ConfigurationExtensions.cs

// <copyright file="ConfigurationExtensions.cs" company="OpenTelemetry Authors">
// Copyright The OpenTelemetry Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// </copyright>

#nullable enable

using System;
using System.Collections.Generic;
using System.Diagnostics;
#if !NETFRAMEWORK && !NETSTANDARD2_0
using System.Diagnostics.CodeAnalysis;
#endif
using System.Globalization;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.DependencyInjection.Extensions;
using Microsoft.Extensions.Options;

namespace OpenTelemetry.Internal;

internal static class ConfigurationExtensions
{
    public delegate bool TryParseFunc<T>(
        string value,
#if !NETFRAMEWORK && !NETSTANDARD2_0
        [NotNullWhen(true)]
#endif
        out T? parsedValue);

    public static bool TryGetStringValue(
        this IConfiguration configuration,
        string key,
#if !NETFRAMEWORK && !NETSTANDARD2_0
        [NotNullWhen(true)]
#endif
        out string? value)
    {
        value = configuration.GetValue<string?>(key, null);

        return !string.IsNullOrWhiteSpace(value);
    }

    public static bool TryGetUriValue(
        this IConfiguration configuration,
        string key,
#if !NETFRAMEWORK && !NETSTANDARD2_0
        [NotNullWhen(true)]
#endif
        out Uri? value)
    {
        if (!configuration.TryGetStringValue(key, out var stringValue))
        {
            value = null;
            return false;
        }

        if (!Uri.TryCreate(stringValue, UriKind.Absolute, out value))
        {
            throw new FormatException($"{key} environment variable has an invalid value: '{stringValue}'");
        }

        return true;
    }

    public static bool TryGetIntValue(
        this IConfiguration configuration,
        string key,
        out int value)
    {
        if (!configuration.TryGetStringValue(key, out var stringValue))
        {
            value = default;
            return false;
        }

        if (!int.TryParse(stringValue, NumberStyles.None, CultureInfo.InvariantCulture, out value))
        {
            throw new FormatException($"{key} environment variable has an invalid value: '{stringValue}'");
        }

        return true;
    }

    public static bool TryGetValue<T>(
        this IConfiguration configuration,
        string key,
        TryParseFunc<T> tryParseFunc,
#if !NETFRAMEWORK && !NETSTANDARD2_0
        [NotNullWhen(true)]
#endif
        out T? value)
    {
        if (!configuration.TryGetStringValue(key, out var stringValue))
        {
            value = default;
            return false;
        }

        if (!tryParseFunc(stringValue!, out value))
        {
            throw new FormatException($"{key} environment variable has an invalid value: '{stringValue}'");
        }

        return true;
    }

    public static IServiceCollection RegisterOptionsFactory<T>(
        this IServiceCollection services,
        Func<IConfiguration, T> optionsFactoryFunc)
        where T : class
    {
        Debug.Assert(services != null, "services was null");
        Debug.Assert(optionsFactoryFunc != null, "optionsFactoryFunc was null");

        services!.TryAddSingleton<IOptionsFactory<T>>(sp =>
        {
            return new DelegatingOptionsFactory<T>(
                optionsFactoryFunc!,
                sp.GetRequiredService<IConfiguration>(),
                sp.GetServices<IConfigureOptions<T>>(),
                sp.GetServices<IPostConfigureOptions<T>>(),
                sp.GetServices<IValidateOptions<T>>());
        });

        return services!;
    }

    private sealed class DelegatingOptionsFactory<T> : OptionsFactory<T>
        where T : class
    {
        private readonly Func<IConfiguration, T> optionsFactoryFunc;
        private readonly IConfiguration configuration;

        public DelegatingOptionsFactory(
            Func<IConfiguration, T> optionsFactoryFunc,
            IConfiguration configuration,
            IEnumerable<IConfigureOptions<T>> setups,
            IEnumerable<IPostConfigureOptions<T>> postConfigures,
            IEnumerable<IValidateOptions<T>> validations)
            : base(setups, postConfigures, validations)
        {
            Debug.Assert(optionsFactoryFunc != null, "optionsFactoryFunc was null");
            Debug.Assert(configuration != null, "configuration was null");

            this.optionsFactoryFunc = optionsFactoryFunc!;
            this.configuration = configuration!;
        }

        protected override T CreateInstance(string name)
            => this.optionsFactoryFunc(this.configuration);
    }
}