using System;
using Google.Apis.Auth.OAuth2;
using Google.Apis.Gmail.v1;
using Google.Apis.Gmail.v1.Data;
using Google.Apis.Services;
using Google.Apis.Util.Store;
using System.Collections.Generic;
using System.IO;
using System.Threading;
using System.Threading.Tasks;
using System.Linq;
using System.Text.RegularExpressions;
using System.Runtime.Remoting.Messaging;


namespace cdrtool
{

class Gmail
    {
        static string[] Scopes = { GmailService.Scope.GmailReadonly };
        static string ApplicationName = "Gmail API .NET Quickstart";


        public static async Task<string> GetMail()
        {
            UserCredential credential;
            string mfa_code = "";

            using (var stream = new FileStream("credentials.json", FileMode.Open, FileAccess.Read))
            {
                string credPath = "token.json";
                credential = await GoogleWebAuthorizationBroker.AuthorizeAsync(
                    GoogleClientSecrets.FromStream(stream).Secrets,
                    Scopes,
                    "user",
                    CancellationToken.None,
                    new FileDataStore(credPath, true));
                //Console.WriteLine("Credential file saved to: " + credPath);
            }

            // Create Gmail API service.
            var service = new GmailService(new BaseClientService.Initializer()
            {
                HttpClientInitializer = credential,
                ApplicationName = ApplicationName,
            });

            // Define the timestamp after which we want to find emails (in Unix time format).
            DateTime afterTimestamp = new DateTime(2024, 01, 01);   // Use this when you cannot generate a new mfs email to test with
            afterTimestamp = DateTime.Now;                      // We do this to ensure we get the latest auth email, usually 2-3 seconds after this fires
            long afterUnixTimestamp = ((DateTimeOffset)afterTimestamp).ToUnixTimeSeconds();

            Logger.Log(1,"Awaiting MFA email (max {0}s)", cdrtool.mfa_delay);
            bool repeat = false;
            int count = cdrtool.mfa_delay;

            do
            {
                // Fetch emails received after the given timestamp
                var request = service.Users.Messages.List("me");
                request.Q = $"after:{afterUnixTimestamp} from:\"Rogers SIP Portal\" ";          //refinement added Sep16 2024
                ListMessagesResponse response = await request.ExecuteAsync();
                var messages = response.Messages?.OrderByDescending(m => m.InternalDate).ToList();
                repeat = (messages == null);
                //Console.WriteLine("Messages count: {0}", (messages != null) ? messages.Count : 0 );

                if (messages != null && messages.Any())
                {
                    //Console.WriteLine("Messages count: {0}",messages.Count);

                    var mostRecentMessage = messages.First();
                    Message message = await service.Users.Messages.Get("me", mostRecentMessage.Id).ExecuteAsync();

                    try
                    {
                        Regex word = new Regex(@".*Your Portal.+([0-9]{6})");        // MFA looking for 6 digit code            //refinement added Sep16 2024
                        Match m = word.Match(message.Snippet);      // .Snippet easily grabs enough plain text to find the MFA code

                        if (m.Success)
                        {
                            Group g = m.Groups[1];
                            //Capture c = g.Captures[0];
                            Logger.Log(6, "Regex Match {0} / Group Count {1} / Captures Count {2} / result={3}", m.Success, m.Groups.Count, m.Captures.Count, g.Value);
                            int code = Convert.ToInt32(g.Value);
                            if ((code >= 0) && (code <= 999999))
                                Logger.Log(5, "Code found successfully {0}", code);

                            mfa_code = g.Value;
                            repeat = false;
                        }
                        else
                        {
                            Logger.Log(1, "No code found in email.");
                        }
                    }
                    catch (Exception e)
                    {
                        Logger.Log(0, "Error parsing Gmail. {0}", e.Message);
                    }
                    
                }
            
                else
                {
                    int incr = 1;
                    if (count <= (cdrtool.mfa_delay - 5) ) incr = 5;
                    count-= incr;
                    System.Threading.Thread.Sleep(1000 * incr);
                    Logger.Log(1, "No message found for {0}s", cdrtool.mfa_delay - count);
                }

            }
            while (repeat && (count > 0) );

            Logger.Log(0, "Emailed MFA Code : {0}", mfa_code);
            return mfa_code;

        }
       

        static string GetPlainTextFromMessageParts(IList<MessagePart> parts)
        {
            if (parts == null)
                return string.Empty;

            foreach (var part in parts)
            {
                //Console.WriteLine("email: type:{0}\nbody:\n{1}", part.MimeType, part.Body.Data);
                if (part.MimeType == "text/plain" && part.Body != null && part.Body.Data != null)
                {
                    return Base64UrlDecode(part.Body.Data);
                }
                else if (part.Parts != null)
                {
                    string text = GetPlainTextFromMessageParts(part.Parts);
                    if (!string.IsNullOrEmpty(text))
                        return text;
                }
            }

            return string.Empty;
        }

        static string Base64UrlDecode(string input)
        {
            string s = input.Replace('-', '+').Replace('_', '/');
            switch (s.Length % 4)
            {
                case 2: s += "=="; break;
                case 3: s += "="; break;
            }
            var bytes = Convert.FromBase64String(s);
            return System.Text.Encoding.UTF8.GetString(bytes);
        }
    }

}