Implementing a basic query parser for where, sort & pagination

Kyoo.Common/Controllers/IRepository.cs

@@ -31,6 +31,27 @@ namespace Kyoo.Controllers
 			Key = key;
 			Descendant = descendant;
 		}
+
+		public Sort(string sortBy)
+		{
+			if (string.IsNullOrEmpty(sortBy))
+			{
+				Key = null;
+				Descendant = false;
+				return;
+			}
+			
+			string key = sortBy.Contains(':') ? sortBy.Substring(0, sortBy.IndexOf(':')) : sortBy;
+			string order = sortBy.Contains(':') ? sortBy.Substring(sortBy.IndexOf(':') + 1) : null;
+			
+			Key = Expression.Lambda<Func<T, object>>(Expression.Property(Expression.Parameter(typeof(T), "x"), key));
+			Descendant = order switch
+			{
+				"desc" => true,
+				"asc" => false,
+				_ => throw new ArgumentException($"The sort order, if set, should be :asc or :desc but it was :{order}.")
+			};
+		}
 	}
 	
 	public interface IRepository<T> : IDisposable, IAsyncDisposable

Kyoo.Common/Utility.cs

@@ -236,5 +236,49 @@ namespace Kyoo
 			
 			return member.Member.Name;
 		}
+
+		public static Expression<Func<T, bool>> ParseWhere<T>(Dictionary<string, string> where)
+		{
+			if (where == null || where.Count == 0)
+				return null;
+			
+			ParameterExpression param = Expression.Parameter(typeof(T));
+			Expression expression = null;
+
+			foreach (KeyValuePair<string, string> cond in where)
+			{
+				string value = cond.Value;
+				string operand = "eq";
+				if (value.Contains(':'))
+				{
+					operand = value.Substring(0, value.IndexOf(':'));
+					value = value.Substring(value.IndexOf(':') + 1);
+				}
+
+				PropertyInfo valueParam = typeof(T).GetProperty(cond.Key); // TODO get this property with case insensitive.
+				// TODO throw if valueParam is null.
+				MemberExpression property = Expression.Property(param, valueParam);
+				ConstantExpression condValue = Expression.Constant(value); // TODO Cast this to the right type (take nullable into account).
+				
+				Expression condition = operand switch
+				{
+					"eq" => Expression.Equal(property, condValue),
+					"not" => Expression.NotEqual(property, condValue),
+					"lt" => Expression.LessThan(property, condValue),
+					"lte" => Expression.LessThanOrEqual(property, condValue),
+					"gt" => Expression.GreaterThan(property, condValue),
+					"gte" => Expression.GreaterThanOrEqual(property, condValue),
+					"like" => throw new NotImplementedException("Like not implemented yet"),
+					_ => throw new ArgumentException($"Invalid operand: {operand}")	
+				};
+
+				if (expression != null)
+					expression = Expression.AndAlso(expression, condition);
+				else
+					expression = condition;
+			}
+			
+			return Expression.Lambda<Func<T, bool>>(expression!);
+		}
 	}
 }

Kyoo/Controllers/Repositories/ShowRepository.cs

@@ -75,7 +75,25 @@ namespace Kyoo.Controllers
 			Sort<Show> sort = default,
 			Pagination page = default)
 		{
-			return await _database.Shows.ToListAsync();
+			IQueryable<Show> query = _database.Shows;
+
+			if (where != null)
+				query = query.Where(where);
+
+			Expression<Func<Show, object>> sortKey = sort.Key ?? (x => x.Title);
+			query = sort.Descendant ? query.OrderByDescending(sortKey) : query.OrderBy(sortKey);
+
+			if (page.AfterID != 0)
+			{
+				Show after = await Get(page.AfterID);
+				object afterObj = sortKey.Compile()(after);
+				query = query.Where(Expression.Lambda<Func<Show, bool>>(
+					Expression.GreaterThan(sortKey, Expression.Constant(afterObj))
+				));
+			}
+			query = query.Take(page.Count <= 0 ? 20 : page.Count);
+
+			return await query.ToListAsync();
 		}
 
 		public async Task<int> Create(Show obj)

Kyoo/Views/API/ShowsAPI.cs

@@ -1,8 +1,11 @@
-using Kyoo.Models;
+using System;
+using Kyoo.Models;
 using Microsoft.AspNetCore.Mvc;
 using System.Collections.Generic;
 using System.Linq;
+using System.Linq.Expressions;
 using System.Threading.Tasks;
+using Castle.DynamicProxy.Generators.Emitters.SimpleAST;
 using Kyoo.Controllers;
 using Microsoft.AspNetCore.Authorization;
 using Microsoft.EntityFrameworkCore;
@@ -35,12 +38,14 @@ namespace Kyoo.Api
 
 		[HttpGet]
 		[Authorize(Policy="Read")]
-		public IEnumerable<Show> GetShows()
+		public async Task<IEnumerable<Show>> GetShows([FromQuery] string sortBy, 
+			[FromQuery] int limit, 
+			[FromQuery] int afterID,
+			[FromQuery] Dictionary<string, string> where)
 		{
-			return _database.LibraryLinks
-				.Include(x => x.Show)
-				.Include(x => x.Collection)
-				.AsEnumerable().Select(x => x.Show ?? x.Collection.AsShow()).ToList();
+			return await _libraryManager.GetShows(Utility.ParseWhere<Show>(where),
+				new Sort<Show>(sortBy),
+				new Pagination(limit, afterID));
 		}
 
 		[HttpGet("{slug}")]