Dynamic Aggregation stages using string template

Related with the issue 102 I wanted to add facet aggregation.

This time I used string templates. ( if it is possible to add facet to the answer in issue 102, it would also help, but anyway I chose string templates this time).

I could dynamically constructed the string template like this, and it worked, but it is dirty:) Do you think this kind of solution is good? Any suggestions?

If the pipeline method would accept input of an array (array of stages), this kind of dynamic (optional) aggregations would be easier? Would you consider adding this feature?

        [HttpGet("search-facet")]
        public async Task<IActionResult> SearchAndFacet(FilterProductDTO dto)
        {

            int page = dto.Page.HasValue ? dto.Page.Value : 1;
            int pageSize = dto.PageSize.HasValue ? dto.PageSize.Value : 10;
            int skip = (page - 1) * pageSize;

            var stages = new List<string>();

            if (!string.IsNullOrEmpty(dto.SearchTerm))
            {
                stages.Add(@"{$match: {
	                      $text: { $search: '<search_term>' }
	                    }}".Replace("<search_term>", dto.SearchTerm));

                stages.Add(@" {$sort: {
	                      score: { $meta: 'textScore' }
	                    }}");
            }

            if (!string.IsNullOrEmpty(dto.CategoryId))
            {
                stages.Add(@" {
                '$match': {
                  'Category': new ObjectId('<category_id>')
                }
              }".Replace("<category_id>", dto.CategoryId));
            }

            if (dto.MinPrice.HasValue)
            {
                stages.Add(@" {
                '$match': {
                  'Price': { $gte: <min_price> }
                }
              }".Replace("<min_price>", dto.MinPrice.Value.ToString(new NumberFormatInfo() { NumberDecimalSeparator = "."})));
            }

            if (dto.MaxPrice.HasValue)
            {
                stages.Add(@" {
                '$match': {
                  'Price': { $lte: <max_price> }
                }
              }".Replace("<max_price>", dto.MaxPrice.Value.ToString(new NumberFormatInfo() { NumberDecimalSeparator = "." })));
            }

            stages.Add(@"{$facet: {
		                      TotalRecords: [
			                    {
			                      $count: 'total'
			                    }
		                      ],
		                      Products: [
			                    {
			                      $skip: <skip>
			                    },
			                    {
			                      $limit: <limit>
			                    }
		                      ]
	                    }}"); //.Replace("<skip>", skip.ToString()).Replace("<limit>", pageSize.ToString()));

            stages.Add(@"{$addFields: {
	                      TotalRecords: {
		                    $arrayElemAt: [ '$TotalRecords.total', 0]
	                      }
	                    }}");

            var template = $"[{string.Join(',', stages)}]";

            var pipeline = new Template<ProductEntity, ProductSearchResultDTO>(template)
                    .Tag("skip", skip.ToString())
                    .Tag("limit", pageSize.ToString());

            var products = await DB.PipelineAsync(pipeline);

            return Ok(products);

        }

[susahin80]

Great, I wil try

[susahin80]

ok thanks, AppendStage method is good enough 😃