using System.Reflection;
using Dpz.Core.MessageQueue.Abstractions;
using Dpz.Core.MessageQueue.Attributes;
using Dpz.Core.MessageQueue.Enums;

namespace Dpz.Core.MessageQueue.RabbitMQ;

/// <summary>
/// 默认消息路由约定实现
/// 约定规则：
/// - Exchange: dpz.{module}.exchange  如：dpz.news.exchange
/// - Queue: dpz.{module}.{type}.queue 如：dpz.news.article.queue
/// - RoutingKey: {module}.{type}.{detail} 如：news.article.ithome
/// </summary>
public class DefaultMessageRoutingConvention : IMessageRoutingConvention
{
    private const string Prefix = "dpz";

    public string GetExchangeName<TMessage>()
    {
        // 检查是否有自定义特性
        var attribute = typeof(TMessage).GetCustomAttribute<MessageRouteAttribute>();
        if (!string.IsNullOrEmpty(attribute?.ExchangeName))
        {
            return attribute.ExchangeName;
        }

        // 约定：从消息类型名称提取模块名
        // 例如：NewsArticleMessage → news
        var typeName = typeof(TMessage).Name;
        var moduleName = ExtractModuleName(typeName);

        return $"{Prefix}.{moduleName}.exchange";
    }

    public string GetQueueName<TMessage>()
    {
        var attribute = typeof(TMessage).GetCustomAttribute<MessageRouteAttribute>();
        if (!string.IsNullOrEmpty(attribute?.QueueName))
        {
            return attribute.QueueName;
        }

        // 约定：dpz.{module}.{type}.queue
        // 例如：NewsArticleMessage → dpz.news.article.queue
        var typeName = typeof(TMessage).Name;
        var (moduleName, typeSuffix) = ParseMessageTypeName(typeName);

        return $"{Prefix}.{moduleName}.{typeSuffix}.queue";
    }

    public string GetRoutingKey<TMessage>()
    {
        var attribute = typeof(TMessage).GetCustomAttribute<MessageRouteAttribute>();
        if (!string.IsNullOrEmpty(attribute?.RoutingKey))
        {
            return attribute.RoutingKey;
        }

        // 约定：{module}.{type}.#
        // 例如：NewsArticleMessage → news.article.#
        var typeName = typeof(TMessage).Name;
        var (moduleName, typeSuffix) = ParseMessageTypeName(typeName);

        return $"{moduleName}.{typeSuffix}.#";
    }

    public ExchangeType GetExchangeType<TMessage>()
    {
        var attribute = typeof(TMessage).GetCustomAttribute<MessageRouteAttribute>();
        return attribute?.ExchangeType ?? ExchangeType.Topic;
    }

    /// <summary>
    /// 从消息类型名称中提取模块名
    /// NewsArticleMessage → news
    /// CacheClearMessage → cache
    /// </summary>
    private static string ExtractModuleName(string typeName)
    {
        // 移除 "Message" 后缀
        var name = typeName.EndsWith("Message", StringComparison.OrdinalIgnoreCase)
            ? typeName[..^7]
            : typeName;

        // 提取第一个词作为模块名（按驼峰命名分割）
        var parts = SplitCamelCase(name);
        return parts.Length > 0 ? parts[0].ToLowerInvariant() : "default";
    }

    /// <summary>
    /// 解析消息类型名称
    /// NewsArticleMessage → (news, article)
    /// CacheClearMessage → (cache, clear)
    /// </summary>
    private static (string ModuleName, string TypeName) ParseMessageTypeName(string typeName)
    {
        var name = typeName.EndsWith("Message", StringComparison.OrdinalIgnoreCase)
            ? typeName[..^7]
            : typeName;

        var parts = SplitCamelCase(name);

        if (parts.Length == 0)
        {
            return ("default", "message");
        }

        if (parts.Length == 1)
        {
            return (parts[0].ToLowerInvariant(), "message");
        }

        // 第一个词是模块名，其余的组合成类型名
        var moduleName = parts[0].ToLowerInvariant();
        var typeSuffix = string.Join(".", parts.Skip(1).Select(p => p.ToLowerInvariant()));

        return (moduleName, typeSuffix);
    }

    /// <summary>
    /// 按驼峰命名分割字符串
    /// "NewsArticle" → ["News", "Article"]
    /// </summary>
    private static string[] SplitCamelCase(string input)
    {
        if (string.IsNullOrEmpty(input))
        {
            return [];
        }

        var words = new List<string>();
        var currentWord = new System.Text.StringBuilder();

        foreach (var c in input)
        {
            if (char.IsUpper(c) && currentWord.Length > 0)
            {
                words.Add(currentWord.ToString());
                currentWord.Clear();
            }

            currentWord.Append(c);
        }

        if (currentWord.Length > 0)
        {
            words.Add(currentWord.ToString());
        }

        return words.ToArray();
    }
}