/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the Elastic License
 * 2.0 and the Server Side Public License, v 1; you may not use this file except
 * in compliance with, at your election, the Elastic License 2.0 or the Server
 * Side Public License, v 1.
 */
package org.elasticsearch.gradle.precommit;

import de.thetaphi.forbiddenapis.cli.CliMain;
import org.apache.commons.io.output.NullOutputStream;
import org.elasticsearch.gradle.OS;
import org.elasticsearch.gradle.dependencies.CompileOnlyResolvePlugin;
import org.gradle.api.DefaultTask;
import org.gradle.api.JavaVersion;
import org.gradle.api.artifacts.Configuration;
import org.gradle.api.artifacts.Dependency;
import org.gradle.api.file.FileCollection;
import org.gradle.api.file.FileTree;
import org.gradle.api.provider.Property;
import org.gradle.api.specs.Spec;
import org.gradle.api.tasks.CacheableTask;
import org.gradle.api.tasks.Classpath;
import org.gradle.api.tasks.CompileClasspath;
import org.gradle.api.tasks.Input;
import org.gradle.api.tasks.InputFile;
import org.gradle.api.tasks.InputFiles;
import org.gradle.api.tasks.Internal;
import org.gradle.api.tasks.Optional;
import org.gradle.api.tasks.OutputFile;
import org.gradle.api.tasks.PathSensitive;
import org.gradle.api.tasks.PathSensitivity;
import org.gradle.api.tasks.SkipWhenEmpty;
import org.gradle.api.tasks.TaskAction;
import org.gradle.process.ExecResult;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Set;
import java.util.TreeSet;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import java.util.stream.Stream;

@CacheableTask
public class ThirdPartyAuditTask extends DefaultTask {

    private static final Pattern MISSING_CLASS_PATTERN = Pattern.compile(
        "WARNING: Class '(.*)' cannot be loaded \\(.*\\)\\. Please fix the classpath!"
    );

    private static final Pattern VIOLATION_PATTERN = Pattern.compile("\\s\\sin ([a-zA-Z0-9$.]+) \\(.*\\)");
    private static final int SIG_KILL_EXIT_VALUE = 137;
    private static final List<Integer> EXPECTED_EXIT_CODES = Arrays.asList(
        CliMain.EXIT_SUCCESS,
        CliMain.EXIT_VIOLATION,
        CliMain.EXIT_UNSUPPORTED_JDK
    );
    private static final String JDK_JAR_HELL_MAIN_CLASS = "org.elasticsearch.bootstrap.JdkJarHellCheck";

    private Set<String> missingClassExcludes = new TreeSet<>();

    private Set<String> violationsExcludes = new TreeSet<>();

    private Set<String> jdkJarHellExcludes = new TreeSet<>();

    private File signatureFile;

    private String javaHome;

    private FileCollection jdkJarHellClasspath;

    private final Property<JavaVersion> targetCompatibility = getProject().getObjects().property(JavaVersion.class);

    @Input
    public Property<JavaVersion> getTargetCompatibility() {
        return targetCompatibility;
    }

    @InputFiles
    @PathSensitive(PathSensitivity.NAME_ONLY)
    public Configuration getForbiddenAPIsConfiguration() {
        return getProject().getConfigurations().getByName("forbiddenApisCliJar");
    }

    @InputFile
    @PathSensitive(PathSensitivity.NONE)
    public File getSignatureFile() {
        return signatureFile;
    }

    public void setSignatureFile(File signatureFile) {
        this.signatureFile = signatureFile;
    }

    @Input
    @Optional
    public String getJavaHome() {
        return javaHome;
    }

    public void setJavaHome(String javaHome) {
        this.javaHome = javaHome;
    }

    @Internal
    public File getJarExpandDir() {
        return new File(new File(getProject().getBuildDir(), "precommit/thirdPartyAudit"), getName());
    }

    @OutputFile
    public File getSuccessMarker() {
        return new File(getProject().getBuildDir(), "markers/" + getName());
    }

    // We use compile classpath normalization here because class implementation changes are irrelevant for the purposes of jdk jar hell.
    // We only care about the runtime classpath ABI here.
    @CompileClasspath
    public FileCollection getJdkJarHellClasspath() {
        return jdkJarHellClasspath.filter(File::exists);
    }

    public void setJdkJarHellClasspath(FileCollection jdkJarHellClasspath) {
        this.jdkJarHellClasspath = jdkJarHellClasspath;
    }

    public void ignoreMissingClasses(String... classesOrPackages) {
        if (classesOrPackages.length == 0) {
            missingClassExcludes = null;
            return;
        }
        if (missingClassExcludes == null) {
            missingClassExcludes = new TreeSet<>();
        }
        for (String each : classesOrPackages) {
            missingClassExcludes.add(each);
        }
    }

    public void ignoreViolations(String... violatingClasses) {
        for (String each : violatingClasses) {
            violationsExcludes.add(each);
        }
    }

    public void ignoreJarHellWithJDK(String... classes) {
        for (String each : classes) {
            jdkJarHellExcludes.add(each);
        }
    }

    @Input
    public Set<String> getJdkJarHellExcludes() {
        return jdkJarHellExcludes;
    }

    @Input
    @Optional
    public Set<String> getMissingClassExcludes() {
        return missingClassExcludes;
    }

    @Classpath
    @SkipWhenEmpty
    public Set<File> getJarsToScan() {
        // These are SelfResolvingDependency, and some of them backed by file collections, like the Gradle API files,
        // or dependencies added as `files(...)`, we can't be sure if those are third party or not.
        // err on the side of scanning these to make sure we don't miss anything
        Spec<Dependency> reallyThirdParty = dep -> dep.getGroup() != null && dep.getGroup().startsWith("org.elasticsearch") == false;
        Set<File> jars = getRuntimeConfiguration().getResolvedConfiguration().getFiles(reallyThirdParty);
        Set<File> compileOnlyConfiguration = getProject().getConfigurations()
            .getByName(CompileOnlyResolvePlugin.RESOLVEABLE_COMPILE_ONLY_CONFIGURATION_NAME)
            .getResolvedConfiguration()
            .getFiles(reallyThirdParty);
        // don't scan provided dependencies that we already scanned, e.x. don't scan cores dependencies for every plugin
        if (compileOnlyConfiguration != null) {
            jars.removeAll(compileOnlyConfiguration);
        }
        return jars;
    }

    @TaskAction
    public void runThirdPartyAudit() throws IOException {
        Set<File> jars = getJarsToScan();

        extractJars(jars);

        final String forbiddenApisOutput = runForbiddenAPIsCli();

        final Set<String> missingClasses = new TreeSet<>();
        Matcher missingMatcher = MISSING_CLASS_PATTERN.matcher(forbiddenApisOutput);
        while (missingMatcher.find()) {
            missingClasses.add(missingMatcher.group(1));
        }

        final Set<String> violationsClasses = new TreeSet<>();
        Matcher violationMatcher = VIOLATION_PATTERN.matcher(forbiddenApisOutput);
        while (violationMatcher.find()) {
            violationsClasses.add(violationMatcher.group(1));
        }

        Set<String> jdkJarHellClasses = runJdkJarHellCheck();

        if (missingClassExcludes != null) {
            long bogousExcludesCount = Stream.concat(missingClassExcludes.stream(), violationsExcludes.stream())
                .filter(each -> missingClasses.contains(each) == false)
                .filter(each -> violationsClasses.contains(each) == false)
                .count();
            if (bogousExcludesCount != 0 && bogousExcludesCount == missingClassExcludes.size() + violationsExcludes.size()) {
                logForbiddenAPIsOutput(forbiddenApisOutput);
                throw new IllegalStateException(
                    "All excluded classes seem to have no issues. " + "This is sometimes an indication that the check silently failed"
                );
            }
            assertNoPointlessExclusions("are not missing", missingClassExcludes, missingClasses);
            missingClasses.removeAll(missingClassExcludes);
        }
        assertNoPointlessExclusions("have no violations", violationsExcludes, violationsClasses);
        assertNoPointlessExclusions("do not generate jar hell with the JDK", jdkJarHellExcludes, jdkJarHellClasses);

        if (missingClassExcludes == null && (missingClasses.isEmpty() == false)) {
            getLogger().info("Found missing classes, but task is configured to ignore all of them:\n {}", formatClassList(missingClasses));
            missingClasses.clear();
        }

        violationsClasses.removeAll(violationsExcludes);
        if (missingClasses.isEmpty() && violationsClasses.isEmpty()) {
            getLogger().info("Third party audit passed successfully");
        } else {
            logForbiddenAPIsOutput(forbiddenApisOutput);
            if (missingClasses.isEmpty() == false) {
                getLogger().error("Missing classes:\n{}", formatClassList(missingClasses));
            }
            if (violationsClasses.isEmpty() == false) {
                getLogger().error("Classes with violations:\n{}", formatClassList(violationsClasses));
            }
            throw new IllegalStateException("Audit of third party dependencies failed");
        }

        assertNoJarHell(jdkJarHellClasses);

        // Mark successful third party audit check
        getSuccessMarker().getParentFile().mkdirs();
        Files.write(getSuccessMarker().toPath(), new byte[] {});
    }

    private void logForbiddenAPIsOutput(String forbiddenApisOutput) {
        getLogger().error("Forbidden APIs output:\n{}==end of forbidden APIs==", forbiddenApisOutput);
    }

    private void throwNotConfiguredCorrectlyException() {
        throw new IllegalArgumentException("Audit of third party dependencies is not configured correctly");
    }

    private void extractJars(Set<File> jars) {
        File jarExpandDir = getJarExpandDir();
        // We need to clean up to make sure old dependencies don't linger
        getProject().delete(jarExpandDir);

        jars.forEach(jar -> {
            FileTree jarFiles = getProject().zipTree(jar);
            getProject().copy(spec -> {
                spec.from(jarFiles);
                spec.into(jarExpandDir);
                // exclude classes from multi release jars
                spec.exclude("META-INF/versions/**");
            });
            // Deal with multi release jars:
            // The order is important, we iterate here so we don't depend on the order in which Gradle executes the spec
            // We extract multi release jar classes ( if these exist ) going from 9 - the first to support them, to the
            // current `targetCompatibility` version.
            // Each extract will overwrite the top level classes that existed before it, the result is that we end up
            // with a single version of the class in `jarExpandDir`.
            // This will be the closes version to `targetCompatibility`, the same class that would be loaded in a JVM
            // that has `targetCompatibility` version.
            // This means we only scan classes that would be loaded into `targetCompatibility`, and don't look at any
            // pther version specific implementation of said classes.
            IntStream.rangeClosed(
                Integer.parseInt(JavaVersion.VERSION_1_9.getMajorVersion()),
                Integer.parseInt(targetCompatibility.get().getMajorVersion())
            ).forEach(majorVersion -> getProject().copy(spec -> {
                spec.from(getProject().zipTree(jar));
                spec.into(jarExpandDir);
                String metaInfPrefix = "META-INF/versions/" + majorVersion;
                spec.include(metaInfPrefix + "/**");
                // Drop the version specific prefix
                spec.eachFile(details -> details.setPath(details.getPath().replace(metaInfPrefix, "")));
                spec.setIncludeEmptyDirs(false);
            }));
        });
    }

    private void assertNoJarHell(Set<String> jdkJarHellClasses) {
        jdkJarHellClasses.removeAll(jdkJarHellExcludes);
        if (jdkJarHellClasses.isEmpty() == false) {
            throw new IllegalStateException(
                "Audit of third party dependencies failed:\n" + "  Jar Hell with the JDK:\n" + formatClassList(jdkJarHellClasses)
            );
        }
    }

    private void assertNoPointlessExclusions(String specifics, Set<String> excludes, Set<String> problematic) {
        String notMissing = excludes.stream()
            .filter(each -> problematic.contains(each) == false)
            .map(each -> "  * " + each)
            .collect(Collectors.joining("\n"));
        if (notMissing.isEmpty() == false) {
            getLogger().error("Unnecessary exclusions, following classes " + specifics + ":\n {}", notMissing);
            throw new IllegalStateException("Third party audit task is not configured correctly");
        }
    }

    private String formatClassList(Set<String> classList) {
        return classList.stream().map(name -> "  * " + name).sorted().collect(Collectors.joining("\n"));
    }

    private String runForbiddenAPIsCli() throws IOException {
        ByteArrayOutputStream errorOut = new ByteArrayOutputStream();
        ExecResult result = getProject().javaexec(spec -> {
            if (javaHome != null) {
                spec.setExecutable(javaHome + "/bin/java");
            }
            spec.classpath(
                getForbiddenAPIsConfiguration(),
                getRuntimeConfiguration(),
                getProject().getConfigurations().getByName(CompileOnlyResolvePlugin.RESOLVEABLE_COMPILE_ONLY_CONFIGURATION_NAME)
            );
            spec.jvmArgs("-Xmx1g");
            spec.setMain("de.thetaphi.forbiddenapis.cli.CliMain");
            spec.args("-f", getSignatureFile().getAbsolutePath(), "-d", getJarExpandDir(), "--allowmissingclasses");
            spec.setErrorOutput(errorOut);
            if (getLogger().isInfoEnabled() == false) {
                spec.setStandardOutput(new NullOutputStream());
            }
            spec.setIgnoreExitValue(true);
        });
        if (OS.current().equals(OS.LINUX) && result.getExitValue() == SIG_KILL_EXIT_VALUE) {
            throw new IllegalStateException("Third party audit was killed buy SIGKILL, could be a victim of the Linux OOM killer");
        }
        final String forbiddenApisOutput;
        try (ByteArrayOutputStream outputStream = errorOut) {
            forbiddenApisOutput = outputStream.toString(StandardCharsets.UTF_8.name());
        }
        if (EXPECTED_EXIT_CODES.contains(result.getExitValue()) == false) {
            throw new IllegalStateException("Forbidden APIs cli failed: " + forbiddenApisOutput);
        }
        return forbiddenApisOutput;
    }

    private Set<String> runJdkJarHellCheck() throws IOException {
        ByteArrayOutputStream standardOut = new ByteArrayOutputStream();
        ExecResult execResult = getProject().javaexec(spec -> {
            spec.classpath(
                jdkJarHellClasspath,
                getRuntimeConfiguration(),
                getProject().getConfigurations().getByName(CompileOnlyResolvePlugin.RESOLVEABLE_COMPILE_ONLY_CONFIGURATION_NAME)
            );

            spec.setMain(JDK_JAR_HELL_MAIN_CLASS);
            spec.args(getJarExpandDir());
            spec.setIgnoreExitValue(true);
            if (javaHome != null) {
                spec.setExecutable(javaHome + "/bin/java");
            }
            spec.setStandardOutput(standardOut);
        });
        if (execResult.getExitValue() == 0) {
            return Collections.emptySet();
        }
        final String jdkJarHellCheckList;
        try (ByteArrayOutputStream outputStream = standardOut) {
            jdkJarHellCheckList = outputStream.toString(StandardCharsets.UTF_8.name());
        }
        return new TreeSet<>(Arrays.asList(jdkJarHellCheckList.split("\\r?\\n")));
    }

    private Configuration getRuntimeConfiguration() {
        Configuration runtime = getProject().getConfigurations().findByName("runtimeClasspath");
        if (runtime == null) {
            return getProject().getConfigurations().getByName("testCompileClasspath");
        }
        return runtime;
    }
}
