using System.Collections.Concurrent;
using System.ComponentModel;
using System.Reflection;

namespace Easy.Core;

public static class EnumExtension
{
    /// <summary>
    /// 缓存
    /// </summary>
    private static readonly ConcurrentDictionary<string, string> EnumDic = new();

    /// <summary>
    /// 获取枚举上定义的Description
    /// </summary>
    /// <param name="value"></param>
    /// <returns></returns>
    public static string Description(this Enum value)
    {
        Type type = value.GetType();
        string vs = value.ToString(), key = $"{type.FullName}_{vs}";
        if (EnumDic.TryGetValue(key, out var description))
        {
            return description;
        }

        FieldInfo fieldInfo = type.GetField(vs);
        if (fieldInfo != null && fieldInfo.GetCustomAttributes(typeof(DescriptionAttribute), false).FirstOrDefault() is DescriptionAttribute descriptionAttribute)
        {
            string desc = descriptionAttribute.Description;
            EnumDic.TryAdd(key, desc);
            return desc;
        }

        return string.Empty;
    }

    /// <summary>
    /// 将 int 值转换为指定枚举类型
    /// </summary>
    /// <typeparam name="T">枚举类型</typeparam>
    /// <param name="value">int 值</param>
    /// <returns>枚举值，如果转换失败则返回 null</returns>
    public static T? ToEnum<T>(this int value) where T : struct, Enum
    {
        if (Enum.IsDefined(typeof(T), value))
        {
            return (T)(object)value;
        }
        return null;
    }

    /// <summary>
    /// 将 int? 值转换为指定枚举类型
    /// </summary>
    /// <typeparam name="T">枚举类型</typeparam>
    /// <param name="value">int? 值</param>
    /// <returns>枚举值，如果转换失败则返回 null</returns>
    public static T? ToEnum<T>(this int? value) where T : struct, Enum
    {
        if (!value.HasValue)
            return null;

        return value.Value.ToEnum<T>();
    }

    /// <summary>
    /// 将 long 值转换为指定枚举类型
    /// </summary>
    /// <typeparam name="T">枚举类型</typeparam>
    /// <param name="value">long 值</param>
    /// <returns>枚举值，如果转换失败则返回 null</returns>
    public static T? ToEnum<T>(this long value) where T : struct, Enum
    {
        if (Enum.IsDefined(typeof(T), value))
        {
            return (T)(object)value;
        }
        return null;
    }

    /// <summary>
    /// 将 long? 值转换为指定枚举类型
    /// </summary>
    /// <typeparam name="T">枚举类型</typeparam>
    /// <param name="value">long? 值</param>
    /// <returns>枚举值，如果转换失败则返回 null</returns>
    public static T? ToEnum<T>(this long? value) where T : struct, Enum
    {
        if (!value.HasValue)
            return null;

        return value.Value.ToEnum<T>();
    }

    /// <summary>
    /// 获取枚举所有值及其 Description 的字典
    /// </summary>
    /// <typeparam name="T">枚举类型</typeparam>
    /// <returns>字典，Key为枚举值，Value为Description</returns>
    public static Dictionary<T, string> GetDescriptionDictionary<T>() where T : struct, Enum
    {
        var result = new Dictionary<T, string>();
        var values = Enum.GetValues(typeof(T));

        foreach (var value in values)
        {
            if (value is T enumValue)
            {
                result[enumValue] = enumValue.Description();
            }
        }

        return result;
    }

    /// <summary>
    /// 获取枚举所有值的列表（包含值和Description）
    /// </summary>
    /// <typeparam name="T">枚举类型</typeparam>
    /// <returns>枚举选项列表</returns>
    public static List<EnumOption<T>> GetEnumOptions<T>() where T : struct, Enum
    {
        var result = new List<EnumOption<T>>();
        var values = Enum.GetValues(typeof(T));

        foreach (var value in values)
        {
            if (value is T enumValue)
            {
                result.Add(new EnumOption<T>
                {
                    Value = enumValue,
                    Description = enumValue.Description()
                });
            }
        }

        return result;
    }
}

/// <summary>
/// 枚举选项
/// </summary>
/// <typeparam name="T">枚举类型</typeparam>
public class EnumOption<T> where T : struct, Enum
{
    /// <summary>
    /// 枚举值
    /// </summary>
    public T Value { get; set; }

    /// <summary>
    /// 描述
    /// </summary>
    public string Description { get; set; } = string.Empty;
}