using ErrorOr;
using Mediator;
using Microsoft.EntityFrameworkCore;
using Musify.Application.Contracts;
using Musify.Application.Shared;
using Musify.Application.Users.Responses;
using X.PagedList.EF;

namespace Musify.Application.Users;

public record GetUserFollowingQuery(long? ViewerId, long UserId, int PageNumber, int PageSize)
    : IQuery<ErrorOr<PaginatedResponse<UserSummaryResponse>>>;

public class GetUserFollowingQueryHandler(IDatabase database)
    : IQueryHandler<GetUserFollowingQuery, ErrorOr<PaginatedResponse<UserSummaryResponse>>>
{
    public async ValueTask<ErrorOr<PaginatedResponse<UserSummaryResponse>>> Handle(GetUserFollowingQuery request, CancellationToken cancellationToken)
    {
        if (!await database.Users.AnyAsync(u => u.Id == request.UserId, cancellationToken))
            return Error.NotFound();

        var followsQuery = database.UserFollows
            .AsNoTracking()
            .Where(f => f.FollowerId == request.UserId);

        var totalCount = await followsQuery.CountAsync(cancellationToken);
        var viewerId = request.ViewerId;

        var page = await followsQuery
            .OrderByDescending(f => f.CreatedAt)
            .Select(f => new UserSummaryResponse(
                f.Followed.Id,
                f.Followed.Name,
                f.Followed.FirstName,
                f.Followed.SecondName,
                f.Followed.ProfilePictureUrl,
                viewerId != null && database.UserFollows.Any(v => v.FollowerId == viewerId && v.FollowedId == f.FollowedId)))
            .ToPagedListAsync(request.PageNumber, request.PageSize, totalCount, cancellationToken);

        return PaginatedResponse<UserSummaryResponse>.FromPagedList(page);
    }
}