001/*
002 * JDrupes Builder
003 * Copyright (C) 2025 Michael N. Lipp
004 * 
005 * This program is free software: you can redistribute it and/or modify
006 * it under the terms of the GNU Affero General Public License as
007 * published by the Free Software Foundation, either version 3 of the
008 * License, or (at your option) any later version.
009 *
010 * This program is distributed in the hope that it will be useful,
011 * but WITHOUT ANY WARRANTY; without even the implied warranty of
012 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
013 * GNU Affero General Public License for more details.
014 *
015 * You should have received a copy of the GNU Affero General Public License
016 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
017 */
018
019package org.jdrupes.builder.api;
020
021import java.util.stream.Stream;
022
023/// A provider of a resource. This interface is intended to be implemented
024/// by providers. It is not intended to be invoked directly. Rather, it 
025/// must be invoked via [BuildContext#get].
026///
027@SuppressWarnings("PMD.ImplicitFunctionalInterface")
028public interface ResourceProvider {
029
030    /// Provide the requested resources.
031    /// 
032    /// This method is never invoked concurrently for the same request
033    /// when invoked through [Project#get]. It may, however, be invoked
034    /// concurrently for different requests. Providers that evaluate all
035    /// possibly provided resources anyway and return only a subset for
036    /// some kinds of request should therefore invoke themselves (through
037    /// [Project#get]) with a request for all resources and filter the
038    /// (automatically cached) result.
039    ///
040    /// @param <T> the type of the requested (and provided) resource
041    /// @param requested the requested resources
042    /// @return the provided resource(s) as stream
043    ///
044    <T extends Resource> Stream<T> provide(ResourceRequest<T> requested);
045}