using System;
using System.IO;
using System.Net;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using Newtonsoft.Json;
using Newtonsoft.Json.Linq;

namespace IvfTl.ControlHost
{
    /// <summary>
    /// control 进程内的本地 HTTP 小服务,只监听 127.0.0.1:port。
    /// 阶段1:/ping、/status。阶段2:/status 补全(rich) + /serial/pause|resume(借串口) + /shutdown(受护栏停止)。
    /// </summary>
    public class ControlHttpServer
    {
        private readonly int _port;
        private readonly Func<StatusDto> _pingProvider;        // /ping 轻量存活
        private readonly Func<object> _statusProvider;         // /status 完整快照(阶段2 §6 三块)
        private readonly Func<string, bool> _shutdownHandler;  // /shutdown(token 校验后安全停机)
        private readonly Func<int, bool> _serialPauseHandler;  // /serial/pause(借串口:control 让路该舱)
        private readonly Func<int, bool> _serialResumeHandler; // /serial/resume(归还:恢复采集)
        private readonly Action<string> _log;
        private HttpListener _listener;
        private CancellationTokenSource _cts;

        public ControlHttpServer(
            int port,
            Func<StatusDto> pingProvider,
            Func<object> statusProvider,
            Func<string, bool> shutdownHandler,
            Func<int, bool> serialPauseHandler,
            Func<int, bool> serialResumeHandler,
            Action<string> log)
        {
            _port = port;
            _pingProvider = pingProvider;
            _statusProvider = statusProvider;
            _shutdownHandler = shutdownHandler;
            _serialPauseHandler = serialPauseHandler;
            _serialResumeHandler = serialResumeHandler;
            _log = log ?? (_ => { });
        }

        public void Start()
        {
            _listener = new HttpListener();
            // 仅本机回环,拒绝外部访问(防外部调停机/借串口)。
            _listener.Prefixes.Add($"http://127.0.0.1:{_port}/");
            _listener.Start();
            _cts = new CancellationTokenSource();
            _log($"ControlHttpServer 监听 http://127.0.0.1:{_port}/");
            Task.Run(() => Loop(_cts.Token));
        }

        private async Task Loop(CancellationToken token)
        {
            while (!token.IsCancellationRequested)
            {
                HttpListenerContext ctx;
                try { ctx = await _listener.GetContextAsync(); }
                catch (Exception ex) { if (!token.IsCancellationRequested) _log("HttpListener 异常:" + ex.Message); break; }
                try { Handle(ctx); }
                catch (Exception ex) { _log("处理请求异常:" + ex.Message); }
            }
        }

        private void Handle(HttpListenerContext ctx)
        {
            string path = ctx.Request.Url.AbsolutePath.TrimEnd('/').ToLowerInvariant();
            string method = ctx.Request.HttpMethod.ToUpperInvariant();
            string body;
            int code = 200;
            switch (path)
            {
                case "/ping":
                    body = JsonConvert.SerializeObject(_pingProvider());
                    break;
                case "/status":
                    body = JsonConvert.SerializeObject(_statusProvider());
                    break;
                case "/shutdown":
                    if (method != "POST") { code = 405; body = Err("method not allowed"); break; }
                    {
                        string token = ReadField(ctx, "token");
                        bool ok = _shutdownHandler != null && _shutdownHandler(token ?? "");
                        code = ok ? 200 : 403;
                        body = "{\"ok\":" + (ok ? "true" : "false") + (ok ? "" : ",\"error\":\"token invalid\"") + "}";
                    }
                    break;
                case "/serial/pause":
                case "/serial/resume":
                    if (method != "POST") { code = 405; body = Err("method not allowed"); break; }
                    {
                        int houseSn = ReadIntField(ctx, "houseSn");
                        bool isPause = path == "/serial/pause";
                        var handler = isPause ? _serialPauseHandler : _serialResumeHandler;
                        bool ok = handler != null && houseSn > 0 && handler(houseSn);
                        code = ok ? 200 : 400;
                        body = "{\"ok\":" + (ok ? "true" : "false") + ",\"houseSn\":" + houseSn + (ok ? "" : ",\"error\":\"bad houseSn or handler\"") + "}";
                    }
                    break;
                default:
                    code = 404; body = Err("not found");
                    break;
            }
            byte[] buf = Encoding.UTF8.GetBytes(body);
            ctx.Response.StatusCode = code;
            ctx.Response.ContentType = "application/json";
            ctx.Response.ContentLength64 = buf.Length;
            ctx.Response.OutputStream.Write(buf, 0, buf.Length);
            ctx.Response.OutputStream.Close();
        }

        private static string Err(string msg) => "{\"ok\":false,\"error\":\"" + msg + "\"}";

        /// <summary>读 POST JSON body 的某字符串字段(失败返回 null)。</summary>
        private string ReadField(HttpListenerContext ctx, string field)
        {
            try
            {
                using (var sr = new StreamReader(ctx.Request.InputStream, ctx.Request.ContentEncoding ?? Encoding.UTF8))
                {
                    string raw = sr.ReadToEnd();
                    if (string.IsNullOrEmpty(raw)) return null;
                    var jo = JObject.Parse(raw);
                    return jo[field]?.ToString();
                }
            }
            catch (Exception ex) { _log("解析请求体异常:" + ex.Message); return null; }
        }

        private int ReadIntField(HttpListenerContext ctx, string field)
        {
            string s = ReadField(ctx, field);
            return int.TryParse(s, out int v) ? v : -1;
        }

        public void Stop()
        {
            try { _cts?.Cancel(); _listener?.Stop(); _listener?.Close(); }
            catch (Exception ex) { _log("ControlHttpServer 停止异常:" + ex.Message); }
        }
    }
}