using Consul;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Hosting.Server.Features;
using Microsoft.Extensions.Configuration;
using System;
using System.Collections.Generic;
using System.Linq;
public static class RegisterCansulExtension
{
    public static void RegisterToConsul(this IApplicationBuilder app, IConfiguration configuration, IApplicationLifetime lifetime)
    {
        lifetime.ApplicationStarted.Register(() =>
        {
            string serviceName = configuration.GetValue<string>("serviceName");
            string serviceIP = configuration.GetValue<string>("serviceIP");
            string consulClientUrl = configuration.GetValue<string>("consulClientUrl");
            string healthCheckRelativeUrl = configuration.GetValue<string>("healthCheckRelativeUrl");
            int healthCheckIntervalInSecond = configuration.GetValue<int>("healthCheckIntervalInSecond");
            ICollection<string> listenUrls = app.ServerFeatures.Get<IServerAddressesFeature>().Addresses;


            if (string.IsNullOrWhiteSpace(serviceName))
            {
                throw new Exception("Please use --serviceName=yourServiceName to set serviceName");
            }
            if (string.IsNullOrEmpty(consulClientUrl))
            {
                consulClientUrl = "http://127.0.0.1:8500";
            }
            if (string.IsNullOrWhiteSpace(healthCheckRelativeUrl))
            {
                healthCheckRelativeUrl = "health";
            }
            healthCheckRelativeUrl = healthCheckRelativeUrl.TrimStart('/');
            if (healthCheckIntervalInSecond <= 0)
            {
                healthCheckIntervalInSecond = 1;
            }


            string protocol;
            int servicePort = 0;
            if (!TryGetServiceUrl(listenUrls, out protocol, ref serviceIP, out servicePort, out var errorMsg))
            {
                throw new Exception(errorMsg);
            }

            var consulClient = new ConsulClient(ConsulClientConfiguration => ConsulClientConfiguration.Address = new Uri(consulClientUrl));

            var httpCheck = new AgentServiceCheck()
            {
                DeregisterCriticalServiceAfter = TimeSpan.FromSeconds(10),//服務啟動多久后注冊
                Interval = TimeSpan.FromSeconds(healthCheckIntervalInSecond),
                HTTP = $"{protocol}://{serviceIP}:{servicePort}/{healthCheckRelativeUrl}",
                Timeout = TimeSpan.FromSeconds(2)
            };

            // 生成注冊請求
            var registration = new AgentServiceRegistration()
            {
                Checks = new[] { httpCheck },
                ID = Guid.NewGuid().ToString(),
                Name = serviceName,
                Address = serviceIP,
                Port = servicePort,
                Meta = new Dictionary<string, string>() { ["Protocol"] = protocol },
                Tags = new[] { $"{protocol}" }
            };
            consulClient.Agent.ServiceRegister(registration).Wait();

            //服務停止時, 主動發出注銷
            lifetime.ApplicationStopping.Register(() =>
            {
                try
                {
                    consulClient.Agent.ServiceDeregister(registration.ID).Wait();
                }
                catch
                { }
            });
        });
    }


    private static bool TryGetServiceUrl(ICollection<string> listenUrls, out string protocol, ref string serviceIP, out int port, out string errorMsg)
    {
        protocol = null;
        port = 0;
        errorMsg = null;
        if (!string.IsNullOrWhiteSpace(serviceIP)) // 如果提供了對外服務的IP, 只需要檢測是否在listenUrls里面即可
        {
            foreach (var listenUrl in listenUrls)
            {
                Uri uri = new Uri(listenUrl);
                protocol = uri.Scheme;
                var ipAddress = uri.Host;
                port = uri.Port;

                if (ipAddress == serviceIP || ipAddress == "0.0.0.0" || ipAddress == "[::]")
                {
                    return true;
                }
            }
            errorMsg = $"The serviceIP that you provide is not in urls={string.Join(',', listenUrls)}";
            return false;
        }
        else // 沒有提供對外服務的IP, 需要查找本機所有的可用IP, 看看有沒有在 listenUrls 里面的
        {
            var allIPAddressOfCurrentMachine = System.Net.NetworkInformation.NetworkInterface.GetAllNetworkInterfaces()
                    .Select(p => p.GetIPProperties())
                    .SelectMany(p => p.UnicastAddresses)
                    // 這里排除了 127.0.0.1 loopback 地址
                    .Where(p => p.Address.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork && !System.Net.IPAddress.IsLoopback(p.Address))
                    .Select(p => p.Address.ToString()).ToArray();
            var uris = listenUrls.Select(listenUrl => new Uri(listenUrl)).ToArray();
            // 本機所有可用IP與listenUrls進行匹配, 如果listenUrl是"0.0.0.0"或"[::]", 則任意IP都符合匹配
            var matches = allIPAddressOfCurrentMachine.SelectMany(ip =>
                    uris.Where(uri => ip == uri.Host || uri.Host == "0.0.0.0" || uri.Host == "[::]")
                    .Select(uri => new { Protocol = uri.Scheme, ServiceIP = ip, Port = uri.Port })
            ).ToList();

            if (matches.Count == 0)
            {
                errorMsg = $"This machine has IP address=[{string.Join(',', allIPAddressOfCurrentMachine)}], urls={string.Join(',', listenUrls)}, none match.";
                return false;
            }
            else if (matches.Count == 1)
            {
                protocol = matches[0].Protocol;
                serviceIP = matches[0].ServiceIP;
                port = matches[0].Port;
                return true;
            }
            else
            {
                errorMsg = $"Please use --serviceIP=yourChosenIP to specify one IP, which one provide service: {string.Join(",", matches)}.";
                return false;
            }
        }
    }
}