariantCulture, out var v) ? v : null;

    // ── Text mirrors for typed inputs ──────────────────────────────────────
    // @bind requires a settable backing field that round-trips text. We keep
    // these in sync with the model and re-parse on @bind:after.

    private string? _minText;
    private string? _maxText;
    private string? _thresholdText;
    private string? _windowText;

    protected override void OnInitialized()
    {
        SyncTextMirrors();
    }

    private void SyncTextMirrors()
    {
        _attributeName = _model.AttributeName ?? string.Empty;
        _matchValueText = _model.MatchValue ?? string.Empty;
        _operatorText = _model.NotEquals ? "ne" : "eq";
        _minText = FormatNullable(_model.Min);
        _maxText = FormatNullable(_model.Max);
        _thresholdText = FormatNullable(_model.ThresholdPerSecond);
        _windowText = FormatNullable(_model.WindowSeconds);
        _directionText = _model.Direction;
        // Sync the analysis-kind selector from the loaded model.
        _analysisKindValue = _model.IsStrictAnalysisKind ? "Strict" : "Advisory";
        _loLoText = FormatNullable(_model.LoLo);
        _loText = FormatNullable(_model.Lo);
        _hiText = FormatNullable(_model.Hi);
        _hiHiText = FormatNullable(_model.HiHi);
        _loLoPriorityText = _model.LoLoPriority?.ToString(CultureInfo.InvariantCulture);
        _loPriorityText = _model.LoPriority?.ToString(CultureInfo.InvariantCulture);
        _hiPriorityText = _model.HiPriority?.ToString(CultureInfo.InvariantCulture);
        _hiHiPriorityText = _model.HiHiPriority?.ToString(CultureInfo.InvariantCulture);
        _loLoDeadbandText = FormatNullable(_model.LoLoDeadband);
        _loDeadbandText = FormatNullable(_model.LoDeadband);
        _hiDeadbandText = FormatNullable(_model.HiDeadband);
        _hiHiDeadbandText = FormatNullable(_model.HiHiDeadband);
        _loLoMessageText = _model.LoLoMessage ?? string.Empty;
        _loMessageText = _model.LoMessage ?? string.Empty;
        _hiMessageText = _model.HiMessage ?? string.Empty;
        _hiHiMessageText = _model.HiHiMessage ?? string.Empty;
    }

    private string _operatorText = "eq";
    private string _matchValueText = string.Empty;

    private async Task OnOperatorChanged()
    {
        _model.NotEquals = (_operatorText == "ne");
        await Emit();
    }

    private async Task OnMatchValueChanged()
    {
        _model.MatchValue = _matchValueText;
        await Emit();
    }

    // ── Expression ─────────────────────────────────────────────────────────

    private RenderFragment RenderExpression() => __builder =>
    {
        <label class="form-label small text-uppercase text-muted fw-semibold mb-1">Trigger expression</label>
        <MonacoEditor Height="120px"
                      Language="csharp"
                      ScriptKind="ScriptAnalysis.ScriptKind.Template"
                      ShowToolbar="false"
                      Value="@(_model.Expression ?? string.Empty)"
                      ValueChanged="OnExpressionChanged"
                      SelfAttributes="@TriggerAttributeMapper.SelfAttributes(AvailableAttributes)"
                      Children="@TriggerAttributeMapper.Children(AvailableAttributes)" />
        <div class="form-text">
            A boolean C# expression — e.g. <code>Attributes["Temperature"] &gt; 80</code>.
        </div>
        @* Analysis-kind selector — Advisory (default) keeps the blank-expression
           finding as a non-blocking warning; Strict escalates it to a deploy-blocking error. *@
        <div class="mt-2">
            <label for="alarm-trigger-kind" class="form-label small text-uppercase text-muted fw-semibold mb-1">
                Analysis kind
            </label>
            <select id="alarm-trigger-kind"
                    class="form-select form-select-sm"
                    style="max-width: 280px;"
                    @bind="_analysisKindValue"
                    @bind:after="OnAnalysisKindChanged">
                <option value="Advisory">Advisory — blank expression is a warning</option>
                <option value="Strict">Strict — blank expression blocks deploy</option>
            </select>
        </div>
    };

    private async Task OnExpressionChanged(string value)
    {
        _model.Expression = value;
        await Emit();
    }

    // Backing field + handler for the Advisory|Strict selector.
    private string _analysisKindValue = "Advisory";

    private async Task OnAnalysisKindChanged()
    {
        _model.IsStrictAnalysisKind = string.Equals(_analysisKindValue, "Strict", StringComparison.OrdinalIgnoreCase);
        await Emit();
    }

    // ── Hint text ──────────────────────────────────────────────────────────

    private string BuildHint()
    {
        var attr = string.IsNullOrWhiteSpace(_model.AttributeName)
            ? "the selected attribute"
            : $"\"{_model.AttributeName}\"";

        return TriggerType switch
        {
            AlarmTriggerType.ValueMatch =>
                $"Triggers when {attr} {(_model.NotEquals ? "is not equal to" : "equals")} \"{_model.MatchValue ?? ""}\".",

            AlarmTriggerType.RangeViolation =>
                _model.Min.HasValue && _model.Max.HasValue
                    ? $"Triggers when {attr} < {Fmt(_model.Min)} or > {Fmt(_model.Max)}."
                    : $"Triggers when {attr} goes outside the configured range.",

            AlarmTriggerType.RateOfChange =>
                $"Triggers when {attr} changes faster than {Fmt(_model.ThresholdPerSecond) ?? "?"} units/sec ({_model.Direction}) over a {Fmt(_model.WindowSeconds) ?? "?"} sec window.",

            AlarmTriggerType.HiLo => BuildHiLoHint(attr),

            AlarmTriggerType.Expression =>
                "Alarm is active while this expression is true.",

            _ => string.Empty
        };
    }

    private string BuildHiLoHint(string attr)
    {
        var parts = new List<string>();
        if (_model.LoLo.HasValue) parts.Add($"LoLo at {Fmt(_model.LoLo)}");
        if (_model.Lo.HasValue)   parts.Add($"Lo at {Fmt(_model.Lo)}");
        if (_model.Hi.HasValue)   parts.Add($"Hi at {Fmt(_model.Hi)}");
        if (_model.HiHi.HasValue) parts.Add($"HiHi at {Fmt(_model.HiHi)}");

        if (parts.Count == 0)
            return $"Triggers when {attr} crosses any configured setpoint (none set yet).";
        return $"Triggers on {attr}: {string.Join(", ", parts)}.";
    }

    private static string Fmt(double? v) =>
        v.HasValue ? v.Value.ToString("0.###", CultureInfo.InvariantCulture) : "";

    private static string FormatNullable(double? v) =>
        v.HasValue ? v.Value.ToString("R", CultureInfo.InvariantCulture) : "";

    private static double? ParseDouble(string? s) =>
        double.TryParse(s, NumberStyles.Float, CultureInfo.InvariantCulture, out var v) ? v : null;

}