inabox/InABox.Core/Postable/PosterEngine.cs

using InABox.Clients;
using InABox.Configuration;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace InABox.Core
{
    public class RepostedException : Exception
    {
        public RepostedException(): base("Cannot process an item twice.")
        {
        }
    }

    public interface IPosterEngine<TPostable>
        where TPostable : Entity, IPostable, IRemotable, IPersistent, new()
    {
        bool Process(IEnumerable<TPostable> posts);
    }

    public interface IPosterEngine<TPostable, TPoster, TSettings> : IPosterEngine<TPostable>
        where TPostable : Entity, IPostable, IRemotable, IPersistent, new()
        where TPoster : IPoster<TPostable, TSettings>
        where TSettings : PosterSettings, new()
    {
    }

    public abstract class PosterEngine<TPostable, TPoster, TSettings> : IPosterEngine<TPostable, TPoster, TSettings>
        where TPostable : Entity, IPostable, IRemotable, IPersistent, new()
        where TPoster : IPoster<TPostable, TSettings>
        where TSettings : PosterSettings, new()
    {
        protected static TPoster Poster = GetPoster();

        private static Type[]? _posters;

        private static TPoster GetPoster()
        {
            _posters ??= CoreUtils.TypeList(
                AppDomain.CurrentDomain.GetAssemblies(),
                x => x.IsClass
                    && !x.IsAbstract
                    && !x.IsGenericType
                    && x.HasInterface(typeof(IPoster<,>))
            ).ToArray();

            var type = _posters.Where(x => typeof(TPoster).IsAssignableFrom(x)).FirstOrDefault()
                ?? throw new Exception($"No poster of type {typeof(TPoster)}.");
            return (TPoster)Activator.CreateInstance(type);
        }

        protected static TSettings GetSettings()
        {
            return PosterUtils.LoadPosterSettings<TPostable, TSettings>();
        }

        protected static void SaveSettings(TSettings settings)
        {
            PosterUtils.SavePosterSettings<TPostable, TSettings>(settings);
        }

        /// <summary>
        /// Returns the <see cref="TSettings.Script"/>, if <see cref="TSettings.ScriptEnabled"/> is <see langword="true"/>;
        /// otherwise, returns <see langword="null"/>.
        /// </summary>
        protected static string? GetScript()
        {
            var settings = GetSettings();
            return settings.ScriptEnabled ? settings.Script : null;
        }

        protected abstract bool DoProcess(IEnumerable<TPostable> posts);

        public bool Process(IEnumerable<TPostable> posts)
        {
            var list = posts.ToList();
            if(list.Any(x => x.PostedStatus == PostedStatus.Posted))
            {
                throw new RepostedException();
            }
            try
            {
                var success = DoProcess(list);
                if (success)
                {
                    foreach (var post in list)
                    {
                        post.Posted = DateTime.Now;
                        post.PostedStatus = PostedStatus.Posted;
                    }
                    new Client<TPostable>().Save(list, "Posted by user.");
                }
                else
                {
                    foreach (var post in list)
                    {
                        post.PostedStatus = PostedStatus.PostFailed;
                    }
                    new Client<TPostable>().Save(list, "Post failed by user.");
                }
                return success;
            }
            catch(Exception e)
            {
                Logger.Send(LogType.Error, "", $"Post Failed: {CoreUtils.FormatException(e)}");
                foreach (var post in list)
                {
                    post.PostedStatus = PostedStatus.PostFailed;
                }
                new Client<TPostable>().Save(list, "Post failed by user.");
                throw;
            }
        }
    }
}