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/*
* Copyright 2022 The Kythe Authors. All rights reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.devtools.kythe.util;
import com.google.common.collect.Streams;
import java.util.Comparator;
import java.util.Optional;
import java.util.ServiceLoader;
/**
* OrderedCompatibilityService defines shared functionality between between JdkCompatibilityShim
* interfaces.
*/
public interface OrderedCompatibilityService {
/** The compatibility level of the provider. */
public enum CompatibilityLevel {
/** This provider is incompatible with the current runtime. */
INCOMPATIBLE,
/**
* This provider is compatible with the current runtime, but should only be used if a COMPATIBLE
* provider can't be found.
*/
FALLBACK,
/**
* This provider is compatible with the current runtime and should be preferred over a fallback,
* if any.
*/
COMPATIBLE
}
/** Indicates the range of runtime versions with which these shims are compatible. */
public static class CompatibilityRange {
private final Runtime.Version minVersion;
private final Optional<Runtime.Version> maxVersion;
private final CompatibilityLevel level;
public CompatibilityRange(Runtime.Version minVersion) {
this(minVersion, Optional.empty(), CompatibilityLevel.COMPATIBLE);
}
public CompatibilityRange(Runtime.Version minVersion, Runtime.Version maxVersion) {
this(minVersion, Optional.of(maxVersion), CompatibilityLevel.COMPATIBLE);
}
public CompatibilityRange(
Runtime.Version minVersion,
Optional<Runtime.Version> maxVersion,
CompatibilityLevel level) {
this.minVersion = minVersion;
this.maxVersion = maxVersion;
this.level = level;
}
/** Returns the minimum known compatible runtime version. */
public Runtime.Version getMinVersion() {
return minVersion;
}
/** Returns the maximum known compatible runtime version, if any. */
public Optional<Runtime.Version> getMaxVersion() {
return maxVersion;
}
/** Returns the compatibility level. */
public CompatibilityLevel getCompatibilityLevel() {
return level;
}
}
/** Returns the compatibility level of the service provider. */
CompatibilityRange getCompatibleRange();
public static <S extends OrderedCompatibilityService> Optional<S> loadBest(Class<S> klass) {
Runtime.Version version = Runtime.version();
return Streams.stream(ServiceLoader.load(klass))
// Filter out incompatible providers.
.filter(p -> isCompatible(version, p.getCompatibleRange()))
// Then find the best.
.max(OrderedCompatibilityService::compareProviders);
}
private static boolean isCompatible(Runtime.Version version, CompatibilityRange range) {
return range.getCompatibilityLevel() != CompatibilityLevel.INCOMPATIBLE
&& version.compareToIgnoreOptional(range.getMinVersion()) >= 0
&& range.getMaxVersion().map(max -> version.compareToIgnoreOptional(max) < 0).orElse(true);
}
private static int compareCompatibilityRanges(CompatibilityRange lhs, CompatibilityRange rhs) {
return Comparator.comparing(CompatibilityRange::getCompatibilityLevel)
.thenComparing(CompatibilityRange::getMinVersion, Runtime.Version::compareToIgnoreOptional)
.compare(lhs, rhs);
}
private static <S extends OrderedCompatibilityService> int compareProviders(S lhs, S rhs) {
return Comparator.comparing(
OrderedCompatibilityService::getCompatibleRange,
OrderedCompatibilityService::compareCompatibilityRanges)
.compare(lhs, rhs);
}
}
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