/*
 * 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.ssl.pem;

import java.io.IOException;
import java.io.InputStream;
import java.io.UncheckedIOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;
import java.security.PrivateKey;
import java.security.cert.X509Certificate;
import java.util.List;
import java.util.Objects;
import java.util.regex.Pattern;
import java.util.stream.Collectors;

import org.springframework.core.io.ResourceLoader;
import org.springframework.util.Assert;
import org.springframework.util.StreamUtils;

/**
 * PEM encoded content that can provide {@link X509Certificate certificates} and
 * {@link PrivateKey private keys}.
 *
 * @author Scott Frederick
 * @author Phillip Webb
 * @since 3.2.0
 */
public final class PemContent {

	private static final Pattern PEM_HEADER = Pattern.compile("-+BEGIN\\s+[^-]*-+", Pattern.CASE_INSENSITIVE);

	private static final Pattern PEM_FOOTER = Pattern.compile("-+END\\s+[^-]*-+", Pattern.CASE_INSENSITIVE);

	private final String text;

	private PemContent(String text) {
		this.text = text.lines().map(String::trim).collect(Collectors.joining("\n"));
	}

	/**
	 * Parse and return all {@link X509Certificate certificates} from the PEM content.
	 * Most PEM files either contain a single certificate or a certificate chain.
	 * @return the certificates
	 * @throws IllegalStateException if no certificates could be loaded
	 */
	public List<X509Certificate> getCertificates() {
		return PemCertificateParser.parse(this.text);
	}

	/**
	 * Parse and return the {@link PrivateKey private keys} from the PEM content.
	 * @return the private keys
	 * @throws IllegalStateException if no private key could be loaded
	 */
	public PrivateKey getPrivateKey() {
		return getPrivateKey(null);
	}

	/**
	 * Parse and return the {@link PrivateKey private keys} from the PEM content or
	 * {@code null} if there is no private key.
	 * @param password the password to decrypt the private keys or {@code null}
	 * @return the private keys
	 */
	public PrivateKey getPrivateKey(String password) {
		return PemPrivateKeyParser.parse(this.text, password);
	}

	@Override
	public boolean equals(Object obj) {
		if (this == obj) {
			return true;
		}
		if (obj == null || getClass() != obj.getClass()) {
			return false;
		}
		return Objects.equals(this.text, ((PemContent) obj).text);
	}

	@Override
	public int hashCode() {
		return Objects.hash(this.text);
	}

	@Override
	public String toString() {
		return this.text;
	}

	/**
	 * Load {@link PemContent} from the given content (either the PEM content itself or a
	 * reference to the resource to load).
	 * @param content the content to load
	 * @param resourceLoader the resource loader used to load content
	 * @return a new {@link PemContent} instance
	 * @throws IOException on IO error
	 */
	static PemContent load(String content, ResourceLoader resourceLoader) throws IOException {
		if (content == null) {
			return null;
		}
		if (isPresentInText(content)) {
			return new PemContent(content);
		}
		try (InputStream in = resourceLoader.getResource(content).getInputStream()) {
			return load(in);
		}
		catch (IOException | UncheckedIOException ex) {
			throw new IOException("Error reading certificate or key from file '%s'".formatted(content), ex);
		}
	}

	/**
	 * Load {@link PemContent} from the given {@link Path}.
	 * @param path a path to load the content from
	 * @return the loaded PEM content
	 * @throws IOException on IO error
	 */
	public static PemContent load(Path path) throws IOException {
		Assert.notNull(path, "Path must not be null");
		try (InputStream in = Files.newInputStream(path, StandardOpenOption.READ)) {
			return load(in);
		}
	}

	/**
	 * Load {@link PemContent} from the given {@link InputStream}.
	 * @param in an input stream to load the content from
	 * @return the loaded PEM content
	 * @throws IOException on IO error
	 */
	public static PemContent load(InputStream in) throws IOException {
		return of(StreamUtils.copyToString(in, StandardCharsets.UTF_8));
	}

	/**
	 * Return a new {@link PemContent} instance containing the given text.
	 * @param text the text containing PEM encoded content
	 * @return a new {@link PemContent} instance
	 */
	public static PemContent of(String text) {
		return (text != null) ? new PemContent(text) : null;
	}

	/**
	 * Return if PEM content is present in the given text.
	 * @param text the text to check
	 * @return if the text includes PEM encoded content.
	 */
	public static boolean isPresentInText(String text) {
		return text != null && PEM_HEADER.matcher(text).find() && PEM_FOOTER.matcher(text).find();
	}

}
