/*

 * Copyright (c) 2014, 2016, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package java.lang.module;

import java.io.BufferedInputStream;

import java.io.BufferedReader;

import java.io.File;

import java.io.IOException;

import java.io.InputStream;

import java.io.InputStreamReader;

import java.io.UncheckedIOException;

import java.lang.module.ModuleDescriptor.Requires;

import java.nio.file.DirectoryStream;

import java.nio.file.Files;

import java.nio.file.NoSuchFileException;

import java.nio.file.Path;

import java.nio.file.attribute.BasicFileAttributes;

import java.util.Collections;

import java.util.HashMap;

import java.util.HashSet;

import java.util.Map;

import java.util.Objects;

import java.util.Optional;

import java.util.Set;

import java.util.jar.Attributes;

import java.util.jar.JarEntry;

import java.util.jar.JarFile;

import java.util.jar.Manifest;

import java.util.regex.Matcher;

import java.util.regex.Pattern;

import java.util.stream.Collectors;

import java.util.stream.Stream;

import java.util.zip.ZipEntry;

import java.util.zip.ZipFile;

import jdk.internal.module.Checks;

import jdk.internal.module.ConfigurableModuleFinder;

import jdk.internal.perf.PerfCounter;

/**

 * A {@code ModuleFinder} that locates modules on the file system by searching

 * a sequence of directories or packaged modules.

 *

 * The {@code ModuleFinder} can be configured to work in either the run-time

 * or link-time phases. In both cases it locates modular JAR and exploded

 * modules. When configured for link-time then it additionally locates

 * modules in JMOD files.

 */

class ModulePath implements ConfigurableModuleFinder {

    private static final String MODULE_INFO = "module-info.class";

    // the entries on this module path

    private final Path[] entries;

    private int next;

    // true if in the link phase

    private boolean isLinkPhase;

    // map of module name to module reference map for modules already located

    private final Map<String, ModuleReference> cachedModules = new HashMap<>();

    ModulePath(Path... entries) {

        this.entries = entries.clone();

        for (Path entry : this.entries) {

            Objects.requireNonNull(entry);

        }

    }

    @Override

    public void configurePhase(Phase phase) {

        isLinkPhase = (phase == Phase.LINK_TIME);

    }

    @Override

    public Optional<ModuleReference> find(String name) {

        Objects.requireNonNull(name);

        // try cached modules

        ModuleReference m = cachedModules.get(name);

        if (m != null)

            return Optional.of(m);

        // the module may not have been encountered yet

        while (hasNextEntry()) {

            scanNextEntry();

            m = cachedModules.get(name);

            if (m != null)

                return Optional.of(m);

        }

        return Optional.empty();

    }

    @Override

    public Set<ModuleReference> findAll() {

        // need to ensure that all entries have been scanned

        while (hasNextEntry()) {

            scanNextEntry();

        }

        return cachedModules.values().stream().collect(Collectors.toSet());

    }

    /**

     * Returns {@code true} if there are additional entries to scan

     */

    private boolean hasNextEntry() {

        return next < entries.length;

    }

    /**

     * Scans the next entry on the module path. A no-op if all entries have

     * already been scanned.

     *

     * @throws FindException if an error occurs scanning the next entry

     */

    private void scanNextEntry() {

        if (hasNextEntry()) {

            long t0 = System.nanoTime();

            Path entry = entries[next];

            Map<String, ModuleReference> modules = scan(entry);

            next++;

            // update cache, ignoring duplicates

            int initialSize = cachedModules.size();

            for (Map.Entry<String, ModuleReference> e : modules.entrySet()) {

                cachedModules.putIfAbsent(e.getKey(), e.getValue());

            }

            // update counters

            int added = cachedModules.size() - initialSize;

            moduleCount.add(added);

            scanTime.addElapsedTimeFrom(t0);

        }

    }

    /**

     * Scan the given module path entry. If the entry is a directory then it is

     * a directory of modules or an exploded module. If the entry is a regular

     * file then it is assumed to be a packaged module.

     *

     * @throws FindException if an error occurs scanning the entry

     */

    private Map<String, ModuleReference> scan(Path entry) {

        BasicFileAttributes attrs;

        try {

            attrs = Files.readAttributes(entry, BasicFileAttributes.class);

        } catch (NoSuchFileException e) {

            return Collections.emptyMap();

        } catch (IOException ioe) {

            throw new FindException(ioe);

        }

        try {

            if (attrs.isDirectory()) {

                Path mi = entry.resolve(MODULE_INFO);

                if (!Files.exists(mi)) {

                    // does not exist or unable to determine so assume a

                    // directory of modules

                    return scanDirectory(entry);

                }

            }

            if (attrs.isRegularFile() || attrs.isDirectory()) {

                // packaged or exploded module

                ModuleReference mref = readModule(entry, attrs);

                if (mref != null) {

                    String name = mref.descriptor().name();

                    return Collections.singletonMap(name, mref);

                }

            }

            // not recognized

            throw new FindException("Unrecognized module: " + entry);

        } catch (IOException ioe) {

            throw new FindException(ioe);

        }

    }

    /**

     * Scans the given directory for packaged or exploded modules.

     *

     * @return a map of module name to ModuleReference for the modules found

     *         in the directory

     *

     * @throws IOException if an I/O error occurs

     * @throws FindException if an error occurs scanning the entry or the

     *         directory contains two or more modules with the same name

     */

    private Map<String, ModuleReference> scanDirectory(Path dir)

        throws IOException

    {

        // The map of name -> mref of modules found in this directory.

        Map<String, ModuleReference> nameToReference = new HashMap<>();

        try (DirectoryStream<Path> stream = Files.newDirectoryStream(dir)) {

            for (Path entry : stream) {

                BasicFileAttributes attrs;

                try {

                    attrs = Files.readAttributes(entry, BasicFileAttributes.class);

                } catch (NoSuchFileException ignore) {

                    // file has been removed or moved, ignore for now

                    continue;

                }

                ModuleReference mref = readModule(entry, attrs);

                // module found

                if (mref != null) {

                    // can have at most one version of a module in the directory

                    String name = mref.descriptor().name();

                    if (nameToReference.put(name, mref) != null) {

                        throw new FindException("Two versions of module "

                                + name + " found in " + dir);

                    }

                }

            }

        }

        return nameToReference;

    }

    /**

     * Locates a packaged or exploded module, returning a {@code ModuleReference}

     * to the module. Returns {@code null} if the module is not recognized

     * as a packaged or exploded module.

     *

     * @throws IOException if an I/O error occurs

     * @throws FindException if an error occurs parsing the module descriptor

     */

    private ModuleReference readModule(Path entry, BasicFileAttributes attrs)

        throws IOException

    {

        try {

            ModuleReference mref = null;

            if (attrs.isDirectory()) {

                mref = readExplodedModule(entry);

            } if (attrs.isRegularFile()) {

                if (entry.toString().endsWith(".jar")) {

                    mref = readJar(entry);

                } else if (isLinkPhase && entry.toString().endsWith(".jmod")) {

                    mref = readJMod(entry);

                }

            }

            return mref;

        } catch (InvalidModuleDescriptorException e) {

            throw new FindException("Error reading module: " + entry, e);

        }

    }

    // -- jmod files --

    private Set<String> jmodPackages(ZipFile zf) {

        return zf.stream()

            .filter(e -> e.getName().startsWith("classes/") &&

                    e.getName().endsWith(".class"))

            .map(e -> toPackageName(e))

            .filter(pkg -> pkg.length() > 0) // module-info

            .distinct()

            .collect(Collectors.toSet());

    }

    /**

     * Returns a {@code ModuleReference} to a module in jmod file on the

     * file system.

     */

    private ModuleReference readJMod(Path file) throws IOException {

        try (ZipFile zf = new ZipFile(file.toString())) {

            ZipEntry ze = zf.getEntry("classes/" + MODULE_INFO);

            if (ze == null) {

                throw new IOException(MODULE_INFO + " is missing: " + file);

            }

            ModuleDescriptor md;

            try (InputStream in = zf.getInputStream(ze)) {

                md = ModuleDescriptor.read(in, () -> jmodPackages(zf));

            }

            return ModuleReferences.newJModModule(md, file);

        }

    }

    // -- JAR files --

    private static final String SERVICES_PREFIX = "META-INF/services/";

    /**

     * Returns a container with the service type corresponding to the name of

     * a services configuration file.

     *

     * For example, if called with "META-INF/services/p.S" then this method

     * returns a container with the value "p.S".

     */

    private Optional<String> toServiceName(String cf) {

        assert cf.startsWith(SERVICES_PREFIX);

        int index = cf.lastIndexOf("/") + 1;

        if (index < cf.length()) {

            String prefix = cf.substring(0, index);

            if (prefix.equals(SERVICES_PREFIX)) {

                String sn = cf.substring(index);

                if (Checks.isJavaIdentifier(sn))

                    return Optional.of(sn);

            }

        }

        return Optional.empty();

    }

    /**

     * Reads the next line from the given reader and trims it of comments and

     * leading/trailing white space.

     *

     * Returns null if the reader is at EOF.

     */

    private String nextLine(BufferedReader reader) throws IOException {

        String ln = reader.readLine();

        if (ln != null) {

            int ci = ln.indexOf('#');

            if (ci >= 0)

                ln = ln.substring(0, ci);

            ln = ln.trim();

        }

        return ln;

    }

    /**

     * Treat the given JAR file as a module as follows:

     *

     * 1. The module name (and optionally the version) is derived from the file

     *    name of the JAR file

     * 2. The packages of all .class files in the JAR file are exported

     * 3. It has no module-private/concealed packages

     * 4. The contents of any META-INF/services configuration files are mapped

     *    to "provides" declarations

     * 5. The Main-Class attribute in the main attributes of the JAR manifest

     *    is mapped to the module descriptor mainClass

     *

     * @apiNote This needs to move to somewhere where it can be used by tools,

     * maybe even a standard API if automatic modules are a Java SE feature.

     */

    private ModuleDescriptor deriveModuleDescriptor(JarFile jf)

        throws IOException

    {

        // Derive module name and version from JAR file name

        String fn = jf.getName();

        int i = fn.lastIndexOf(File.separator);

        if (i != -1)

            fn = fn.substring(i+1);

        // drop .jar

        String mn = fn.substring(0, fn.length()-4);

        String vs = null;

        // find first occurrence of -${NUMBER}. or -${NUMBER}$

        Matcher matcher = Pattern.compile("-(\\d+(\\.|$))").matcher(mn);

        if (matcher.find()) {

            int start = matcher.start();

            // attempt to parse the tail as a version string

            try {

                String tail = mn.substring(start+1);

                ModuleDescriptor.Version.parse(tail);

                vs = tail;

            } catch (IllegalArgumentException ignore) { }

            mn = mn.substring(0, start);

        }

        // finally clean up the module name

        mn =  mn.replaceAll("[^A-Za-z0-9]", ".")  // replace non-alphanumeric

                .replaceAll("(\\.)(\\1)+", ".")   // collapse repeating dots

                .replaceAll("^\\.", "")           // drop leading dots

                .replaceAll("\\.$", "");          // drop trailing dots

        // Builder throws IAE if module name is empty or invalid

        ModuleDescriptor.Builder builder

            = new ModuleDescriptor.Builder(mn, true)

                .requires(Requires.Modifier.MANDATED, "java.base");

        if (vs != null)

            builder.version(vs);

        // scan the entries in the JAR file to locate the .class and service

        // configuration file

        Stream<String> stream = jf.stream()

            .map(e -> e.getName())

            .filter(e -> (e.endsWith(".class") || e.startsWith(SERVICES_PREFIX)))

            .distinct();

        Map<Boolean, Set<String>> map

            = stream.collect(Collectors.partitioningBy(s -> s.endsWith(".class"),

                             Collectors.toSet()));

        Set<String> classFiles = map.get(Boolean.TRUE);

        Set<String> configFiles = map.get(Boolean.FALSE);

        // all packages are exported

        classFiles.stream()

            .map(c -> toPackageName(c))

            .distinct()

            .forEach(p -> builder.exports(p));

        // map names of service configuration files to service names

        Set<String> serviceNames = configFiles.stream()

            .map(this::toServiceName)

            .filter(Optional::isPresent)

            .map(Optional::get)

            .collect(Collectors.toSet());

        // parse each service configuration file

        for (String sn : serviceNames) {

            JarEntry entry = jf.getJarEntry(SERVICES_PREFIX + sn);

            Set<String> providerClasses = new HashSet<>();

            try (InputStream in = jf.getInputStream(entry)) {

                BufferedReader reader

                    = new BufferedReader(new InputStreamReader(in, "UTF-8"));

                String cn;

                while ((cn = nextLine(reader)) != null) {

                    if (Checks.isJavaIdentifier(cn)) {

                        providerClasses.add(cn);

                    }

                }

            }

            if (!providerClasses.isEmpty())

                builder.provides(sn, providerClasses);

        }

        // Main-Class attribute if it exists

        Manifest man = jf.getManifest();

        if (man != null) {

            Attributes attrs = man.getMainAttributes();

            String mainClass = attrs.getValue(Attributes.Name.MAIN_CLASS);

            if (mainClass != null)

                builder.mainClass(mainClass);

        }

        return builder.build();

    }

    private Set<String> jarPackages(JarFile jf) {

        return jf.stream()

            .filter(e -> e.getName().endsWith(".class"))

            .map(e -> toPackageName(e))

            .filter(pkg -> pkg.length() > 0)   // module-info

            .distinct()

            .collect(Collectors.toSet());

    }

    /**

     * Returns a {@code ModuleReference} to a module in modular JAR file on

     * the file system.

     */

    private ModuleReference readJar(Path file) throws IOException {

        try (JarFile jf = new JarFile(file.toString())) {

            ModuleDescriptor md;

            JarEntry entry = jf.getJarEntry(MODULE_INFO);

            if (entry == null) {

                // no module-info.class so treat it as automatic module

                try {

                    md = deriveModuleDescriptor(jf);

                } catch (IllegalArgumentException iae) {

                    throw new FindException(

                        "Unable to derive module descriptor for: "

                        + jf.getName(), iae);

                }

            } else {

                md = ModuleDescriptor.read(jf.getInputStream(entry),

                                           () -> jarPackages(jf));

            }

            return ModuleReferences.newJarModule(md, file);

        }

    }

    // -- exploded directories --

    private Set<String> explodedPackages(Path dir) {

        try {

            return Files.find(dir, Integer.MAX_VALUE,

                              ((path, attrs) -> attrs.isRegularFile() &&

                               path.toString().endsWith(".class")))

                .map(path -> toPackageName(dir.relativize(path)))

                .filter(pkg -> pkg.length() > 0)   // module-info

                .distinct()

                .collect(Collectors.toSet());

        } catch (IOException x) {

            throw new UncheckedIOException(x);

        }

    }