001/*
002 * SPDX-License-Identifier: Apache-2.0
003 *
004 * Copyright 2024-2026 The Enola <https://enola.dev> Authors
005 *
006 * Licensed under the Apache License, Version 2.0 (the "License");
007 * you may not use this file except in compliance with the License.
008 * You may obtain a copy of the License at
009 *
010 *     https://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package dev.enola.thing.repo;
019
020import dev.enola.common.context.TLC;
021import dev.enola.common.convert.ConversionException;
022import dev.enola.thing.Thing;
023import dev.enola.thing.impl.OnlyIRIThing;
024
025import org.jspecify.annotations.NonNull;
026
027import java.io.UncheckedIOException;
028
029/**
030 * AlwaysThingProvider is a {@link ThingProvider} which never returns null, but always a Thing.
031 *
032 * <p>The Thing WILL have the requested IRI - but if no such Thing is known (e.g. was pre-loaded, or
033 * could be fetched), then the returned Thing ONLY has an IRI - and no properties (nor datatypes).
034 *
035 * <p>This is useful in some situations where callers don't want to distinguish "non-existent"
036 * Things; e.g. to have a {@link dev.enola.thing.metadata.ThingMetadataProvider} always work, or so.
037 */
038public class AlwaysThingProvider implements ThingProvider {
039
040    // TODO Make this the private and built-in default, and remove @Nullable from ThingProvider
041
042    public static final AlwaysThingProvider CTX =
043            new AlwaysThingProvider(
044                    // TODO Rethink EmptyThingProvider... convenient - but hides errors! So not?
045                    TLC.optional(ThingProvider.class).orElse(EmptyThingProvider.INSTANCE));
046
047    private final ThingProvider delegate;
048
049    public AlwaysThingProvider(ThingProvider delegate) {
050        this.delegate = delegate;
051    }
052
053    @Override
054    public @NonNull Thing get(String iri) throws UncheckedIOException, ConversionException {
055        var thing = delegate.get(iri);
056        if (thing == null) return new OnlyIRIThing(iri);
057        else return thing;
058    }
059}