BackEnd/Tasks/FetchVideos.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Google.Apis.YouTube.v3;
using Microsoft.EntityFrameworkCore;

namespace YTManager.Tasks {
    public class FetchVideos {
        // Get a bunch of videos from youtube that the channel generated.
        public static async Task<List<Models.Video>> Get_YTVideos(string channelID, int max = 50) {
            // YT API access key
            var youtubeService = new YouTubeService(new Google.Apis.Services.BaseClientService.Initializer()
            {
                ApiKey = "AIzaSyCuIYkMc5SktlnXRXNaDf2ObX-fQvtWCnQ",
                ApplicationName = "testingapppp"
            });

            // Max cannot be larger than 50, so clamp it.
            max = max > 50 ? 50 : max;

            // Search youtube for all the relevant data of the channel.
            var videos_query = youtubeService.Search.List("snippet");
            videos_query.ChannelId = channelID;
            videos_query.Order = SearchResource.ListRequest.OrderEnum.Date;
            videos_query.MaxResults = max;
            var videos_response = await videos_query.ExecuteAsync();

            // Convert the response into models.
            var videos = videos_response.Items?
                .Where(i => i.Id.Kind == "youtube#video")
                .Select(newvid => new Models.Video
                {
                    Title = newvid.Snippet.Title,
                    Description = newvid.Snippet.Description,
                    YoutubeID = newvid.Id.VideoId,
                    AddedToYT = newvid.Snippet.PublishedAt.GetValueOrDefault(),
                    AddedtoDB = DateTime.Now,
                    ThumbnailURL = newvid.Snippet.Thumbnails.Medium.Url,
                    Tags = new string[] {}
                }).ToList();

            // Search youtube to get the length and tags for each video.
            var duration_query = youtubeService.Videos.List("contentDetails,snippet");
            duration_query.Id = string.Join(',', videos.Select(v => v.YoutubeID));
            var duration_response = await duration_query.ExecuteAsync();
            
            // Pair each video with the result.
            foreach(var contentdetail in duration_response.Items.Where(i => i.Kind == "youtube#video")){
                var vid = videos.Single(v => v.YoutubeID == contentdetail.Id);

                // Yes, really, ISO8601 time span => c#'s TimeSpan is not in TimeSpan, it's in xmlconvert! Wtf?!
                vid.Duration = System.Xml.XmlConvert.ToTimeSpan(contentdetail.ContentDetails.Duration);

                // Copy over all the created tags if any tags were provided.
                if (contentdetail.Snippet.Tags != null)
                    vid.Tags = contentdetail.Snippet.Tags.Select(t => t.ToLower()).ToArray();
            }

            // Send back the parsed vids.
            return videos;
        }

        // Gets some info about a youtube channel.
        public static async Task<Models.Channel> Get_YTChannel(string channelID) {
            // YT API access key
            var youtubeService = new YouTubeService(new Google.Apis.Services.BaseClientService.Initializer()
            {
                ApiKey = "AIzaSyCuIYkMc5SktlnXRXNaDf2ObX-fQvtWCnQ",
                ApplicationName = "testingapppp"
            });

            // Search youtube for all the relevant data of the channel.
            var query = youtubeService.Channels.List("snippet");
            query.Id = channelID;
            query.MaxResults = 1;
            var response = await query.ExecuteAsync();

            // Parse the response into a channel.
            return new Models.Channel {
                Description = response.Items.First().Snippet.Description,
                Title = response.Items.First().Snippet.Title,
                ThumbnailURL = response.Items.First().Snippet.Thumbnails.Medium.Url,
                YoutubeID = channelID,
                AddedtoDB = DateTime.Now,
                Refreshed = DateTime.MinValue,
                UserTags = new string[]{},
                Videos = { }
            };
        }

        // Update videos for all our channels.
        public static async Task MassUpdate(string dbstr) {
            // Get the interface to the database.
            var ops = new DbContextOptionsBuilder<MediaDB>();
            ops.UseNpgsql(dbstr);

            // Get all the channels from the db that expired.
            var threshold = DateTime.Now.Subtract(TimeSpan.FromMinutes(60));
            var channel_ids = await 
                (new MediaDB(ops.Options)).Channels
                .Where(ch => ch.Refreshed < threshold)
                .Select(ch => ch.YoutubeID)
                .ToListAsync();

            // For each channel, do an update.
            channel_ids.ForEach(async id => await ChannelUpdate(dbstr, id));
        }

        // Update videos for just one channel.
        public static async Task ChannelUpdate(string dbstr, string youtubechannelIDstr) {
            // Get the interface to the database.
            var ops = new DbContextOptionsBuilder<MediaDB>();
            ops.UseNpgsql(dbstr);
            var db = new MediaDB(ops.Options);

            // Get the channel from the db when including it's videos.
            var channel = await db.Channels
                .Include(c => c.Videos)
                .SingleOrDefaultAsync(ch => ch.YoutubeID == youtubechannelIDstr);

            // Update the channel if it was found.
            if (channel != null) {
                // Get all the new videos for the channel.
                var Videos = await Get_YTVideos(channel.YoutubeID);

                // Get all the videos which haven't been put into this channels videos.
                var newvids = Videos
                    .Where(nv => !channel.Videos.Any(cv => cv.YoutubeID == nv.YoutubeID));

                // Say what channel all the videos came from.
                foreach (var v in newvids)
                    v.Channel = channel;

                // Say the channel has been refreshed.
                channel.Refreshed = DateTime.Now;

                // Add all the videos to the databse.
                await db.Videos.AddRangeAsync(newvids);

                // Update the videos this channel refers to.
                channel.Videos.AddRange(newvids);

                // And say the database should be changed.
                await db.SaveChangesAsync();
            }
        }
    }
}