/*
 * 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.web.server.servlet;

import java.io.File;
import java.net.JarURLConnection;
import java.net.URL;
import java.net.URLConnection;
import java.security.CodeSource;
import java.util.Arrays;
import java.util.Locale;
import java.util.function.Function;

import org.apache.commons.logging.Log;
import org.jspecify.annotations.Nullable;

/**
 * Manages a {@link ServletWebServerFactory} document root.
 *
 * @author Phillip Webb
 * @since 4.0.0
 */
public class DocumentRoot {

	private static final String WAR_SOURCE_DIRECTORY_ENVIRONMENT_VARIABLE = "WAR_SOURCE_DIRECTORY";

	private final Log logger;

	private final File rootDirectory;

	private final String[] commonDocRoots;

	private @Nullable File directory;

	public DocumentRoot(Log logger) {
		this(logger, new File("."), System::getenv);
	}

	DocumentRoot(Log logger, File rootDirectory, Function<String, @Nullable String> systemEnvironment) {
		this.logger = logger;
		this.rootDirectory = rootDirectory;
		this.commonDocRoots = new String[] { getWarSourceDirectory(systemEnvironment), "public", "static" };
	}

	private static String getWarSourceDirectory(Function<String, @Nullable String> systemEnvironment) {
		String name = systemEnvironment.apply(WAR_SOURCE_DIRECTORY_ENVIRONMENT_VARIABLE);
		return (name != null) ? name : "src/main/webapp";
	}

	@Nullable File getDirectory() {
		return this.directory;
	}

	public void setDirectory(@Nullable File directory) {
		this.directory = directory;
	}

	/**
	 * Returns the absolute document root when it points to a valid directory, logging a
	 * warning and returning {@code null} otherwise.
	 * @return the valid document root
	 */
	public final @Nullable File getValidDirectory() {
		File file = this.directory;
		file = (file != null) ? file : getWarFileDocumentRoot();
		file = (file != null) ? file : getExplodedWarFileDocumentRoot();
		file = (file != null) ? file : getCommonDocumentRoot();
		if (file == null && this.logger.isDebugEnabled()) {
			logNoDocumentRoots();
		}
		else if (this.logger.isDebugEnabled()) {
			this.logger.debug("Document root: " + file);
		}
		return file;
	}

	private @Nullable File getWarFileDocumentRoot() {
		return getArchiveFileDocumentRoot(".war");
	}

	private @Nullable File getArchiveFileDocumentRoot(String extension) {
		File file = getCodeSourceArchive();
		if (this.logger.isDebugEnabled()) {
			this.logger.debug("Code archive: " + file);
		}
		if (file != null && file.exists() && !file.isDirectory()
				&& file.getName().toLowerCase(Locale.ENGLISH).endsWith(extension)) {
			return file.getAbsoluteFile();
		}
		return null;
	}

	private @Nullable File getExplodedWarFileDocumentRoot() {
		return getExplodedWarFileDocumentRoot(getCodeSourceArchive());
	}

	private @Nullable File getCodeSourceArchive() {
		return getCodeSourceArchive(getClass().getProtectionDomain().getCodeSource());
	}

	@Nullable File getCodeSourceArchive(@Nullable CodeSource codeSource) {
		try {
			URL location = (codeSource != null) ? codeSource.getLocation() : null;
			if (location == null) {
				return null;
			}
			String path;
			URLConnection connection = location.openConnection();
			if (connection instanceof JarURLConnection jarURLConnection) {
				path = jarURLConnection.getJarFile().getName();
			}
			else {
				path = location.toURI().getPath();
			}
			int index = path.indexOf("!/");
			if (index != -1) {
				path = path.substring(0, index);
			}
			return new File(path);
		}
		catch (Exception ex) {
			return null;
		}
	}

	final @Nullable File getExplodedWarFileDocumentRoot(@Nullable File codeSourceFile) {
		if (this.logger.isDebugEnabled()) {
			this.logger.debug("Code archive: " + codeSourceFile);
		}
		if (codeSourceFile != null && codeSourceFile.exists()) {
			String path = codeSourceFile.getAbsolutePath();
			int webInfPathIndex = path.indexOf(File.separatorChar + "WEB-INF" + File.separatorChar);
			if (webInfPathIndex >= 0) {
				path = path.substring(0, webInfPathIndex);
				return new File(path);
			}
		}
		return null;
	}

	private @Nullable File getCommonDocumentRoot() {
		for (String commonDocRoot : this.commonDocRoots) {
			File root = new File(this.rootDirectory, commonDocRoot);
			if (root.exists() && root.isDirectory()) {
				return root.getAbsoluteFile();
			}
		}
		return null;
	}

	private void logNoDocumentRoots() {
		this.logger.debug("None of the document roots " + Arrays.asList(this.commonDocRoots)
				+ " point to a directory and will be ignored.");
	}

}
