// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System;
using System.Diagnostics.Metrics;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Diagnostics.Metrics.Configuration;
using Microsoft.Extensions.Options;
 
namespace Microsoft.Extensions.Diagnostics.Metrics
{
    /// <summary>
    /// Extensions for <see cref="IMetricsBuilder"/> for enabling metrics based on <see cref="IConfiguration"/>.
    /// </summary>
    public static class MetricsBuilderConfigurationExtensions
    {
        /// <summary>
        /// Reads metrics configuration from the provided <see cref="IConfiguration"/> section and configures
        /// which <see cref="Meter">Meters</see>, <see cref="Instrument">Instruments</see>, and <see cref="IMetricsListener">IMetricsListeners</see> are enabled.
        /// </summary>
        /// <param name="builder">The <see cref="IMetricsBuilder"/>.</param>
        /// <param name="configuration">The <see cref="IConfiguration"/> section to load.</param>
        /// <returns>The original <see cref="IMetricsBuilder"/> for chaining.</returns>
        public static IMetricsBuilder AddConfiguration(this IMetricsBuilder builder, IConfiguration configuration)
        {
            if (builder is null)
            {
                throw new ArgumentNullException(nameof(builder));
            }
 
            if (configuration is null)
            {
                throw new ArgumentNullException(nameof(configuration));
            }
 
            builder.Services.AddSingleton<IConfigureOptions<MetricsOptions>>(new MetricsConfigureOptions(configuration));
            builder.Services.AddSingleton<IOptionsChangeTokenSource<MetricsOptions>>(new ConfigurationChangeTokenSource<MetricsOptions>(configuration));
            builder.Services.AddSingleton(new MetricsConfiguration(configuration));
            return builder;
        }
    }
}