using AIK.Models.HttpPolicy;
using AIK.Service.IService;
using Flurl;
using Flurl.Http;
using Microsoft.Extensions.Logging;
using System;
using System.IO;
using System.Net;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Security.Authentication;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace AIK.Service.Service
{
    public class HttpClientService : IHttpClientService
    {
        private readonly ILogger<HttpClientService> _logger;
        private readonly RetryPolicyConfig _config;
        private readonly IFlurlClient _flurlClient;
        private readonly BouncyCastleTlsHandler _tlsHandler;

        public HttpClientService(IHttpClientFactory httpClientFactory, ILogger<HttpClientService> logger, RetryPolicyConfig config = null)
        {
            _logger = logger;
            _config = config ?? new RetryPolicyConfig();

            // Win7 系统 SChannel 未启用 TLS 1.2 时，.NET Framework 的 HttpClient/HttpWebRequest
            // （底层全部走 SChannel）无法协商 TLS 1.2。改用 BouncyCastle 纯托管 TLS 实现
            // （BouncyCastleTlsHandler），完全绕过 SChannel，在 Win7 上可直接与只接受 TLS 1.2+
            // 的服务器（key.aikkey.cn）握手。Handler 内部已处理 SNI、证书链校验与 gzip/deflate 解压。
            _tlsHandler = new BouncyCastleTlsHandler();
            _flurlClient = new FlurlClient(new HttpClient(_tlsHandler));
        }

        // GET 方法
        public async Task<string> GetStringWithTimeoutAsync(string url, TimeSpan? timeout = null, CancellationToken cancellationToken = default)
        {
            var response = await ExecuteAsync(url, HttpMethod.Get, null, timeout, null, cancellationToken);
            ThrowIfNotSuccess(response);
            return await response.Content.ReadAsStringAsync();
        }

        // POST JSON 方法
        public async Task<string> PostJsonWithTimeoutAsync(string url, string jsonData, TimeSpan? timeout = null, CancellationToken cancellationToken = default)
        {
            var content = new StringContent(jsonData, Encoding.UTF8, "application/json");
            var response = await ExecuteAsync(url, HttpMethod.Post, content, timeout, null, cancellationToken);
            ThrowIfNotSuccess(response);
            return await response.Content.ReadAsStringAsync();
        }

        public async Task<HttpResponseMessage> GetWithTimeoutAsync(string url, TimeSpan? timeout = null, CancellationToken cancellationToken = default)
        {
            return await ExecuteAsync(url, HttpMethod.Get, null, timeout, null, cancellationToken);
        }

        public async Task<HttpResponseMessage> PostWithTimeoutAsync(string url, HttpContent content, TimeSpan? timeout = null, CancellationToken cancellationToken = default)
        {
            return await ExecuteAsync(url, HttpMethod.Post, content, timeout, null, cancellationToken);
        }

        public async Task<byte[]> GetByteArrayWithTimeoutAsync(string url, TimeSpan? timeout = null, CancellationToken cancellationToken = default)
        {
            var response = await ExecuteAsync(url, HttpMethod.Get, null, timeout, null, cancellationToken);
            ThrowIfNotSuccess(response);
            return await response.Content.ReadAsByteArrayAsync();
        }

        /// <summary>
        /// 流式下载文件到指定路径。直接走 BouncyCastleTlsHandler 的流式通道（SendStreamingAsync），
        /// 响应体逐段读取、每段带空闲超时（60s）、无总时长限制，避免大文件因 30s 总超时而失败。
        /// 支持断点续传：resumeOffset&gt;0 时携带 Range 头，服务器返回 206 则从文件末尾追加写入；
        /// 服务器忽略 Range 返回 200 时则整文件覆盖重写。
        /// </summary>
        public async Task DownloadToFileWithProgressAsync(string url, string filePath, IProgress<double> progress = null, CancellationToken cancellationToken = default, long resumeOffset = 0)
        {
            using var request = new HttpRequestMessage(HttpMethod.Get, url);
            if (resumeOffset > 0)
            {
                request.Headers.Range = new RangeHeaderValue(resumeOffset, null);
            }
            using var response = await _tlsHandler.SendStreamingAsync(request, cancellationToken).ConfigureAwait(false);

            if (!response.IsSuccessStatusCode)
            {
                throw new HttpRequestException($"下载失败: HTTP {(int)response.StatusCode} ({response.StatusCode}) - {url}");
            }

            // 判断服务器是否接受 Range（206 = 部分内容，Content-Range 提供完整文件总大小）
            var contentRange = response.Content.Headers.ContentRange;
            bool resumed = resumeOffset > 0 && contentRange != null && contentRange.HasRange && contentRange.Length.HasValue;

            long baseOffset = resumed ? resumeOffset : 0;
            FileMode mode = resumed ? FileMode.Append : FileMode.Create;
            long totalBytes = resumed
                ? contentRange.Length.Value
                : (response.Content.Headers.ContentLength ?? -1) + baseOffset;
            long receivedBytes = baseOffset;

            using (var source = await response.Content.ReadAsStreamAsync().ConfigureAwait(false))
            using (var target = new FileStream(filePath, mode, FileAccess.Write, FileShare.None, 81920, useAsync: true))
            {
                var buffer = new byte[81920];
                int read;
                while ((read = await source.ReadAsync(buffer, 0, buffer.Length, cancellationToken).ConfigureAwait(false)) > 0)
                {
                    await target.WriteAsync(buffer, 0, read, cancellationToken).ConfigureAwait(false);
                    receivedBytes += read;
                    if (totalBytes > 0 && progress != null)
                    {
                        progress.Report(Math.Min(100.0, receivedBytes * 100.0 / totalBytes));
                    }
                }
                await target.FlushAsync(cancellationToken).ConfigureAwait(false);
            }

            // 完整性校验：连接被中途掐断时 EOF 提前结束，实际字节数 < 总大小，必须视为失败（由调用方重试续传）
            if (totalBytes > 0 && receivedBytes != totalBytes)
            {
                throw new HttpRequestException($"下载不完整: 预期 {totalBytes} 字节，实际 {receivedBytes} 字节 - {url}");
            }

            progress?.Report(100.0);
        }

        #region 附带Token权限的方法
        public async Task<string> GetStringWithTimeoutAndTokenAsync(string url, string token, TimeSpan? timeout = null, CancellationToken cancellationToken = default)
        {
            var response = await ExecuteAsync(url, HttpMethod.Get, null, timeout, token, cancellationToken);
            ThrowIfNotSuccess(response);
            return await response.Content.ReadAsStringAsync();
        }

        public async Task<string> PostJsonWithTimeoutAndTokenAsync(string url, string jsonData, string token, TimeSpan? timeout = null, CancellationToken cancellationToken = default)
        {
            var content = new StringContent(jsonData, Encoding.UTF8, "application/json");
            var response = await ExecuteAsync(url, HttpMethod.Post, content, timeout, token, cancellationToken);
            ThrowIfNotSuccess(response);
            return await response.Content.ReadAsStringAsync();
        }
        #endregion

        // 每个请求独立设置超时，避免并发请求互相覆盖；Flurl 的 SendAsync 不自动抛非 2xx，由 ThrowIfNotSuccess 统一处理
        private async Task<HttpResponseMessage> ExecuteAsync(string url, HttpMethod method, HttpContent content, TimeSpan? timeout, string token, CancellationToken cancellationToken)
        {
            var request = _flurlClient.Request(url)
                .WithTimeout(timeout ?? _config.DefaultTimeout);
            if (!string.IsNullOrEmpty(token))
            {
                request = request.WithHeader("token", token);
            }
            return (await request.SendAsync(method, content, HttpCompletionOption.ResponseContentRead, cancellationToken)).ResponseMessage;
        }

        private static void ThrowIfNotSuccess(HttpResponseMessage response)
        {
            if (response.IsSuccessStatusCode)
            {
                return;
            }

            var message = $"Response status code does not indicate success: {(int)response.StatusCode} ({response.StatusCode}).";
            throw new HttpRequestException(message);
        }
    }
}