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

namespace Musify.Application.Users
{
    public record GetUsersQuery(int PageNumber, int PageSize, string? UsernameSearch, long? ViewerId = null)
        : IQuery<ErrorOr<PaginatedResponse<UserSummaryResponse>>>;

    public class GetUsersQueryHandler(IDatabase database)
        : IQueryHandler<GetUsersQuery, ErrorOr<PaginatedResponse<UserSummaryResponse>>>
    {
        public async ValueTask<ErrorOr<PaginatedResponse<UserSummaryResponse>>> Handle(GetUsersQuery request, CancellationToken cancellationToken)
        {
            var usersQuery = database.Users
                .AsNoTracking()
                .AsQueryable();

            if (!string.IsNullOrEmpty(request.UsernameSearch))
            {
                var normalizedUsername = request.UsernameSearch.Trim().ToUpperInvariant();
                usersQuery = usersQuery.Where(u => u.NormalizedName.Contains(normalizedUsername));
            }

            var totalCount = await usersQuery.CountAsync(cancellationToken);
            var viewerId = request.ViewerId;
            var pagedUsers = await usersQuery
                .OrderBy(u => u.Name)
                .Select(u => new UserSummaryResponse(
                    u.Id,
                    u.Name,
                    u.FirstName,
                    u.SecondName,
                    u.ProfilePictureUrl,
                    viewerId != null && database.UserFollows.Any(f => f.FollowerId == viewerId && f.FollowedId == u.Id)))
                .ToPagedListAsync(request.PageNumber, request.PageSize, totalCount, cancellationToken);

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