using System.Text;
using Microsoft.Net.Http.Headers;

namespace WorkerService1;

public class WechatRobot
    {
        private const string ApiUrl = "https://qyapi.weixin.qq.com";
        private const int TextUtf8MaxLength = 2000;
        private const int MarkdownUtf8MaxLength = 4000;
        private string _key;

        private static readonly MediaTypeHeaderValue ApplicationJson =
            new MediaTypeHeaderValue("application/json")
            {
                Charset = "utf-8"
            };

        private readonly HttpClient _client;
        private readonly ILogger<WechatRobot> _logger;

        public WechatRobot(ILogger<WechatRobot> logger, HttpClient client)
        {
            client.BaseAddress = new Uri(ApiUrl);
            this._logger = logger;
            _client = client;
            _key = "e68b3791-e040-4c9b-9ac0-6f424e662185";
        }

        public async Task SendText(string content, bool isAtAll)
        {
            await this.Post($"/cgi-bin/webhook/send?key={_key}", BuildTextBody(content, isAtAll));
        }

        public async Task SendMarkdown(string content)
        {
            await this.Post($"/cgi-bin/webhook/send?key={_key}", BuildMarkdownBody(content));
        }

        private string BuildTextBody(string content, bool isAtAll)
        {
            var result = new StringBuilder("{\"msgtype\": \"text\",");
            result.Append("\"text\": {");
            result.Append($"\"content\": \"{Substring(content, TextUtf8MaxLength)}\",");
            if (isAtAll)
            {
                result.Append($"\"mentioned_list\":[\"@all\"]");
            }

            result.Append("}}");

            return result.ToString();
        }

        private string BuildMarkdownBody(string content)
        {
            var result = new StringBuilder("{\"msgtype\": \"markdown\",");
            result.Append("\"markdown\": {");
            result.Append($"\"content\": \"{Substring(FilterSpecialChar(content), MarkdownUtf8MaxLength)}\"");
            result.Append("}}");

            return result.ToString();
        }

        /// <summary>
        /// 截取字符串
        /// </summary>
        /// <param name="content">字符串内容</param>
        /// <param name="maxLength">字符串最大长度</param>
        /// <returns>如果长度超出则按照 maxLength 截取返回，若没超出则原样返回 </returns>
        private string Substring(string content, int maxLength)
        {
            var bytes = Encoding.UTF8.GetBytes(content);
            if (bytes.Length > maxLength)
            {
                var temporaryBytes = bytes.Take(maxLength).ToArray();
                return $"{Encoding.UTF8.GetString(temporaryBytes)}";
            }

            return content;
        }

        /// <summary>
        /// 过滤 markdown 特殊字符
        /// </summary>
        /// <param name="content"></param>
        /// <returns></returns>
        private string FilterSpecialChar(string content) => content?.Replace("\"", "''").Replace("`", "'");

        private async Task Post(string url, string parameters)
        {
            try
            {
                HttpContent content = null;
                if (!String.IsNullOrEmpty(parameters))
                {
                    content = new StringContent(parameters, Encoding.UTF8);
                    if (content.Headers.ContentType != null)
                    {
                        content.Headers.ContentType.MediaType = "application/json";
                        content.Headers.ContentType.CharSet = "utf-8";
                    }
                }

                var resp = await _client.PostAsync(url, content);
                await resp.Content.ReadAsStringAsync();
            }
            catch (Exception ex)
            {
                this._logger.LogError(ex, $"WechatRobot Post fail,Url:{url},Parameters:{parameters}");
            }
        }
    }