// 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.Collections.Generic;

namespace Microsoft.Extensions.Configuration
{
    /// <summary>
    /// Builds key/value-based configuration settings for use in an application.
    /// </summary>
    public class ConfigurationBuilder : IConfigurationBuilder
    {
        private readonly List<IConfigurationSource> _sources = new();

        /// <summary>
        /// Gets the sources used to obtain configuration values.
        /// </summary>
        public IList<IConfigurationSource> Sources => _sources;

        /// <summary>
        /// Gets a key/value collection that can be used to share data between the <see cref="IConfigurationBuilder"/>
        /// and the registered <see cref="IConfigurationProvider"/> providers.
        /// </summary>
        public IDictionary<string, object> Properties { get; } = new Dictionary<string, object>();

        /// <summary>
        /// Adds a new configuration source.
        /// </summary>
        /// <param name="source">The configuration source to add.</param>
        /// <returns>The same <see cref="IConfigurationBuilder"/>.</returns>
        public IConfigurationBuilder Add(IConfigurationSource source)
        {
            ArgumentNullException.ThrowIfNull(source);

            _sources.Add(source);
            return this;
        }

        /// <summary>
        /// Builds an <see cref="IConfiguration"/> with keys and values from the set of providers registered in
        /// <see cref="Sources"/>.
        /// </summary>
        /// <returns>An <see cref="IConfigurationRoot"/> with keys and values from the registered providers.</returns>
        public IConfigurationRoot Build()
        {
            var providers = new List<IConfigurationProvider>();
            foreach (IConfigurationSource source in _sources)
            {
                IConfigurationProvider provider = source.Build(this);
                providers.Add(provider);
            }
            return new ConfigurationRoot(providers);
        }
    }
}