using System;
using System.Linq;
using Microsoft.Extensions.Configuration;

namespace GerstITS.Examples.Api.Configurations;

public static class IConfigurationExtensions
{
    #region Methods

    public static TEnum GetFlaggedEnum<TEnum>(this IConfiguration configuration, string key)
        where TEnum : struct, IConvertible
    {
        ThrowsAnExceptionIfTypeIsNotAnEnumeration<TEnum>();

        return (TEnum)(object)(configuration.GetSection(key)?
                                            .Get<TEnum[]>() ?? Enumerable.Empty<TEnum>())
                                            .Sum(i => (int)(object)i);
    }

    private static void ThrowsAnExceptionIfTypeIsNotAnEnumeration<TEnum>() where TEnum : struct, IConvertible
    {
        if (!typeof(TEnum).IsEnum)
            throw new InvalidOperationException($"{typeof(TEnum)} is not supported.");
    }

    #endregion
}