ODataSomething.cs

using System;
using System.Data.Common;
using System.Net.Mime;
using System.Threading;
using System.Threading.Tasks;
using FastEndpoints;
using i3Hcs.ModelApi;
using i3v.Esi.OData;
using i3v.Esi.OData.Serialization;
using Microsoft.OData.UriParser;

namespace ODataSomething;

internal sealed class GetRuntimeEntitySetEndpoint(
    RuntimeModelService _modelService,
    ODataJsonResponseWriter _jsonResponseWriter)
    : Endpoint<GetRuntimeEntitySetRequest>, IAsyncDisposable
{
    private DbConnection? _dbConnection;
    private DbDataReader? _dbReader;

    public async ValueTask DisposeAsync()
    {
        if (_dbReader != null) await _dbReader.DisposeAsync();
        if (_dbConnection != null) await _dbConnection.DisposeAsync();
    }

    public override void Configure()
    {
        Get("/{EntitySet}",
            "/{EntitySet}({ObjectId})",
            "/{EntitySet}({ObjectId})/{PropertyName}");
        Group<ODataGroup>();
    }

    public override async Task HandleAsync(GetRuntimeEntitySetRequest req, CancellationToken ct)
    {
        var request = HttpContext.Request;
        var edm_model = _modelService.GetModel();

        var entity_set = edm_model.FindDeclaredEntitySet(req.EntitySet);
        if (entity_set == null) {
            await SendNotFoundAsync(ct);
            return;
        }

        var request_path = HcsODataUtils.GetCanonicalRequestPath(request);
        var service_path = new Uri(request_path, HcsODataUtils.GetODataRouteServicePath(request_path, entity_set));

        var parse_map = HcsODataUtils.GetEntitySetParseMap(edm_model, request_path, service_path,
            new ODataUriParserSettings {
                MaximumExpansionDepth = 1,
                MaximumExpansionCount = 4
            });

        var odata_query = ODataEntitySetSelectQueryBuilder.CreateSelectQuery(parse_map, _modelService);

        _dbConnection = _modelService.CreateModelDbConnection();
        await _dbConnection.OpenAsync(ct);

        long? total_row_count = parse_map.IncludeRowCount
            ? ODataEntitySetSelectQueryBuilder.GetRowCount(_dbConnection, parse_map, _modelService)
            : null;
        var sql_cmd = odata_query.Command;
        sql_cmd.Connection = _dbConnection;

        _dbReader = await sql_cmd.ExecuteReaderAsync(ct);

        if (odata_query.HasKeysetSegment && !await _dbReader.ReadAsync(ct)) {
            await SendNotFoundAsync(ct);
        } else {
            await SendResultAsync(new BodyWriterResult(MediaTypeNames.Application.Json,
                _ => _jsonResponseWriter.WriteODataJson(HttpContext.Response.BodyWriter, _dbReader, odata_query,
                    new Uri(service_path, "/EntitySet"), total_row_count)));
        }
    }
}