Add project files.

JSMR.Infrastructure/Common/Queries/SearchProvider.cs

@@ -0,0 +1,59 @@
+using JSMR.Application.Common.Search;
+using Microsoft.EntityFrameworkCore;
+using System.Linq.Expressions;
+
+namespace JSMR.Infrastructure.Common.Queries;
+
+public abstract class SearchProvider<TItem, TCriteria, TSortField, TBaseQuery> : ISearchProvider<TItem, TCriteria, TSortField>
+    where TCriteria : new()
+    where TSortField : struct, Enum
+{
+    public async Task<SearchResult<TItem>> SearchAsync(SearchOptions<TCriteria, TSortField> options, CancellationToken cancellationToken = default)
+    {
+        IQueryable<TBaseQuery> baseQuery = GetBaseQuery();
+        IQueryable<TBaseQuery> filteredQuery = ApplyFilters(baseQuery, options.Criteria);
+
+        int total = await filteredQuery.CountAsync(cancellationToken);
+
+        IOrderedQueryable<TBaseQuery> orderedQuery = ApplySorting(filteredQuery, options.SortOptions);
+        IOrderedQueryable<TItem> selectQuery = GetSelectQuery(orderedQuery);
+
+        TItem[] items = await selectQuery
+            .Skip((options.PageNumber - 1) * options.PageSize)
+            .Take(options.PageSize)
+            .ToArrayAsync(cancellationToken);
+
+        return new SearchResult<TItem>()
+        {
+            Items = items,
+            TotalItems = total
+        };
+    }
+
+    protected abstract IQueryable<TBaseQuery> GetBaseQuery();
+    protected abstract IQueryable<TBaseQuery> ApplyFilters(IQueryable<TBaseQuery> query, TCriteria criteria);
+
+    private IOrderedQueryable<TBaseQuery> ApplySorting(IQueryable<TBaseQuery> query, SortOption<TSortField>[] sortOptions)
+    {
+        IOrderedQueryable<TBaseQuery>? ordered = null;
+
+        for (int i = 0; i < sortOptions.Length; i++)
+        {
+            var (field, direction) = (sortOptions[i].Field, sortOptions[i].Direction);
+            bool isDescending = direction == SortDirection.Descending;
+
+            IOrderedQueryable<TBaseQuery> applyFirst(Expression<Func<TBaseQuery, object>> selector) => isDescending ? query.OrderByDescending(selector) : query.OrderBy(selector);
+            IOrderedQueryable<TBaseQuery> applyNext(Expression<Func<TBaseQuery, object>> selector) => isDescending ? ordered!.ThenByDescending(selector) : ordered!.ThenBy(selector);
+
+            Expression<Func<TBaseQuery, object>> selector = GetSortExpression(field);
+
+            ordered = (i == 0) ? applyFirst(selector) : applyNext(selector);
+        }
+
+        return ordered ?? GetDefaultSortExpression(query);
+    }
+
+    protected abstract Expression<Func<TBaseQuery, object>> GetSortExpression(TSortField field);
+    protected abstract IOrderedQueryable<TBaseQuery> GetDefaultSortExpression(IQueryable<TBaseQuery> query);
+    protected abstract IOrderedQueryable<TItem> GetSelectQuery(IOrderedQueryable<TBaseQuery> query);
+}