Cache with false and exception capture

.ResultCaptured() decorates a provider to capture false results and thrown exceptions into IResult wrapper.

IProvider<double, double> squareProvider = Providers.Func((double x) => x * x);
IProvider<double, IResult<double>> squareResultProvider = squareProvider.ResultCaptured();
WriteLine(squareResultProvider[10].Value); // -> "100"

.ResultOpened() adapts IResult<T> back into T. Any captured exceptions are rethrown.

IProvider<double, double> squareProvider = Providers.Func((double x) => x * x);
IProvider<double, IResult<double>> squareResultProvider = squareProvider.ResultCaptured();
IProvider<double, IResult<double>> squareCachedResultProvider = squareResultProvider.Cached();
IProvider<double, double> squareCachedProvider = squareCachedResultProvider.ResultOpened();
WriteLine(squareCachedProvider[10]); // -> "100"

The combination of four providers wraps the provider to capture false results and exceptions.

IProvider<string, XDocument> docProvider =
    Providers.Func<string, XDocument>(XDocument.Load)
    .ResultCaptured() // Captures exception
    .Cached()         // ConcurrentDictionary
    .ResultOpened();  // Rethrows exception

XDocument doc = docProvider["http://avalanche.fi/sitemap.xml"];

.ValueResultCaptured() and .ValueResultOpened() captures result into value-typed struct ValueResult<T> which causes less heap allocatation.

IProvider<string, XDocument> docProvider =
    Providers.Func<string, XDocument>(XDocument.Load)
    .ValueResultCaptured() // Captures exception
    .Cached()              // ConcurrentDictionary
    .ValueResultOpened();  // Rethrows exception

XDocument doc = docProvider["http://avalanche.fi/sitemap.xml"];

.InvalidateCache(deep) proceeds invalidation through decoration stack when deep: true.

// Integer printer, cached
IProvider<int, string> intPrinter =
    Providers.Func<int, string>(i => i.ToString())
    .ResultCaptured() // Captures exception
    .Cached()         // ConcurrentDictionary
    .ResultOpened();  // Rethrows exception

// Print integers to strings
string print1 = intPrinter[10];
string print2 = intPrinter[10];
// Compare object reference
WriteLine(object.ReferenceEquals(print1, print2)); // "True"

// Invalidate cache
intPrinter.InvalidateCache(deep: true);
// Compare object reference
WriteLine(object.ReferenceEquals(print1, intPrinter[10])); // "False"

Result

IResult is the interface for types that hold result values and exceptions.

/// <summary>Evaluation result</summary>
public interface IResult
{
    /// <summary>Evaluation status</summary>
    ResultStatus Status { get; set; }
    /// <summary>Result value</summary>
    object? Value { get; set; }
    /// <summary>Error object</summary>
    Exception? Error { get; set; }
    /// <summary>(optional) Request that was used to create this result</summary>
    object? Request { get; set; }
}

/// <summary>Evaluation status </summary>
public enum ResultStatus : int
{
    /// <summary>No evaluation</summary>
    Unassigned = 0,
    /// <summary>Resulted to no value</summary>
    NoResult = 1,
    /// <summary>Resulted to successful value</summary>
    Ok = 2,
    /// <summary>Resulted to error</summary>
    Error = 3,
}

IResult<T> is same with type generics.

/// <summary>Evaluation result</summary>
public interface IResult<T> : IResult
{
    /// <summary>Result value, valid only if <see cref="ResultStatus.Ok"/></summary>
    new T Value { get; set; }
}

IResult.Error contains captured exception.

IResult<double> result = squareResultProvider[double.NaN];
WriteLine(result.Error); // -> "ArgumentException"

.AssertValue<T>() returns value or rethrows captured exception.

IResult<double> result_ = squareResultProvider[10];
WriteLine(squareResultProvider[10].AssertValue<IResult<double>, double>()); // -> "100"
WriteLine(squareResultProvider[double.NaN].AssertValue<IResult<double>, double>()); // -> "100"

ResultProvider

ResultProviderBase<Key, Value> can be used as base implementation for providers that capture exceptions right into IResult.

public class SquareResultProvider : ResultProviderBase<double, double>
{
    protected override bool TryGetValue(double x, out double value)
    {
        // NaN
        if (double.IsNaN(x)) throw new ArgumentException("NaN");
        // Infinity
        if (double.IsInfinity(x)) throw new ArgumentException("Infinity");
        // Assign value
        value = x * x;
        // Return
        return true;
    }
}

IProvider<double, IResult<double>> squareResultProvider = new SquareResultProvider();
WriteLine(squareResultProvider[10].Value); // -> "100"

Full Example

Full example

using System;
using System.Xml.Linq;
using Avalanche.Utilities.Provider;
using static System.Console;

class provider_result
{
    public static void Run()
    {
        {
            // <01>
            IProvider<double, double> squareProvider = Providers.Func((double x) => x * x);
            IProvider<double, IResult<double>> squareResultProvider = squareProvider.ResultCaptured();
            WriteLine(squareResultProvider[10].Value); // -> "100"
            // </01>
        }
        {
            // <02>
            IProvider<double, double> squareProvider = Providers.Func((double x) => x * x);
            IProvider<double, IResult<double>> squareResultProvider = squareProvider.ResultCaptured();
            IProvider<double, IResult<double>> squareCachedResultProvider = squareResultProvider.Cached();
            IProvider<double, double> squareCachedProvider = squareCachedResultProvider.ResultOpened();
            WriteLine(squareCachedProvider[10]); // -> "100"
            // </02>
        }
        {
            // <03>
            IProvider<string, XDocument> docProvider =
                Providers.Func<string, XDocument>(XDocument.Load)
                .ResultCaptured() // Captures exception
                .Cached()         // ConcurrentDictionary
                .ResultOpened();  // Rethrows exception

            XDocument doc = docProvider["http://avalanche.fi/sitemap.xml"];
            // </03>
        }
        {
            // <04>
            IProvider<string, XDocument> docProvider =
                Providers.Func<string, XDocument>(XDocument.Load)
                .ValueResultCaptured() // Captures exception
                .Cached()              // ConcurrentDictionary
                .ValueResultOpened();  // Rethrows exception

            XDocument doc = docProvider["http://avalanche.fi/sitemap.xml"];
            // </04>
        }

        {
            // <10>
            // Integer printer, cached
            IProvider<int, string> intPrinter =
                Providers.Func<int, string>(i => i.ToString())
                .ResultCaptured() // Captures exception
                .Cached()         // ConcurrentDictionary
                .ResultOpened();  // Rethrows exception

            // Print integers to strings
            string print1 = intPrinter[10];
            string print2 = intPrinter[10];
            // Compare object reference
            WriteLine(object.ReferenceEquals(print1, print2)); // "True"

            // Invalidate cache
            intPrinter.InvalidateCache(deep: true);
            // Compare object reference
            WriteLine(object.ReferenceEquals(print1, intPrinter[10])); // "False"
            // </10>
        }

        {
            try
            {
                // <20B>
                IProvider<double, IResult<double>> squareResultProvider = new SquareResultProvider();
                WriteLine(squareResultProvider[10].Value); // -> "100"
                // </20B>
                // <20C>
                IResult<double> result = squareResultProvider[double.NaN];
                WriteLine(result.Error); // -> "ArgumentException"
                // </20C>
                // <20D>
                IResult<double> result_ = squareResultProvider[10];
                WriteLine(squareResultProvider[10].AssertValue<IResult<double>, double>()); // -> "100"
                WriteLine(squareResultProvider[double.NaN].AssertValue<IResult<double>, double>()); // -> "100"
                // </20D>
            }
            catch (Exception) { }
        }
    }

    // <20>
    public class SquareResultProvider : ResultProviderBase<double, double>
    {
        protected override bool TryGetValue(double x, out double value)
        {
            // NaN
            if (double.IsNaN(x)) throw new ArgumentException("NaN");
            // Infinity
            if (double.IsInfinity(x)) throw new ArgumentException("Infinity");
            // Assign value
            value = x * x;
            // Return
            return true;
        }
    }
    // </20>
}