using AutobusApi.Application.Common.Exceptions;
using AutobusApi.Application.Common.Interfaces;
using AutobusApi.Domain.Entities;
using MediatR;
using Microsoft.EntityFrameworkCore;

namespace AutobusApi.Application.Routes.Commands.UpdateRoute;

public class UpdateRouteCommandHandler : IRequestHandler<UpdateRouteCommand>
{
    private readonly IApplicationDbContext _dbContext;

    public UpdateRouteCommandHandler(IApplicationDbContext dbContext)
    {
        _dbContext = dbContext;
    }

    public async Task Handle(
        UpdateRouteCommand request,
        CancellationToken cancellationToken)
    {
        var route = await _dbContext.Routes
            .Include(r => r.RouteAddresses)
            .SingleAsync(r => r.Id == request.Id, cancellationToken);

        if (route == null)
        {
            throw new NotFoundException();
        }

        var compaper = new RouteAddressEqualityComparer();

        var routeAddressesToBeRemoved = route.RouteAddresses
            .ExceptBy(request.Addresses.Select(
                a => new RouteAddress
                {
                    AddressId = a.Id,
                    Order = a.Order 
                }), 
                ra => new RouteAddress 
                {
                    AddressId = ra.AddressId,
                    Order = ra.Order
                }, 
                compaper
            ).ToList();

        var remainingRouteAddresses = route.RouteAddresses
            .ExceptBy(routeAddressesToBeRemoved.Select(
                ratbr => new RouteAddress
                {
                    AddressId = ratbr.AddressId,
                    Order = ratbr.Order 
                }), 
                ra => new RouteAddress 
                {
                    AddressId = ra.AddressId,
                    Order = ra.Order
                },
                compaper
            ).ToList();

        var newRouteAddresses = remainingRouteAddresses
            .UnionBy(request.Addresses.Select(
                a => new RouteAddress 
                {
                    AddressId = a.Id,
                    Order = a.Order
                }),
                rra => new RouteAddress 
                {
                    AddressId = rra.AddressId,
                    Order = rra.Order
                },
                compaper
            ).ToList();

        route.RouteAddresses = newRouteAddresses.ToList();

        await _dbContext.SaveChangesAsync(cancellationToken);
    }

    private class RouteAddressEqualityComparer : IEqualityComparer<RouteAddress>
    {
        public bool Equals(RouteAddress? x, RouteAddress? y)
        {
            return x?.AddressId == y?.AddressId && x?.Order == y?.Order;
        }

        public int GetHashCode(RouteAddress obj)
        {
            return obj.AddressId.GetHashCode() + obj.Order.GetHashCode();
        }
    }
}