using Microsoft.EntityFrameworkCore;
using Nuuru.Server.Data;
using Nuuru.Server.Models;

namespace Nuuru.Server.Services
{
    public interface IWatchService
    {
        Task<bool> ToggleWatchAsync(Guid userId, WatchTargetType targetType, int targetId);
        Task EnsureWatchingAsync(Guid userId, WatchTargetType targetType, int targetId);
        Task<bool> IsWatchingAsync(Guid userId, WatchTargetType targetType, int targetId);
        Task<IEnumerable<Guid>> GetWatcherUserIdsAsync(WatchTargetType targetType, int targetId);
        Task<int> GetWatchCountAsync(WatchTargetType targetType, int targetId);
    }

    public class WatchService : IWatchService
    {
        private readonly ApplicationDbContext _context;

        public WatchService(ApplicationDbContext context)
        {
            _context = context;
        }

        public async Task<bool> ToggleWatchAsync(Guid userId, WatchTargetType targetType, int targetId)
        {
            var existing = await _context.Watches
                .FirstOrDefaultAsync(w => w.UserId == userId && w.TargetType == targetType && w.TargetId == targetId);

            if (existing != null)
            {
                _context.Watches.Remove(existing);
                await _context.SaveChangesAsync();
                return false;
            }

            _context.Watches.Add(new Watch
            {
                UserId = userId,
                TargetType = targetType,
                TargetId = targetId,
                CreatedAt = DateTime.UtcNow
            });
            await _context.SaveChangesAsync();
            return true;
        }

        public async Task EnsureWatchingAsync(Guid userId, WatchTargetType targetType, int targetId)
        {
            var alreadyWatching = await _context.Watches
                .AnyAsync(w => w.UserId == userId && w.TargetType == targetType && w.TargetId == targetId);

            if (alreadyWatching) return;

            _context.Watches.Add(new Watch
            {
                UserId = userId,
                TargetType = targetType,
                TargetId = targetId,
                CreatedAt = DateTime.UtcNow
            });
            await _context.SaveChangesAsync();
        }

        public async Task<bool> IsWatchingAsync(Guid userId, WatchTargetType targetType, int targetId)
        {
            return await _context.Watches
                .AnyAsync(w => w.UserId == userId && w.TargetType == targetType && w.TargetId == targetId);
        }

        public async Task<IEnumerable<Guid>> GetWatcherUserIdsAsync(WatchTargetType targetType, int targetId)
        {
            return await _context.Watches
                .Where(w => w.TargetType == targetType && w.TargetId == targetId)
                .Select(w => w.UserId)
                .ToListAsync();
        }

        public async Task<int> GetWatchCountAsync(WatchTargetType targetType, int targetId)
        {
            return await _context.Watches
                .CountAsync(w => w.TargetType == targetType && w.TargetId == targetId);
        }
    }
}