using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;


namespace ServerCore;


// HANDOVER: AWS SDK 연동하는 주요 함수를 호출해주는 Wrapper 클래스 이다.

public static class AwsHelper
{
    // EC2에서 실행중인 상태 종류
    public enum Ec2RunningState
    { 
        None = 0,

        False = 1,  //EC2에서 실행하고 있지 않다 !!!
        True = 2    //EC2에서 실행중이다 !!!
    };

    private static readonly string MetaDataTokenUrl = "http://169.254.169.254/latest/api/token";
    private static readonly string MetaDataInstanceIdUrl = "http://169.254.169.254/latest/meta-data/instance-id";
    private static readonly string MetaDataIpV4Url = "http://169.254.169.254/latest/meta-data/public-ipv4";

    private static Ec2RunningState RunningState = Ec2RunningState.None;

    public static async Task<string> getAwsInstanceId()
    {
        var aws_meta_token = string.Empty;

        try
        {
            aws_meta_token = await getAwsMetaDataToken();
            
            using (var client = new HttpClient())
            {
                var request = new HttpRequestMessage(HttpMethod.Get, MetaDataInstanceIdUrl);
                request.Headers.Add("X-aws-ec2-metadata-token", aws_meta_token);
                request.Headers.Accept.Add(new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/json"));

                var response = await client.SendAsync(request);
                response.EnsureSuccessStatusCode();

                return await response.Content.ReadAsStringAsync();
            }
        }
        catch(Exception e)
        {
            var err_msg = $"Exception !!!, Failed to function in getAwsInstanceId() !!! : exception:{e}, awsMetaToken:{aws_meta_token}";
            Log.getLogger().fatal(err_msg);
        }

        return string.Empty;
    }

    public static string getAwsPublicIPv4OrEthernetIPv4()
    {
        if (true == AwsHelper.isRunningOnEC2().GetAwaiter().GetResult())
        {
            return AwsHelper.getPublicIPv4().GetAwaiter().GetResult();
        }

        return NetworkHelper.getEthernetLocalIPv4();
    }

    private static async Task<bool> isRunningOnEC2()
    {
        if (Ec2RunningState.None != RunningState) 
        { 
            if(Ec2RunningState.True == RunningState) { return true; }
            else if(Ec2RunningState.False == RunningState) { return false; }
        }

        var aws_meta_token = string.Empty;

        try
        {
            aws_meta_token = await getAwsMetaDataToken();

            if(false == aws_meta_token.isNullOrWhiteSpace())
            {
                RunningState = Ec2RunningState.True;
                return true;
            }
        }
        catch (HttpRequestException httpEx)
        {
            var err_msg = $"HttpRequestException !!!, Failed to function in isRunningOnEC2() : exception:{httpEx}, awsMetaToken:{aws_meta_token}";
            Log.getLogger().debug(err_msg);
        }
        catch (Exception e)
        {
            var err_msg = $"Exception !!!, Failed to function in isRunningOnEC2() : exception:{e}, awsMetaToken:{aws_meta_token}";
            Log.getLogger().error(err_msg);
        }

        // EC2 환경이 아닌 경우
        RunningState = Ec2RunningState.False;
        return false;
    }
    
    private static async Task<string> getPublicIPv4()
    {
        var aws_meta_token = string.Empty;

        try
        {
            aws_meta_token = await getAwsMetaDataToken();
            
            using (HttpClient client = new HttpClient())
            {
                var request = new HttpRequestMessage(HttpMethod.Get, MetaDataIpV4Url);
                request.Headers.Add("X-aws-ec2-metadata-token", aws_meta_token);
                request.Headers.Accept.Add(new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/json"));

                var response = await client.SendAsync(request);
                response.EnsureSuccessStatusCode();

                return await response.Content.ReadAsStringAsync();
            }
        }
        catch (Exception e)
        {
            var err_msg = $"Exception !!!, Failed to perform in getPublicIPv4() !!!  : exception:{e}, awsMetaToken:{aws_meta_token}";
            Log.getLogger().error(err_msg);
            return await Task.FromResult(string.Empty);
        }
    }
    
    private static async Task<string> getAwsMetaDataToken()
    {
        try
        {
            using (var client = new HttpClient())
            {
                var request = new HttpRequestMessage(HttpMethod.Put, MetaDataTokenUrl);
                request.Headers.Add("X-aws-ec2-metadata-token-ttl-seconds", "21600");
                request.Headers.Accept.Add(new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/json"));

                var response = await client.SendAsync(request);
                response.EnsureSuccessStatusCode();

                return await response.Content.ReadAsStringAsync();
            }
        }
        catch(Exception e)
        {
            var err_msg = $"Exception !!!, Failed to function in getAwsMetaDataToken() !!! : Exception:{e}";
            Log.getLogger().debug(err_msg);

            throw;
        }
    }
}