ApplicationHub/ApplicationHub.Data.EF/Utils/QueryResolver.cs

using System.Linq.Expressions;
using ApplicationHub.Domain.Contracts;
using ApplicationHub.Domain.Contracts.Linq;
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Query;

namespace ApplicationHub.Data.EF.Utils;

public class QueryResolver<TModel, TEntity> where TEntity : class
{
    public IQueryable<TEntity> Find(IIncludableQueryable<TEntity, object?> dbSet, Expression<Func<TModel, bool>>? where = null, int? limit = null, int? offset = null, List<KeyValuePair<Expression<Func<TModel, bool>>, OrderDirection>>? order = null)
    {
        IQueryable<TEntity>? expression = null;
        if (where != null)
        {
            var whereConverter = new EntityExpressionConverter<TModel, TEntity>(where.Parameters.Single());
            expression = dbSet.Where(whereConverter.Convert(where));
        }

        if (offset.HasValue)
        {
            expression = expression == null
                ? dbSet.Skip(offset.Value)
                : expression.Skip(offset.Value);
        }

        if (limit.HasValue)
        {
            expression = expression == null
                ? dbSet.Take(limit.Value)
                : expression.Take(limit.Value);
        }

        if (order != null && order.Any())
        {
            foreach (var orderDescription in order)
            {
                var orderConverter = new EntityExpressionConverter<TModel, TEntity>(orderDescription.Key.Parameters.Single());
                var convertedOrder = orderConverter.Convert(orderDescription.Key);
                switch (orderDescription.Value)
                {
                    case OrderDirection.Asc:
                        expression = expression == null
                            ? dbSet.OrderBy(convertedOrder)
                            : expression.OrderBy(convertedOrder);
                        break;
                    case OrderDirection.Desc:
                        expression = expression == null
                            ? dbSet.OrderByDescending(convertedOrder)
                            : expression.OrderByDescending(convertedOrder);
                        break;
                }
            }
        }

        return expression ?? dbSet.Where(x => true);
    }
    
    public IQueryable<TEntity> Find(DbSet<TEntity> dbSet, Expression<Func<TModel, bool>>? where = null, int? limit = null, int? offset = null, List<KeyValuePair<Expression<Func<TModel, bool>>, OrderDirection>>? order = null)
    {
        IQueryable<TEntity>? expression = null;
        if (where != null)
        {
            var whereConverter = new EntityExpressionConverter<TModel, TEntity>(where.Parameters.Single());
            expression = dbSet.Where(whereConverter.Convert(where));
        }

        if (offset.HasValue)
        {
            expression = expression == null
                ? dbSet.Skip(offset.Value)
                : expression.Skip(offset.Value);
        }

        if (limit.HasValue)
        {
            expression = expression == null
                ? dbSet.Take(limit.Value)
                : expression.Take(limit.Value);
        }

        if (order != null && order.Any())
        {
            foreach (var orderDescription in order)
            {
                var orderConverter = new EntityExpressionConverter<TModel, TEntity>(orderDescription.Key.Parameters.Single());
                var convertedOrder = orderConverter.Convert(orderDescription.Key);
                switch (orderDescription.Value)
                {
                    case OrderDirection.Asc:
                        expression = expression == null
                            ? dbSet.OrderBy(convertedOrder)
                            : expression.OrderBy(convertedOrder);
                        break;
                    case OrderDirection.Desc:
                        expression = expression == null
                            ? dbSet.OrderByDescending(convertedOrder)
                            : expression.OrderByDescending(convertedOrder);
                        break;
                }
            }
        }

        return expression ?? dbSet.Where(x => true);
    }
}