/*

 * Copyright (c) 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 jdk.internal.module;

import java.io.IOException;

import java.io.UncheckedIOException;

import java.lang.module.ModuleDescriptor;

import java.lang.module.ModuleReader;

import java.lang.module.ModuleReference;

import java.net.URI;

import java.util.Objects;

import java.util.function.Supplier;

/**

 * A ModuleReference implementation that supports referencing a module that

 * is patched and/or can be tied to other modules by means of hashes.

 */

public class ModuleReferenceImpl extends ModuleReference {

    // location of module

    private final URI location;

    // the module reader

    private final Supplier<ModuleReader> readerSupplier;

    // non-null if the module is patched

    private final ModulePatcher patcher;

    // ModuleTarget if the module is OS/architecture specific

    private final ModuleTarget target;

    // the hashes of other modules recorded in this module

    private final ModuleHashes recordedHashes;

    // the function that computes the hash of this module

    private final ModuleHashes.HashSupplier hasher;

    // ModuleResolution flags

    private final ModuleResolution moduleResolution;

    // cached hash of this module to avoid needing to compute it many times

    private byte[] cachedHash;

    /**

     * Constructs a new instance of this class.

     */

    public ModuleReferenceImpl(ModuleDescriptor descriptor,

                               URI location,

                               Supplier<ModuleReader> readerSupplier,

                               ModulePatcher patcher,

                               ModuleTarget target,

                               ModuleHashes recordedHashes,

                               ModuleHashes.HashSupplier hasher,

                               ModuleResolution moduleResolution)

    {

        super(descriptor, Objects.requireNonNull(location));

        this.location = location;

        this.readerSupplier = readerSupplier;

        this.patcher = patcher;

        this.target = target;

        this.recordedHashes = recordedHashes;

        this.hasher = hasher;

        this.moduleResolution = moduleResolution;

    }

    @Override

    public ModuleReader open() throws IOException {

        try {

            return readerSupplier.get();

        } catch (UncheckedIOException e) {

            throw e.getCause();

        }

    }

    /**

     * Returns {@code true} if this module has been patched via --patch-module.

     */

    public boolean isPatched() {

        return (patcher != null);

    }

    /**

     * Returns the ModuleTarget or {@code null} if the no target platform.

     */

    public ModuleTarget moduleTarget() {

        return target;

    }

    /**

     * Returns the hashes recorded in this module or {@code null} if there

     * are no hashes recorded.

     */

    public ModuleHashes recordedHashes() {

        return recordedHashes;

    }

    /**

     * Returns the supplier that computes the hash of this module.

     */

    ModuleHashes.HashSupplier hasher() {

        return hasher;

    }

    /**

     * Returns the ModuleResolution flags.

     */

    public ModuleResolution moduleResolution() {

        return moduleResolution;

    }

    /**

     * Computes the hash of this module. Returns {@code null} if the hash

     * cannot be computed.

     *

     * @throws java.io.UncheckedIOException if an I/O error occurs

     */

    public byte[] computeHash(String algorithm) {

        byte[] result = cachedHash;

        if (result != null)

            return result;

        if (hasher == null)

            return null;

        cachedHash = result = hasher.generate(algorithm);

        return result;

    }

    @Override

    public int hashCode() {

        int hc = hash;

        if (hc == 0) {

            hc = descriptor().hashCode();

            hc = 43 * hc + Objects.hashCode(location);

            hc = 43 * hc + Objects.hashCode(patcher);

            if (hc == 0)

                hc = -1;

            hash = hc;

        }

        return hc;

    }

    private int hash;

    @Override

    public boolean equals(Object ob) {

        if (!(ob instanceof ModuleReferenceImpl))

            return false;

        ModuleReferenceImpl that = (ModuleReferenceImpl)ob;

        // assume module content, recorded hashes, etc. are the same

        // when the modules have equal module descriptors, are at the

        // same location, and are patched by the same patcher.

        return Objects.equals(this.descriptor(), that.descriptor())

                && Objects.equals(this.location, that.location)

                && Objects.equals(this.patcher, that.patcher);

    }

    @Override

    public String toString() {

        StringBuilder sb = new StringBuilder();

        sb.append("[module ");

        sb.append(descriptor().name());

        sb.append(", location=");

        sb.append(location);

        if (isPatched()) sb.append(" (patched)");

        sb.append("]");

        return sb.toString();

    }

}