using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Threading.Tasks;

namespace Admin.NET.Core.Service;

public static class ProxyHelper
{
    private static List<(string ip, int port)> _proxyList = new();
    private static readonly Random _random = new();

    /// <summary>
    /// 初始化代理池并验证可用性
    /// </summary>
    /// <param name="filePath">CSV 文件路径，每行格式：ip,port</param>
    /// <param name="testUrl">可用性验证的测试地址，建议用目标网站或者 https://httpbin.org/ip</param>
    public static async Task LoadAndValidateProxiesAsync(string filePath, string testUrl = "https://httpbin.org/ip")
    {
        if (!File.Exists(filePath)) throw new FileNotFoundException("代理IP文件不存在", filePath);

        var lines = File.ReadAllLines(filePath);
        var tempList = new List<(string ip, int port)>();

        foreach (var line in lines.Skip(1)) // 跳过表头
        {
            var parts = line.Split(',');
            if (parts.Length >= 2 && int.TryParse(parts[1], out var port))
            {
                tempList.Add((parts[0], port));
            }
        }

        // 异步验证代理是否可用
        var tasks = tempList.Select(proxy => IsProxyAvailableAsync(proxy.ip, proxy.port, testUrl));
        var results = await Task.WhenAll(tasks);

        _proxyList = tempList.Where((proxy, index) => results[index]).ToList();

        Console.WriteLine($"✅ 验证通过的代理数量：{_proxyList.Count}");

        if (!_proxyList.Any())
            throw new Exception("没有可用的代理IP，请检查代理池是否失效");
    }

    /// <summary>
    /// 验证代理是否可用
    /// </summary>
    private static async Task<bool> IsProxyAvailableAsync(string ip, int port, string testUrl)
    {
        try
        {
            var handler = new HttpClientHandler
            {
                Proxy = new WebProxy(ip, port),
                UseProxy = true,
            };

            using var client = new HttpClient(handler);
            client.Timeout = TimeSpan.FromSeconds(5);

            var response = await client.GetAsync(testUrl);
            return response.IsSuccessStatusCode;
        }
        catch
        {
            return false;
        }
    }

    /// <summary>
    /// 使用随机代理发起 GET 请求，并支持重试
    /// </summary>
    public static async Task<string> GetWithRandomProxyAsync(string url, int maxRetry = 5, int delayBetweenRetry = 1000)
    {
        if (!_proxyList.Any()) throw new Exception("代理列表为空，请先调用 LoadAndValidateProxiesAsync()");

        for (int attempt = 0; attempt < maxRetry; attempt++)
        {
            var (ip, port) = _proxyList[_random.Next(_proxyList.Count)];

            try
            {
                var handler = new HttpClientHandler
                {
                    Proxy = new WebProxy(ip, port),
                    UseProxy = true,
                };

                using var client = new HttpClient(handler);
                client.Timeout = TimeSpan.FromSeconds(10);

                var response = await client.GetAsync(url);
                response.EnsureSuccessStatusCode();
                return await response.Content.ReadAsStringAsync();
            }
            catch (Exception ex)
            {
                Console.WriteLine($"❌ 代理 {ip}:{port} 请求失败（第 {attempt + 1} 次）: {ex.Message}");
                await Task.Delay(delayBetweenRetry);
            }
        }

        throw new Exception("多次尝试使用代理请求失败");
    }
}