/*

 * 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 sun.tools.jar;

import jdk.internal.org.objectweb.asm.*;

import java.io.IOException;

import java.io.InputStream;

import java.security.MessageDigest;

import java.security.NoSuchAlgorithmException;

import java.util.HashMap;

import java.util.HashSet;

import java.util.Map;

import java.util.Set;

/**

 * A FingerPrint is an abstract representation of a JarFile entry that contains

 * information to determine if the entry represents a class or a

 * resource, and whether two entries are identical.  If the FingerPrint represents

 * a class, it also contains information to (1) describe the public API;

 * (2) compare the public API of this class with another class;  (3) determine

 * whether or not it's a nested class and, if so, the name of the associated

 * top level class; and (4) for an canonically ordered set of classes determine

 * if the class versions are compatible.  A set of classes is canonically

 * ordered if the classes in the set have the same name, and the base class

 * precedes the versioned classes and if each versioned class with version

 * {@code n} precedes classes with versions {@code > n} for all versions

 * {@code n}.

 */

final class FingerPrint {

    private static final MessageDigest MD;

    private final byte[] sha1;

    private final ClassAttributes attrs;

    private final boolean isClassEntry;

    private final String entryName;

    static {

        try {

            MD = MessageDigest.getInstance("SHA-1");

        } catch (NoSuchAlgorithmException x) {

            // log big problem?

            throw new RuntimeException(x);

        }

    }

    public FingerPrint(String entryName,byte[] bytes) throws IOException {

        this.entryName = entryName;

        if (entryName.endsWith(".class") && isCafeBabe(bytes)) {

            isClassEntry = true;

            sha1 = sha1(bytes, 8);  // skip magic number and major/minor version

            attrs = getClassAttributes(bytes);

        } else {

            isClassEntry = false;

            sha1 = sha1(bytes);

            attrs = new ClassAttributes();   // empty class

        }

    }

    public boolean isClass() {

        return isClassEntry;

    }

    public boolean isNestedClass() {

        return attrs.nestedClass;

    }

    public boolean isPublicClass() {

        return attrs.publicClass;

    }

    public boolean isIdentical(FingerPrint that) {

        if (that == null) return false;

        if (this == that) return true;

        return isEqual(this.sha1, that.sha1);

    }

    public boolean isCompatibleVersion(FingerPrint that) {

        return attrs.version >= that.attrs.version;

    }

    public boolean isSameAPI(FingerPrint that) {

        if (that == null) return false;

        return attrs.equals(that.attrs);

    }

    public String name() {

        String name = attrs.name;

        return name == null ? entryName : name;

    }

    public String topLevelName() {

        String name = attrs.topLevelName;

        return name == null ? name() : name;

    }

    private byte[] sha1(byte[] entry) {

        MD.update(entry);

        return MD.digest();

    }

    private byte[] sha1(byte[] entry, int offset) {

        MD.update(entry, offset, entry.length - offset);

        return MD.digest();

    }

    private boolean isEqual(byte[] sha1_1, byte[] sha1_2) {

        return MessageDigest.isEqual(sha1_1, sha1_2);

    }

    private static final byte[] cafeBabe = {(byte)0xca, (byte)0xfe, (byte)0xba, (byte)0xbe};

    private boolean isCafeBabe(byte[] bytes) {

        if (bytes.length < 4) return false;

        for (int i = 0; i < 4; i++) {

            if (bytes[i] != cafeBabe[i]) {

                return false;

            }

        }

        return true;

    }

    private ClassAttributes getClassAttributes(byte[] bytes) {

        ClassReader rdr = new ClassReader(bytes);

        ClassAttributes attrs = new ClassAttributes();

        rdr.accept(attrs, 0);

        return attrs;

    }

    private static final class Field {

        private final int access;

        private final String name;

        private final String desc;

        Field(int access, String name, String desc) {

            this.access = access;

            this.name = name;

            this.desc = desc;

        }

        @Override

        public boolean equals(Object that) {

            if (that == null) return false;

            if (this == that) return true;

            if (!(that instanceof Field)) return false;

            Field field = (Field)that;

            return (access == field.access) && name.equals(field.name)

                    && desc.equals(field.desc);

        }

        @Override

        public int hashCode() {

            int result = 17;

            result = 37 * result + access;

            result = 37 * result + name.hashCode();

            result = 37 * result + desc.hashCode();

            return result;

        }

    }

    private static final class Method {

        private final int access;

        private final String name;

        private final String desc;

        private final Set<String> exceptions;

        Method(int access, String name, String desc, Set<String> exceptions) {

            this.access = access;

            this.name = name;

            this.desc = desc;

            this.exceptions = exceptions;

        }

        @Override

        public boolean equals(Object that) {

            if (that == null) return false;

            if (this == that) return true;

            if (!(that instanceof Method)) return false;

            Method method = (Method)that;

            return (access == method.access) && name.equals(method.name)

                    && desc.equals(method.desc)

                    && exceptions.equals(method.exceptions);

        }

        @Override

        public int hashCode() {

            int result = 17;

            result = 37 * result + access;

            result = 37 * result + name.hashCode();

            result = 37 * result + desc.hashCode();

            result = 37 * result + exceptions.hashCode();

            return result;

        }

    }

    private static final class ClassAttributes extends ClassVisitor {

        private String name;

        private String topLevelName;

        private String superName;

        private int version;

        private int access;

        private boolean publicClass;

        private boolean nestedClass;

        private final Set<Field> fields = new HashSet<>();

        private final Set<Method> methods = new HashSet<>();

        public ClassAttributes() {

            super(Opcodes.ASM5);

        }

        private boolean isPublic(int access) {

            return ((access & Opcodes.ACC_PUBLIC) == Opcodes.ACC_PUBLIC)

                    || ((access & Opcodes.ACC_PROTECTED) == Opcodes.ACC_PROTECTED);

        }

        @Override

        public void visit(int version, int access, String name, String signature,

                          String superName, String[] interfaces) {

            this.version = version;

            this.access = access;

            this.name = name;

            this.nestedClass = name.contains("$");

            this.superName = superName;

            this.publicClass = isPublic(access);

        }

        @Override

        public void visitOuterClass(String owner, String name, String desc) {

            if (!this.nestedClass) return;

            this.topLevelName = owner;

        }

        @Override

        public void visitInnerClass(String name, String outerName, String innerName,

                                    int access) {

            if (!this.nestedClass) return;

            if (outerName == null) return;

            if (!this.name.equals(name)) return;

            if (this.topLevelName == null) this.topLevelName = outerName;

        }

        @Override

        public FieldVisitor visitField(int access, String name, String desc,

                                       String signature, Object value) {

            if (isPublic(access)) {

                fields.add(new Field(access, name, desc));

            }

            return null;

        }

        @Override

        public MethodVisitor visitMethod(int access, String name, String desc,

                                         String signature, String[] exceptions) {

            if (isPublic(access)) {

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

                if (exceptions != null) {

                    for (String e : exceptions) {

                        exceptionSet.add(e);

                    }

                }

                // treat type descriptor as a proxy for signature because signature

                // is usually null, need to strip off the return type though

                int n;

                if (desc != null && (n = desc.lastIndexOf(')')) != -1) {

                    desc = desc.substring(0, n + 1);

                    methods.add(new Method(access, name, desc, exceptionSet));

                }

            }

            return null;

        }

        @Override

        public void visitEnd() {

            this.nestedClass = this.topLevelName != null;

        }

        @Override

        public boolean equals(Object that) {

            if (that == null) return false;

            if (this == that) return true;

            if (!(that instanceof ClassAttributes)) return false;

            ClassAttributes clsAttrs = (ClassAttributes)that;

            boolean superNameOkay = superName != null

                    ? superName.equals(clsAttrs.superName) : true;

            return access == clsAttrs.access

                    && superNameOkay

                    && fields.equals(clsAttrs.fields)

                    && methods.equals(clsAttrs.methods);

        }

        @Override

        public int hashCode() {

            int result = 17;

            result = 37 * result + access;

            result = 37 * result + superName != null ? superName.hashCode() : 0;

            result = 37 * result + fields.hashCode();

            result = 37 * result + methods.hashCode();

            return result;

        }

    }

}