Indicator Catalog

Indicator catalog development

File

src/Indicators/{category}/{Indicator}/{Indicator}.Catalog.cs

Builder pattern

public static partial class Ema
{
    /// <summary>
    /// EMA Common Base Listing
    /// </summary>
    internal static readonly IndicatorListing CommonListing =
        new CatalogListingBuilder()
            .WithName("Exponential Moving Average")
            .WithId("EMA")
            .WithCategory(Category.MovingAverage)
            .AddParameter<int>("lookbackPeriods", "Lookback Period",
                description: "Number of periods for the EMA calculation",
                isRequired: true, defaultValue: 20, minimum: 2, maximum: 250)
            .AddResult(nameof(EmaResult.Ema), "EMA", ResultType.Default, isReusable: true)
            .Build();

    /// <summary>
    /// EMA Series Listing
    /// </summary>
    internal static readonly IndicatorListing SeriesListing =
        new CatalogListingBuilder(CommonListing)
            .WithStyle(Style.Series)
            .WithMethodName("ToEma")
            .Build();

    /// <summary>
    /// EMA Stream Listing
    /// </summary>
    internal static readonly IndicatorListing StreamListing =
        new CatalogListingBuilder(CommonListing)
            .WithStyle(Style.Stream)
            .WithMethodName("ToEmaHub")
            .Build();

    /// <summary>
    /// EMA Buffer Listing
    /// </summary>
    internal static readonly IndicatorListing BufferListing =
        new CatalogListingBuilder(CommonListing)
            .WithStyle(Style.Buffer)
            .WithMethodName("ToEmaList")
            .Build();
}

Method naming

.WithMethodName() must be in style-specific listings, NOT in CommonListing.

IndicatorListing.ResultRecordType is derived from the method name when the listing is built — do not set it by hand and do not add a builder method for it. Naming a method of the wrong style (e.g. ToEma on the Buffer listing) makes it report the wrong result shape.

Parameter patterns

• AddParameter<T>() — primitive value types (typically int or double)
• AddEnumParameter<T>() — enum types
• AddDateParameter() — DateTime
• AddSeriesParameter() — IReadOnlyList<T> where T : IReusable
• minimum and maximum required for all numeric parameters
• parameterName must match the bound method's parameter name exactly — a mismatch makes a catalog-bound caller silently receive the default instead of the value it supplied
• Declare parameters as an unbroken run in signature order, skipping none in the middle; ListingExecutor binds them positionally and picks an overload by argument count
• isRequired: false must mean omitting the argument yields defaultValue — so use it only when the parameter has a C# default equal to defaultValue, or when the listing declares no defaultValue at all and promises nothing (VWAP startDate). When the argument can only be dropped by selecting a shorter overload that behaves differently while a defaultValue is advertised — ToPrs(sourceEval, sourceBase) computes no PrsPercent — use isRequired: true, and reach the shorter form with WithoutParam(name) at execution time

Result patterns

• dataName uses nameof(TResult.Property), not a string literal, so a renamed result property fails the build instead of a test — e.g. .AddResult(nameof(EmaResult.Ema), "EMA", ...)
• displayName stays a string literal; it is a human label, not a member name
• isReusable: true only for the property mapping to IReusable.Value
• ISeries models: all results must have isReusable: false
• Exactly one isReusable: true per IReusable indicator

Categories

Registration

Add entries inside the host repository's catalog populator method. The backing collection is a private static readonly List<IndicatorListing> declared at the top of the catalog file; the host repository determines its field name (shown below as listings).

Indicators are grouped alphabetically by indicator ID (abbreviation) and separated by a blank line. Each block is preceded by a short comment header — // {Abbreviation} ({Full Name}) when an abbreviation is conventional, otherwise just // {Full Name}. Within a block, the preferred order for the style listings is Buffer → Series → Stream:

// EMA (Exponential Moving Average)
listings.Add(Ema.BufferListing);
listings.Add(Ema.SeriesListing);
listings.Add(Ema.StreamListing);

// HMA (Hull Moving Average)
listings.Add(Hma.BufferListing);
listings.Add(Hma.SeriesListing);
listings.Add(Hma.StreamListing);

Series-only indicators (no streamable variant) register a single SeriesListing line in the same alphabetical position; e.g.:

// Beta
listings.Add(Beta.SeriesListing);

Prohibited

• .WithMethodName() in CommonListing
• Wrong indicator method name
• isReusable: true for ISeries models
• Multiple isReusable: true results per indicator
• A dataName as a string literal where nameof can reach the member
• A parameterName that names a member the library does not have
• isRequired: false with a defaultValue the C# signature does not apply when the argument is omitted

Testing

tests/Library/Indicators/{folder}/{Indicator}/{Indicator}CatalogTests.cs:

[TestClass]
public class EmaCatalogTests : TestBase
{
    [TestMethod]
    public void EmaSeriesListing()
    {
        var listing = Ema.SeriesListing;
        listing.Name.Should().Be("Exponential Moving Average");
        listing.Style.Should().Be(Style.Series);
        listing.MethodName.Should().Be("ToEma");
    }
}

tests/Library/Common/Catalog/Catalog.Binding.Tests.cs additionally enforces, for every listing in the catalog, that MethodName resolves to a real method of the listing's own style, that each dataName resolves to a property on that method's result record, and that each parameterName forms a contiguous, in-order run in the signature. A listing naming a member the library does not have fails there. It does not check parameter types or value semantics, so keep writing the per-indicator test.