/*
 * 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;

import java.io.File;
import java.net.URI;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.function.Function;

import javax.xml.namespace.QName;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;

import org.gradle.api.artifacts.ConfigurationContainer;
import org.gradle.api.artifacts.ResolvedArtifact;
import org.gradle.api.artifacts.dsl.DependencyHandler;
import org.w3c.dom.Document;
import org.w3c.dom.NodeList;

import org.springframework.boot.build.bom.Library.Group;
import org.springframework.boot.build.bom.Library.ImportedBom;
import org.springframework.boot.build.bom.Library.Link;
import org.springframework.boot.build.bom.Library.Module;
import org.springframework.boot.build.bom.ResolvedBom.Bom;
import org.springframework.boot.build.bom.ResolvedBom.Id;
import org.springframework.boot.build.bom.ResolvedBom.JavadocLink;
import org.springframework.boot.build.bom.ResolvedBom.Links;
import org.springframework.boot.build.bom.ResolvedBom.ResolvedLibrary;
import org.springframework.boot.build.xml.XmlDocument;

/**
 * Creates a {@link ResolvedBom resolved bom}.
 *
 * @author Andy Wilkinson
 */
class BomResolver {

	private final ConfigurationContainer configurations;

	private final DependencyHandler dependencies;

	private final DocumentBuilder documentBuilder;

	BomResolver(ConfigurationContainer configurations, DependencyHandler dependencies) {
		this.configurations = configurations;
		this.dependencies = dependencies;
		this.documentBuilder = XmlDocument.builder();
	}

	ResolvedBom resolve(BomExtension bomExtension) {
		List<ResolvedLibrary> libraries = new ArrayList<>();
		for (Library library : bomExtension.getLibraries()) {
			List<Id> managedDependencies = new ArrayList<>();
			List<Bom> imports = new ArrayList<>();
			for (Group group : library.getGroups()) {
				for (Module module : group.getModules()) {
					Id id = new Id(group.getId(), module.getName(), library.getVersion().getVersion().toString());
					managedDependencies.add(id);
				}
				for (ImportedBom imported : group.getBoms()) {
					Bom bom = bomFrom(resolveBom(
							"%s:%s:%s".formatted(group.getId(), imported.name(), library.getVersion().getVersion())));
					imports.add(bom);
				}
			}
			List<JavadocLink> javadocLinks = javadocLinksOf(library).stream()
				.map((link) -> new JavadocLink(URI.create(link.url(library)), link.packages()))
				.toList();
			ResolvedLibrary resolvedLibrary = new ResolvedLibrary(library.getName(),
					library.getVersion().getVersion().toString(), library.getVersionProperty(), managedDependencies,
					imports, new Links(javadocLinks));
			libraries.add(resolvedLibrary);
		}
		String[] idComponents = bomExtension.getId().split(":");
		return new ResolvedBom(new Id(idComponents[0], idComponents[1], idComponents[2]), libraries);
	}

	private List<Link> javadocLinksOf(Library library) {
		List<Link> javadocLinks = library.getLinks("javadoc");
		return (javadocLinks != null) ? javadocLinks : Collections.emptyList();
	}

	Bom resolveMavenBom(String coordinates) {
		return bomFrom(resolveBom(coordinates));
	}

	private File resolveBom(String coordinates) {
		Set<ResolvedArtifact> artifacts = this.configurations
			.detachedConfiguration(this.dependencies.create(coordinates + "@pom"))
			.getResolvedConfiguration()
			.getResolvedArtifacts();
		if (artifacts.size() != 1) {
			throw new IllegalStateException("Expected a single artifact but '%s' resolved to %d artifacts"
				.formatted(coordinates, artifacts.size()));
		}
		return artifacts.iterator().next().getFile();
	}

	private Bom bomFrom(File bomFile) {
		try {
			Node bom = nodeFrom(bomFile);
			File parentBomFile = parentBomFile(bom);
			Bom parent = null;
			if (parentBomFile != null) {
				parent = bomFrom(parentBomFile);
			}
			Properties properties = Properties.from(bom, this::nodeFrom);
			List<Node> dependencyNodes = bom.nodesAt("/project/dependencyManagement/dependencies/dependency");
			List<Id> managedDependencies = new ArrayList<>();
			List<Bom> imports = new ArrayList<>();
			for (Node dependency : dependencyNodes) {
				String groupId = properties.replace(dependency.textAt("groupId"));
				String artifactId = properties.replace(dependency.textAt("artifactId"));
				String version = properties.replace(dependency.textAt("version"));
				String classifier = properties.replace(dependency.textAt("classifier"));
				String scope = properties.replace(dependency.textAt("scope"));
				Bom importedBom = null;
				if ("import".equals(scope)) {
					String type = properties.replace(dependency.textAt("type"));
					if ("pom".equals(type)) {
						importedBom = bomFrom(resolveBom(groupId + ":" + artifactId + ":" + version));
					}
				}
				if (importedBom != null) {
					imports.add(importedBom);
				}
				else {
					managedDependencies.add(new Id(groupId, artifactId, version, classifier));
				}
			}
			String groupId = bom.textAt("/project/groupId");
			if ((groupId == null || groupId.isEmpty()) && parent != null) {
				groupId = parent.id().groupId();
			}
			String artifactId = bom.textAt("/project/artifactId");
			String version = bom.textAt("/project/version");
			if ((version == null || version.isEmpty()) && parent != null) {
				version = parent.id().version();
			}
			return new Bom(new Id(groupId, artifactId, version), parent, managedDependencies, imports);
		}
		catch (Exception ex) {
			throw new RuntimeException(ex);
		}
	}

	private Node nodeFrom(String coordinates) {
		return nodeFrom(resolveBom(coordinates));
	}

	private Node nodeFrom(File bomFile) {
		try {
			Document document = this.documentBuilder.parse(bomFile);
			return new Node(document);
		}
		catch (Exception ex) {
			throw new RuntimeException(ex);
		}
	}

	private File parentBomFile(Node bom) {
		Node parent = bom.nodeAt("/project/parent");
		if (parent != null) {
			String parentGroupId = parent.textAt("groupId");
			String parentArtifactId = parent.textAt("artifactId");
			String parentVersion = parent.textAt("version");
			return resolveBom(parentGroupId + ":" + parentArtifactId + ":" + parentVersion);
		}
		return null;
	}

	private static final class Node {

		private final XPath xpath;

		private final org.w3c.dom.Node delegate;

		private Node(org.w3c.dom.Node delegate) {
			this(delegate, XPathFactory.newInstance().newXPath());
		}

		private Node(org.w3c.dom.Node delegate, XPath xpath) {
			this.delegate = delegate;
			this.xpath = xpath;
		}

		private String textAt(String expression) {
			String text = (String) evaluate(expression + "/text()", XPathConstants.STRING);
			return (text != null && !text.isBlank()) ? text : null;
		}

		private Node nodeAt(String expression) {
			org.w3c.dom.Node result = (org.w3c.dom.Node) evaluate(expression, XPathConstants.NODE);
			return (result != null) ? new Node(result, this.xpath) : null;
		}

		private List<Node> nodesAt(String expression) {
			NodeList nodes = (NodeList) evaluate(expression, XPathConstants.NODESET);
			List<Node> things = new ArrayList<>(nodes.getLength());
			for (int i = 0; i < nodes.getLength(); i++) {
				things.add(new Node(nodes.item(i), this.xpath));
			}
			return things;
		}

		private Object evaluate(String expression, QName type) {
			try {
				return this.xpath.evaluate(expression, this.delegate, type);
			}
			catch (XPathExpressionException ex) {
				throw new RuntimeException(ex);
			}
		}

		private String name() {
			return this.delegate.getNodeName();
		}

		private String textContent() {
			return this.delegate.getTextContent();
		}

	}

	private static final class Properties {

		private final Map<String, String> properties;

		private Properties(Map<String, String> properties) {
			this.properties = properties;
		}

		private static Properties from(Node bom, Function<String, Node> resolver) {
			try {
				Map<String, String> properties = new HashMap<>();
				Node current = bom;
				while (current != null) {
					String groupId = current.textAt("/project/groupId");
					if (groupId != null && !groupId.isEmpty()) {
						properties.putIfAbsent("${project.groupId}", groupId);
					}
					String version = current.textAt("/project/version");
					if (version != null && !version.isEmpty()) {
						properties.putIfAbsent("${project.version}", version);
					}
					List<Node> propertyNodes = current.nodesAt("/project/properties/*");
					for (Node property : propertyNodes) {
						properties.putIfAbsent("${%s}".formatted(property.name()), property.textContent());
					}
					current = parent(current, resolver);
				}
				return new Properties(properties);
			}
			catch (Exception ex) {
				throw new RuntimeException(ex);
			}
		}

		private static Node parent(Node current, Function<String, Node> resolver) {
			Node parent = current.nodeAt("/project/parent");
			if (parent != null) {
				String parentGroupId = parent.textAt("groupId");
				String parentArtifactId = parent.textAt("artifactId");
				String parentVersion = parent.textAt("version");
				return resolver.apply(parentGroupId + ":" + parentArtifactId + ":" + parentVersion);
			}
			return null;
		}

		private String replace(String input) {
			if (input != null && input.startsWith("${") && input.endsWith("}")) {
				String value = this.properties.get(input);
				if (value != null) {
					return replace(value);
				}
				throw new IllegalStateException("No replacement for " + input);
			}
			return input;
		}

	}

}
