dotnet-cqrs/OpenHarbor.CQRS.DynamicQuery/DynamicQueryHandlerBase.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using OpenHarbor.CQRS.DynamicQuery.Abstractions;
using PoweredSoft.DynamicQuery;
using PoweredSoft.DynamicQuery.Core;

namespace OpenHarbor.CQRS.DynamicQuery;

public abstract class DynamicQueryHandlerBase<TSource, TDestination>
    where TSource : class
    where TDestination : class
{
    private readonly IQueryHandlerAsync _queryHandlerAsync;
    private readonly IEnumerable<IQueryableProvider<TSource>> _queryableProviders;
    private readonly IEnumerable<IAlterQueryableService<TSource, TDestination>> _alterQueryableServices;
    private readonly IEnumerable<IDynamicQueryInterceptorProvider<TSource, TDestination>> _dynamicQueryInterceptorProviders;
    private readonly IServiceProvider _serviceProvider;

    public DynamicQueryHandlerBase(IQueryHandlerAsync queryHandlerAsync, 
        IEnumerable<IQueryableProvider<TSource>> queryableProviders,
        IEnumerable<IAlterQueryableService<TSource, TDestination>> alterQueryableServices,
        IEnumerable<IDynamicQueryInterceptorProvider<TSource, TDestination>> dynamicQueryInterceptorProviders,
        IServiceProvider serviceProvider)
    {
        _queryHandlerAsync = queryHandlerAsync;
        _queryableProviders = queryableProviders;
        _alterQueryableServices = alterQueryableServices;
        _dynamicQueryInterceptorProviders = dynamicQueryInterceptorProviders;
        _serviceProvider = serviceProvider;
    }

    protected virtual Task<IQueryable<TSource>> GetQueryableAsync(IDynamicQuery query, CancellationToken cancellationToken = default)
    {
        if (_queryableProviders.Any())
            return _queryableProviders.ElementAt(0).GetQueryableAsync(query, cancellationToken);

        throw new Exception($"You must provide a QueryableProvider<TSource> for {typeof(TSource).Name}");
    }

    public virtual IQueryExecutionOptions GetQueryExecutionOptions(IQueryable<TSource> source, IDynamicQuery query)
    {
        return new QueryExecutionOptions();
    }

    public virtual IEnumerable<IQueryInterceptor> GetInterceptors()
    {
        var types = _dynamicQueryInterceptorProviders.SelectMany(t => t.GetInterceptorsTypes()).Distinct();
        foreach (var type in types)
            yield return _serviceProvider.GetService(type) as IQueryInterceptor;
    }

    protected async Task<IQueryExecutionResult<TDestination>> ProcessQueryAsync(IDynamicQuery query, CancellationToken cancellationToken = default)
    {
        var source = await GetQueryableAsync(query, cancellationToken);
        source = await AlterSourceAsync(source, query, cancellationToken);
        var options = GetQueryExecutionOptions(source, query);
        var interceptors = GetInterceptors();

        foreach (var interceptor in interceptors)
            _queryHandlerAsync.AddInterceptor(interceptor);

        var criteria = CreateCriteriaFromQuery(query);
        var result = await _queryHandlerAsync.ExecuteAsync<TSource, TDestination>(source, criteria, options, cancellationToken);
        return result;
    }

    protected virtual async Task<IQueryable<TSource>> AlterSourceAsync(IQueryable<TSource> source, IDynamicQuery query, CancellationToken cancellationToken)
    {
        foreach (var t in _alterQueryableServices)
            source = await t.AlterQueryableAsync(source, query, cancellationToken);

        return source;
    }

    protected virtual IQueryCriteria CreateCriteriaFromQuery(IDynamicQuery query)
    {
        var criteria = new QueryCriteria
        {
            Page = query?.GetPage(),
            PageSize = query?.GetPageSize(),
            Filters = query?.GetFilters() ?? new List<IFilter>(),
            Sorts = query?.GetSorts() ?? new List<ISort>(),
            Groups = query?.GetGroups() ?? new List<IGroup>(),
            Aggregates = query?.GetAggregates() ?? new List<IAggregate>()
        };
        return criteria;
    }
}