/*
 * 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
 * outer 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 String basename;
    private final String entryName;
    private final int mrversion;

    private final byte[] sha1;
    private final ClassAttributes attrs;
    private final boolean isClassEntry;

    static {
        try {
            MD = MessageDigest.getInstance("SHA-1");
        } catch (NoSuchAlgorithmException x) {
            // log big problem?
            throw new RuntimeException(x);
        }
    }

    public FingerPrint(String basename, String entryName, int mrversion, byte[] bytes)
            throws IOException {
        this.basename = basename;
        this.entryName = entryName;
        this.mrversion = mrversion;
        if (isCafeBabe(bytes)) {
            isClassEntry = true;
            sha1 = sha1(bytes, 8);  // skip magic number and major/minor version
            attrs = getClassAttributes(bytes);
        } else {
            isClassEntry = false;
            sha1 = null;
            attrs = null;
        }
    }

    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 basename() {
        return basename;
    }

    public String entryName() {
        return entryName;
    }

    public String className() {
        return attrs.name;
    }   

    public int mrversion() {
        return mrversion;
    }

    public String outerClassName() {
        return attrs.outerClassName;
    }

    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 outerClassName;
        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.ASM6);
        }

        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.outerClassName = 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.outerClassName == null) this.outerClassName = 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.outerClassName != 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;
        }
    }
}