/*
 * Copyright 2012-present the original author or authors.
 *
 * 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
 *
 *      https://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 org.springframework.boot.build.bom.bomr;

import java.time.Duration;
import java.util.ArrayList;
import java.util.Collection;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.SortedSet;
import java.util.function.BiFunction;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.springframework.boot.build.bom.Library;
import org.springframework.boot.build.bom.Library.Group;
import org.springframework.boot.build.bom.Library.ImportedBom;
import org.springframework.boot.build.bom.Library.Module;
import org.springframework.boot.build.bom.Library.VersionAlignment;
import org.springframework.boot.build.bom.bomr.version.DependencyVersion;

/**
 * Standard implementation for {@link LibraryUpdateResolver}.
 *
 * @author Andy Wilkinson
 */
class StandardLibraryUpdateResolver implements LibraryUpdateResolver {

	private static final Logger logger = LoggerFactory.getLogger(StandardLibraryUpdateResolver.class);

	private final VersionResolver versionResolver;

	private final BiFunction<Library, DependencyVersion, VersionOption> versionOptionResolver;

	StandardLibraryUpdateResolver(VersionResolver versionResolver,
			BiFunction<Library, DependencyVersion, VersionOption> versionOptionResolver) {
		this.versionResolver = versionResolver;
		this.versionOptionResolver = versionOptionResolver;
	}

	@Override
	public List<LibraryWithVersionOptions> findLibraryUpdates(Collection<Library> librariesToUpgrade,
			Map<String, Library> librariesByName) {
		List<LibraryWithVersionOptions> result = new ArrayList<>();
		for (Library library : librariesToUpgrade) {
			if (isLibraryExcluded(library)) {
				continue;
			}
			logger.info("Looking for updates for {}", library.getName());
			long start = System.nanoTime();
			List<VersionOption> versionOptions = getVersionOptions(library);
			result.add(new LibraryWithVersionOptions(library, versionOptions));
			logger.info("Found {} updates for {}, took {}", versionOptions.size(), library.getName(),
					Duration.ofNanos(System.nanoTime() - start));
		}
		return result;
	}

	protected boolean isLibraryExcluded(Library library) {
		return library.getName().equals("Spring Boot");
	}

	protected List<VersionOption> getVersionOptions(Library library) {
		List<VersionOption> options = new ArrayList<>();
		VersionOption alignedOption = determineAlignedVersionOption(library);
		if (alignedOption != null) {
			options.add(alignedOption);
		}
		for (VersionOption resolvedOption : determineResolvedVersionOptions(library)) {
			if (alignedOption == null || !alignedOption.getVersion().equals(resolvedOption.getVersion())) {
				options.add(resolvedOption);
			}
		}
		return options;
	}

	private VersionOption determineAlignedVersionOption(Library library) {
		VersionAlignment versionAlignment = library.getVersionAlignment();
		if (versionAlignment != null) {
			Set<String> alignedVersions = versionAlignment.resolve();
			if (alignedVersions != null && alignedVersions.size() == 1) {
				DependencyVersion alignedVersion = DependencyVersion.parse(alignedVersions.iterator().next());
				if (!alignedVersion.equals(library.getVersion().getVersion())) {
					return new VersionOption.AlignedVersionOption(alignedVersion, versionAlignment);
				}
			}
		}
		return null;
	}

	private List<VersionOption> determineResolvedVersionOptions(Library library) {
		Map<String, SortedSet<DependencyVersion>> moduleVersions = new LinkedHashMap<>();
		for (Group group : library.getGroups()) {
			for (Module module : group.getModules()) {
				moduleVersions.put(group.getId() + ":" + module.getName(),
						getLaterVersionsForModule(group.getId(), module.getName(), library));
			}
			for (ImportedBom bom : group.getBoms()) {
				moduleVersions.put(group.getId() + ":" + bom,
						getLaterVersionsForModule(group.getId(), bom.name(), library));
			}
			for (String plugin : group.getPlugins()) {
				moduleVersions.put(group.getId() + ":" + plugin,
						getLaterVersionsForModule(group.getId(), plugin, library));
			}
		}
		List<VersionOption> versionOptions = new ArrayList<>();
		moduleVersions.values().stream().flatMap(SortedSet::stream).distinct().forEach((dependencyVersion) -> {
			VersionOption versionOption = this.versionOptionResolver.apply(library, dependencyVersion);
			if (versionOption != null) {
				List<String> missingModules = getMissingModules(moduleVersions, dependencyVersion);
				if (!missingModules.isEmpty()) {
					versionOption = new VersionOption.ResolvedVersionOption(versionOption.getVersion(), missingModules);
				}
				versionOptions.add(versionOption);
			}
		});
		return versionOptions;
	}

	private List<String> getMissingModules(Map<String, SortedSet<DependencyVersion>> moduleVersions,
			DependencyVersion version) {
		List<String> missingModules = new ArrayList<>();
		moduleVersions.forEach((name, versions) -> {
			if (!versions.contains(version)) {
				missingModules.add(name);
			}
		});
		return missingModules;
	}

	private SortedSet<DependencyVersion> getLaterVersionsForModule(String groupId, String artifactId, Library library) {
		return this.versionResolver.resolveVersions(groupId, artifactId);
	}

}
