using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using System;

namespace YTManager.Controllers {
    [Produces("application/json")]
    [Route("api/Channels")]
    public class ChannelsController : Controller {
        // Custom return type for API accesses. Done this way to ensure we
        // always return the expected data regardless of the underlying model.
        struct Channel_ForAPI {
            public string Title;
            public string Description;
            public string ID;
            public List<string> User_Tags;
            public List<string> Video_IDs;

            public Channel_ForAPI(Models.Channel c) {
                Title = c.Title;
                Description = c.Description;
                ID = c.YoutubeID;
                Video_IDs = c.Videos.Select(v => v.YoutubeID).ToList();
                User_Tags = c.UserTags == null ? new List<string>() : c.UserTags.ToList();
            }
        }

        // DB context used for all these calls.
        private readonly MediaDB db;

        // Maximum number of channels to return per query.
        private readonly int max_per_query = 10;

        // Constructor to fetch the db context.
        public ChannelsController(MediaDB context) => db = context;

        // Returns the most recently added channels.
        [HttpGet]
        public async Task<IActionResult> Get() {
            // Log this to the terminal.
            Console.WriteLine($"{DateTime.Now} == Channels GET");

            // Get all the relevant channels.
            var chanels = await db.Channels
                .Include(c => c.Videos)
                .OrderByDescending(i => i.AddedtoDB)
                .Take(max_per_query)
                .ToListAsync();

            // Convert them to what we will send out.
            var converted = chanels
                .Select(ch => new Channel_ForAPI(ch))
                .ToList();

            // Convert all the videos to what we will send back.
            return Ok(converted);
        }

        [HttpPost("{channelid}")]
        public async Task<IActionResult> PostChannel([FromRoute] string channelid) {
            Console.WriteLine($"{DateTime.Now} == Channels POST -> {channelid}");

            // Verify the channel looks resonable.
            var expected_len = "UCyS4xQE6DK4_p3qXQwJQAyA".Length;
            if (channelid.Length != expected_len)
                return BadRequest($"Length should be {expected_len} but is {channelid.Length}");

            // Only add it to the databse if it's not in there already.
            if (db.Channels.Any(c => c.YoutubeID == channelid))
                return BadRequest($"Channel {channelid} is already in DB!");

            // Get the channel contents from youtube.
            var channel = await Tasks.FetchVideos.Get_YTChannel(channelid);

            // Add it to the databse.
            await db.Channels.AddAsync(channel);
            await db.SaveChangesAsync();

            // Say all went ok.
            return Ok();
        }
    }
}