using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Primitives;

namespace BuildFlow.Platform.Tests;

/// 极简字典实现的 IConfiguration，仅供测试使用。
/// 完整实现 GetSection/GetChildren，让 GetValue<T> 扩展方法（走 ConfigurationBinder）能正确工作。
/// 注意：ConfigurationBinder.GetValue 内部调用 GetSection(key).Value，故必须返回有效 section。
internal sealed class DictionaryConfiguration : IConfiguration
{
    private readonly Dictionary<string, string?> _values = [];

    public string? this[string key]
    {
        get => _values.TryGetValue(key, out var v) ? v : null;
        set => _values[key] = value;
    }

    // 支持集合初始化器语法：new DictionaryConfiguration { ["k"] = "v" }
    public void Add(string key, string? value) => _values[key] = value;

    IEnumerable<IConfigurationSection> IConfiguration.GetChildren() =>
        _values.Select(kv => (IConfigurationSection)new LeafSection(kv.Key, kv.Value)).ToList();

    IChangeToken IConfiguration.GetReloadToken() => EmptyChangeToken.Instance;

    IConfigurationSection IConfiguration.GetSection(string key) =>
        new LeafSection(key, _values.TryGetValue(key, out var v) ? v : null);

    private sealed class LeafSection(string key, string? value) : IConfigurationSection
    {
        public string Key => key;
        public string Path => key;
        public string? Value { get; set; } = value;

        string? IConfiguration.this[string childKey]
        {
            get => null;
            set { }
        }

        IConfigurationSection IConfiguration.GetSection(string childKey) =>
            new LeafSection($"{key}:{childKey}", null);

        IEnumerable<IConfigurationSection> IConfiguration.GetChildren() => [];

        IChangeToken IConfiguration.GetReloadToken() => EmptyChangeToken.Instance;
    }

    /// <summary>永不变更的占位 IChangeToken，避免引入额外包依赖。</summary>
    private sealed class EmptyChangeToken : IChangeToken
    {
        public static readonly EmptyChangeToken Instance = new();
        public bool ActiveChangeCallbacks => false;
        public bool HasChanged => false;
        public IDisposable RegisterChangeCallback(Action<object> callback, object? state) =>
            new NoopDisposable();

        private sealed class NoopDisposable : IDisposable
        {
            public void Dispose() { }
        }
    }
}