NadekoBot/NadekoBot.Core/Modules/Games/Common/PollRunner.cs

using System.Threading.Tasks;
using Discord;
using NadekoBot.Core.Services.Database.Models;
using NadekoBot.Core.Services;
using System;
using System.Threading;

namespace NadekoBot.Modules.Games.Common
{
    public class PollRunner
    {
        public Poll Poll { get; }
        private readonly DbService _db;

        public event Func<IUserMessage, IGuildUser, Task> OnVoted;

        private readonly SemaphoreSlim _locker = new SemaphoreSlim(1, 1);

        public PollRunner(DbService db, Poll poll)
        {
            _db = db;
            Poll = poll;
        }

        public async Task<bool> TryVote(IUserMessage msg)
        {
            PollVote voteObj;
            await _locker.WaitAsync().ConfigureAwait(false);
            try
            {
                // has to be a user message
                // channel must be the same the poll started in
                if (msg == null || msg.Author.IsBot || msg.Channel.Id != Poll.ChannelId)
                    return false;

                // has to be an integer
                if (!int.TryParse(msg.Content, out int vote))
                    return false;
                --vote;
                if (vote < 0 || vote >= Poll.Answers.Count)
                    return false;

                var usr = msg.Author as IGuildUser;
                if (usr == null)
                    return false;

                voteObj = new PollVote()
                {
                    UserId = msg.Author.Id,
                    VoteIndex = vote,
                };
                if (!Poll.Votes.Add(voteObj))
                    return false;

                var _ = OnVoted?.Invoke(msg, usr);
            }
            finally { _locker.Release(); }
            using (var uow = _db.UnitOfWork)
            {
                var trackedPoll = uow.Polls.Get(Poll.Id);
                trackedPoll.Votes.Add(voteObj);
                uow.Complete();
            }
            return true;
        }

        public void End()
        {
            OnVoted = null;
        }
    }
}