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

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> 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();
            }
        }

        // 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 = 20;

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

        // Returns the most recently added channels.
        [HttpGet]
        public async Task<IActionResult> Get() {
            // Get all the relevant channels.
            var chanels = await db.Channels
                .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);
        }
    }
}