using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Neo.Afx.Services;

namespace Neo.Afx.WinService.Messages
{
    /// <summary>
    /// A base class for sending batches of SMS's or emails.
    /// </summary>
    public abstract class MessageSender : Worker, IExecutable
    {
        readonly MessageTypeEnum _messageType;

        #region Initialization

        /// <summary>
        /// Initializes a new instance of the <see cref="MessageSender"/>
        /// class with the given configuration section and verbose logging.
        /// </summary>
        /// <param name="messageType">The type of the message.</param>
        protected MessageSender(MessageTypeEnum messageType)
        {
            _messageType = messageType;
        }

        #endregion

        #region MessageType

        /// <summary>
        /// Gets the message type being handled.
        /// </summary>
        protected MessageTypeEnum MessageType
        {
            get
            {
                return _messageType;
            }
        }

        #endregion

        #region Abstract Methods

        protected abstract void InitializeSender(MessageDatabase database);

        protected abstract void FinalizeSender(MessageDatabase database);

        protected abstract bool ShouldRun(int count, out string error);

        protected abstract bool SendMessage(Message message, List<DocumentContent> attachments, char recipientSeparator, out string error);

        #endregion

        #region Run

        /// <summary>
        /// Sends the messages.
        /// </summary>
        public void Run()
        {
            var trace = new StringBuilder();

            using (var database = new MessageDatabase(Settings["ConnectionString"]))
            {
                try
                {
                    InitializeSender(database);

                    var maxRetries = Int32.Parse(Settings["MaxRetries"]);
                    var recipientSeparator = Settings["RecipientSeparator"][0];

                    var messages = database.GetPendingMessages(MessageType).ToList();
                    if(messages.Count > 0)
                    {
                        string error;
                        var shouldRun = ShouldRun(messages.Count, out error);

                        if(!shouldRun)
                        {
                            trace.AppendLine(error);
                        }
                        else
                        {
                            #region Send messages

                            var n = 0;
                            
                            foreach(var message in messages)
                            {
                                List<DocumentContent> attachments = null;

                                if(MessageType == MessageTypeEnum.Email)
                                {
                                    attachments = database.GetAttachments(message).ToList();
                                }

                                var successful = SendMessage(message, attachments, recipientSeparator, out error);
                                if(successful)
                                {
                                    n++;
                                    message.SentDate = DateTime.Now;
                                }
                                else
                                {
                                    trace.AppendFormat("Send Message {0} failed: {1}", message.MessageID, error);
                                    trace.AppendLine();
                                    message.Retries++;
                                    if(message.Retries >= maxRetries)
                                    {
                                        message.IsCancelled = true;
                                    }
                                }
                                message.UpdatedByID = UserID;
                                message.UpdatedDate = DateTime.Now;
                                database.Update(message, false);
                            }
                            database.Save();

                            trace.Insert(0, string.Format("Sent {0} of {1} messages.\n", n, messages.Count));

                            #endregion
                        }
                    }
                }
                finally
                {
                    FinalizeSender(database);
                }
            }

            TraceInfo = trace.ToString();
        }

        #endregion
    }
}