using LiteCqrs;
using Microsoft.EntityFrameworkCore;
using TeleWave.Application.Common.Interfaces;
using TeleWave.Application.Common.Models;

namespace TeleWave.Application.Programming.Groups.GetGroup;

public sealed class GetGroupQueryHandler(IAppDbContext dbContext, GroupElementResolver resolver)
    : IQueryHandler<GetGroupQuery, Result<GroupDto>>
{
    public async Task<Result<GroupDto>> Handle(
        GetGroupQuery query,
        CancellationToken cancellationToken
    )
    {
        var group = await dbContext
            .Groups.AsNoTracking()
            .Include(g => g.Items)
            .FirstOrDefaultAsync(g => g.Id == query.Id, cancellationToken);
        if (group is null)
            return Result.Failure<GroupDto>(GroupErrors.NotFound);

        var info = await resolver.ResolveAsync(
            group.Items.Select(i => (i.ElementKind, i.ElementId)),
            cancellationToken
        );

        var items = group
            .Items.OrderBy(i => i.Position)
            .Select(i =>
            {
                info.TryGetValue((i.ElementKind, i.ElementId), out var element);
                return new GroupItemDto(
                    i.Id,
                    i.ElementKind,
                    i.ElementId,
                    // Элемент мог исчезнуть из библиотеки между чисткой и чтением — показываем прочерк,
                    // а не роняем весь экран группы.
                    element?.Name
                        ?? "—",
                    i.Weight,
                    i.Position,
                    element?.UnitCount ?? 0,
                    element?.ShowKind,
                    element?.Audience,
                    element?.Year,
                    element?.PosterImageId
                );
            })
            .ToList();

        return Result.Success(
            new GroupDto(
                group.Id,
                group.Name,
                group.Description,
                GroupFilter.FromJson(group.FilterJson),
                group.ItemCount,
                group.UnitCount,
                group.TotalDuration.TotalSeconds,
                group.StatsComputedAt,
                items
            )
        );
    }
}